does anyone know if a 300ex cylinder head will bolt up to a 250sx without any mods. needed? i wanted to put a 4 valve head on seeing as how there are better cams available for the 300ex. plus, if i ported and polished the head and installed a 300cc big bore, i might be able to beat a 300ex and other quads of that caliber. from pictures i've seen, the heads look identical including the mounting bolt locations. any help would be a big help. thanks.

 

Years ago, Dirtwheels did an article on a project TRX300 with a 300EX 4 valve head. The power gain wasn't worth the price from best I recollect. They didn't actually say it like that, but they weren't impressed from what I gathered.

I also remember a long list of mods the engine builder ended up using to make it all work together right.

 

knowsalot, i wanted to put the 300ex head on because when i get my 300 big bore kit, i want something that has an availability for better cams and flows more than my stock 250 head. i don't plan on using it alone. my question was, would it bolt on with no problems? thanks for the help though, i appreciate it.

 

I have never attempted this swap myself, so I cannot answer your question about direct fitment.

sorry

 

i appreciate the help anyways, i hope someone with some knowledge of this can help me. thanks again knowsalot.

 

id like to try this mod also, if it works, or if you try it, keep my posted on your progress....maybe i can give you some help.....

 

if you could find someone that knows about 300ex cylinder heads, i would apprectiate some help. what does the tube coming out of the intake side of the cylinder head do? i think it is a breather tube, but not sure. is it an oil return line or what?
if anyone know, please respond to this thread. any help would be apprectiated. thanx in advance.