Stroker crank

Spotted 3MM stroker cranks for sale on E-bay. They don't give much info about them, except that they are new. I would love to do this mod in conjunction with the Athena big bore. Someone quick with math figure that up and tell us what the final displacement would be!



Anybody else seen these or used one yet?

Mark

i need to start reading twice apparently.

((3.1415 / 4) * 77 ^ 2 * 53.6 * 1 ) / 1000 ~= 249cc

so

((3.1415 / 4) * 77 ^ 2 * 56.6 * 1 ) / 1000 ~= 264cc

spacecadet wrote:

((3.1415 / 4) * 77 ^ 2 * 53.6 * 1 ) / 1000 ~= 249cc

so

((3.1415 / 4) * 77 ^ 2 * 56.6 * 1 ) / 1000 ~= 264cc

well im bored at work so heres more math yay!

solving for the bore of the 290 kit:

sqrt((290* 1000) ) / ((3.1415/4) * 53.6) ~= 83

so with the big bore and stroker:

((3.1415 / 4) * 83^ 2 * 56.6 * 1 ) / 1000 ~= 306cc


approximately, also assuming my math is right, which is usually a bad assumption to make.

dont buy it, i already talked with hot rods and they confirmed the first batch of cranks had the wrong the timing chain sprocket and they were re-called. He said the new stroker crank will be available around july-ish.

Hey guys, I know this a real old thread but was there ever a correct one released? Also, has anyone installed it?

I still see the Hot Rods cranks on e-bay but I wasn't sure if they had the same issue as the older ones.

I'm wanting to do a stroker but I was hoping to do it at the same time as the big bore kit. Wasn't sure if anyone had programmer settings or a review of the stroker. Thanks guys!!

liftdt4r wrote:

Hey guys, I know this a real old thread but was there ever a correct one released? Also, has anyone installed it?

I still see the Hot Rods cranks on e-bay but I wasn't sure if they had the same issue as the older ones.

I'm wanting to do a stroker but I was hoping to do it at the same time as the big bore kit. Wasn't sure if anyone had programmer settings or a review of the stroker. Thanks guys!!

Thumper Racing is doing a stroker crank. Contact Travis.

http://www.ebay.com/itm/Hot-Rods-Stroker-Crankshaft-08-12-Yamaha-WR250-R-08-11-WR-250-X-Crank-3mm-263C-/130636220414?pt=Motorcycles_Parts_Accessories&hash=item1e6a8687fe&vxp=mtr#ht_1661wt_906

What about these? Is anyone running one? I heard some of the older ones had a problem with one of the gears.

liftdt4r wrote:

http://www.ebay.com/itm/Hot-Rods-Stroker-Crankshaft-08-12-Yamaha-WR250-R-08-11-WR-250-X-Crank-3mm-263C-/130636220414?pt=Motorcycles_Parts_Accessories&hash=item1e6a8687fe&vxp=mtr#ht_1661wt_906

What about these? Is anyone running one? I heard some of the older ones had a problem with one of the gears.

These guys are about 2 hrs from me. I'll check them out next time I'm in their neck of othe Woods.

Can anyone explain the benefits of the Stroker Crank Kit?

I noticed on Hot Rod Products website, they list a gain of 3mm in piston travel which makes sense that it allows more gas & air, thus more compression and more power. Are there any other benefits or details that contribute to the kit's power gain?

An extra 3mm of stoke bumps up the displacement, as well as compression as long as all other things remain the same.

I seem to recall someone posting a comment pertaining to squish bands. He mentioned that he had built some fast car motors in his day, and that the squish band in our little motors was quite large. Not exactly power-making friendly.
For a quick read about squish bands read this:
http://www.nrhsperformance.com/tech_squish.shtml

It's written about Harleys and Buells, but the principles are the same.

https://wr250rforum.forumotion.com/t4820p20-bent-connecting-rod

That's where the guy was talking about clearances. He referred to it as "quench" though.

Longer stroke = more torque. On the flip side, longer stroke also decreases maximum RPM before catastrophic damage.

Soo.. I know it's been a long time, but has anyone done this mod yet? Either the Hot Rod or the Thumper Racing 3mm crank?

woodygumdrops wrote:

Soo.. I know it's been a long time, but has anyone done this mod yet? Either the Hot Rod or the Thumper Racing 3mm crank?

As soon as I get home...

I know it's been a while but I am looking to go big bore this winter and want to do a stroker crank at the same time.

Has anyone done this yet?

I'm mainly curious as to how to reflash the programmer. I know FMF will do it for a big bore kit but not sure if they'd do it for a stroker too or then which settings to run. ANy help would be appreciated. Thanks guys!!

I'm waiting on parts...

I'm also running the Power Commander w/Autotune, so I can't comment on the other programmers.

Hi all my stroker crank will be here next week. I've run the Athena 290 kit for two full years of racing and training. I have a full ported head and it gets new valves a springs this time. This bike is not street legal. It's striped to the last wire. I will be happy to post pictures and answer any questions..

slvdirtrider wrote:

Hi all my stroker crank will be here next week. I've run the Athena 290 kit for two full years of racing and training. I have a full ported head and it gets new valves a springs this time. This bike is not street legal. It's striped to the last wire. I will be happy to post pictures and answer any questions..

everybody loves the illegal stuff! Lets see this bad boy! whats your setup like?

I have almost 1000 miles on my WRR Athena/Hot Rods stroker winter project. Bike is a 2010 with 48ooo miles and has had nothing internal done to the engine, until now. From about 8000 miles I had done the basic uncork with a Power commander V and Autotune.
Install was not difficult and everything went smoothly with the exception of the cam chain tensioner which I was leery of the stocker, so I bought a mechanical. I have had no oil usage with the 2 ring Athena piston so far and I will keep a close eye on it. Original setup never used any oil so I would rarely check it.
Power of bike is very nice and bike will now lift front wheel in 2nd gear - short shift from 1st no clutch abuse just throttle. Vibration is so close to stock that I would have to ride a stocker back to back to tell the difference. I do believe that this would have come out completely differently without the Power Commander, even the idle fuel changed.
I was expecting a tired engine when I pulled it apart - never showed any tired symptoms but with 48000 miles I figured it just had to need piston, valves, crank bearings etc. I should have just left it alone - everything, even the valves looked fine. I think Yamaha built one tough little engine here.

Nice   

I'm assembling one slowly. I bought a Thumper balanced 306 kit from an inmate with a 3 ring CP piston.
The crank is in the cases & ssw ported the head. As soon as Travis (Thumper) gets done with the nodular iron cool flow sleeve he's making for me & installed in the used Athena jug I procured I'll get mine together.

Wound up having Thumper Racing re plate the used Athena cylinder from the spare engine I bought. The crank was no big deal to install. I had to improvise a puller/pusher to pull & install the crank. SSW ported the head.
 There is no downside to the build, three ring 83mm Thumper Racing piston, 3mm stroker crank balanced to the piston. It's just as smooth as it always was & the new found power made a very fun bike an absolute hoot. 2nd gear throttle wheelies happen quick, the midrange is as strong as the engine was at peak before.

*Bump

4play wrote:

Wound up having Thumper Racing re plate the used Athena cylinder from the spare engine I bought. The crank was no big deal to install. I had to improvise a puller/pusher to pull & install the crank. SSW ported the head.
 There is no downside to the build, three ring 83mm Thumper Racing piston, 3mm stroker crank balanced to the piston. It's just as smooth as it always was & the new found power made a very fun bike an absolute hoot. 2nd gear throttle wheelies happen quick, the midrange is as strong as the engine was at peak before.

Hey, still going strong?

Looking into this build myself. How high does the compression ratio work out at with the stroker and is the porting needed?