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[Tv]

G'day All
I have been messing around with a Mikarb VM24 on my Bullet 350. When I'm accelerating, all seems fine, then I start to cruise and the engine splutters and carries on, surges and stutters like Porky Pig. Like, it wont just cruise along. If I gas it, it takes off and behaves OK but it wont ride smoothly in that cruise zone. Any clues. One thing I havent been able to understand is the mixture screw. I can set it by the book and the engine ticks over nicely. Does this mixture affect the whole range of carburation or is it only for the tick over.

Regards
Tv

[Brazilla]

Someone with more experience may be able to say if I'm wrong on this one but I think the mixture screw only affects the pilot jet which controls idle (although it remains active during other throttle positions) the throttle slide affects 1/8 to 1/4 throttle so could be your issue. I have a similar issue at the moment although when I run with 'choke' all is fine. I have ordered the richer throttle slide for mine to try but I'm not certain that is the issue. Good luck!

[Leon Novello]

Click on Technical Notes in the menu (Mikcarb carburettors) on the left. Or click on here.
http://www.hitchcocksmotorcycles.com/pi ... s_-_a4.pdf

[Gwilly]

May be an idea to do a plug chop after cruising quarter to mid throttle range for a mile or so..

It could be that its running weak or rich in that range and either lifting or dropping the needle by 2 notches may improve things..

[PeteF]

Just to confirm - the "choke" plunger on the 350 is down for off unlike the 500 which has a lever and the lever is up for off. It's not a choke at all really, just an enrichment circuit. It might just perform as you describe if you have it wrong.

[wilf]

Good point PeteF.

[Brazilla]

Yes, thanks Pete. I can confirm I mean enrichment circuit on when the plunger is in the up position. Runs fine like that, problems present when plunger is down, think this may mean I'm too lean? Sorry TV, don't mean to hijack your thread

[Tv]

G'day, thanks for the replies. I am familiar with the choke operation. It's not that. I have since moved the needle 1 notch back to where it was before I started my 'carby tuning' education. I did also notice the mixture screw was nearly all the way out as the spring was not holding it in place. I stretched the spring a bit so that looks OK now. I cant ride it for a couple of days but when I do, if it is still playing up, I will try the plug chop. Thanks for your help. Regards Tony

[PeteF]

Mmmm - if the mixture screw is screwed that far out it can't be right. Try screwing all the way in, then 2 turns out. That should get you in the ball park.