Can't sync #4

[galaskog]

Hi Everyone,
After some hours of reading discussions on previous topics and stories I started to make valve clearance set and carb sync on my GS1000. (Haynes served as axuluary reading.)

Tha bike is an 81 GS1000L what I bought from a frend a year ago. It had 75000Km that time and I run 2k last year.
The condition of the bike (Before I started to mess with it.): At high RPM some black smoke out of eyhaust, sometimes firing to exhaust when cut off throttle, I feelt missing some power on the high end (Could not run faster then 140km/h).

Reccomendation by the prewious owner was: get the valves clearance set and carb synced.

I changed a few shims and got every clearance<0.08mm. No rough wearings on the camshaft side. (At #2 and #3 the gap was >0.2mm before shim change.)

Started carb sync, after change #3 and #4 plugs due to some spark problems, I tired to set up iddle with pilot air. The odd thig was that it was so hard to hear and see any changes from 0-2 turns out. So I did some adjusment but I'm close to the original setup.
Next was the sync with vacuum guages.

http://pg.photos.yahoo.com/ph/galask...nm=b6f8re2.jpg
http://pg.photos.yahoo.com/ph/galask...e2.jpg&.src=ph

Problem: All guages has some (0,1-0,2bar) wibration @ 3000RPM. (Higher it was smoothered.)
And I was not able to get No. 4 down to the others.

http://pg.photos.yahoo.com/ph/galaskog/detail?.dir=9587re2&.dnm=14acre2.jpg&.src=ph

(#1, #2,#3 are about 0.1 bar, while #4 is 0.5 bar.)

Any idea how to get rid of the guage indicator's wibration?
Why I was not able to set #4?
Sorry to be so long.
Regards:
Greg
(Hungary / Budapest)

[madjack57754]

I will assume your using gauges The vibration is probably pulsing from the intake tract. You will need to create a small reservoir to dampen the pulse. I've used a longer hose and a pair of vice grips as an adjustable line clamp to create a dam effect in the line. loosen the clamp until it starts to vibrate then tighten until the needle settles down. Is it possible that you have the valve shimmed a bit to tight and when the motor starts to heat and expand the valve is held open just a touch?

[tconroy]

Have you tried lowering it to just 1750 rpm's to see what happens.did you close off the vacumn line?I used a merc gauge on my vm carbs and they were smooth as can be but on my cv carbs they jump all around.

[chef1366]

You might have an intake leak on #4.

[galaskog]

I will assume your using gauges The vibration is probably pulsing from the intake tract. ... Is it possible that you have the valve shimmed a bit to tight and when the motor starts to heat and expand the valve is held open just a touch?

Thanks for the idea I'll try to create reservoir and bottleneck for the vacuum lines.

It is possible to have a tini opening afte the heat up (My smallest fleever was 0,05mm but I'll get a thinner one.) but the fireing was coming right from cold start.

Have you tried lowering it to just 1750 rpm's to see what happens.did you close off the vacumn line?I used a merc gauge on my vm carbs and they were smooth as can be but on my cv carbs they jump all around.

The difference was the same only the pulsation of the pointers were higher (And all vacuum smaller.) with low RPM.
When I was take off the wacum line the gauge goes to 0 as this is a mechanical one. The carb is a VM tipe (See photo on hiperlink.)

You might have an intake leak on #4.

Is is possible to have an intake leak and have even higher vacum? (Or all others has a leak?)

When I tried to make a test run it did not run above 7000 in gear 1. (I tried for test only.)

Thanks for replys.
Greg

[SqDancerLynn1]

Sometimes after numerous syncs, so called mechanics & unknowns you need to start over. I would go back & start with a mechanical sync....
CV carbs! Back off the idle screw & adjust carb 3 (base line carb) until it just closes. Adj idle screw until you can slide a 1/8" drill under the throdle blade from the intake side. Then adj the others using same 1/8 drill. Re assemble- don't forget to readjust the idle screw before trying to start..
Same basic proceedure for the VM carbs,

[Steve]

I did a friend's '79 550 just after Christmas and was pleased to see how easy it was to sync the VM carbs. Was it just me, or is there no "master" carb with the VMs? Seemed to me that they all anchor to the throttle rod that goes through the tops of all the carbs and adjustments are made off of that.


.

[j.ess]

you are sucking air some where. With cv carbs, the merc will bounce some, I would not worry about that. I think you need to find a baseline with your air/fuel screws(somewhere around 1 1/2 maybe 2 depending on altitude) and leave them be until you sync up. Either way sync up first, then worry about your air screws on a case by case basis by reading plugs.