350 honda foreman big red ?

[dustrunner]

is it possible to take the piston and top end of a 350 foreman and put it on a 250es big red ? the bottom ends look identical ?

[captainweezy]

I really doubt it. If that was the case the 350x would fit also because I am pretty sure a 350x top end will interchange with a 350 fourtrax.

[swampthang]

Yes and no. You can put a 350 Foreman or 300ex top end on but you will have to have a reverse grind cam made because the 250es and 300 fourtrax engine spin backwards from the 350 Foreman and 300ex. I also believe there are issues with rod length because the 250 doesnt have as much stroke. There are guys building 4 valve fourtrax 300 engines which is very similair to the 250 so I imagine it could be done with the right machine work and money. Its possible to build a 250es with well over 500cc with different cylinder sleeves,stroker cranks,etc...you just need the know how and big wallet pockets.

[Hurricane635]

I'm pretty sure it can be done but you will need to use the trx350 crank also. As long as you use the first gen model.

[dustrunner]

ok... thanks...but my wallets got a hole in it bigger than the one in my head.....

[Gearheadtom]

I believe the 300 top ends will work tho... not sure on any mods that need done tho.

[Hurricane635]

The trx300 cyl. and head will work, but not the piston, it's got a larger pin.

[swampthang]

If you go to highlifter.com and do a search theres plenty of info on guys building the 300 and 350 foreman engines. I believe you can press a foreman 400/450 rod on a 250es use the stock sleeve for a foreman 450 and that should give you around 380cc with all honda oem parts. I know this works for the 300 I think it should work on a 250 as well.

If I was building a dream engine for a 250es it would have the 4 valve foreman 350 complete top end, stroker crank, huge displacement sleeve prolly end up around 600cc, race cam with ported and polished head,54% gear reduction and a set of 32'' gorillaz. Anyone want to donate some money to my dream project?