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Do I Need a New Cylinder?? Picture Added

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Yesterday I pulled the top end on my 02 crf450. The gentleman I bought it from had already had kibblewhite valves and springs installed as well as a stock 04 piston and cam chain tensioner about 50 hours ago. I have checked the valves every 10 hours for the 30 hours I have owned it and they have not moved from .004/.010. I pulled the thing apart because I thought it would be time to replace the rings and possibly the piston and wanted to go with a high compression piston. The piston looks good and shows no signs of blowby.

But the cylinder has two gouges on the exhaust side where the piston skirt contacts the wall. These can easily be felt with a fingernail and it also feels as there is a low spot in between them. The crosshatch on the bore looks good. I do not have an inside mic to check for and out of round condition.

Should I replace the cylinder?

What is the break in and installation for a new cylinder? Does it come ready to assemble out of the box? Or does it need to be honed?

And lastly where would be the best(cheapest) place to get a new cylinder, JE hi-comp piston, and a gasket kit?

Sorry for the long post, but I wanted to be as detailed as possible:blah:

Thanks

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Unless your compression is low, and or the bike does not seem to be running right, then you could replace the cylinder. I found very cheap price for a new cylender here: http://cgi.ebay.com/ebaymotors/New-2002-CRF450R-Cylinder-02-CRF450-12100-MEB-670_W0QQcmdZViewItemQQcategoryZ35595QQihZ011QQitemZ320089956994QQtcZphoto

The bike ran perfect when I tore it down. I just want to put in a high compression piston because the piston is at about 50 hours. I want to address the cylinder now as well because of the gouges. Does a new out of the box cylinder need any prep before assembly?

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A suggestion would be to buy an Athena kit since you are looking for more grunt.

Not a bad deal at $734.95 when considering the cylinder, piston, gasket kit and HP too! Gets a five star rating from MXA.

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should have left it alone till it started running bad. I have close to 150 hours on mine with no problems at all. especially since the valves havent moved. just my .02

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A suggestion would be to buy an Athena kit since you are looking for more grunt.

Not a bad deal at $734.95 when considering the cylinder, piston, gasket kit and HP too! Gets a five star rating from MXA.

Yeah I'm not really trying to spend that much. I can get the 02 cylinder, a JE piston kit and a gasket set for like 375.

I am going to get a picture of the clyinder. The indentation I am speaking of is more of a dent than a gouge, no rough edeges at all, right where the piston skirt is on the exhaust side at TDC.

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I would replace it.

The new cylinder will be ready to go on. Just clean it out real well with ATF and a white paper towel, then contact cleaner till it comes out clean.

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garage.php?do=viewattachment&attachmentid=45954

Picture of the section of cylinder wall that is in question...

This is the exhaust side and the two gouges created by the piston skirt can easily be felt with a finger and fingernail.

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It might come out with a hone.

Not unless it was a diamond hone. If he can feel the mark with a finger nail its significant. He's got nothing to loose by running a hone down in there and trying though.

Something else comes to mind here though...its an 02, thats had the top end rebuilt once already. The bottom end of the thing needs attetion, you can bet your ass on it. Id be hard pressed to correct the top end at this point and forget it. Unless he just wanted to off the aging bike... :excuseme:

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Not unless it was a diamond hone. If he can feel the mark with a finger nail its significant. He's got nothing to loose by running a hone down in there and trying though.

Something else comes to mind here though...its an 02, thats had the top end rebuilt once already. The bottom end of the thing needs attetion, you can bet your ass on it. Id be hard pressed to correct the top end at this point and forget it. Unless he just wanted to off the aging bike... :excuseme:

I went ahead and just ordered a new jug this morning. The two dent/gouges are fairly significant and I doubt they would come out with a dingleball hone.

This is my first crf, what are the common bottom end problems?

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This is my first crf, what are the common bottom end problems?

You will want a new crank if it has over 200 hours.

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You will want a new crank if it has over 200 hours.

Cam - can you explain why? Is it because they got out of round? Do they break do to the 11000rpm style motor?

I trailride my CRF but would imagine crank replacement as a massive job?

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If the bike has seen nothing but trail riding, you can go longer on the crank. An advanced MX'er would want to replace the crank at 200 hours because the small end of the rod galls the big end goes out of round and the main bearings are often starting to brinell.

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