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02 cr125r rebuild with 03 Jug?

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Hi all, new guy to the forum.

So down to business...I have an 02 cr125r that I stuck a piston in. Measured the bore diameter and it was too loose. Now I'm rebuilding it, just going with a new jug instead of sleeving and wondering if the 2003 jug would bolt on to the 02 lower end, I heard the 03 had a better top end design?

Or even the best year jug that will bolt right up?

Thanks,

Rooster

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Did you match the piston with the cylinder? If I am not mistaken, depending on the cylinder you have, you will need either an A, B, C, or D coded piston.

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The last time it was rebuilt I replaced the piston with a wiseco pro-lite, pn#676M I do believe. 54.00mm dia and I do believe the bore is 54.00 standard?

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I don't own a CR125 but I thought I had read something about there being a code on your cylinder with one letter being A, B, C, or D, then you just get the corresponding piston.

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Nope, just checked the catalog...one pn for all replacement pistons. But like I said my bore is 54.3mm or 54.4 right now, and leaves way too much room for movement, plus the piston scuffed the walls. So instead of waiting to get a sleeve put in I just wanna get a new jug for it and I heard the 03&up years had improved porting and a better powervalve so I was wanting to go that route...if not I'll just get an 02 jug

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You have some wrong information. I believe you are confusing the 250 info with the 125s

http://motocrossactionmag.com/Main/News/ASK-THE-MXPERTS-What-Are-The-Best-2003-Honda-CR125-2691.aspx

ProX makes pistons from 53.94-53.97 for the A-D sizes. You need to measure your bore and piston. Not just go off what is stamped or marked in their press literature.

54.50 is the big bore 134 piston.

04 will not work on the 02-03 motors for the cylinder. neither will 05-07. different motors.

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Wiseco has the same part number for both the 02 and 03 piston kits. I am assuming that it will work to bolt an 03 cylinder on an 02 bottom end. If you have the ability to visually inspect the cylinders side by side, you will know for sure.

As far as the 54.5 piston being for the 134, that is incorrect. the 56mm piston is the 134, the 57mm piston for 139 and the 58mm piston for the 144.

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Hi all, new guy to the forum.

So down to business...I have an 02 cr125r that I stuck a piston in. Measured the bore diameter and it was too loose. Now I'm rebuilding it, just going with a new jug instead of sleeving and wondering if the 2003 jug would bolt on to the 02 lower end, I heard the 03 had a better top end design?

Or even the best year jug that will bolt right up?

Thanks,

Rooster

You could send your 02 cylinder to millenium and have it replated. when you get it back your cylinder will be better then stock. If you are in a hurry, they do cylinder exchange, you could probably get them to ship you a cylinder and then you ship them yours back and they give you a core refund.

http://www.mt-llc.com/

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http://www.dirtrider.com/reviews/motocross/141_0308_2003_125cc_mx_compared/index.html

I want to get this thing up and running as fast as possible, and a new jug was the best bet. That in mind I was reading the above article and it said the 03 cr125 was a noticeably more powerful bike. I do believe they changed the porting a bit and it got a new powervalve right?

Also, the bikes had the wiseco in it since spring...it's not raced, Taken to the track every once in a while but just for practice. Measured the bore with a micrometer again today and it came in at 54.28. So I'm guessing the years of wear and tear just made the cylinder stretch.

I was just wondering if the 03 jug would bolt up because I thought I saw somewhere the bolt pattern is different?

Otherwise, I've got an 02 jug I can order and have in between next tues-day after Christmas.

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You could send your 02 cylinder to millenium and have it replated. when you get it back your cylinder will be better then stock. If you are in a hurry, they do cylinder exchange, you could probably get them to ship you a cylinder and then you ship them yours back and they give you a core refund.

http://www.mt-llc.com/

That seems like a very good deal...how fast do they ship?

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That seems like a very good deal...how fast do they ship?

I couldn't tell you how fast they ship. I have always used Eric Gorr since both times I needed my cylinders replated I sent them to him for the bb kit. I would call them and get details.(Eric Gorr uses them to do his bb boring and replating, then he does his porting once they are done).

Edited by frdbtr

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Also different intake so keep that in mind. You would be money ahead to have your 02 cylinder replated....or send it all to EG and do the big bore kit to it.

Is the plating visually worn off your jug?

Since the intake is on the crankcase it shouldn't make much difference. BTW when you go to service honda and look at the cylinders they specify 02-03 so I am pretty sure that the 03 cylinder will bolt right up to an 02.

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all the motor parts are 02-03 in the honda fische. Same motor. There is tweaks, but replacement parts are all the same.

for articles on more power, they are the same bike. Read different magazines, you get different opinions.

You are right on the bore, 56mm for the 134. largest you can go in the 02-03 bikes.

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Thanks all...just ordered a the new jug....

Getting it ported and polished after christmas when I have time to dial in the carb,

For now I'm throwing a wiseco pro lite back in it.

it has a slightly dented procircuit platinum pipe, and a cycra powerflow rear fender to round out the current motor mods...

Thanks for the help,

Rooster

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Thanks all...just ordered a the new jug....

Getting it ported and polished after christmas when I have time to dial in the carb,

For now I'm throwing a wiseco pro lite back in it.

it has a slightly dented procircuit platinum pipe, and a cycra powerflow rear fender to round out the current motor mods...

Thanks for the help,

Rooster

I like the pro lite pistons. Run them in both my 2 strokes (pretty much have to when you have bb's on both of them). They are more expensive then stock but are also more durable.

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