is this true about 250r top end swap?!?!?!?

[quadgod89]

i heard u can take a polaris 400 top end and put it on a 250r bottem end to make it a bigger cc's and more power cheaper than a big bore kit.....is that true and what would i face to make this work awesome....would i need a custom pipe? also just a thought i was having would a cr250r's top end with the PV fit on my 250r with a little modifying?
i have a 88 250r and wanna get more ponies outta it for the race season coming up....i race flattrack so the more power the better it is.....all answer's/suggestion's are appreciated

oh and the engine mod's just consist of a fmf fatty pipe and pc2 silencer,bored .40 over with a wiseco pro-lite piston and that's basically it..

thank's again
Jake

[RideRed04]

Yeah, the polaris cylinder will work, I believe that you need some case machining though.

http://www.atvsource.com/articles/product_reviews/2001/112601_mpracing_polanda_engine.htm

[beerock]

From all the reading ive read about this conversion the polanda is more TROUBLE then anything.

a 350 or a 370 pro x cylinder will last longer and beat the polaris.

if your motor is fairly un modified id say try a port job on your cylinder before you go crazy with big bores. You would be amazed by the difference in power with a nice port job.

if ya got some scratch ...
get a pro built Power Valve cylinder for trx bottom end

[Predator36]

I have seen the Polaris cylinders on the Honda's and agree that a good power valve cylinder is a better setup. I have seen up to 450cc with a stroker PSI setup. However the rest of the engine could not handle this extra power and was always breaking something.

[AndrewRRR]

The general consensus on Polondas is to stay away from them! As it says in Todd's (250r admin.) signature "The polonda's exist solely to bring the 250r down to the (competitive) level of a Polaris!".
Get your R ported by a good engine builder. There is a lot of power to be found there. If you still want more power look into big bores.

Originally posted by Predator36
I have seen the Polaris cylinders on the Honda's and agree that a good power valve cylinder is a better setup. I have seen up to 450cc with a stroker PSI setup. However the rest of the engine could not handle this extra power and was always breaking something.

my 310 power valve was built on top of a new crank & all new bearings & a few other new things all gears inspected etc ..
is about 9 months since it was built w/60 to 70 reasonably hard hours on it so far & all is well...:D

[AndrewRRR]

I agree. My 350r is a 4mill stroker big bore and when I disassembled it a few weeks ago it looks just fine. I have put about a year and a half of hard dune riding on it. I am sold on these NiCaSil coatings, I think they really help.