recent purchase '82 RJ SECA idling high rpm when warm

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.

 

Hi zhalbert

Same here!

Thank you oh mighty fitz!

Have a nice steady idle at 990-1030, (can go lower even!)

Just re-vacuum synched, and all 4 dials steady at @8 o'clock (idle mixture screws 2 and one half turns out.

Its obviously got to be colortuned, and I have just sent for one, so will update when received and performed colourtuning.....

Not taken for a run yet, so just waiting for a gap in this torrential rain here, and will take it out for a spin........hopefully everything will hold up(?)

Regs.

 

DO NOT set the idle too low; it's a plain bearing motor and it needs its oil pressure. It should be set at 1050~1100rpm; the fact that it's capable of idling lower just means you got it sync'ed up with adjustment left on the knob. Good going.

 

My colortune plug has just arrived.....

Been reading the 'science', in the notes.....
Referring to my symptom when idling (in zhalbert's thread...), it would seem that the intermittent 'popping' or backfiring whatever, at #s 3, or 4, could be due to an misfiring cylinder, now and again, due to incorrect mixture in one of (or both) the carbs......

"......When there is less air in the mixture, there is not enough oxygen to complete the burning process so some carbon monoxide is not changed to carbon dioxide and hydrocarbons (unburnt fuel) may be present in the exhaust................."misfiring may occur, and hydrocarbon levels. in the exhaust gas will rise"

:roll: Sounds like my symptom....(?)

Will attempt the colortune, and obviously, if I can fine tune ok, (and the symptom is eradicated) it is just the adjustment, but if I cannot fine tune on either cylinder, it points to pilot mixture screw component(s) inspection and/or reconditioning......?

Anything to add, anyone, in support or otherwise, of my diagnosis...?

8) Thanks to everyone who has contributed to my threads, and helped me along the way...........

Regs.

 

RE: misfire (in your other thread) http://xjbikes.com/Forums/viewtopic/p=3 ... tml#338059 may have nothing to do with mixtures...

 

You're right fitz - not mixture issue!

:lol: I think i've sorted it.....clamp on carb manifold to inlet head, was misplaced slightly on carb #3. (where the noise of 'sucking' or 'blowing' was coming from)

Repositioned it. (it wasnt sitting completely 'square' around the carb throttle mouth) Tightened it up.....started machine....reached temperature,......blipped throttle......no more symptoms!

And engine is idling more 'rhythmically', @1000 rpm without a little 'backfire' everytime I blip throttle.

Response is 'good' too...but not done colortune yet.....

Also want to take out for a good 5-10 mile run first, to see what it settles down to after....

Regs.

 

**************LATEST TODAY******************************
Talk about speak too soon.........

Just took it for 10mile run and halfway through idle rose to 1500, and at one point 2000! (at lights, had to turn off)

Thought it might have been change of vacuum pipe, as it had 'ridden up' the spigot spike, when I examined it when I got home....

Changed it back to the old pipe, and got it up to temperature again, (idle screw adjustment fully out), and up it went again to 1500, and stayed at that til I turned off.

If I blipped the throttle, the idle would come back down to 1000, then steadily, (sort of like a trot, into a canter) it goes up again to 1500+

Push down on the vacuum pipe, where it joins petcock, and also where it joins manifold, still wont bring the idle down...so its not that....?

Did spray test all around carb mouths, and where I had repaired the cracks in the manifolds - no drastic increase in revs.

I am presuming this is a vacuum leak again - but where?

The increase only occurs when bike reaches operating temperature, and it is only (?) +500+

Could it be that with taking the carbs off the rebench sync twice, that I've removed some seal off the cracks in the manifolds, and it only starts to leak at highest pressure, ie when at operating temp?

The throttle is not trapped anywhere, and the choke plungers are all down....

:roll: One thing I do remember when I was cleaning the carbs, and refurbishing them......one of the rubber diaphragm's had two very slight grazes, two cm apart........I held it up to a bright light, and could see no light coming through, so as per this site's guidlines, I 'assumed', it would need no repair..............? Could this be a cause of high idling once temperature is reached....

It was idling fine, and I had vacuum synched also. (see earlier in thread) It seems that something has happened, since I took it out for a test ride....

:? Anyone..............??

 

***************LATEST!!******************************

:wink: I really have sorted it this time......(?)

8O The return to high idling was due to my vacuum to petcock pipe leaking at the manifold spigot, (although couldnt hear or 'feel' it)
Also, I suspect, spigot plugs, on other three manifolds not seated correctly.........ie with spring clip sat in 'grooves'!!

Re-positioned, again, and tightened up fully, #3 (the original 'puffing' or 'blowing' intermittently) carb to manifold bracket.
Moved the vacuum pipe to petcock, from #3 manifold, to #1 manifold (easier access, and it doesnt matter which # manifold it is on(?)

Back to a nice easy 950-1000rpm idle, at temperature.

Didnt count my chickens tho' - re-vac synched (didnt need hardly any adjustment, apart from 3 and 4)

:lol: Just took out for a 20 mile run, and man is it S-M-O-O-T-H!!?

Had a few quick spurts of acceleration, up to 70mph, and then watched idle when I had to stop at lights/roundabout.......bike was well up to temperature by now, and NICE AND STEADY, @ 995rpm.....!!

Checked when I got home, and a nice quiet 995 still......
So pleased! - and I havent even colortuned yet.....

Thank you to everyone, who has contrbuted to my thread, and helped me to resolve my high-idling issue....!!!

Regs.

 

Excellent.

Now turn the idle up to 1050~1100.

 

Yes ok fitz!

Just read again in thread earlier....

What does that mean incidentally, 'a plain bearing motor, and it needs it's oil pressure'?

Why is it necessary?

Does it not get enough oil to cool or something, if the idle is less than 1050rpm, and the pressure is too low, and it overheats.....??

Regs.

 

In a plain-bearing motor, it's the oil pressure that keeps the bearings from digging into the crank. PLUS the fact that these motors depend on an "oil spray" system for cooling.