stroking help?

[weed]

ok so if my buddy were to put a 4mm stoker on his 250r, what all really needs to be done to the motor besides that?? And how reliable would that be??
what kind of power gains are we talking here??????

[dovesprings250R]

You will need a cylinder head spacer and longer studs for it to work. Most guys that stroke the crank also go with a big bore cylinder 330 or larger on the 250Rs. With that big of cylinder you have to machine the cases for the cylinder to fit. That is a lot of work. As far as reliability it really depends on the quality of the work done, how it is re assembled and how/ where it is ridden. Without going with a big bore cylinder I don't think it would do a whole lot better than a nicely ported 250 cylinder with the stock crank. More low end perhaps. As far as the big bore option, that will rip but can be hard to ride for some guys, espcially with a stock swingarm. Hope this helps. Check out www.esr250.com for big bore/long rod engine kits and info.

[weed]

he plans on putting the stroker in and leaving everything else stock, maybe i can convince him to do a mild port/polish!!

[weed]

wait a second, a 4mm stroker on a 250, would that make it like a 295mm??????

[ridetrikes250R]

no it would not be a 295mm nor a 295CC LOL:wtf: , it would be a 270cc, you cannot install a 4mm stroker, without a plate or porting, your piston timing will be completely different, and will have to be reported to correct that problem, a well ported 4mm stroker motor will lay a easy 50 to the rear wheels, and do it reliably, i would suggest if hes got the money for the crank (300 bones weisco) porting for correction(250 bones easy) and decking with the head milled(125bones+) then go for it.... if he is just looking for a huge increase in horses i would go with a esr or lrd 310 kit, bolts on bolts up and runs like a son of a gun....my personal bike has a 310 on it, i got her dialed in really nice now and it SPANKED a 295 (270 sleeved motor stroked 5mm) and at the end of the day i still had more power throughout the band then he did, save your freind some money get him to go a pro-x cylinder and down the road add a 4mm or 5mm stroker, then its into the 65RWHP+, i own a esr cylinder and will never go back to anything else
Adam

[hrc85250r]

4mm stroke makes it like a 262 or so. basically, if your going to do this, at LEAST have the cylinder ported and all stroking will give you with that small amount of added stroke is a few more ft-lbs of torque. you probably wont be able to feel it, and if the barrel wont flow more air what the point of trying to pump more with a stroker? tell him to have it ported, get a nice pipe for it and your stroker will be being used properly.

[Troll]

Stock crank and cyl.


269.2 cc sleeper motor. With the right pipe/porting it will make about 60 rear wheel HP and will rev quickly because the piston weight is very near stock at 300.9 grams

Found here; http://www.macdizzy.com/sixtynine.htm

Other good info here; http://www.macdizzy.com/bore.htm


:shrug: ......................................................:D

[jasonb32]

whats your buddy looking for ? more bottom - mid- or top?
does he race? what class is he going to be in?
theres only so much room between the cases and the rod at bdc -bottom dead center so is it gonna be a stroked/ de stroked crank or a long rod?
try a good - port/polish ,pro series reeds,pipe silencer, jetts ,and a smaller front sprocket will help but will reduce top speed
unless you already have and it still isn't enough