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No middle ground!!!

  • Thread starter Thread starter ColinClayton
  • Start date Start date
C

ColinClayton

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I have an 83 550L that has MAJOR idling issues. What are the chances that the carb bodies have become so warped that they need replacement? They are mikuni dual barrel carbs.
It will stall when coming to a stop usually after it warms up, but sometimes when colder as well. If I raise the idle via the idle adjustment screw, it will hang and the RPMS will not come back from 1500 -2000 down to idle while shifting or at a standstill.
I also cannot get a strong idle. It feels weak no matter what, like its about to stall. The only thing that has helped is turning in the mixture screws all the way in. Then the bike seems like it has a strong idle, it even seems to ride smoother, and have more power, but after I ride it around the block a few times, then it won't idle at all, and doesn't want to start.
Ive almost rebuilt this entire bike trying to correct this godforsaken problem and nothing I do corrects it.
 
Of course you have cleaned these marvelous carbs correctly and blown out all the passages ?? When warmed up, and at idle ,the bike runs on the idle circuit passages- attempting to compensate for gummed up passages by fiddling with the idle stop screw leads to erratic behavior and difficult cold start as throttle plates need to be just about closed for enricher circuit to function correctly.
 
I have cleaned these carbs so many times I could do it blindfolded with one hand tied behind my back.
 
Aother thing you might want to check too, just in case, would be the intake boots & orings!!! Also, the boots from the airbox to the carbs too.
Ray.
 
I took them apart and used beryymans chemical dip. I replaced the o rings but not the intake boots. There doesn't seem to be an air leak and they are in good condition.
 
If the idle is hanging , you have an air leak. Get new intake manifold o rings. Cycleorings.com. 5$ or so.
You know having the mixture screws all the way in is wrong, so the turning mixture screws is not the solution. Theoretically you could have them at 1.5 turns out or 4 turns out and the bike will still run. Your racing idle or no idle issue are likely air leak related and you keep heating different symptoms because you keep turning the mixture screws and the master idle screw.
 
I dont think carb bodies get warped really, unless you're talking about the oldie worldie AMAL or bing carburetors.

Check pilot jet, all the jets for that matter, look through the hole into a light the hole must not be blocked and perfectly round.
The brass can be corroded on the inside because of all the **** mixed in the gas.
In my experience this is what is causing bad idle most of the time, even the slightest imperfection in the pilot jet.
Depending on how the mixture screw works turning it all the way in most likely means your not getting enough gas in the mixture at low RPM.

If you raise the idle no wonder it wont go down at a stoplight :P, you know how to adjust it right?
Lower the idle until it stalls then raise it till it barely keeps running, then with the mixture screw adjust it so that RPM rises.
When RPM rises a little bit adjust the idle screw again to lower it until it barely keeps running again en then repeat the process.
Keep repeating until you have found the "sweet spot" then up the idle just a little.

Also check float level and float needle.

Look more closely at the intake boots, deform the rubber and you might see cracks, I hope not they are relatively expensive.
 
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Amen! Send them to the "chef" and be done with it. It's worth every penny and stops the brain damage?
 
For those interested, the problem ended up being that the carburetors were out of sync.
 
Did you replace the carb boot O-rings yet?

BTW, you might want to check the Newbie Mistakes thread linked in my signature. Inside you will read about the need to replace the carb boot O-rings.
 
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