big bore?

[goRED]

Wanted to bore my 250 but was wondering how big I can go without loosing reliability. Doent have anything done to the motor already, everything is stock.

[redrider419]

If you want the most power out of a stock 250r cylinder I'd stay stroke it. +4 strokers with spacer plate are popular...I don't know much about them but they work like a charm...my buddies is a stroker and its very very fast. Some more technical 250r guys on the forums would be the ones to talk too.

[atv fan 28]

Some good porting will help you out greatly. And also getting a pipe that matches the porting will help also. Everything needs to match up.

[jcs003]

make sure your engine is healthy. compression test, leak down test. inspect your clutch. sometimes a freshened up engine is what a bike needs. i know guys who rode their bike for a few years without checking it out and were wondering why everyone was faster. they threw in new piston and clutch plates and their pants got filled.lol

as stated above; a good port job will also surprise you on the amount of power it creates.

[goRED]

Originally posted by redrider419
If you want the most power out of a stock 250r cylinder I'd stay stroke it. +4 strokers with spacer plate are popular...I don't know much about them but they work like a charm...my buddies is a stroker and its very very fast. Some more technical 250r guys on the forums would be the ones to talk too.

What do u meen by a spacer plate? A plate that goes between the head and the bottem end so the piston doesnt hit

[machwon]

Most of the 4mm strokers use a spacer plate between the crankcases and the cylinder. I would recommend good porting and a race cut head to start. You would also want a good pipe and carb to go with that set up. After that I recommend you go with a 350 kit, next you can add a stroker crank. Next go to a more custom set up in a puma, sabre or other. To me the question of how big can you go, is how thick is your wallet? If you have a ballpark budget with a list of parts you already have, I can give you a better direction if you like.

[Grande Huevos]

the original question wasnt how big can u go it was how big can u go without losing reliability. i was wondering the same thing when i first fell in love w the 250R and after doing lots of research and calling multiple builders i came up w the conclusion that the 330 is as big as u want to go w full reliability and being able to go on those long country cruise rides without worrying about any problems. when u hit the 350 u have to mod the case to except the big cylinder and piston, and that will cost u some bank. like everyone els said there r many things u can do to add power and not effect reliability, a good carb, pipe,reeds , advanced timing, cr 250 ignition,good filter or eliminator kit, and port work. the poss r almost endless!! I would avoid a stroker crank if i were u because then that starts to make things more coplicated when it comes to mods such as port work and what not. i asked some questions on running a stroker crank and the replies i got were pretty interesting and totaly made me change my mind, if u wanna do a search on my posts u can see what everbody had to say. anywho my 2 cents is to go w a ported 310 or 330 w pipe carb reeds and no stroker

[RyanWsly]

a lot of this would depend on what you planned on doing with it, you will get more accurate responses. that being said, everything I've ever read or heard is a bolt on kit is as reliable as a stock engine for the most part.