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OEM ,hotrods or stroker crank? best piston?

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my 06 250x is in for a rebuild and I'm not sure what crank to use.

I rode mostly trails with some roads, never at or near rev limiter and maintain it well. i got over 200hr out of the stock engine (valves,piston,rings etc) and i am only rebulding it because its winter and its smoking. valves are still good. i run a stage 2 cam and a jardine full exhaust, ccc mods and backfire screen removed. 

the stock crank has a little bit more side play than id like and for peace of mind i want to replace it and all the gaskets and such. i have a top end already to go with kibbklewhite ss valves a and cam chain as well as every other little gasket and oring and clip i need.

with the cam and pipe should i run an 08 13.5:1 r piston? I've heard these are better. 

also im not sure which crank to use. will a 2mm stroker add much power? is OEM better than hotrods? I've heard hotrods are poorly balanced but that was on old posts and I've heard nothing recent. I'm mainly concerned about longevity and reliability. the bike won't be getting driven all that much but as my second bike i don't want to have to work on it all the time. its the classic "do it once and do it right". overall i would like a little bit more power but mainly more bottom end torque. it will be my bike for traveling with slower quads and maybe a couple big trips (>800km) and friends to drive.

sorry for the long post but i can't find much recent info on this.

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I havent used a stroker crank assembly so cant comment on that from experience.

I have used the hotrods crank assembly and also have used a hotrods connecting rod when having the oem crank rebuilt and have had no problems with either. The most obvious difference between the oem crank and hotrods crank assemblies would be the small end of the rod has a bushing installed in the hotrods connecting rod. The Oem connecting rod doesnt use a bushing in the small end.

That honda piston should work fine and is priced less than a wiseco piston with the same comp ratio. Was surprised that you have the stage 2 cam installed.

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Same here, since you mentioned an interest in mostly low-to-mid torque rather than top end HP, a Stage 2 cam doesn't seem the best suited.

Often posted dyno chart shows the Stage 1 pretty much equivalent to the X cam on the bottom and the R cam at higher revs.

but the stock X cam still having a slight advantage right off idle (4000-5000rpm).

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I want a stage 1 cam but this cam came with the bike and i like it for when I'm racing friends but i don't need it. if i could trade someone for a stage 1 i would. my buddy has a stock 250x and i find mine feels the same up until around 7000 rpm and then his falls off and mine keeps pulling hard until redline. i figured using a stroker crank would give me more of the bottom end i want without killing the top. i need a crank and the difference in price is less than a new cam so i figured i might go the stroker route depending on what people had to say. does a higher comp piston add more torque or low end? any benefit or downside? stock x is 12.9:1 and a drop in 08 r is 13.5:1. i eventually want to put a athena 280 in it but not for a while. I'm enjoying my 300 a lot right now but i still love the 250x. they are a great bike i think

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Heres a link that you might like that says a little bit about the hotords stroker kit.

 

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On 3/27/2017 at 7:16 AM, mlatour said:

Same here, since you mentioned an interest in mostly low-to-mid torque rather than top end HP, a Stage 2 cam doesn't seem the best suited.

Often posted dyno chart shows the Stage 1 pretty much equivalent to the X cam on the bottom and the R cam at higher revs.

but the stock X cam still having a slight advantage right off idle (4000-5000rpm).

Might want to specify which R cam your talking about, the 08 R cam is much different than a stage 1 especially in the higher rpm range.

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I searched and found the chart, looks like they tested using a '04 R cam.

hotcam1.jpg

 

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Yeah and thats with a 140 main, not to many people run a 140 but it also doesnt say anything about any other mods being done unless there was some info before or after the graph.

Kinda have to assume those dyno results were done using an otherwise stock 250X but who knows what year it was when that test was run.

Anyway it does show the differences between those cams.

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Mine is perhaps an exception,

with an otherwise stock engine & exhaust and only three 1" holes cut in the top of the airbox,

I conservatively chose to run a #135 (2 sizes up from stock) with the stock #40 pilot and NLAT non-adjustable needle.

 

On the relatively low speeds technical trails I ride,

off-idle throttle response and acceleration is more than fine* and it surely doesn't feel lean when occasionally going WOT.

(*this year actually added a 12oz flywheel to tame down the response)

 

The dyno chart shows a minimal advantage for the stock X cam between 6000 and 7000 rpms,

(no doubt below 6K as well but not recorded)

Not big numbers but myself wouldn't trade away low end torque for any top end gains at 9K+ rpms on a trail & off-road oriented bike.

Edited by mlatour

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Yeah with an almost entirely stock engine or bike that is used for light throttle, low speed type riding I can see where the stock cam seems or is a suitable choice. In that case that dyno graph would be more useful if it showed data below the 6K rpm range, because you likely spend more time below 6K rpm than above.

On the flip side of that until you actually get some riding time on the same bike that has some-and I mean more than just a cam alone-good power adding modifications and makes more power everywhere in the rpm range is hard to know what you may be missing. I know some guys are not interested in spending more $ and time to get more power "especially" not knowing what they will end up with, so often times the bike will get sold and get replaced with usually a bigger displacement bike.

Imo the bike actually gets easier to ride, is more versatile and fun by a long shot with more power added, also the 250X is easily capable of handling more power without any out of the ordinary issues. Its the main reason we still have the same bike I bought new in 2005!

 

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i finally decided and i ordered a 2mm stroker and bottom end kit and a 08r piston as well as some transmission bearings. theres a lot of parts in these engines. il post back when i get it running. i wanted a bit more power to keep me driving this and not my husky all the time

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