Jetting help PLEASE

[jerelzayas]

What's up guys I just ordered the mikuni vm30 round slide for my shee and I'm looking for a baseline on what jets to put in, my stock carbs have 370 mains, 25 pilots and 2nd notch from bottom on needle 

[Yaxy]

So if we understand correctly, you are no longer using the 28s and now purchased 30 mm carbs?

 

I have been running 28 Mikuni Flat slides on my banshees for 20+ years.  Great carbs for trail, sand pits, seasonal road riding.  Just some thoughts:

#15 pilot is stock on these carbs, try size #20

Put air box and lid back on,  Remove snorkel and if you want drill a few holes in the airbox lid that's fine

Place the air screw at 1.5 turn out.  If your low end isn't good turn air screw all the way in.  If throttle response is just ok go up to a #25 pilot and repeat this process.  You should not need more than a #25 pilot.  There is no right or wrong answer on how many turns out the airscrew should be just leave yourself some room for fine adjustments.

 

[jerelzayas]

3 hours ago, Yaxy said:

So if we understand correctly, you are no longer using the 28s and now purchased 30 mm carbs?

 

I have been running 28 Mikuni Flat slides on my banshees for 20+ years.  Great carbs for trail, sand pits, seasonal road riding.  Just some thoughts:

#15 pilot is stock on these carbs, try size #20

Put air box and lid back on,  Remove snorkel and if you want drill a few holes in the airbox lid that's fine

Place the air screw at 1.5 turn out.  If your low end isn't good turn air screw all the way in.  If throttle response is just ok go up to a #25 pilot and repeat this process.  You should not need more than a #25 pilot.  There is no right or wrong answer on how many turns out the airscrew should be just leave yourself some room for fine adjustments.

 

No sir I had the 26mm and I went to the 30mm

[Yaxy]

Ok.  So I would try 30 pilot and 320 main jets. 

 

FYI: I am not sure what the Outside Diameter is on the input flange on the carb thus you may have to open up the  hole in the intake boot.

 

 

[jerelzayas]

7 minutes ago, Yaxy said:

Ok.  So I would try 30 pilot and 320 main jets. 

 

FYI: I am not sure what the Outside Diameter is on the input flange on the carb thus you may have to open up the  hole in the intake boot.

 

 

 The engine side is 40mm and bell side 58mm but, I bought boots to fit bith sides already, ok ill try those jets and see what I get 

[Toybreaker]

buy new boots, a vacuum leak will pop your pistons.

[jerelzayas]

11 minutes ago, Toybreaker said:

buy new boots, a vacuum leak will pop your pistons.

I put yamabond black on the boots and gaskets to be on the safe side, figured out the boots leaked air when i did the leak down test, how are the billet one piece intakes with built in crossover ?

[Yaxy]

Replace the boots every so often before they crack and you should never need to use silicone in this area. The factory gaskets should be enough. 

 

Chris

 

[jerelzayas]

7 minutes ago, Yaxy said:

Replace the boots every so often before they crack and you should never need to use silicone in this area. The factory gaskets should be enough. 

 

Chris

 

Ok good to know I bought new boots for the new carbs