Recommend jet size By virtualmind (Read 1,332 times)

[virtualmind]

Hi guys. Can you recommend me a good main jet size for a stock 50cc gy6? The carb is pz18j and the stock jet is number 79, but the scoot seems to be running a bit lean. I set the needle at the mid position. The spark plug is still white-ish. I run it mostly on 3/4 throttle. I live in Europe at sea level if it makes a differrnce. Thanks in advance and sorry for my bad english. Cheers.

[rks]

I'd get something like this: Jets

Might start with an 85, see how it goes. If it wants to bog when more than half throttle is applied....it's too big. If it runs ok with an 85, in time, you should see the color of the plug shift towards tan.

You certainly won't need the 95 if you still have a stock airbox and exhaust system. Nice to have the larger sizes on hand, in case you decide to make more upgrades to your scoot, at a later date.

Lastly....you have no reason to apologize for your english......well done virtualmind

[seanstr]

I had this problem, figuring out the right jet for the main jet. Try like rks stated, go up then slowly go down in size. Too lean can do damage, too rich won't. Make sure the valves are adjusted correctly, air filter clean spark plug wire is good, etc, before you attempt jet changes. Fuel filter too.

There is computation you can use. the inner diameter of the carb going to the engine times a constant = main jet size, where the constant is a bit less than 4 to 5. It gave me the courage to go down far enough to find the correct jet size.

Do one change and check results.