any tips for my 1st top end rebuild

[T-MAC]

I'm changing the piston/rings for my first time in my 99 CR250, have take the cylinder off and just am about to start taking the piston off but just have a few questions.

Should I clean the cylinder out with anything? It looks pretty clean and smooth in there. My piston is in good shape, the only reason I'm in there is because my powervalve was stuck open and figured I may as well put the new one in. My old one had about 15 hours on it.

Does anyone have any tips for doing the power valve? I am most worried about lining it up when I put the cylinder back on. How do I know if its lined up properly?

Should I put anything on the gaskets or just do them dry? Any tips to remove the old gasket residue?

I didnt remove the cylinder head but should I just to put a new head gasket in as it came with my gasket kit?

As you can tell im pretty new to this so any other tips would be appreciated.

 

[_JOE_]

TAKE YOUR TIME

I'm not familiar with the PV setup on that, sorry.

I've always just used brake parts cleaner and paper towels to clean cylinders.

You can get liquid gasket remover that works decent. Or very carefully use a razor blade. I usually install my gaskets dry.

Make sure you check the ring end gap. It rarely needs adjusting, but it's certainly worth a look.

Definately do the head gasket. You are akready in there, why risk it? Also makes it much easier to get it all cleaned out.

 

[whenfoxforks-ruled]

Your manual tells you to replace the power valve every 15 hours? What brand of oil do you mix? All the motor parts get washed in as hot a soapy water as you can stand. What does not come clean goes to the parts washer, the clean stuff gets a wd-40 wipe down and the bore gets 2 stroke oil. After the parts washer it goes back in the soapy water. On assembly put 2 stroke oil on the piston, ring, and top end bearing. I put the exhaust valves in clean and dry.

 

[kschilk]

In most cases, soap and warm water is the best way to go...I prefer Dawn dishsoap, it seems to work best to remove any oils or solvents. The problem with most cleaners and solvents, is that they most all leave an oily film behind. Small particles can adhere to it, especially dust and gasket residue.

Gaskets should be put on dry, do the head gasket too and use proper torques. Permatex Gasket Remover (spray) works well on tough gaskets but you have to be cautious about overspray, it can damage certain materials (don't get it on your skin, either). Other than that, I'd recommend a BRASS scraper....plastic works in rare instances but brass can scrape off the tougher ones, without damaging the mating surface. Sorry, I'm not really familiar with any PVs.

*BTW...caution with brake cleaners! They are safe on most materials but some will dissolve or weaken certain types of plastics, nylon, and teflon. Be careful around any composite parts.

 

[T-MAC]

Thanks for the help guys. My bike is back together and runs better than ever!!