I got questions

[TRX-330]

I got questions for you engine guys that know more than me haha. So ya i know a 350x head will fit on the 300ex cylinder, butt the valve's are different and you would need to mod a 300ex piston to work. Im thinking about building a race engine with the bottom end i have laying around(needs cracked in half cleaned up) or parting that out and buying a 250x bottom end due to it has a kick start. I wanted to put a 350x head on when i found out you could do it, butt due to the problems you would encounter with the stock 300ex/250x piston and stuff, i thought well maybe i could get a good used 350x cylinder or sleeve have the 300ex jug bored to fit the 350x sleeve in then buy a 350x high comp piston and rings. BTW is the 400ex and 350x the same bore?

Butt give me all the info you know of cause im not sure if this will work just one of those things that popped into my head. Thanks

[honda250xrider]

save yourself the hassle, just get a 330 kit or so, im sure u can find one for cheap, get yourself a cam and then you will have a decent performing engine. I have went through so many motors/combinations on the 300ex/250x to where i would just stick with something simple and plan to upgrade in the future. I would have to say just to have fun with i would just use a .40 bore 12:1 piston, webcam 231 grind, along with a k@n and pipe you should be just fine for having lots of fun and being able to have decent power all around.

You would be running into so many problems doing the swap piston clearance decking issue's and what not. along with i dont even think the wrist pin is the same size as the 350x. a speical piston would also have to be made so that it would not interfere with the valves. all together i would have to say its just a bad idea no offense. If your looking for big power out of the motor there are alot of people out there still making kits, the most recent motor before sold had a 406 stroker +3 intake +1.5 ex. valves, custom cam from FST, TC pipe, full race port job, valve job, decked head, forget the compression it was around 12:5-13:5 cant remember excatly right now, that motor has crazy torque but ran very hott.

[TRX-330]

damn haha i was looking for a way to do it without buying all brand new stuff. and kinda wanted to have fun with it by doing that. But i understand that it would just be to hard with all the mods u would have to do.

and hmmmmmmm a 406 sounds baddass hahaha id need a ton of money to do that.

whats the difference between the 250x and 300ex bottom end besides the kick start, i forget what it is off hand

[JIMFROMTEXCO]

the jug from a 350x would never work out right on the 300. the throw of the engine would be way to short in that. it wouldnt build any compression. the 350x head really sucks with no bearings on the cam.

if you want to open the head up on your 300, gasket match taper the port out to the inside diameter ofr the copper washer using a die grinder. leave the intake ruff it will help atomize the fuel. just dont get to carried away with it.

[TRX-330]

My head is ported and polished