1982 GS650L carb problem-HELP!!!

[michael cloutier]

Anyone got any ideas why my 650 wants to idle HIGH(3800-4200rpm)after its warm? The carbs have been cleaned and gone through. She seems to hold a good idle just after turning off the choke, but then continues to climb and stay there in neutral. I turned down the idle screw to no avail. HELP!!!!, before I smoke my clutch in record time!!!

[Big T]

Air leaks

Did you replace the O rings in the carbs?

Between intake and head?

New intakes?

Sealed airbox?

Pods?

[Nessism]

http://www.thegsresources.com/_forum/showthread.php?t=171846

Please check #2

[Octain]

You have a vacuum leak someplace.

[mike-s]

I has a similar problem, turned out to be an air leak, at the diaphragm caps! Thankfully i have spare carbs & could swap out the damaged one.

[Johnny Drummond]

Hi Michael, the guys are right-you have an air leak, my wifes 550 did exactly the same thing.Take off the tops of the carbs one at a time so you don't mix them up and remove the diaphragms, stretch them out where the rib is and you will probably find a rough place-thats your leak.Here is a quick sketch that I did for Redman when he had the same problem sadly if you find this kind of damage the only thing you can do is replace the diaphragm in question. don't know how confident you are but here is a sketch of what you will find when you strip the diaphragm for replacement and this is the best way to put the diaphragms back into the carbs hope I'm not insulting your inteligence with these-oh and put a small amount of grease into the groove to stop the diaphragm locating lug twisting out as you put the cap back on. Hope this helps.Johnny

[tom203]

I has a similar problem, turned out to be an air leak, at the diaphragm caps! Thankfully i have spare carbs & could swap out the damaged one.

Are you serious? seems to be that any airleak that caused high idle would be after throttle plates.

[mike-s]

Are you serious? seems to be that any airleak that caused high idle would be after throttle plates.

Aside from the CV cap dint, i have no other reason why I had an airleak of any sort. I performed numerous attempts at fixing this thing, removing them, tearing then down. Replacing o rings everywhere, checking for airleaks on everything but the caps as i never thought that would be the cause of the problem.

I identified the leak as one plunger was coming down 3x as fast as the other when removed and checked by hand, and i knew that wasn't a good thing. Identifying the why consisted of sealing up the intake side of the carb and plugging all vent points on the carb and then blowing into the carb venturi side. I heard a slight whistle of air, then got some highly soapy water i brushed over all possible leak points and got some bubbling on the cv cap. Problem area identified. I rechecked the diaphragm was seated correctly and closed her up and tested again. Problem still there, I swapped plungers/diaphragms, problem still there. I swapped caps. Bingo, leak gone.

But i know i had an air-leak in the CV cap. I tried writing down what i believed was happening in the tuning with what was happening where when cold warm and hot and I ended up confusing myself doing so .

To abbreviate it, when doing the sync I had to open the butterfly on one carb to make up for the plunger basically doing a poor job. It ran like a bucket of crap when warming up and due to the plunger not rising at all, was an absolute piece of horse poo at anything over 2/3 throttle or above 95km/h, in any gear, don't ask me about it's abilities when it came to uphills.

Once it was up to operating temp and because the airleak had me sync it sufficiently unevenly, no matter how far out i adjusted the idle adjustment, there was always going to be enough extra fuel/air coming through the one problematic carb at idle as that butterfly was still open enough to rev the engine out while the other butterfly was fully closed.

So it's still able to rev out, but it's not because of an extra lean condition, but because what "worked" when the engine was moderately warm was now far far out of sync when the engine was up to operating temperature, if you get my drift.

This also explains why i had an insane quantity of carbon buildup in the left cylinder from it running rich, when the right one was carbonless and as clean as a whistle.

It was a royal pain in the arse to track this problem down, and now i've had it happen I would hope that i'd be able to diagnose a repeat offence of this in the future. But personally i would rather stick with never having this kind of headache ever again.

[tom203]

But i know i had an air-leak in the CV cap. I tried writing down what i believed was happening in the tuning with what was happening where when cold warm and hot and I ended up confusing myself doing so .



It was a royal pain in the arse to track this problem down, and now i've had it happen I would hope that i'd be able to diagnose a repeat offence of this in the future. But personally i would rather stick with never having this kind of headache ever again.

That was really good detective work - you were relentless! Wow. remind me to avoid those siamesed carbs.

[mike-s]

It's not that it was siamesed, it was simply a twin carb setup. This same issue could potentially affect any multi-carb setup.
Also the bike was effectively off the road for 9 months while i had a go at it, gave up disheartened, tried again, gave up, got it re-registered, tried again and got it sorted.
Was not easy to figure out, but I am thankfull i did.

[spchips]

You are probably lean, but not necessarily an air leak. Did you replace the intake boots or just the O rings? If the airbox, filter, and cover are installed, and it still rises, try adjusting the valves.

If the valves are out of adjustment, the engine will be a lot more tempermental in its idle. If you haven't don this yet, give it a shot, then try backing out your idle mixture screws a half turn at a time across the board until it gets better.

[janner]

make sure your slides are all returning at the same rate, as one slide sticking will upset the idle too as the others wait for it to catch up