Carb sync and idle drops with Gunson

Hi!
I have a problem twith my ST1100'97 after carb cleaning.
Do i understand correctly that when sync carb at the right side (1st and 3d cyl) the front bolt is balansing 1-3 and the rear bolt balansing 13-24 carb pairs?
And the problem is that if i have a good balance IN pairs it breaks after i begin sync pairs. Is it normal?
To do IDLE drop procedure i use Gunson ColorTune. Another problem is I can't understand the best mixture setting and color of splash in GunsonSpark - always my sparks make dirty after 15-250 km.
In Colortune manual written that to engines after 1983 best mixture will near the engine drops.
After using colortune and lose in this battle i try to do IDLE drop literally as in manual but engine warm up so fast and i can't do good regulation (ofcouse in this choise i use digital tahometer).


PS Sorry for my "broken" English...

Sorry I can't help you with the GunsonSpark questions, I'm not familiar with this device; but...

when doing a carb sync on the ST1100, there is NO balancing one cylinder bank against another, or as a "pair." The individual screws for the #1, #2, and #3 carbs control and affect ONLY that carb. Use each carb's adjusting screw to balance that carb, and that carb alone, against the #4 carb (the 'base carb'). Do the individual carbs in any order.

The base idle is adjusted during the procedure as necessary to 1,200 +/- 100 rpm by turning the idle adjust knob in the fuel filler cap area.

What manual are you using to do the carb sync procedure?

John
via iPhone 6

John OoSTerhuis said:

Sorry I can't help you with the GunsonSpark questions, I'm not familiar with this device; but...
when doing a carb sync on the ST1100, there is NO balancing one cylinder bank against another, or as a "pair." The individual screws for the #1, #2, and #3 carbs control and affect ONLY that carb. Use each carb's adjusting screw to balance that carb, and that carb alone, against the #4 carb (the 'base carb'). Do the individual carbs in any order.
The base idle is adjusted during the procedure as necessary to 1,200 +/- 100 rpm by turning the idle adjust knob in the fuel filler cap area.
What manual are you using to do the carb sync procedure?

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Thanks for that, sir!
That is more clearly for me. Is normal that when i ajusting for example 3d cylinder vacuum in 1st cylinder changes?
When sync i set idle speed about 1250 rpm but ut flow +-100 rpm. This is the problem to do idle drop procedure.
I used this http://3rdwheelmotorcycletouring.com/fix-it-projects/how-to-synchronize-the-carburetors-on-a-honda-st1100/ manual and some information from STOC. I use analog vacuummeters and digital tachometer/ Fuel cu-off valve was removed.
But i was confused with the problem above - if ajust 3d cyl vacuum changes in 1st cyl and if i change vacuum in 1st cyl it changes vacuum in 2d and 4th cyl togeter...
Do i understant right that of i do good sync rpm must flow +-50 rpm with use digital tachometer?

Big thanks!

ilyuhich said:

....Is normal that when i ajusting for example 3d cylinder vacuum in 1st cylinder changes?

Click to expand...

It's normal for the other cyclinders' gages to show a fluctuation while adjusting one carb, but they should settle down and return to where they were before. Unless the carbs were so far off that adjusting one carb causes an overall large change in the engine rpm. Then go to the idle adjust knob and get the idle to spec and try again with that carb.

When sync i set idle speed about 1250 rpm but ut flow +-100 rpm. This is the problem to do idle drop procedure.

Click to expand...

An rpm fluctuation like that indicates a badly out of sync set of carbs. When properly sync'd there should be almost no discernible rpm change at idle.

I used this http://3rdwheelmotorcycletouring.com/fix-it-projects/how-to-synchronize-the-carburetors-on-a-honda-st1100/ manual and some information from STOC.

Click to expand...

Those instructions in the link are fine. Where did you get the idea that carb banks should be sync'd one side to another? That one carb screw controlled carbs other that its own? My guess is that by trying to do that you have really screwed up the carbs. If it's any consolation, you wouldn't be the first to make this mistake as the Haynes Manual for the ST1100 has instructions that tell one to do it that (WRONG!) way.

I use analog vacuum meters and digital tachometer....

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I much prefer a common reservoir manometer. I have an old one with mercury that is very accurate. For just the regular carb sync, the ST's instrument panel rpm gage is all that's needed. For the idle drop procedure, a high end (expensive!) digital rpm gage is necessary to do the adjustment accurately/properly.

But i was confused with the problem above - if ajust 3d cyl vacuum changes in 1st cyl and if i change vacuum in 1st cyl it changes vacuum in 2d and 4th cyl togeter...

Click to expand...

I think your carbs are way out of sync. At this point I'm not sure how to get them back to near normal to be able to do a proper sync. Maybe inspect the carb screws and see if you can tell if they are screwed in or out an inordinate amount and try to center them before trying again. Or just try to balance each in turn with #4 and keep adjusting the idle as necessary. Put a fan in front of the radiator so the engine doesn't get too hot during a prolonged attempt.

Do i understant right that of i do good sync rpm must flow +-50 rpm with use digital tachometer?....

Click to expand...

If you mean the idle drop procedure AFTER the carbs are properly sync'd, then yes, in order to do the idle drop you'll need a very good digital tachometer to detect the little 50 rpm drop. You'll also need the special Honda tool to reach the pilot screws to make the actual adjustment.

John

Ok. i understand. And remember one more thing - if i take out tip from 1st or 3d spark plug the engine drops rpm about 100 rpm and if i do it from other side 2d or 4th engine go near stall and can stop.
This means that i have problem with carb sync before carb remove. Great.
Your help will be very useful for me.

Hi.
I made this wonderful procedure of cleaning carbs and idle drop procedure. After your information it was quite simple and result is good. But still have one problem - when I try to ajust mixture in 1st cylinder at idle speed bike didn't respond in anyway. I try many positions of idle screw and test how bike go on the road. Finally choose one. It is good and better than early but I think it is not the best. Thinking about problem with 1st cylinder now. It makes me nervous.
Still I think that there is the problem with engine oil - it leaks from valve stem seal (don't know how it will in English correctly). Compression is about 12.5 kg in each cylinder and I think that is "oil compression". Have anybody ideas how a can diagnose this?

update
I think today the problem with was solved. I turn IDLE screw on 1st cylinder fully in until it stop and only in this adjustment I take a good performance from bike. Ride about 200 km in different ride techniques (slow-fast etc.) and it is still OK. I think that the problem in fuel level in carburetor in this situation. But I have no much time to do good test. It is only one trip in this season to party of end 2015 season to Moscow and return (about 1700 km full way) on next holidays.

From your second to the last post it sounds like you may have missed getting the low speed jet clean or the low speed passage in the body is plugged on that carburetor. Did you use carb spray with a nozzle to verify open passageway in jet and carb?

sporthog93 said:

From your second to the last post it sounds like you may have missed getting the low speed jet clean or the low speed passage in the body is plugged on that carburetor. Did you use carb spray with a nozzle to verify open passageway in jet and carb?

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My season is not closed in this year. But I spend many time with my little son and have no time to read and write posts. Sorry.
I check all the passageways not only with carb spray. I check it and blow every hole with compressor. There was not many garbage but I found a piece of grass in one jet. Everything was clean. But problem with 1 cyl raises again. I discuss this with my coclubmans and we think that I have a problem with valve steam seals because I have compression 12.5 kg in each cylinder and my bike eats engine oil about 2 liters on 8 000 km. Now I wait end of this season (today is +7 celsium and little rainy) and than will remove right head to inspect its condition.