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stock top end rebuild, is honing a must?

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I am rebuilding my boys top end on his CRF50. putting new piston and rings in it. its a 2004 that is stock from the day we got it, now my youngest races it and needs a new top end.

can i just put a new piston and rings in it, or should it be honed?

i need to get this together by thursday. i have not pulled it apart yet either to see what the cylinder walls look like.

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Best to hone it to cut any glaze and prepare the surface for the new rings.

Here's a link from Flex-Hone with some good info if you haven't done it before on a 2-smoke:

http://www.tomorrowstechnician.com/Content/Site301/SmartProducts/CommonPractices_00000000930.pdf

Wiseco makes cylinder brushes that give very good results.

http://www.wiseco.com/PDFs/Catalogs/CB07/Comp-ComprsrSleevesHoneBrushes.pdf

+1 on using a brush. (in fact Wiseco recommends not using a ball-hone to deglaze a Nikasil cylinder).

Never use a rigid hone on a 2T. I'm not a fan of using a Scotchbrite pad.

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The CRF50 cylinder is not Nikasil coated, you can use a small automotive disc brake 3-arm hone that fits in a hand drill. Spray WD-40 liberally on the cylinder walls, use a medium speed and keep the drill moving in and out to achieve the crosshatch pattern desired.

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even if i do a little will i be able to use the stock piston and rings. i bought std size already.

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Just breaking the glaze with a ball or brush hone should not remove much material at all. Just hone enough to make a light, 45-degree pattern on the cylinder.

If you have a "ridge" at the top of the cylinder (where the ring didn't wear the wall) needs to be removed so the new ring doesn't hit it. They're pretty obvious (usually). Since the cylinder isn't plated (as posted above), you can use a ridge reamer to get rid of it.

Using a rigid hone (like a brake hone) removes much more material from any high spots until the pressure is spread out along the length of the stones. Also, if you catch the edge of a rigid stone in a port, you can scratch the hell out of the cylinder. The other bad thing about spring-loaded rigid hones is that they tilt, so if you hit a high spot on one end of a stone, it puts extra pressure (by reducing surface area contact) on the opposite end. Not a good thing.

Fwiw, if the cylinder isn't "true" (i.e. circular and cylindrical) you might need to have it oversized anyway. Not to say that you can't just re-piston and ring it if it isn't perfect; lots of people do, but taking the time to check and correct an unseen problem now could save you some time and $$ later.

GL! :banana:

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thanks all. i found a flex hone in the local area. i will give it a good rim job and get her back together tonight.

i have not even pulled it apart yet. if its bad, i will just go grab a new cylinder, they are not expensive.

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