250 Desmo idle issue

[Duccout]

I have a Mikuni on my 250 now, but when the Amal was fitted the engine revs would not drop at tick-over, and I could not find out why; the carb was in good condition, the slide was unworn and there were no air leaks, but an air leak from somewhere must have been the cause.


Cheers,

Colin

[Duccout]

Just a thought: could float level affect tick-over speed? If it was too high maybe that would cause the revs to rise?



Cheers,

Colin

[Dan C]

Thanks for the thoughts Graeme and Colin.

I'll pm you Graeme about those bits.
Colin, I'll be checking the float level again.

Just an up date, I took it to the Taree rally. Before I left I changed the main jet to a 125 as I felt the 110 might have been a bit restrictive. (I would have gone to a 120 but didn't have one on hand). It did make a difference, considerably better pickup from half throttle up. And the bike was a joy to ride, everything felt just right, we sat on the tail of a fairly sedately ridden Bonneville and had a ball through the curves. The gearbox gets a work out and it needs to be kept on the boil but 20 out 10 for fun factor!

Unfortunately though it didn't last the full run, not long after lunch it starting misfiring with all the symptoms of fuel starvation and shortly thereafter expired altogether!! I'm only just home so haven't had time to diagnose it. The battery is showing 6.5v and there is spark. Fuel flows freely from the taps to the carb. Next will be to make sure there's no blockage(s) or other issues in the carb and then it will be back to the electrics.....gotta love our singles

Cheers
Dan

[ranton_rambler]

Just because you have a spark when the plug is out doesn’t mean it will spark under compression.
I went all round the Wrekin and ended up with a new plug having tested everything else!

[Duccout]

Bummer! My guess is sparks.




Colin

[Dan C]

Bummer! My guess is sparks.

You win Colin. Coil was RS. Fitted a new one and it runs fine.
Interestingly it feels like it may have helped the idle issue but I wont know until I take it for a run and get it properly warm.

Cheers
Dan