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Post by unabashedpraise on Mar 15, 2007 12:17:34 GMT -5
I was wondering if anyone could help me id this carb. It came on the bike and I know it is not the original. I would like to find the "preset" positions of all the screws to get the bike running with out any smoke at all. When I first got it, it smoked alot when it firest started. Then after some adjustments it only smokes a little when I throttle up quickly. The plug shows some carbon buildup, but not as bad as it was.   It is a Mikuni, but other than that...  Any help is greatly appreciated. |
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Post by colinjay on Mar 15, 2007 23:06:13 GMT -5
Hi,
The carbie is a VM series Mikuni, hard to tell the size but I would guess a 36mm as that is a size commonly fitted to SR's.
Apart from the Idle screw, which adjusts the idle rpm, the only other adjusting screw is the air/mixture screw, which adjusts the air mixture at idle. This screw only effects the fuel air mixture at idle, and has no effect once you open the throttle. It is normally adjusted from 1 to 2 turns out from seated. To adjust without knowing the exact setting, warm the engine, then set your idle speed, then them gentle/slowly adjust the air screw in / out from the 1 1/2 turns out position and see if the engine revs rise momentarily. The position where the revs rise is the approximate setting.
What is the color of the smoke your engine is blowing?
Blue smoke is normally oil smoke, while black smoke is from a rich mixture. If the smoke is blue changing the carbie will not do much.
If it is black smoke jetting changes will help, however, advise on jetting is difficult, as it is dependant on much more than just the carbie. You have to consider, the overal condition of the engine, wear wise along with the state of tune of the engine, i.e. hot cam? flowed head?, type and size of air cleaner? type of exhaust pipe? etc.
If the puff of smoke is at a mid throttle opening, lowering the needle (raising the clip) may help, but it is all very much trial and error. The only real scientific was to set up a carbie is to run the bike on a dyno with an exhaust gas analyser. You can get a fairly good set-up by doing jetting runs and plug chops, but that require a good deserted road and a lot of patience and the skill to read the spark plug.
CJ
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Post by StewRoss on Mar 16, 2007 1:04:47 GMT -5
Hi, Yes a Mikuni, possiby a 36 or a 38mm carby...you can tell by removing it and measuring the outlet size. The pic shows you have the cable adjustment a little loose as well...is this how it is? If so you'll need to adjust the cable length adjuster to bring it down correctly. You should have at least a few mm of slack at the grip (grip turning slack). Then make sure you don't get the engine revving up as you turn the bars after adjustment...if you do loosen it off a bit until it is OK. I always prefer there to be as little slack as possible. There is stuff on carb adjustment written on here on other posts. Have a look around. SR  |
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Post by fivehundredgermany on Mar 19, 2007 18:25:14 GMT -5
Mikuni VM34 ??  |
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Post by fenz on Mar 22, 2007 4:37:36 GMT -5
Yep well spotted Stew.Dont leave it like that to long or it will chew the cable out where it is rubbing on the adjuster on top of the carb.
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Any help is greatly appreciated.
