My lt is equipped with fmf gold series, uni air filter and a keihin PJ38mm. If i change the carb for a PWK39mm will i have a good difference in power?

 

What year do you have?
also, without any major mods like porting, head work, or good reeds/cage, then a 39 will be too much. I ouldn't go past a 38pwk. But a PWK is better than a PJ. I went from a 36mm Mikuni to a 35mm keihin PWK, and mine ran better.

 

its a 1990 lt250r... he runs great with the keihin PJ 38mm, it was impossible to have this light brown spark plug with the old mikuni 34mm bt with the keihin it took 30min of tuning and thats it. The thing is... if theres a even more difference with the pwk well i would get one. I'm not thinking about porting it, the power is strong enought, all those ds650 , raptors and predators are already scared of me. Soon i will post some pictures of my lt, pretty clean.

 

IF the engien runs well right now then leave it alone. You need to really open that engine up and make it flow well with porting and the like, before you go to a 39 or larger. A stock is a 36 correct? You've already made a huge leap over stock. If it rips now then why **** with it?

 

34mm Mikuni is stock

 

ok, i will save my money to do some porting. Correct me if i'm wrong...porting is limited to the sleeve, intake and exhaust right?

 

You can also port the cases, but, its a little extreme. Just take you head and cylinder to a porting guy and they will kow what to do. On the head, have them polish the dome and shave about .020 off. It raises the compression a little for more power.