265 stroker ?

[2fiddyr]

i am about to rebuild by motor for the upcomming year
i am running a 86 board out to a 265, i am wondering about using a 88 crank with my 86 bottom end or what is the best combo to get the most power for mx using my stock jug ??

[wilkin250r]

An 88 crank uses a longer rod, but it's not a stroker. You have the exact same stroke as an 86 crank, 72mm.

[2fiddyr]

gotcha so whats it going to take to stay on the 450s i need help picking the proper componets to make this motor rip

[elbine69]

well ill tell ya that with my stock cylinder just bored.20 over with a 38mm carb and a fmf exhaust ive beaten 450's. so with the 265 u should have no problem.

[2fiddyr]

i think the fact im runnin a stock carb is holdin me back is a 38mm as carb in order?

[TheFontMaster]

My 250r is all stock except that it's bored .010 over, cool head, and sparks racing exaust. I haven't been able to get a good drag race with my friend that has a 450r, but for the little that we were racing I was keeping right up, and started to pull ahead once I hit 4th and 5th gear. And that is still with the stock carb.

[Eddiesanders250]

for the carb go with the 39mm pwk.

[wicked265R]

building a true stroker motor wouldnt help you keep up with 450r's, it would rip past them. 450r's are fastm but not as fast a a stroked 250r motor, they are just crazy fast.

[wilkin250r]

Originally posted by 2fiddyr
gotcha so whats it going to take to stay on the 450s i need help picking the proper componets to make this motor rip

What kind of porting do you have?

[2fiddyr]

thats just it i dont have porting i just have a 86 board to a 265 stock carb, fmf fatty,cool head
and last year i started racing mx i really need help setting up this motor theres some good shops around here but i dont know what set up will really rip using my stock clyinder ???????

[XCredrider]

i have mine ported and polished by paul turner for mid to top and it flat rips. stock carb with fmf fatty and cr head gasket. some other small stuff here and there. but a 450 cant keep ekpp up with mine

[wilkin250r]

Originally posted by 2fiddyr
thats just it i dont have porting i just have a 86 board to a 265 stock carb, fmf fatty,cool head

Porting is an absolute must for decent power. You can get into a debate about who and where does the best porting, but in all reality, any decent reputable shop will give you a quality port job.

Almost any place that does porting can also do head modifications for higher compression, and they usually can do them together as a package deal. I really recommend some sort of head modifications (or an aftermarket head) to go along with your new port job.

At this point, if you're looking for more power, I'd recommend a port job over a new carb, if you have to choose one or the other because of limited funds.

[gunslinger]

I must say this is a great thread,,,been tring to figure out i'm going to do w/t my stock motor and ,,,well i'm lost:confused: all i know is i want a extra motor to have as spare so while my 15yr son & me are working on one we can still ride:D .What do you do to get a stroked 250r motor?????????

so keep posting :macho

[readybeartoe]

I think you need a "stroker crank "with the rod pin closer to the outside of the crank. I saw one that was 4 mm. but unless you already have the bottom end apart or need to replace you crank now it could be expensive to do. I would just clean up the ports on the top end and put a whole day aside to get to know the charactoristics of how your motor likes to run and to jet your carb to your motor. Man! This was time consuming but WELL WORTH IT! Did I mention Cheap. Now I know exactly what changes to make to lean it out when needed. Depending on the weather.
I have a 86 motor w/Pro design Cool head (19cc Dome) using a CR head gasket with a Prox .070 over piston, V-force carbon fiber reeds, and a LRD pipe (shortest position). I mildly ported the Jug mainly cleaning it up where needed and smoothed it out! I run race gas 40-1 and this thing makes me VERY HAPPY!!! I can pull a holeshot against the 450s on good dirt. It's NOT blazing fast on top end but if you race MX , on most tracks you'll never need to be wrapped out in 6th gear anyway. ...Make sure your igntion is good also. I got a Janssen coil last year and now it revs much better than my 20 year old stock one. LOL!
I have two 250rs, the only difference was that >one was a long rod 89 bottem end and the other one was a short rod 86. Both had 86 style pistons and jugs ported about the same. They were too close to say one was better than the other but The longer rod might have made just a little more power. Very little.

[wilkin250r]

Originally posted by gunslinger
What do you do to get a stroked 250r motor?????????

First, look at exactly what a stroker crank is, and how 2-strokes work, pay close attention to the factors that determine port timing.

A stroker in a 2-stroke is no small task. For a 4-stroke, you can almost throw it in, and be good to go. But on a 2-stroke, a stroker crank changes all the port timings, and not necessarily in a good way. The stroker wants to rev slower because of the longer stroke, but the changes in port timing want to rev faster, so you get a bit of a mis-match that needs to be corrected.

Often, if you already have a ported cylinder, it can't be used with a stroker crank, because the ports have already been altered too far. Sure, it's easy to remove material to make ports bigger, but not so easy to ADD material to make them smaller.

You can throw a Cool-Head on your stock cylinder, rejet, and be good to go. It's almost a bolt-on modification. But a stroker isn't nearly so simple. Because it affects your port timing, and your port timing affects you power band and influences your pipe, it's the sort of thing that really needs to be planned from the beginning.

It's not just a matter of throwing in a new crank and you're set to go. If you're going to be doing a stroker crank, your ENTIRE engine must be designed around that stroker crank, by somebody that knows what they are doing.

[slamdak8782]

I have an idea about this and wonder if anybody has tried it. Stroke the crank the width of the piston change between 87 and 89. With the short rod and use the long rod piston. Then use 89 top end. Would that work out ok for power. Timing would be different but. The ports would match perfect like they did before. Timing would be similar to the 89 but exhaust would open later and boost ports would open earlier. So really you could port by cutting the bottom of the exhaust due to the longer stroke as well as the bottom of the boost ports. What do you guys think. Increased duration of the exhaust and the intake?

[wicked265R]

Wilkin= My hero:D