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Erratic choke, slow rpm return

  • Thread starter Thread starter Bortasqu
  • Start date Start date
B

Bortasqu

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Hey, I got pointed to this site from a facebook group to see if you got any tips on what's wrong with this bike.

Short story short: Rebuilt carbs, everything inside new exept slider pins and diaphragms. Fuel/air mix screws are very sensitive, they are turned out 2 turns from bottom now on all carb bodies. I can control the rpm with the choke, and the engine is very reliant on it to keep going even when varm. And the gas kinda sticks when you rev it. It also needs a valve adjustment, but that is another time.

I filmed a youtube video showing what it's like just now.

 
Have you tried raising the idle speed?

Also, exactly how did you "rebuild" the carbs? Complete strip, dip poke and spray?

You NEED to do the valve adjustment BEFORE you do the final carb sync. Did you even vacuum sync the carbs?
 
Raising idle speed doesn't change much.
Stripped everything that could be dismantled, cleaned and put back together.
Does the valve exhaust timing affect the idle speed that much? I have not vacuum synchronized the carbs, I don't have the required tools for it.
 
Bortasqu said:
Raising idle speed doesn't change much.
Click to expand...
Not sure what you're saying. Are you saying that you can't raise the idle or that it doesn't change how quickly you return to idle? A slow return to idle is usually a sign of a vacuum leak or lean condition.

Stripped everything that could be dismantled, cleaned and put back together.
Does the valve exhaust timing affect the idle speed that much? I have not vacuum synchronized the carbs, I don't have the required tools for it.
Click to expand...

Did you follow the carb rebuild tutorial? In order to get these running right you can't skimp on the cleaning process. A complete disassembly, complete dip, poking through every opening and spraying carb cleaner through every passage is the only way to ensure that all passages and openings are clear.

You NEED to vacuum sync the carbs. If you don't have the equipment then buy, beg borrow or steal(jk) one. You'll need to do it and do it AFTER your valve adjustment. A poorly adjusted (valves and carbs) bike will run like crap.
 
You're probably dead on with the idle/rpm issue, I took out the spark plugs today and #1 & 2 where very sooty, and 3 & 4 where brown'ish. It's very slow to return to idle from 2-4k rpm. Also hard to start again after it warmed up.

I followed the carb tutorial to the point, from this video https://www.youtube.com/watch?v=95nlrP-yn2I
Also adjusted the floats inside to factory 22.4mm +-

Ok, vacuum synch and valve adjustment is on the list to do first. I didn't realize how important those two where to this bike.
 
With all due respect for Z1 that made that video, it's a terrible rebuild tutorial. You NEED to degang all the carbs and soak them in carb/parts cleaner for several hours. Cleaning only the jets does not make for a complete rebuild. Spritzing carb cleaner in the passages alone does not clean them out.

Did you replace the intake o-rings that are between the head and the intake boots?
 
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I watched your video. Sounds like it's not running on all cylinders. :-k

I like to start with the mixture screws out three full turns before starting my tuning session. That provides a richer mixture that helps a colder engine run better. It is sort of like running it on partial "choke" because a slightly-rich mixture will burn easier than one that is slightly-lean.

Yes, valve adjustement is critical. Mainly because it is so small. Virtually any decrease in clearance can leave the valves hanging open, which is not good.

And, when doing a carb sync and a valve adjustment, to the valve adjustment FIRST. That will ensure that all the cylinders are pulling the proper amount of air, then the carb sync will ensure they are pulling equally.

.
 
JTGS850GL said:
With all due respect for Z1 that made that video, it's a terrible rebuild tutorial. You NEED to degang all the carbs and soak them in carb/parts cleaner for several hours. Cleaning only the jets does not make for a complete rebuild. Spritzing carb cleaner in the passages alone does not clean them out.

Did you replace the intake o-rings that are between the head and the intake boots?
Click to expand...

Yeah, the o-rings are new. And it's not those bad type o-rings that deteriorates after 3 months.

Steve said:
I watched your video. Sounds like it's not running on all cylinders. :-k

I like to start with the mixture screws out three full turns before starting my tuning session. That provides a richer mixture that helps a colder engine run better. It is sort of like running it on partial "choke" because a slightly-rich mixture will burn easier than one that is slightly-lean.

Yes, valve adjustement is critical. Mainly because it is so small. Virtually any decrease in clearance can leave the valves hanging open, which is not good.

And, when doing a carb sync and a valve adjustment, to the valve adjustment FIRST. That will ensure that all the cylinders are pulling the proper amount of air, then the carb sync will ensure they are pulling equally.
Click to expand...

Thanks a lot for your replies guys. I should probably start looking into adjusting the valves first, where should I start? I looked it up on the internet and, I see an ocean of information.

Edit: Wait...can the automatic timing chain adjuster cause the valves to open differently?
 
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Do yourself a favor, stop looking all over the place, and use the resources on this page:

Bikecliff's Site

It's become the GS forum resource site. Most of the information there is tried and true. The factory service manuals are the best resource for "straight from the horses mouth" information. There's a write-up for doing the valve adjustment there too.
 
That's a nice site, I'll be looking into that one more often.

But the additional question I added in the previus reply is not of importance, yea?
 
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