Top end rebuild

[cr2504life]

It is just about time for a top end rebuild on my cr. The previous owner had a new sleeve put in and i know that i will have to bore it out a little(slight scratches in the bore). I was wondering when i do this will i need to modify the exhaust valve to avoid contact with the piston? If so how do i go about this? I will also be replacing the main bearings. Do i need any special tools to do this. Ive heard that sometimes you need a press and a "case puller"??? Is this true? Also after the rebuild what compression numbers should i look for? Thanks

 

[cr2504life]

I was also wondering what break in procedures you guys use. I ve heard about a couple different methods and was wondering what one works the best.

 

[cr2504life]

Nobody have any input?? :(

 

[reelrazor]

Okay. No you shouldn't have to mod the powervalve if you are just going to do a light hone, LIGHT is the keyword here. You are better off with light scratches than excessive piston clearance. If you go up a bore size you need to check the clearance between the piston and valve(insert piston in bore w/o rings and use a feeler guage to ensure clearance). Careful work with a file on the powervalve will get you teh clearance you need(I think they call for .070" but don't quote me).

You can get around the press usually, but it is nice to have. You will NEED a bearing knife though(usually). A real seal driver is nice to have too.

I am a big fan of heat-cycling as break-in. A little heavy on the oil mix. Start it and run, idle/just off idle 'til the enrichment isn't needed. Idle, blip, blip..not too much throttle, blip blip a little more. Don't load it, keep it in neutral. Get it all the way warm(thermostat open-cyclinder and head hot to the touch). Shut it down, let it cool all the way. Do it again, slow warm up, blip blip half throttle at most. Maybe ride it around easy-all the way warm. Shut off, let cool again. Repeat, adding more throttle and load. Work up to giving it short full throttle bursts over four or five cycles. Call it good.

If you really want to know when it is broken in, give it a compression test after shutting it down each time. The comp # will climb as it breaks in. When it peaks, it is broken in.