anyone ridden a 390ex, or any 300 stroker?

[maddmatt02]

alright, first off, I am kind of a speed junkie(actually acceleration more so than top speed), I really like my girls YFZ, I would have no problem with it being faster though, and if it was mine I would make it faster. so far its just got a pro-flow kit w/ K&N, full DR D pipe and its down a tooth in front. but I dont have any issues with its performance. my sister has a 11:1 I think 330 with a web cam, P&P head, uni filter, FMF full exhaust, running 14/38 and out in the dunes when it was fresh, of course it got beat, but not as bad as I was thinking. I was on the 330 against my girl on her 450, and whe we took off the 450 didnt walk away that fast until I was basically done pulling and the 450 had alot to still go so it then pulled away nicely.

anyways, I have been debating on engines to put in my frame after I get sick of the little 281. but I only knew of the 330 kits. I have now found a 349 powroll big bore stroker and a FST 390 big bore stroker.

if I were to have my head P&P'd, seats cut with oversize valves, hardened rockers with a nice cam, 390 kit around 11:1, maybe a FCR, full exhaust. would it be a nice, quick, enjoyable bike or would I always wish Id have just thrown a 450 in there? I know it wont be able to ever be like a modded 450, but i plan to buy a 450r or kfx450 someday and kinda like the idea of getting as much out af a 300 just to show people up on a 300 with a oem appearance engine.

[honda250xrider]

i have had a 352, 365, 406 all of which were stroker motors, I had the 352 stroker/big bore with mild port and polish, mild cam, exhaust regular things. I would say this was the funnest out of all the combinations i had, Simply because it ran a bit warm but nothing terribly bad, it would start up whenever you wanted it to with no problems at all. it had good power all the way around and i did get to beat a few 450's even with this motor. I would say stick with the lowest stroker/big bore you can find for dependablity and maintance wise.

if you upgrade to the 395/406 or whatever you will look into doing my maintance than actual riding time. I had +3 intake valves +1.5 exhaust custom cam, 12:1 compression with it being a stroker it will increase to 13:1 just a little fyi. with a vavle job decked head, full race port and polish. The motor was insane on how much power it had in the little package but it simply was annoying on how much you had to maintain it. every ride i had to be doing something to it. They simply just lose the dependability that they once had.

My 352 stroker had the #320 webcam in it( im pretty sure that was the number) with +1 intake. mild port and polish, tc exhaust k@n, lectron carb, 12:1 compresion. And simply was the best combination i have found with reliablity and performance on these machines

[maddmatt02]

well if I bought the piston and had my crank modd'd at the same place and its a kit package, wouldnt the cr they state be the cr you get, because they know what crank your gonna be running and would machine a piston accordingly so you arent gonna sway from what the kit states? and im sure the decked head brought it up a bit as well for you.


also, what did you have to do to it all the time?

[JohnT_98300EX]

I am looking to do the same kind of thing to my EX this year.
My first thought is the head P + P and a mild cam. (more for torque than top end rush) This was recomended to me as the first step I should take. It will uncork some power and help get the most from a bigger bore / stroke motor after the fact.
In looking at big bore / stroker kits the poweroll has options as low as 10.5 to 1 compresson so I am leaning that way. Pump gas is a must and I want to ride, not wrench. Plus I keep hearing that a stock 300EX starter can have trouble with compressions of 11-1 or higher.

[maddmatt02]

im pretty sure the 330 my sister rides is a 11:1 330 and the starter has no problems.

[2muchquad]

I run the pro fab 385kit(86mm piston,actuallyu only 370plus cc or so)with the stock stroke for reliability and i must say that the power is impressive for a 300ex based machine.I have several different cams i run from a sparks to a wb 1805,just depends. also run a fcr carb which is definately one of the best mods for "actual returns" with performance.An oil cooler will help as it does run a bit warm but its not too bad.They make a lot of torque so stroking wouldnt be necessary imo unless one wanted max cc but what for?:D

[maddmatt02]

did you just run a 39mm or get a 37 off of a crf250x?

[2muchquad]

i am currently running the 39mm fcr off a yz400f but i also have a 37mm from a 250f that i may try later on.The 39mm runs awesome though,havent really felt the need to try the smaller version fcr.

[maddmatt02]

how did you manage to fanagle that big carb into the little boot? and when its in there is there room to get a wrench onto the bolts holding the manifold to the head easily, so you dont have to fit the carb in that boot more than one time.

[2muchquad]

i used a reducer,a 37mm fcr can be made to fit a 300ex boot with lots of fiddling and a heat gun though:) You cant get the 39 to fit though:(

[maddmatt02]

yeah cuz I remember it was somewhat of a PITA to get a 39FCR into the 400ex boot, and it stretched it enough that even al the way opened the stock hoseclamp came nowhere near being big enough anymore.