"Stuck" idle when warm on 550 ltd

Hi everyone!

I just rebuilt my carbs on my '81 550 ltd and am pretty sure I did everything correctly (initial adjustments included); I put everything back together, and it starts/runs fine, but now I have this problem where, when warm, my engine is not going back to idle. I have to "pull" it back down with the clutch when stopped and in 1st gear.
- Can it be my throttle cable that is being squeezed under the tank?

Also I think I'm running pretty rich as I can smell it?
- Is it just a problem with the adjustment of the air screws? I did set them at the proper level indicated in the manual (1-1/8 turn if i remember correctly).

Lastly, after rebuilding the carbs is a vacuum test/synchronizing the carbs required?

Thank you for the help!

Couturier wrote: ...just rebuilt my carbs on my '81 550 ltd...starts/runs fine, but now I have this problem where, when warm, my engine is not going back to idle. I have to "pull" it back down with the clutch when stopped and in 1st gear.
- Can it be my throttle cable that is being squeezed under the tank?....

A possible issue with the throttle cable could be ruled out by disconnecting the cable at the carbs so that the slides will close without any interference from the cables.

If it's not a cable issue, the racing idle could result from an air leak, perhaps in the carb holders (maybe they are old, hard, cracked and worn out).

Could test for air leakage through the carb holders at lowest attainable idle by spraying WD40 around the carb holders and noticing whether the spraying causes any change in idle speed or any smoking from the exhaust, either of which would indicate that the WD40 is being ingested into a combustion chamber.

Also check the vacuum plug/caps to assure no air leakage.
And for any missing or defective o'rings that might be required on the pilot adjustment screws.

See information in the following links, courtesy of KZr Member loudhvx:
home.comcast.net/~loudgpz/GPZweb/index.html#home
home.comcast.net/~loudgpz/GPZweb/Mnls/Mnls.html

Good Fortune!

550 mills are notoriously cold blooded, they race on the choke when cold.
Try adjusting tickover when hot.

Yes, you need to synch the carbs - that makes a big difference particularly to idle and low rpms.

I will definitely check for air leakage and synchronize the carbs as soon as I have the time.

What do you mean by tickover?

(This is my first motorcycle, I'm learning as i go...)

I'll be back with more developpements.

J

tickover=idle speed.

(English to American translation)


The manual pilot airscrew setting can be altered quite a bit, particularly if you have altered the pipe or airbox. a lot of them are around 2 - 2.5 turns out-what matters is getting the best result.

Building a bike is one thing-the fine tuning on the road often takes longer than you think.

On your carbs, the Idle Mix Screws are Air Screws, adding air to the slow/ pilot circuit. If the idle is hanging, then you may well have an air leak/ vacuum leak. The Air Screws at 1-1/8 as per Ma Kaw, might be to lean. Try 3/4 turn, fastest smooth Idle when hot adjustment. If any 1 screw is much different than another, then you have an issue on that carb/ cylinder.