Need help jetting mikuni vm22-133 for methanol

[Lawndart]

Need help jetting my Mikuni VM22-133 for methanol.

I'm collecting parts for GX200 clone that will need to run on methanol. I have a new Mikuni VM22-133 that I plan to use on it. (not a Mikuni clone). I'm hoping to get some, in the ballpark jetting before start up. All help will be appreciated.

clone GX200
head, -50
valves, in, 28.5
ex, 25
springs, 32Lb
cam, .275
rod, ARC stock .303
piston, Honda flat top with thin rings
ARC flywheel

 

[65ShelbyClone]

Does the carb have gas-sized jets in it now? If so, start with jets that have ay least double the flow area of your current ones.

To find the flow area, take the jet orifice radius, multiply by Pi (3.14159, Greek symbol Π), and then square the result:

A = (Π ×R)²

To find the jet diameter based on flow area, rearrange the equation like so:

R = √(A/Π)

Then multiply by two to get the diameter.

 

[Havasu Dave]

Or as we used to say, "pie are not square, it round."

Good rule of thumb. The 4 stroker kart guys probably have some good places to start too.

 

[Phil1958]

here's a few memories i have from running methanol in
my kawasaki tecate:

1 - run the engine hot. block off the air intakes to keep
the motor up to temp.

2 - stoichiometric for methanol is 6.4:1, gasoline is 15:1
so you will need much bigger jets. do what 65ShelbyClone said.

3 - look into running an oil mix to keep your upper end lubricated.

4 - check your oil, methanol corrodes, it's tough on seals.

5 - buy what you need, methanol is hygroscopic, it absorbs
water, don't buy 20 gallons and store it.

6 - learn how to tune using gasoline before stepping up to
methanol.

7 - methanol burns slower than gasoline. your timing
advance must be far ahead that of gasoline.


ciao!

 

[Lawndart]

Thanks everyone.

65Shelby, It looks like I need to invest in a good calculator.

Phil1958, Thanks for the tips on methanol. Methanol is new to me and the only reason I'm running it is because all the people I talk to about this engine think gas is for lawnmowers, and I like the smell of it. I do have experience with this carb and others like it, just not in this application, z50,crf50 strokers and bigger bikes. Do you have a methanol to oil ratio I can play with? I fly model airplanes too and mixing methanol and oil is not a big deal. Nitro methane?

I have been reading a lot of old posts and emailing people trying to get more info about this carb and methanol.
Mikuni vm22-133 on gas, main jet #120-#130 pilot jet #15-17
Mikuni vm22-133 on methanol, one of the guys I talked to said, main jet #200 pilot jet #20 the other guy did not have experience with this carb but did have experience with some like it on Jr.dragsters and said main jet #150 pilot jet #x2, He also added that the engine need to run rich on the bottom and lean on the top, and that the head timp needed to be 365 and the exhaust timp 1260.

If anyone has more to add please feel free. All help is appreciated.