Mikuni vm18 tuning help

I have tried 3 different jets, 2 of which 4 stroke at full throttle the other which bogs at full throttle, and I’m stumped. I’ve messed with the air/fuel screw and can’t get it right, is there anything else it could be

Re: Mikuni vm18 tuning help

Dirty30 Dillon /

You are providing no specific information regarding your build/setup, and you haven't stated what jets you have tried.

How can you expect someone to give advice on jetting when you haven't bothered to put in the effort to give us the details?

Re: Mikuni vm18 tuning help

Nick Dildine /

It’s all stock besides the carb. The 55 jet bogs and the 60/65 fourstroke

Re: Mikuni vm18 tuning help

Dirty30 Dillon /

> Nick Dildine Wrote:

> -------------------------------------------------------

> It’s all stock besides the carb. The 55 jet bogs and the 60/65

> fourstroke

All stock what?

Re: Mikuni vm18 tuning help

Put the dang motor on the phone . It would be more help .

DETAILS . Be Specific . Is this a '60 Checy with a straight 6 or a '99 dorito with a hubble and afterburner or ???

Re: Mikuni vm18 tuning help

Who cares. Stock anything that is going to be a bear to tune.

Re: Mikuni vm18 tuning help

Emil Kniemel /

The stock 30 idle jet is gonna be too rich for stock. Its too rich for most cylinder kits

Re: Mikuni vm18 tuning help

Marino Mariano /

Hello just for anybody googling the mikuni Vm18 on a Peugeot 103… I have the same setup with an after market pipe. Stock. Main jet was 90 and was too high I got a 55,60,65 now and still have top end WOT bogging, I ordered a 12.5 idle jet and will share the result here. I have found NO other posts online with the same situation and the OP and myself.

Stock 103 besides pipe, VM18 carb (stock main jet 90, stock idle 30) noticed improvement as I tried 70-55 main jets, realized idle jet is big and read the latest reply on this thread so I’m hoping this will resolve the bogging issue.

Re: Mikuni vm18 tuning help

A vm18 is too much for most stock cylinders even at the smallest available main jet, which is a 50. The idle jet needs to come down considerably as well. You can run them but they're not ideal unless at least some port work is done.

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