Mikuni too rich or too lean?

  • Thread starter Thread starter boulevard
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boulevard

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I have just installed new mikuni vm30s on my cl360. Valves and points are set. Compression is good. After about 15 minutes it started acting funny... I had a hard time keeping it from dying at idle. Kept raising the idle. When I stopped I noticed that it had a exhaust/smoke coming out of the carb/intake. While I was riding I thought it was rich and then read my manual and thought it was lean. They are the prejetted mikuni from dcc with quality pods and cheap 12" mufflers.
It runs perfect until it warms up...I remember that being a way of determining lean or rich but can't remember which one.


Boulevard
 
Have you checked your plugs and get a reading off them? The jetting from DCC is close, but still not ideal. The pilot jets they provide (50s) are way too big. The throttle slide should also be a 2.5 instead of a 3.0. Finally, change the needle jet to a P4 or P5. I have the above mentioned mods to the DCC carbs on my 350, and it idles/pulls thru the gears perfectly. My needle is one notch above center and air screw is 1.25 turns out. The 150 main is fine

What could be happening is you're fouling the plugs after a bit, hence the problem keeping it running. Make the above changes, new plugs, and you should be set.
 
Generally speaking if it runs better when cold and gets worse when warm its jetted too rich. With that said, you have to tackle the jetting one step at a time, start with the idle jetting, get that sorted and then move on to the other circuits, only making one change at a time. Do you have the Mikuni VM manual? If not, you can find one here: http://www.mb5web.com/forum/index.php?topic=90.0
 
Re: Mikuni too rich or too lean?

Thanks for the help I just opened the and changed from the 50 to a 45 idle... Took it for a ride and it was great for ten minutes and I couldn't get it to idle again. I restarted and a lot of smoke came out of the breather on top of the engine. Hrm. I am about to recheck the valves. Sucks

Boulevard
 
Re: Mikuni too rich or too lean?

Just to complete a thread I ended up using the 40 idle jet. That's two down from the 50 that came installed. The 45 had the mix screw all the way in. I am running pods with straight pipes and good for nothing emgo shorty mufflers.

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