So I swithched from the nt carb to the hp carb on a bullet train 2 stroke motor. The bike seemed to run faster and at higher rpm with the nt carb. It is 4 stroking a little on the top end. If i put in a leaner jet will the bike get those rpms back and that little extra speed?
Jet change
- Thread starter Kman123
- Start date
It is four stroking at high speed. Getting there is no problem. But it seems that the nt carb got lets say 1000 more rpm than the hp carb. If I put in a leaner jet should i get higher rpm out of the hp carb?
GreasyChris
Well-Known Member
If its 4 stroking then it's running rich. If you change the jet to a leaner jet the 4 stroking will go and it should rev out more. You will gain more speed because the engine is running more efficiently with the proper mixture. It's a test and tune kind of thing. When I set up my carb I take a screw driver and the jets with me while I'm riding and adjust accordingly until I find the sweet spot. Don't go to lean tho because you risk over heating.
Ok so I read that the stock jet is .70 mil so I will start with .69 and down? Thanks.
GreasyChris
Well-Known Member
Stock is usually 70. Yup just keep going down till you find the sweet spot.
Great. Will do. Thx.
How can you overheat it by puting in a leaner jet? Its oil mix. Not sure what that means.
GreasyChris
Well-Known Member
A leaner fuel mixture burns hotter therefore there engine runs hotter. A rich mixture burns cooler and lowers combustion temperature resulting in a cooler running engine.
Tyler6357
Well-Known Member
Usually these little engines will run leaner after they are warmed up. If it's 4 stroking at top end I would try a smaller jet on the hp carb, maybe #65
