Topic: 550 engine "hunt"/ varying speed at idle

[Mortimer]

Hello, I am in need of your collected wisdom once more!

Is there any reason why the engine speed should be going up and down while idleing without anyone touching the throttle? 

The suspicion is that the fault lies in the carbs, maybe something's a bit loose/ dodgy?

The bikes a '78 550k3, with pods, 115 main jets, and a 4-into-1 exhaust that doesn't quite fit right (that'll be sorted soon). HOWEVER, it was still a bit dodgy at idle even before messing about with the carbs began (original jets, airbox was left on etc.

My thinking is possibly the butterfly valves (the ones that twist open when you yank the throttle, right?) could be loose, I noticed one of the screws in is not original but hadn't noticed them flapping about when I was looking about them before.

Any help much appreciated,

M.

[mlinder]

This is usually caused by poorly synchronised carbs.

[Mortimer]

Ah OK, that would make sense. Time to break out the carb-tune I guess

Cheers

[aptech77]

This is usually caused by poorly synchronised carbs.

+1.9875

[HondaMan]

About 2 weeks ago, a beautifull 550 cafe' showed up here with a similar symptom. It turned out to be:

1. Two of the carb synch port screws were loose.
2. The timing on 2-3 was advanced about 4 degrees.
3. The points gaps were .010" on 1-4 and .008" on 2-3, and the ground arm on both sets of points were bent (misaligned points), apparently on purpose!
4. Each carb had a different idle air screw setting.
5. Two of the carbs had very low float bowl levels from misadjusted floats.
6. Three of the carbs had plugged or partially plugged jets from someone using silicone sealant on the float bowl gaskets, which now was floating around in the bowls.

His bike had been "worked on" by a local mechanic at the Ducati shop before he bought the bike from that wrench...