low compression

[98blaster]

dude your starting to annoy me and all your info is from wikapedia did you ever even build an engine before i hope someone else comes on here and is able to tell you your wrong cause im just getting pissed i do this sh*t for a living not on bikes but on race cars and performance diesels but and internal combustion engine is the same princibles no matter what its in

 

[con8quest6]

well thats unfortunate that you do it for a living and dont know what compression PSI measurement is for...but anyways..yeah..your right, im not going to waste any more time or brain power on you.

 

[98blaster]

i know what compression psi measurement is used for but you stated that nomatter what you do to a cylinder or head the psi never changes unless you change cam or port timing the reason the cam and port timing change compression is due to overlap and you will lose a little bit of compression from this overlap is when both valves are open at the
same time to help pull more fuel into the cylinder or on the 2 stroke the ports are open longer to acheive the same goal you cant just say oh my compression is down must be those rings on a 2 stroke normally it is but there are also other things that can cause low comp like leaking gaskets on 4 stroke there are alot more possibilities like valves and such hense the need for a leak down test to be sure what is wrong

 

[con8quest6]

Dynamic CR

 

[mike11743]

So I got this motor apart and it turns out there is a wiseco piston in there. Everything looks good. There is a ton of hard ass carbonm on the top of the piston but ill probably just scrape it off. No scoring on the cylinder walls and no up and down play in the crank. There is a little side to side play in both the top end bearing and rod bearing. I assume this is normal right?? Also Ive rebuilt motors before without honing them. I think I might just do this with this one because it is in such good shape. Opinions??

 

[Kennedy_Power]

if you ahve a factory yamaha piston buy factory yamaha rings. make sure to check teh piston for any cracking.. inside and out.. if thats all good.. then re reing it and hone the cylinder.. IMO hold off on that wiseco swap til you need a bore.. really you should check that cylinder for out of round and taper wear... if either are out of spec.. you need a bore.

Have the bore checked with a bore gauge for out-of-round and taper.
You will wear out the rings quickly if you have one or both conditions.

 

[mike11743]

well...for anyone interested in my outcome I got the cylinder checked out and its not out of round or taper. I decided not to get it honed and just throw in the rings as is. Ive done this a couple times before on some of my old bikes and theve held up for a decent time. Hopefully so does my blaster. Luckilly I had gaskets at home already so my rebuild is complete. It has about 120 lbs of compression cold which is good enough for me.