Stroker 250r

[wilkin250r]

Does anybody have experience with stroker cranks in the 250r? I've seen some pretty big bores, but not much in the way of stroker cranks. Is there a reason to this? Perhaps the stroker cranks don't like high revs?

Since I put my big 340PV in my quad, I'm trying to think of ideas for building my backup engine. I don't think I want another huge bore, but I was thinking perhaps a 265 with a stroker crank, probably end up around 310 or so.

So far I haven't contacted any engine builders. Anybody know of a source for stroker cranks?

[AndrewRRR]

Stroker cranks can really give you a power boost. You typically get more low and midrange power but they can rev too. My engine builder built one that I believe is a 8 or 10mm stroker that revs to 10K.
My R has a 330 bore with a 4mm stroker which makes it a 350cc. Later this year if I have some extra money I'm going to go to a 8 mil crank, although i'm still toying with the idea of a 10mm stroker crank in a pilot jug (520cc). My motor guy did one of those. With it running richer than crap and basically no tuning it was hitting 3.94 100yd times. His goal is to get it to run mid 3's.
ESR sells 4mm and 5mm cranks (I got mine there) for pretty cheap, but if you put out a lot of power get it welded, i twisted mine 8 thousandths out of true. Twister also makes great cranks but they are spendy (like around $1000 for the billet ones).

[Narly R]

Het Andrew my engine is just like yours, but im not shure what all EGZACLY is in there, but it is a 330 with a 350 crank. I dont know much about a stoker, so could I have a 350 crank, but not a stroker crank?:confused: j/w

[NTPracing22]

whats the stroke of an original 86 crank? i have no idea, and its something i should know. thanks

[310Rduner]

72mm is stock stroke.

[wilkin250r]

I'm not sure of the exact terminology. When you say a 8mm stroker, is that total increase in stroke (move the rod 4mm out on the crank) or is that moving the rod 8mm, giving you a total of 16mm increase in stroke?

[wilkin250r]

Originally posted by AndrewRRR
Stroker cranks can really give you a power boost. You typically get more low and midrange power but they can rev too. My engine builder built one that I believe is a 8 or 10mm stroker that revs to 10K.


Did you see a significant increase in vibration? I'm having some problems with vibration on my 340PV. It vibrates so much that it won't rev very high, so I have to gear it really tall to get the speed out of it, and the gearing is causing problems with the powerband...

[310Rduner]

I'm pretty sure the measurement is based on mm's out from the center of the crank.. like 8mm total spread equally out on both sides... i read that on here somewhere... i dont think they just measure it just 8mm longer from the end..

i may be wrong tho.. :(

[AndrewRRR]

It's total increase in stroke. Like stock stroke is 72mm and I have a 4mm stroker crank so my stroke is 76mm now. My bore is also 76mm which is pretty standard for a 330 topend. I didn't notice any vibration increase over stock, and still waaaay less than my stock CR250 was.

[310Rduner]

when did you have a stock cr250?? you talking in your dirtbike.. or in a trx frame???:confused:

who made the rod?...& does it use the stock crank in the assembly?

[honda350r]

Andrew are you talking about Packard?

[wilkin250r]

Originally posted by AndrewRRR
It's total increase in stroke. Like stock stroke is 72mm and I have a 4mm stroker crank so my stroke is 76mm now. My bore is also 76mm which is pretty standard for a 330 topend. I didn't notice any vibration increase over stock, and still waaaay less than my stock CR250 was.

So you didn't notice any vibration increase over stock? My 340 vibrates like a mofo...

I'm beginning to wonder if the counter-balance was put back together properly :confused: I've never been inside the cases, is it even possible to put it in wrong?

[310Rduner]

I think its possible to mis-align the gear on the counter balancer when you have it taken off if they dont size it up right.

When my Counter-balancer blew i actually had jim, Honda350R do it.. im not sure if it's the same guy as Above.. but im pretty sure it is.. he owns a rebuilding company i guess..

He charged 35 for the total work including cost of the bearing and i had it back within a week of Sending it out.. everything on it was GREAT...

I'd deffinately recommend dealing with him than any of the 65- 85 dollars at the major companies like CT or Lrd..

It's been in 6 months and i havent had a single problem with it.:)

[wilkin250r]

I am totally willing to give someone a couple hundred to get rid of this vibration.

I should probably call Duncan Racing to see what they have to say about the matter...

[Chef]

Check to see that your pipe isnt laying on your water pump. Mine picked up an extreme vibration, and thats what it is. Vibrated itself abotu a 3/4 inch deep dent, and now it quit.

[wilkin250r]

After getting off the phone with Duncan Racing, they say this thing isn't supposed to vibrate this much, and most likely the counter-balance is off.

So should I send it to Duncan Racing, or somebody else that might be able to do it cheaper?

[310Rduner]

Look at my post above.. send it to Honda350R... it really isnt that complicated of a thing for them to do.. all that is necessary is to press off the bearing.. mark the spot on the gear for where it was and then press it back on.

I'm sure theres more to it.. but thats the basics. the places like ct or lrd all over charge... they wanted to charge 45 for JUST the bearing.. honda350r charged me 15 for it..

MUCH better deal. and i have No vibration what so ever..

here is the counter balancer after i got it back from Jim.

[wilkin250r]

Originally posted by Chef
Check to see that your pipe isnt laying on your water pump. Mine picked up an extreme vibration, and thats what it is. Vibrated itself abotu a 3/4 inch deep dent, and now it quit.

The vibration isn't a rattle, I can feel it through the handlebars and it's making my hands go numb, at high RPMs I can barely hold on.

[Chef]

Mine was shakin my bike so bad that it was goin through the pegs and the frame and up my back and makin my butt go numb....lol

This is on a 425 PV though...so it might just shake like that. Who knows? No one else on this board I have talked to has one this big thats not a stroker.

[wilkin250r]

Originally posted by Chef
Mine was shakin my bike so bad that it was goin through the pegs and the frame and up my back and makin my butt go numb....lol

This is on a 425 PV though...so it might just shake like that. Who knows? No one else on this board I have talked to has one this big thats not a stroker.

I was looking at that 425PV, but then the deal came along for this motor, so I jumped on it. Stupid me...

[honda350r]

310 duner,I am the same honda350r that you sent the balancer to! I am glad yu are happy and would give any one the same deal!!! Just PM with your needs !!

Jim

[AndrewRRR]

Originally posted by 310Rduner
when did you have a stock cr250?? you talking in your dirtbike.. or in a trx frame???:confused:

I mean in my dirtbike. That thing would make your butt go numb if you sat there idling it, the R is way nicer even though it's huge by comparison.
I am using a ESR 4mm stroker crank, they use the stock honda rod (I think) which is supposedly stronger than a hot rod. I picked it up for like $450 for a new one (they can stroke yours for like $300). LRD wanted $1000.
I was gonna use Packard or K&T, but I found someone that has been consistently beating them recently and he's local to boot so I used him :devil: The bikes weren't done in time for Sand Mountain this year, but the 520R and the banshee triple are freakishly fast.
Keep in mind if you stroke a R 5mm or more you need to trench the cases.

[wilkin250r]

Originally posted by AndrewRRR

I am using a ESR 4mm stroker crank, they use the stock honda rod (I think) which is supposedly stronger than a hot rod.


The bikes weren't done in time for Sand Mountain this year, but the 520R and the banshee triple are freakishly fast.



The ESR website says that you have to use their top ends kits with their stroker cranks. Is that true, or can I use their stroker crank with any top end?


Does every state have a Sand Mountain?

[Chef]

No, not every state has its own Sand Mountain. Sand Mountain is in Nevada I believe, and its just one big dune. Its so huge, that the whole riding area is basically one dune I think. Like 1000 feet.

[AndrewRRR]

Originally posted by wilkin250r
The ESR website says that you have to use their top ends kits with their stroker cranks. Is that true, or can I use their stroker crank with any top end?


Does every state have a Sand Mountain?

It works with any big bore. You might need spacers to keep the port heights right. I went to a long rod with a 86 piston so I needed a base plate. They probably say use their motors because they know they are setup for them.

I guess Sand Mountain, NV (now under fire by the damn treehuggers) is where all the big name engine builders go to shoot it out Memorial Day weekend.

[SandTrix]

you can build any size of cylinder you want to run a stroker motor. we will have a stroker motor out at LS Sand Dunes in Oklahoma very soon. just waiting on the parts.

[wilkin250r]

Sand Mountain in Nevada is my playground, I live about 2 hours away, but I've seen a "Sand Mountain" in other states also. I know there is reference to a Sand Mountain in Kentucky, Tennessee, and Alabama.

If any of you guys ever come to Sand Mountain in NV, let me know, I'll go ride it with you...

I realize that you can put a stroker crank into any motor, I just didn't know if ESR did something special to their stroker cranks that only allowed them to work with their engine kits.

How much power increase do you see with a stroker? Will a 310 kit with a 4mm stroker (stroker increases it to 327cc) out run a 330kit with a stock stroke?

[ThorChick]

Originally posted by wilkin250r

How much power increase do you see with a stroker? Will a 310 kit with a 4mm stroker (stroker increases it to 327cc) out run a 330kit with a stock stroke?

That would come down to porting, setups, and riding ability. The strokers tend to give them a lot fatter midrange power and keep the top end. Usually an engine with a big fat powerband will outrun one with a really peaky narrow powerband. Pretty much all the drag guys use big stroker motors if that tells you anything. Plus, there is the old cliche: There is no replacement for displacement.
I've never seen a 310R stroked, but it should be pretty fast. I usually try to keep the bore and stroke square or oversquare (bore larger than stroke). Stock stroke is 72mm, stock bore is 66mm (I believe). Mine (LRD 330 with a ESR 4mm stroker) is square 76mmX76mm, although another motor done by my engine builder was a 8mm stroker 76mmX80mm and it ran a 4.1 in the 100yd drags (on alky).

[AndrewRRR]

Oops, computer was still signed on to Kacy's name! :eek:
That last post was by me.