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General Category >> Rubber Side Down! >> Jetting Mikuni VM-36
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Message started by MachoManRandy on 04/30/17 at 18:19:56

Title: Jetting Mikuni VM-36
Post by MachoManRandy on 04/30/17 at 18:19:56

I'm working on tuning my Mikuni VM-36 on my '86 Savage.

Experiencing a lot of popping and inconsistency in the 1/3 throttle range and it decelerates hard when I close the throttle. Can't keep it happy when coasting as it seems to want to speed up all the time. Snappy, but sketchy.

Since buying it, I put in the VM-36, new throttle cable from Lancer, turned the air box into a tool box and put in a pod filter, changed the petcock for the raptor, cleaned the tank and put in all new line, added a fuel filter. I also put on a new battery, igniter, coil, and solenoid.

The previous owner put a straight pipe on it, which looks good, but makes it difficult for me to know what I need for proper jetting.

After reading Lancer's "Mikuni Jets for VM and CV carbs + Tuning Info" post, I believe I need a smaller Main Jet and a larger Pilot Jet, but the question is: by how much? I've spent a lot getting it to this point, and I'd hate to buy a bunch of jets I don't need.

Currently running:
Main Jet: 310
Pilot Jet: 35

From researching, I think I may need a 144-152.5 Main and a 50-55 Pilot, but I'm not sure. :-?

Anyone know what size pilot and main I should be using? (elevation 2188 ft)

Title: Re: Jetting Mikuni VM-36
Post by verslagen1 on 04/30/17 at 19:16:58

21362D2F2C253D302B2A440 wrote:

From researching, I think I may need a 144-152.5 Main and a 50-55 Pilot, but I'm not sure. :-?

That's what you need for the stock carb... not the VM.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1262724030

Title: Re: Jetting Mikuni VM-36
Post by Ruttly on 04/30/17 at 22:06:00

I'll recommend that you get a muffler first. Trying to jet with straight pipe is tough and still will be down on power. Should have bought the whole setup from Lancer , he gets right , but anyways get your pipe a muffler you like first.

Title: Re: Jetting Mikuni VM-36
Post by LANCER on 05/01/17 at 02:47:03

I typically start a VM carb (without any mod's) with a #20 pilot, #190 main jet, and the needle on the 2nd groove, for a stock engine. This gets you in the neighborhood, but fine tuning is always needed. Engines are different and intakes and mufflers, or lack there-of, change final jetting requirements.

BUT, you NEED a good muffler.

You can get mufflers with mild, moderate or louder baffles if that is your desire, but a straight pipe or just a header with a tiny baffle will always be hard to jet/tune. IDEALLY, an exhaust system should have a muffler with 2x the volume of the cylinder/s. For our single cylinder LS650 that equates to a muffler with a 1,300cc volume. That yields the most power/torque. Ever notice the bulbous mufflers on sport bikes ?

The best bang for the buck is a lightly used Dyna, there are some on eBay for $25/pr. , or a lightly used tunable Supertrapp, or Cone Engineering, a host of others.

Title: Re: Jetting Mikuni VM-36
Post by MachoManRandy on 05/03/17 at 07:02:51

Thanks for the advice. Jets are on the way and I'll get a muffler as soon as I can. I will miss the clean look of the straight pipe, but more power is always good ;D