350x head on 250sx bottom end?

[oldway]

Is it possible? I cant find a 350x anywhere in Ontario Canada for last 2 years. Not looking to build a racer, just have more power for hills and deep mud.

[Custom200]

I cant see that working with out major major work, wouldnt be worth it in the slightest. A 300 fourtrax 2x4 motor will swap in pretty neatly for a bit more umph, Look into that.

[nitrometh king]

Have you tried opening the exhaust up a little or finding a cam with a little more
duration or even boring out the motor how much more power do u want?? Also if you mill your head it'll bump up compression and give you lots more power and torque

[JohnR.]

I'd do what the other guys suggested. Bump the compression up a couple of points then do a cam, exhaust, and carb on it. I wouldn't mill the head unless I had to, it will alter your cam timing since the cam is in the head.

John

[nitrometh king]

There's only two ways to incerese compression on a engine that seals as good as possible and that's a smaller combustion chamber or domed piston so if u can't get a domed piston it's too milling the head And bigger carb does make more top end power but not bottom

[JohnR.]

I'm not sure what your point is. Like I said, I wouldn't mill the head unless I head to, meaning if I couldn't get a higher compression piston I would mill the head. As for the carb, if you get a properly sized one it will not hurt your bottom end power but will help it in the middle and top. Adding an exhaust is primarily going to help your higher RPM power too and if you add a larger head pipe it might even hurt your low end a little but that doesn't mean you shouldn't put one on. Besides, if you're upping compression, adding an exhaust, and changing the cam I couldn't see why you would keep the stock carb rather than going to a slightly bigger aftermarket one along with an assortment of jets and needles.

John

[J-roc]

What about looking into an XR250R top end? My XR200R engine is interchangeable with my atc200s engine... might work the same for your application. I can go from a 7.8:1 compression to a 10.0:1 by just using the cylinder, piston, head,.. and the cam and carb are larger too. Probably cheaper then all that engine work too.

Food for thought.

[matt drover]

i seen that done before back home.the trx 300 motor swaped worked out prety good.

[MHR]

Is it possible? I cant find a 350x anywhere in Ontario Canada for last 2 years. Not looking to build a racer, just have more power for hills and deep mud.

ive done a 300ex head swap i had to mod the piston and make new rocker arms because the engine is reverse rotation.