mikuni carbs

[mud91]

I've had a 1/4 trottle bog, I thought because the pilot in there was too big ^65^..So i went to a 30 and tried that. The more I turned the screws in the better it ran till they bottem out. I then look into mikuni website and this model vm28 came with stock 60 pilots and 290 mains. Could it be this model has to use 60's not the 65's that are in there now. Going to get some tommorrow to see what happens. Anybody mikuni guru's out there.

[Yaxy]

If I am not mistaking VM28 is a round slide carb. If so, 60 is way to big, You should be in the 30 range. I have a Mikuni brochure at home that gives me all the sizes and all the factory components and part numbers. If you would like I can check for you. Either way 60 and 290 seem way to large for factory settings.

 

Chris

[Ducman]

The 28mm round slide should not be all that different as far as jet size compared to stock. My 34mm flat slides came with around #60 pilots and a #35 pilot is what is worked for me. The needle was also way to rich the way the carb came. However the main that came in the carb was very close. 290 may be pretty close for you. Your bog might also be somewhat from the needle.

[sredish]

Your bog might also be somewhat from the needle.

386582[/snapback]

 

Yes, I agree with the idea that the pilot may be too much and I also agree that the bog may be partly from the needle. At 1/4 throttle, the pilot is transitioning into the needle. You could have a case where the pilot is too rich and the needle is not tuned well either. Try playing with the needle clips to see if you can get it to run better.

 

Scott

[Yaxy]

Here is what my Mikuni manual says, dated 2004

 

Pilot - 60

Main -200

Needled Jet - N-8 (169)

Jet Needle - 5F21

 

Assuming the above

 

 

What I would do is start with 30 pilot and 290 ,main.

 

Sync carbs slides based on cables and then do the idle screws. (IMPORTANT)

Set air screw on side of carb at 1.5 turns out.

Ride shee, put around crack throttle, If still hestiant than turn in pilot all the way. If problem persists but is much better you need to go to the next larger size pilot and try the above again.

 

If you think pilot of 30 is rich you need to start playing with the needle clip position and then possible you may need to swith needles.

 

Personally I think 30 will be the ticket and not much larger unless you are not running the air box or have any kind of wild porting.

 

Chris

Edited June 28, 2005 by Chris Yax

[mud91]

well I don't have the ari box, I have the pods..Right now I'm 30 pilots w/ 310mains with the needle in 3rd clip, air screw all the way in. Should I trying going to the 2nd from taperd end on the needle, that will richen it up or should I get a bigger pilot.

[Yaxy]

Typically there is a transistion of fuel between the pilot circuit and the Needle Jet/Needle. Through my experiences a bog off throttle response is caused by not having the carbs in sync or to lean of a pilot jet.

 

My recommendation is to go to 35 pilot, leave the needle where it is, turn out your air screws 1.5 turns. If better in comparison with the 30's then you are on the right track.

 

If bog is still there then turn in air screws all the way. I highly doubt you would need a pilot bigger than a 35. After this I would try richening the needle clip one position.

 

Chris