recent purchase '82 RJ SECA idling high rpm when warm

Hi anyone.
I have just joined XJBIKES
Recently purchased XJ650 RJ SECA. Had to go back under warranty cos running @ 3000+ idling when warmed up. They had it for one week, and had carbs off and balanced carbs etc. over two labour days etc.
Warranty now run out, and still idles at 1500+/- when warmed up.
Is this too high still? Sounds it, uneconomical on fuel, and wont come down any, even when reduce the idling screw right down....Manual says warm idling should be 950+/- 100rpm(?) *CORRECTION. Will come down a tad, if put into gear and slowly engage clutch, but this just creates premature clutch wear surely?
Saw an article that said check rubber boots between carbs and ports for cracks, clean and silicone seal, and after inspection, done the outside boots for this (but not yet looked under tank for numbers 2 and 3)
Vendor says that they have greatly improved it, but it is an old bike and I must accept that it won't run like a new one......?!
Anyone got any other ideas.....ie heard about valve clearances, shims or something, and air filter, whatever....
Regs
Pl

 

check valve clearances -> sync carbs

 

There is a LONG list of reasons why the Bike might be behaving like that.
Long.
All ... Fine-tuning related.

When I'm introduced to an Engine that does not respond to efforts made to have it run better, ... before getting heavily involved, ... I need to know what is the present condition of the Engine.

I'd conduct a Compression Test and see where things are at.

 

Welcome to the site! You need to give more information in your signature line (what year bike, mileage, any modifications etc.) and turn on your location feature (in case someone is near and can help you).

What your vendor (seller?) told you is a lie. Just because a bike is not new does not mean it can't run right, or be tuned, or be as good as it was the day it rolled out of the factory. They said that to you because they are clueless (99% of their experience is with <15yr old bikes) and they don't want to mess with it anymore. And if your fuel economy is bad then they did not greatly improve it.

As for your issue. There can be multiple causes, but as you will learn there is one sure fix. To make sure all needed maintenance has been done and done correctly. Bottom line you need proper valve clearances, proper carb operation: 1)clean 2)floats set 3)synched 4)mixture right, good plugs, no air leaks anywhere. If you follow the advice you'll get in here you will get it fixed. Use the search tool and look up threads on the above topics.

I am no expert on carbs (becoming one though) but sounds like your getting too much fuel. Either from your pilot mixture setting or enrichment circuit (wrongly called choke). One thing you can check easily is to see if your enrichment plungers are being released all the way when you close it off with the lever. There is one for each carb and a little fork lifts them when you engage the choke. They should drop free (2mm or so) and not be touched by the fork when it is off. Rick is our resident carb guru so heed his advice. Does it run right otherwise? No backfiring, lugging, smoke, etc.?

 

Thank you all, for your contributions!
In answer to MercuryMan, in particualr, as I am new, I am finding it rather confusing to navigate and check all the necessary buttons etc. I. will take your advice (signature line info, and turning on location feature) I'll get there!
My bike is an XJ650 RJ SECA, 1982, 29,000 MILEAGE, IMPORTED TO UK FROM USA, no engine modifications, that I know of. It has been resprayed in 1990's, to a red, (Cardinal?, as per the Canadian?) from the original silver and blue spec USA. Frame and engine no. 5V2-003440, which pertains to USA RJ SECA 1982. NOT Maxim.
The bike otherwise, I am very happy with. It starts first time, runs smooth, and acceleration etc. is fine. (this suggests that compression is ok, but I bet someone would suggest otherwise(?)!
Only other irritating thing (apart from the idling!) is hard to select gears, when engine is cold, (I know its a shaftie, and I've already got an XV535, which selects gears much better when cold!), and selection is slightly better when warm.
I will be able to carry out some of the tests myself, but I haven't got a garage, I am not a mechanic with access to the tools that are needed to do carb checks, valve clearances etc, and winter is coming on, as you over the pond, have already had experience of(!!!)
Thank you so much, and keep suggestions coming........
Appreciated.
Dale Grantham
Radford
Nottingham
UK

 

It wasn't a "suggestion." What's just been explained to you is the solitary raw truth of the matter.

-Old XJs can be made to run like new, or better; a whole lot of us have done it successfully.

-Certain things HAVE TO BE attended to, and regularly, or you can damage the motor.

-Valve clearances: The initial check and adjustment was to have been done at 3000 miles; it is also due every 5000 miles thereafter. The valve train on these motors doesn't loosen; the valve clearances get tighter until bad things happen if not set right.

-Carbs: Cleanliness and proper float valve operation are critical to how the bike performs as well as fuel economy. Float levels are important, and only have a 3mm adjustment tolerance. A proper running vacuum sync when all of the above have been attended to will be necessary; however it cannot be performed accurately if the valves are not in spec FIRST.

From the factory service manual:



Your "vendor" likely had no idea or didn't want to get involved in TRULY bringing the bike into spec; he just wanted to get it running well enough for you to go away until the warranty expired.

In order to get a 4-cylinder, 4-carb motor to behave 100% properly, it has to be rather finely tuned. Such fine tuning is impossible if the engine itself isn't operating to spec. There is no "quick fix" for this, sorry.

 

Thank you bigfitz52!
I have a collection of old test certificates as history only, but no mention of any service(s) etc. been done, which may have given evidence of last valve clearance checks etc....
Had been (8) previous owners, any one of which MIGHT have done this at any given time, but I have to go by current symptoms, to assume haven't been done for a long time and DO need to be done, which you have pointed out to me, before undertaking any carb tests etc.
which would have a big chance of solving the problem...........
I have always looked after the bikes I have had in the past, and done necessary checks, and any repairs needed etc. at the regular intervals.
The same is not of all individual bike owners, and I have to assume these checks have not been done for quite a while, and that's why this problem persists.
Thank you
D. Grantham

 

****************LATEST UPDATE****************************

:? Finally got round to doing valve clearances. I have taken two days or more and have really enjoyed it.
They obviously had not been checked for quite a while because 7 out of the 8 valves needed adjusting. (no 1 exhaust ok)
All that needed to be adjusted were too tight, apart from no. 1 intake, which was too big (probably accounts for the slightly sooty plug?)

PLEASE ADVISE ME I HAVE GOT CLEARANCES RIGHT FOR USA MODEL RJ650 SECA 1981/2 (NON-YICS) not Maxim

These are what I have set them to having been told from site, (but Haynes says different).........

INTAKE: 0.11 - 0.15
EXHAUST: 0.16 - 0.20

Haynes says both INTAKE AND EXHAUST should be
0.16 - 0.20 for RJ650????

Bit worried now......
Someone please put my mind at ease, or I have wasted two days setting to wrong clearances........!!!!!!!!!!

 

Haynes is indeed wrong on this one, if you followed what we have on this site, you should have done it correctly.

I was worried at first about this as well, but there are a couple of errors in the Haynes that this site has set correct--what finally convinced me I could really trust people here over the manual was reading about how Haynes had switched the jet screw numbers around, and how that had screwed a member up who had done everything on the system to get it running right, until they found out the manual was wrong here. Switched them as per the forum, and voila, worked perfect.

So you did it right. Go ahead and scratch it out in your manual and correct it.

 

As above, the Haynes is wrong so you got it right. If your bike still has the original decals in the sidecovers, the correct clearances are listed there as well I do believe.

So it took since last November until now before you finally checked your clearances? How many miles went by in the interim?

I'm concerned about intake #1. How "big" was that clearance?

 

I've just spent 1 hour typing a long, detailed reply, (including anecdote about oil squirting in my eye, after reinstalling shim! Ha Ha!) and lost it when reviewing, so this will be briefer...!!!!!
In reply to bigFitz, only a couple of hundred or so - no difference to symptoms.....been using my Virago 535...
Flushed engine and changed oil and filter....
Results now valve clearances checked, shims measured and recorded, and shims swapped about to accomodate etc..........need two new shims..sent to California for them
Must have been a long time since these were adjusted....7 out of the 8 needed changing..........
The two spare shims I have now are, 2.85, and 2.70

AS IT IS NOW....

INTAKE: (0.11-0.15)
NO 1: clearance: 0.11-12, installed 2.75
NO 2: clearance: 0.15, installed 2.75 (CLOSE?)
NO 3: clearance: 0.14-15, installed 2.80 (CLOSE?)
NO 4: clearance: 0.06-10 (out of spec) was 2.70 installed, sent for 2.65

EXHAUST:
NO 1: clearance: 0.18, installed 2.65
NO 2: clearance: 0.14-15 (out of spec) was 2.65 installed, sent for 2.60
NO 3: clearance: 0.16-17, installed 2.65
NO 4: clearance: 0.18-19, installed 2.70 (CLOSE?)

As for the intakes where I have accentuated ''CLOSE'', surely they are at their best gap, because it has been brought to my attention that adjustments need to be made when the gap gets too narrow, at the lower end of the specified range, and that's why problems start to occur...??
Exhaust NO' s ''CLOSE''? or OK?...any suggestions.

Is what I have done correct...and is my engine potentially on the way to recovering from this irritating overcomsumption, and high idling, in operating temperature....?

By the way, is it that the shims don't wear(?), but the cam bucket/or follower whatever, that wears, and that's why shims themselves need to be changed to reinstate the correct clearances.......bought a micrometer anyway!!!
Let me know...........

Thanks for all your support....

 

PS.
The No 1 valve intake gap WAS 2.0 (should have been 0.11-15)
Put a 2.75 shim in instead of 2.70, and now gap is 0.11-12
Regards

 

I'll make this real easy on you.

Especially if you're using metric feelers.

In spec is in spec. An intake valve at .15mm is in spec. Leave it. An exhaust valve at .19 is in spec. Leave it.

Out of spec is out of spec. Those you fixed.

Don't worry about close. I've got an intake valve on one of the 550s that's been sitting at .11 for the last two clearance checks, defiantly remaining IN spec.

For the first half of the life of the motor or so, or until they've been adjusted a few times and have "settled down" the valves "pound" themselves deeper into their seats, causing the clearances to tighten up. This is why the initial clearance check at 3K miles was so important, yet oft-neglected.

You need to do this again in 5000 miles, and every 5000 thereafter. Eventually you will find that only one or two need adjusting, eventually none or some may even loosen slightly. But they do need to be monitored as recommended, especially during the pounding-in process, for the motor to end up being solid for the long run.

 

Thanks Fitz
Will update when complete, and tested for consumption/idling again. Later............

 

*****************LATEST***********************
:?
Shims just arrived, and installed.....checked all clearances again........problem!!

No. 1 Exhaust clearance: a tight 0.155 (so 1.50-154)??
No. 3 Exhaust clearance: 1.50-1.54 (1.55 wont clear!)??

Both seem to be too tight for correct spec.

I may have measured wrong in the first instance because, I had recorded 0.18 (NO. 1) and 0.16-7 (No. 3), initially, and checked them again (!!)

Do the clearances change for exhausts, when installing new shims in other intakes and/or exhausts? (only changed shim in intake 4, and exhaust 2)

Obviously, should be 1.60 - 2.0 for the exhausts?

I think I have to acquire two new shims for the two exhausts.

Please advise.........

Regs. :?

 

Update from Sat. June 02............

Didnt get reply from my Sat presentation, so updating again today....
XJ650 RJ SECA - VALVE CLEARANCE UPDATE...... :? :x

Exhaust no 1 @154 (a very tight 155) - out of spec (currently installed 2.65)
Exhaust no 3 @150-154 - out of spec (currently installed 2.65)

I have only got feeler guages with increments of 0.05 (mm) lowest, and then go up in grades of 0.10, 0.15, 0.20 etc.
This limits me in exact accuracy of clearances, but it is obvious these exhaust measurements are too tight and out of spec..... :x :?

Need two 2.60 shims, and sent for in UK, 'cos site in California where I got other two from last week, has only got one 2.60 left.........

This might interest one or two of you......
Been looking for used vacuum guage set....

Was talking to chap on Wollaton Park, in Nottm. today, at the Autokarna, who seemed to know a lot about the XJ series, and I told him I was just doing my valve clearances, cos I had issues with poor consumption, and high idling (1500-2000rpm) at machine operating temperature (with the headlamp turned OFF - have installed switch to drive in daylight without light on - drops to @1500 with light ON) etc, and he suggested that it was most likely the carb synchronisation./float levels....but when I mentioned the XJowners site, and their 'experts' recommendations that yes, it could well be that, but first to ascertain this theory, the valve clearances must be checked and put in spec. beforehand, he hastily agreed with me.....valve clearances - and if still got symptoms - THEN carb fuel levels and synchronisation!
He went on to mention the problems with the carbs on the XJ series because of the Japanese needing to adhere to the emissions levels brought in, in the US, and this had implications with the choke /air jet(ok-fuel enrichment system!) screws and the air filters, or something(?)...how when synchronising, and/or changing to cone filters, you have to change the main air jets (bigger, or smaller (?).....also said these Mikuni carbs with the diaphragm at the top (under the four-screw plate) are prone to diaphragm rubbers withering or something which also creates problems with performance......and butterfly throttle valves, instead of sliding ones, aren't so efficient , be careful of rubber washers may be worn when reinstalling after cleaning - got them right way round? etc. etc. ...and on, and on! (anyone got anything to add to all this....)??? :?

Anyway, you may or may not be aware in US that it is Diamond Jubilee weekend for HM Queen Elizabeth II, in UK (and Commonwealth, for that matter), and so there is a Bank Holiday Monday AND Tuesday.
I, for myself am not that interested, apart from the annoying fact that it means I will have to wait an extra two days for my shims to arrive!!!

If anyone has anything to offer, as to my current valve clearance situation, or anything else as regards what my chance encounter with guy on Wollaton Park, and his views on XJs carbs etc, be glad to here from you....

Regs.
Dale

 

Dale,

Shims can be purchased from www.wemoto.com on the south coast, possibly a bit late for you.

however you may want to check out theit online store for other common parts. delivery and speed will be a definite improvement.

 

Thanks Redbeard!
Thats exactly where I have ordered them from yesterday ( had WEMOTO saved for a long time on favourites list)
It's cost me £20 tho' for two shims and postage, whereas, when I got two from USA last week, it only worked out at £14! (as I say in previous message, he has only got one 260 left, so I plumbed for WEMOTO, obviously quicker (I hope!)
Thanks for reply!
Regards
Dale

 

****************UPDATE*********************

Received last two shims needed today and installed (2 x 2.60 - both on exhausts 1. & 3. respectively)
Wouldnt start at first, and flattened battery, but hooked up to charger for a while, and heated up my spark plugs, and blew hot air down plug-holes - first time.

Got it to idling temperature, and still hanging at 1400, -if I bring down idling screw lower it just zeros and eventually cuts out.

So, still got the problem, even with valve clearances bang-on!

Went round my local bike shop, and I told him about it. (pretty sure from all the diaglogue we've had on the site, its either vacuum leakage, somewhere, or float height wrong on one on the carbs?, or sticking piston valve, or, or...or...!!!???)
One thing I do know, its definitely not the valve clearances....!!!

He suggested, being 30-year old, it could be a withered carb diaphragm(?), or vacuum pipe, from petcock to carbs, check air filter...etc

I have sprayed carb cleaner round the boots, and manifolds and it doesnt get higher (the revs), but if I spray underneath the boots, it climbs slightly then.....he suggested that, is probably because they are cooling temporarily...with the spray........?

I told him about the much talked-about throttle shaft seal leaks, on this site, and he said he has never had to replace them on a carburettor...? (unless the throttle shaft seal is the 'diaphragm')

Where are the thottle shafts, and how do I replace the 'o' rings in them , or 'seals' whatever..... cant see them in Haynes' diagram listed....

Realise Ive got to pull the carbs, and do a complete clean, overhaul, float levels, synch, buy some vacuum guages, more expense....
:?
Is the diaphragm, the throttle seal?
Regs.
Dale

 

http://www.xj4ever.com/hitachi%20thrott ... 0seals.pdf

 

Thanks Durk
Think I can manage that. Very informative.
Just one thing - I assume you replace the seals, and/or 'o' rings (we are looking for worn, split, etc?) Anything else? And what size are they, where do you get them from individually.....I dont think you get them with a basic rebuild kit......?
Excuse my ignorance, I SHALL do a search for them, but in the meantime, if you know......?
Many regards
Dale

 

Get ahold of XJ4Ever. Even shipping to the UK, it won't take long to get your parts, the correct parts, in hand.

Your Seca has Hitachi cabs, not Mikunis; although the "theory of operation" is the same.

The diaphragms are part of the slide assembly and are located directly under the "hats." They CAN develop pin holes or tears over time; often they're fine.

Anybody that's "never had to replace" a throttle shaft seal hasn't worked on too many carbs; or he's not very good at what he does.

 

****************************LATEST UPDATE*******************
As I've obviously got vacuum leak somewhere (probably at the throttle valve seals) I've pulled the carbs, done a wet float set (2-4mm), checked the filter to carb boots (clean), the carb-to-head manifolds (there is some cracking, but it doesnt go all the way thro', and I didnt get any +revs, when I sprayed around them anyway, when idling) Sealing them all the same....
The vacuum spigots are clean....
Broke the carbs, checked the diaphragm (in #1, a bit of dirt above needle?) Got the rest to check........THEN........ :lol:
took the fuel rail apart....old black disintegrated part of 'o' ring? smeared all over it! Every 'o' ring at least worn, one with bits broken off...possible reason for high idling(?) Perhaps.....going to get into the throttle shafts tomorrow and see the state of their seals (bet they are poor also...)
Thanks fitz for xjforever prompt - will no doubt be purchasing this weekend from them....

til tomorrows next episode..... :wink:
Regs
Dale

 

*********************LATEST TODAY***************
Just stripped carbs down, cleaned them, checked diaphragms, (one has very slight wear in two places, but cant see light through...?)

Removed the throttle shafts and seals the seals look ok to me, but I cant compare with new alike (?)

I have replaced the 'o' rings on the fuel rails, which when compared with the new I've put on you can tell they were worn (thinner), and one was damaged also (the one on rail between 1 and 2 carb, I think, where there was sludgy leak all over the rail...) - could this have been the cause of high rpm's once at machine temperature??

I made two attempts to send pics of the existing throttle shaft seals (and the replaced 'o' rings, but wouldnt accept from camera, or my mobile (too big and I dont know how to put them to 500 x 500) - from your experience must I replace them? (I know someone has been in to these in the past, as the butterfly screws have been removed before - maybe someone has replaced the seals not long ago....but NOT the 'o' rings??

You'll probably advise that replace them anyway, (the throttle seals) cos the only way of telling if theyre worn or not, is to put the carbs back on the bike (and eliminating all other possible vaccum leaks), and if the problem still remains, then it is the throttle seals....??!!
They are a little 'loose' on the shafts, one or two....

Let me know, from your experience, how to proceed....

Regs.

 

Just removed the replacement fuel line 'o' rings - theyre correct diameter, but too thick, and wont allow line to slip into carburettor....
ordering some from xj4ever, along with throttle shaft seals.....adios

 

All good advice from other people... BUT - usually, before you start changing shims etc, I'd advise you MAKE SURE that the idle adjusting screw is set properly (I always get into trouble from others on here for suggesting this simple check above everything else - However, it proved to make a significant difference on my XJ).

This adjustment screw is EXTREMELY sensitive to minute adjustments because, as it acts directly on the throttle, it opens/closes the butterflies on the carbs. You might find that backing it off a little once the engine is warm allows you to drop the idle speed back to 1000rpm. Just my two-penn'orths-worth...

 

Thanks Nige
Been there and done all that a long time ago, and the lowest revs, I can get (even now I've adjusted shims) in operating temperature is 1500-2000, with idle screw turned down to lowest before it will just cut out.
Its been established that its a vacuum leak, and its and/or between the air intake carb boots, the vacuum spigots, the carb to head manifolds, or THE THROTTLE SHAFT, AND FUEL-TO-CARB SUPPLY PIPE SEALS, AND O-RINGS.
Im just on that case now, done the investigation, found the worn parts and ordering the necessaries.......watch this space.....!
Thanks for your reply.....
Regs.
Dale

 

**************LATEST******************
Done wet float level test. Broke carbs, and removed carb to head manifolds (cracked in various places - just sealing with silicon now) Air box to carb boots examined closely and are ok.

When I dismantled carbs, found that fuel supply o-rings were worn and had deposited on one part, a sludgy, residue (cause of vacuum leak?)
The throttle shaft seals look ok, but I have sent for both seals and o-rings from Chacal, and will replace both.

The carbs were filthy on the outside, and I have meticulously cleaned them, the best I can - the insides jets etc and bodies seemed relatively clean, (the firm I bought this from, told me when it was sent back that they had had the carbs off, and worked on them) apart from the float bowls, which had a sort of brown stain in the bottom of them, (rust from inside tank, in fuel?) which I cleaned out.

Can't proceed any further (dry bench synch, vacuum synch on bke etc), until my carb parts arrive, and I can reassemble everything.......
Have attached a pic which I have now managed to reduce, of the used o-rings. Hope you can see it.
Later
Dale

 

Please Note: The pic includes new o-rings, that I attempted to replace with, but they were too wide in guage, (wouldnt insert into carb fuel shaft when fitted) so I've sent for proper ones from chacal......

 

PIC OF SHAFT SEALS REMOVED FOR REPLACEMENT(?)

 

***********LATEST JULY 13**************

Replaced throttle seals with new ones. Replaced carb fuel-pipe o rings with new ones.

Thoroughly cleaned carburettors, every nook and cranny. (as mentioned following the many threads, over the past few weeks/years!)
Passed the 'clunk' test

Installed new bolts and spring washers in float bowls
Put an extra seal of bike innertube on top of already silicone-sealed, cracks in inlet manifolds.

Made an apparatus to hold carbs completely level (copied from thread on this site) from pvc plumbing equipment, and wet-set the float levels again -they were in fact the same as when I did it from holding it in a vice!!)

All are in spec - #s, 1-3, 2-3mm below gasket level, #4 is 3.1-2 below gasket level mark.
Bench-synched carbs, using a fine-guage paper clip.

Re-installed carbs to machine (after some deliberation and help from this site(!) - see other thread!!)

Started up with choke-initially idled steady at 1150, then all of a sudden, when warmed up,(and choke off) shot up to 2400 and stayed at that(?)

Turned it off.

Idle screw is fully 'out' and throttle is loosened right off.

I know I've just changed valve shims to spec, so requires vacuum synch, and I have bought a 4-dial guage to perform this task, but....?

The idle mixture screws are about 1/2 way out from seated position when bench synched - would turning them back down tighter slightly, bring the idle down....?

This smells of vacuum leak again, otherwise....?I only sealed the mouths of the inlet manifolds with red high temperature instant gasket seal, (12 hours ago) over the old gaskets, and I havent tried a 'spray carb cleaner around them' test yet....

:? Is this situation normal, before doing vacuum synch, after valve shim adjustments.....until you've vacuum synched, using guages.....???

Thanks....

 

Did you make sure that the choke (actually an enrichment circuit) actually closes completely?

When you say the idle screws are "half way out" what do you mean exactly? We measure the initial settings of these screws in the number of "turns" and "half way out" might be more than the 2 1/2 turns from bottom recommended.

The inlet manifold should have a proper o-ring or gasket (not sure which for your model). I'm not sure how well the red instant gasket would work, but I wouldn't recommend it.

High idle is quite normal if you haven't set the pilot mixture screws correctly or synced. Get to doing that stuff.

 

Thanks Manbot

Sorry. I meant the synch screws, (when doing the bench synch) not the pilot mixture screws, are all screwed approx 1/3 to1/2 way 'up', effectively when only ' a sliver of light', can be seen when viewing thro' each carb mouthpiece/venturi.

Could it be that the butterflies are set so wide open (guage of a small paperclip), that this is causing the high idle (if a vacuum leak is not the culprit, - or the pilot mixture screws not set 2 and 1 half turns out?)

Cant remember if they (the actual pilot mixure screws) are screwed right down, or not, - will look tomorrow. - and do vacuum leak test!

:wink: I can get some new manifold gaskets (if tests necessitate) off a site in Europe - £10 (inc pp)
Thanks.....

 

Oh, and the enrichment circuit is closing properly as well.....
Regs.

 

Yes and Yes. A bench sync only gets you close enough to get the bike started. You got that far. Do a running sync, and your butterflies will be set properly for the different vacuum your 4 cylinders produce.

Then set the mixture screws (2.5 turns is also just a STARTING point). The Gunson ColorTune plug works great for this. After setting the mixtures, sync again, etc, until all the cylinder mixtures are tuned and all are pulling the same vacuum.

 

Just been trying to synch, using vacuum gauges. Waited til op temp reached. Got the 1 and 2, and 3 and 4 as level as poss, but when temp reached, still high idle. 2.5-3.0 rpm.
Kept tweaking synch screws, and got it down a bit more. Idle screw, is all way out....turned off. Throttle is slack, with 0-10mm til plays takes up.
When I blipped throttle would only come down slowly, to @2000rpm
Tweaked again.....turned off
Turned on again, and racing up and up, to 5krpm+!!!
Have I blown a gasket or something? Really worried....
Will try again when cooled down (I didnt have a fan on)
Regs.

 

HELP!! :!:
Ive let the motor cool down for 1/2 hour, and started again, and it just keeps racing up to 5+K!!!
Turned off.

I did notice a little 'pop' of air, up from carbs/manifold area, when I pressed starter button to restart engine, just before I got this problem (between 1 and 2?)

Turning the synch screws out, is having no effect now ( I could press down on the throttle linkage, before, and that would bring RPMs right down til it cut out almost... this has little, or no effect either.......... :cry:

The throttle is not sticking, and idle screw is all the way out, anti-clockwise?

Please someone tell me I haven't done something major down below?

I was doing so well, it would idle very low, with adjustment, (til op temp) and now this.... :cry:

Any ideas? Had this experience before when trying to synch?

 

You didn't blow a gasket or anything.

You're over-adjusting. You probably have it so far out of sync now that you're going to need to pull the rack and re-bench sync. Don't feel bad, we've all done it.

And then don't attempt to sync until it IS up to operating temp.

 

Thanks fitz

Made me feel better, knowing its something that many people have endured in the past....

Just took the carbs off, and there are no butterflies stuck wide open or anything, - but on closer inspection #s 1, 2, and 3 are all at 2-3mm!! #4 looks more or less fully closed.
Explains the 5k+ idle!!?

Like you said, in my effort to get lowest idle I could, I have overadjusted (I dont think I tried to actually synch until op temp. tho(?)) to the point of 'no return' so to speak.
I actually got a decent synch, on 1 +2, and 3 +4, (3 and 4) slightly higher/lower, cant remember which now) on the dials of the guage, but I wanted a lower idle......!!
This time when I bench synch, I'm going to use a lesser guage base (a certain guitar string I have in my posession) than the paperclip I used at first, enabling the butterflies to close to a tighter gap, when throttle fully 'off' and therefore the lower idle can be attained(?)

:roll: Think this is logical in theory, and find out if in practice?
Regs.

 

Several members recommend a business card torn into even strips instead of the paperclip or string. Because it's flat and bends to mold the curve of the inlet, it gives a more narrow setting so that it doesn't rev as high.

Might give that a try too.

 

Thank you Bill

Only just got your message, and in meantime have re-bench synched, with a guitar string which is 66% guage of the origina paper clip which I used.

Set them bottom dead centre of venturis

Have reinstalled carbs back onto bike now, so cant use this method right now. Will try and see if I can get a lower idle, with the smaller gap I have created(?) from this guitar wire.

Your method makes more precise sense, as it fits more snug, over a larger area, a concave shape for the convex shape of the bottom of the butterfly as it closes in the venturi.

:wink: If I still get the problem, and have to resynch again, I will use this method.
Regs.

 

Now when you sync:

TINY tweaks; blip throttle wait for engine to settle down.

TINY tweaks. One eighth of a turn is a LOT.

If the idle rises, turn it down with the main knob. Blip throttle wait for engine to settle down.

If the idle drops too low, turn it up with the main knob. Blip throttle wait for engine yadadayadda you know.

Keep a common household fan blowing on the fully warmed-up motor during the process. If it becomes "unruly" and doesn't want to properly respond to inputs, shut the bike off and let it cool for a bit.

If you have your valves in spec, truly clean carbs, accurately set floats, no vacuum leaks, and got a good bench sync, the vacuum sync process should go very quickly, and usually requires just a small amount of adjustment. Think of it as "touching up" or "fine tuning" the sync you already have.

 

Hi

I had the same problem on an older bike. Turned out the bike was running too lean, even at 2 and a half out. Everything was clean and in sync. Dont ask me why, but when I turned all my mix screws out 4 and a half (practically max), it held idle much better when warm. A later probe check at the local yamaha shop, proved that 4 and a half out was creating the right idle mix.
The problem had been, that I had set the idle to high when cold, because otherwise the mix was so lean, that it couldnt run. And when it got hot, the idle ran away.

Try it. Its worth a shot. I know its not what everyone and the books say, but it actually worked for me.

Tell me your results

Good luck

Dan

 

*****LATEST***********

Ive just attempted vacuum synch, after taking off carbs, and bench synching again (earlier report
)
Up to operating temperature....

Took it steady, and #s 1 and 2, level out at 13 inches (250mm) on the dials. #s 3 and 4 at 11 inches (150mm) on the other two dials.

I cannot get less than 1400rpm when in synch...(350 too high)

Rather, I can get in to come down somewhat, if I turn #1 mixture screw, but then it shows #1 and 2 are out of synch....?

(I havent touched the pilot mix screws yet - think they are at 2 and one half turns out)

There is also an intermittent 'popping' sound coming from around either #3 or #4 carb mouth/manifold area, ????????like an escape of air, its definitely blowing, not sucking (I think!!)
Just done a vac leak test with wd40 whilst idling at 1250 - 300 - no increase in rpm whatsoever....

Any ideas .....do I check pilot mix screws, or have I got to rebench synch, with butterflies closed more, using finer medium. (closed even?)
Regs.

 

You're missing the concept on bench sync'ing.

First off, with the idle knob fully backed off, ALL 4 butterflies need to be closed COMPLETELY.

The "sync" process is to get them all moving the same amount at the same time, when they move.

Trying to "sync" to the fully closed position via feelers of some sort is why this is driving you crazy.

Back the main knob off all the way, and be sure all 4 close fully.

Then, screw the knob in until the butterflies begin to open, and set #3 (the one controlled ONLY by the idle knob) so that it is halfway covering one of the tiny holes in the top of the carb throat. (Or to any other "duplicable" position.) Adjust the other three to match #3. Back the knob off all the way again and ensure they all still close fully.

Trying to "synchronize" the amount of drag on whatever feeler you're using is counterproductive.

Also understand: #1 is controlled by #2; whatever you do with #2 it will move #1 as well. #4 is independent. And #3 is only moved via the knob, which is why it's "home base," the one the others are adjusted TO.

Adjusting the main knob of course, moves them all.

 

OK fitz
So there are 3 synch screws right?

The #3 butterfly gap is the one you set first with your guage, with the main adjuster knob I did this, but with the knob fully out, I didnt advance it, so the butterflies just started to open (you set #4 butterfly with the #3 synch screw down to what you set #3 with the adjuster knob)

But you said #4 was independent - surely the #3 sync screw adjusts the gap for #4 to the gap you set for #3 butterfly?

Then I went to #2 butterfly, (I was following from a thread on this site) set my guage at bottom dead centre in that, using #1 sync screw, so that it grabbed, then put guage in #1 butterfly, and adjusted, so that #s 1 and 2, both 'grabbed' the guage tight.

SO WHAT IS THE #2 SYNC SCREW FOR? - I thought it was for syncing #s 1 and 2, with #s 3 and 4, when finally vacuum synching.

Blipped the throttle bar a bit, looked up to the light, and checked all were more or less the same gap.

I think when I went to synch #s 1, and 2, I didnt open and close down with the throttle bar onto the guage in #2, - Im not sure - I may have just adjusted the #1 synch screw down onto it.

I have got a steady idle, when in operating temperature, when properly(?) vacuum synced, (equal on the dials) its just that the idle is too high still, and as I say it will start to come down if I tighten #1 screw, but then the guage says it is not in sync with #2(?)

Could be that Ive set the gap too big for #s 1 and 2, in error, when bench synching, but that wasnt apparent when viewing throught the carb mouths...

The main adjuster knob is all the way out from the very onset.

Im sorry, Im confusing myself now with all this....

Regs.

 

Going to pull the carbs again, and re bench sync, with the throttles CLOSED. (or as closed as they can be and still start)
Later.......

 

THERE IS NO #3 SYNC SCREW. And you're still missing the point.

There are screws on 1, 2 and 4. Those get adjusted to 3. #2 carries #1 along for the ride.

They should all close at the same time. They should all open together.

Do what I suggested. Back the main knob off, and be sure they're ALL CLOSED. Then, using the main knob, open #3 to a "duplicate-able" position, like covering 1/2 of one of the bypass holes. Then DUPLICATE said position with the others.

Don't try to "sync" to fully closed, or open just a hair. Sync to #3 when it's in a position you can replicate with the others.

When you're done, unscrew the main knob fully. They should all still close completely. And when you turn the main knob IN, they should all open exactly together. If not; re-sync.

You should then need to turn the idle knob in a tad for the bike to run. All the way out should mean all 4 throttles FULLY closed. And that's the way you want it; as long as they then all move together when they open.

 

:wink: Gotya fitz!
Thats the way Im gonna do it....
Regs.

 

@pauldale999 - wanted to let you know that I just redid my bench sync and that was definitely the problem. This time, I followed Fitz's instructions and just got really OCD about the strips of index card having the same feeling when pulling against the almost-closed butterfly. I reinstalled, colortuned, and she idles like a champ now.