Carb tune issue?

carbs on. bike runs, idles great. Got air box etc all put back together. Again, idles great. bench synced before putting them back on
Hook up the carbtune, get 3 and 4 balanced, 1 and 2 appear way off... now the idle takes off to like 3000rpm... try backing out idle screw so it's not even touching the throttle, still wants to idle high.

suggestions?

 

idle air screws were set to 2 1/2 turns out from a soft seat as a baseline?

 

yes 2 and a half out.

 

always start with 1/2, get those right first. now turn the idle knob till it touches, set 3/4. now set the 12/34 pairs. the idle knob always has to touch. even if the engine races keep going.
one of the butterflys is holding the other three open, you have to make sure it's #3 that is controlled by the idle knob that's in control. the idle knob hast touch

 

so hearing this it sounds like I need to take the carbs off the bike, again, and re-bench synch?
also, you say keep going even if the engine is racing? what do you do when it's all over and done and you still having a racing engine then?
I get that it must be one of the other butterflies besides #3 holding the rest stuck open. Any way to correct for this and get it back to number 3 like it should without doing a re-bench synch?
I suppose I screwed up synching 4 to 3, 1 to 2 then getting those to match 3?

 

No don't pull carbs yet, start bike back off SNYC screw or tighten #1 see if idle drops or increases adjust, go to number 4 (3) repeat then adjust 2/3 .. just did mine had a popping and slight hanging idle, adjusted till it was about perfect... I would not bother with mixture screws just yet. anyway just some random thoughts.

 

understood. just tempted to take them off and bench sync again to get #3 sorted first.
I agree that this is unlikely the mixture screws, but can't hurt to snug back down and back out again to be sure...

 

I'd rather go to the dentist than pull carbs.
Your going to do the same thing with the carbs off. If you keep the idle screw touching while you sync it will always control the idle. If it gets way up, like 6k
Shutdown and back the idle off till it just touches. Don't need to make it perfect first time through, you'll need to go back through it several times to get it right on

 

understood. I think maybe im just misunderstanding what exactly i need to do from here with the carbs on already. Taking them off and having the visual will help.

 

Something to try, use a piece of matchbook type paper as a feeler gauge between the idle screw and the tang on #3. Make it loose with the knob then use the sync screw to make it tight, real tight.
That should get 3 in control and reduce racing.
Or pull the rack

 

well... pretty frustrated.
pulled rack. re-bench synch. re-set the air/fuel mixture screws just to be sure...
put back on, idles well. attempt carbtune again and run into same issues. synch 1 to 2... synch 3 to 4. it starts to take off a bit. back off the idle.. start to adjust 1/2 to #3 and it just keeps racing. just pulled rack again in frustration and re-bench synced... I must be missing something here?

 

I just came into the house to post the same question. Engine will idle fine until I attempt to ride the bike then the engine RPM increases to 4000 + RPM. Going to attempt the above.

 

just put back on again after re-bench sync.... again, idles great.
initial tune as shown...

 

Followed the above directions it is now idling fine. Need to synch the carbs. I normally only work on twins and single cyclinder bike and had cut two of the hoses off my mercury sticks plugging the ends of the lines, need to run to the hardware store for some 3/16 line.

Thank you I am happy that I found this Forum.

 

I feel like it should not be this far out of sync after a pretty solid bench synch and idling very well...

 

you could have some vacuum leaks

 

about to go and test that theory... been thinking about all day.

 

about to go and test that theory... been thinking about all day.
at the same time... that does not make sense to me as it idles great right off of a bench sync..?
Could be leaking with the carbtune on?

 

Could be.
Have you set the idle mixtures yet?
Your vacuum levels can be all over the place (carb to carb) until you do. After mixtures are set to near-ideal, then do the runing synch and see how far out you are from being balanced.
Did you by chance happen to do a compression check? If so, how do your compression numbers compare to where the vacuum readings are at?

 

I don't want to hijack the thread. However, would a lean mix cause this issue? I have a similar situation and am planning to readjust the screws from 2 turns to 2 and a half turns.

 

http://www.xjbikes.com/forums/threads/compression-numbers-650-seca.73392/
From previous thread of mine in oct 2015
Finally got around to doing valve shims. Finished that without issue, valves now all in spec. While I was at it I figured it would be a good time to check compression as I had not done that yet. Keep in mind this was done with tank off, carbs off, valve cover sitting loose on top of motor, all plugs out, engine dead cold. Not standard operating procedure I know...
Initially got:
#1 - 80 #2 - 110 #3- 40 #4 - 110.
1 and 3 obviously not good... I decided to let bike sit a few min and try again, thinking "well, it's been sitting minimum 5 yrs... Stuck rings maybe?"

On 2nd go round...
#1 - 90 to 100 or so #2- 110 #3 - 90 #4 - 110.
Better.. but still..
Thoughts?

as for vacuum... I tested at idle with propane, no change in idle. So I think we're clear there.

As for idle mixture. I reset them at 2.5 turns out. Are you suggesting I colortune them before trying to sync?

 

Yes. Colortune before running synch. The idle fuel mixture will effect the synch, so you synch after mixtures have been set. It's really a back-and-forth process once you get to really fine-tuning them, but having the mixtures set first helps.

 

ahhhh.... I see...
I shall report back
Thank you!

 

so tried the colortune.
4-3-2 all look good. 1 looked good as well actually, but was some backfiring at the vac cap port. tried making it richer, got worse. made leaner, this smoothed it out. still burner blue, but made the idle climb to 3000-3500. will post pics of the carbtune after doing the colortune in a bit.

 

it might but so could other things like vac leaks



edit to answer

 

is your vac cap port not capped? it should be

 

Thanks, XJ550H. I plan to re-send the carbs within the next two weeks. I will reset the screws before then. I can't wait for the carb clinic to get here, where I can learn how to maintain the bike

 

I had the carbtune on it

 

re send?
i edited my answer

 

Re-sych... Stupid spell check.

 

so tried the colortune.
4-3-2 all look good. 1 looked good as well actually, but was some backfiring at the vac cap port. tried making it richer, got worse. made leaner, this smoothed it out. still burner blue, but made the idle climb to 3000-3500.
pics as below...

 

Right now you have cylinders fighting one-another. Do a running synch and see if she smooths out (balance 1 and 2, then 3 and 4, and finally 1/2 balanced to 3/4).

The idle speed will need to be adjusted as you bring the carbs into balance. As the cylinders stop fighting each-other the idle will start to rise.

I know it sounds like the idle is smooth now, but it's not anywhere near as smooth as it will be with the carbs in balance and the cylinders working in harmony.

 

I have not tried yet... Im affraid... ha I will get to that.
Unfortunately the next week or two going to be extremely busy and may not get the time I need.
Unless I can sneak away early somehow and give it a try.

also, as it sits now, idling at aprox 3000-3500

 

as it sits right now the idle is 3000-3500. If it climbs... how do i overcome that? don't think i have any room to play with on the idle screw right this sec

 

If the idle screw is backed that far out then you need to make sure the enrichment plungers are all closed, make sure that the throttle cable isn't keeping the throttle plates open, or/and revisit your bench synch. I think you probably have more idle screw adjustment than you think you do.

2 1/2 turns out on the idle mixture screws, with a solid bunsen-blue all around, pretty well rules out vacuum leaks, but it wouldn't hurt to check again with carb cleaner. Some leaks are intermittant and won't be caught with propane unless you hover around for a while.

 

Plungers are all closed... Ive had the carbs off twice already today and re-benched. throttle cable is not opening the plates at idle. did the propane torch test for vac leaks... 2.5 turns on 4-3-2... 1 I had at 2.5 but was having some backfiring at te vac port, backed it out half a turn at a time to 3.5 currently... this smoothed it out, still bunsen blue, but idle now 3000-3500...

 

You're compensating for a vacuum leak on that cylinder.
Carb cleaner. Spray it. Wait for it to vaporize and get pulled in. I'm thinking the leak might be at the throttle shaft seals.

 

replaced those when I rebuilt the carbs, but sure I can try that.

 

I have had some issues with my color tune when it has sat for a long time with out being used. Those slide valves can stick and give you a false reading. Then there you are taking the sync out of adjustment trying to get the columns matched. Just for grins put the caps on 3 of the intakes and use one cylinder to check the reading for each of the columns. If you get the same reading 4 times then good. The gage isn't lying to you and you can go after the carbs. I had to spray pure silicone into the color tune to get it to work correctly. Lots of guys have gone to gages due to this problem with that gage.

 

I have had plenty of issues with the mercury type sync/vacuum gauges in the past, and use a set of dial gauges myself. I had a bike actually suck the mercury out of a set of yellow motion pro gauges when I was younger, and it scared the crap out of me as I was afraid that there was now mercury mist in the air that got blown out the exhaust of the bike ( I was working in a shop, not outdoors). While I do like how steady the mercury type tools are, the dial type are super easy to use and once set up right are a bit easier to read I feel. I got a fairly cheap set off ebay a few years back and I love them.

 

Interesting... I will investigate this after checking for vac leaks more thoroughly

 

Also I didn't see were you installed the sync tool. This is a YCS motor right?

 

He's using a Morgan Carbtune. It uses stainless steel rods to measure vacuum. Never needs calibrated, and you can't suck the rods out of it.

 

The YICS tool is not needed to synch the carbs unless you need to pass an emissions test, and even then you probably don't need it.

 

Have you checked the intake manifold gasket for the cylinder that's seems to be running lean? That was my problem.

 

So I unhooked the carbtune... vac caps and vac hose back on (clamped). warmed the bike up, turned the idle screw on number one back to 2.5 turns out from seated. no popping...
sprayed very liberally with carb cleaner on the boots from engine to carbs as well as all throttle shaft seals. Zero change in idle.

also, before starting bike, always check the oil.... saw this below... what is that crap!? opened oil cap, didnt think it smelled like gas... started bike... the oil level drops like should but that weird looking crap hangs where it is in pic.

 

sprayed carb clean aaaaaallll over, no idle change.

 

The stuff on the sight glass looks like condensation. If so it will go away after the engine is good and warm. If it hangs around then you'll need to pull the clutch cover and clean your sight glass.

No vac leak... grrrrr.

Well it could be sticky rods in the manometer I guess.
Does the idle sound like a sewing machine, or is it "chuggy"?
When synched it should sound like a brand-new inline four; sewing machine smooth.

 

it really does sound good... I donno what to say. I'll make a video of it again sometime... there is a vid from previous post a little while back before trying this sync process.
http://www.xjbikes.com/forums/threads/650-seca-reborn.86298/