300ex race motor

[IRISH-RACER-14]

so im gona build a 300ex race motor from scratch...should i just get a bottom end stock and work my way up?should i get a 250x motor or 300ex?

[John451]

My quad rips past 400ex's It's a 1998 300ex it has a stock bottom end bored out to 350, ported and polished, stage 2 hotcam, wiseco 11:1 piston, with a white bros e-series... Now that I think about it the last guy problably had it re geared because there's not much overlap with the gears which i like.

[ZSNOW]

you can't bore a 300 that big. if its a 350 its been stroked.

and if ur going to build an MX motor build a 250x. no battery/starter/drive clutchs/lighter crank. less rotating mass more horsepower and more peaking..and the quad is gonna be 25+ pounds lighter.

and when u buy the bottom end. split the cases, pull the crank and put in a +3 mill stroker crank and get a 76 mill piston which will bring you up to just about the 300 limit

[John451]

hey, thanks i bought it bored and did the rest. Now what does stroking it add? I know that it brings the piston down so it increases the draw for more fuel which gives it more punch especially in the bottom end but can you get just a stroker piston where they move the wristpin? like the 11:1 and stuff or do you have to get a new crank? Who makes stroker cranks? and where can you get them?

[John451]

well w/e bored and stroked lol. it might actually even be a 12:1 cuz it cannot be jump started in dirt it has to be on pavement

[ZSNOW]

my 14:1 piston can be jumped in the dirt. just gotta do it right;)

[John451]

shyt lol. The starter blew on mine cuz it was too much for it. but i did jump it in the dirt once but it took like 3 trys pushing it up and runiing with it down a huge hill and jumping on it lol. it did have the stock tires on it then but it still woulda been hard. like you can sit on a hilll with it in gear and it won't move at all.