Ok rebuilt the top end for my buddy(my old zuki) because he lost all compression. Well got it all back together and now there is a knocking sound. I used the old long screw driver method trying to find it but I could not here anything, it sounds smooth. Now this is a 51mm wiseco( i know should have used the zuki) but when the motor went up it already had the 51 wiseco in it. Hardly any damage to the cylinder, just had to home it lightly and put new piston in it. I believe he ran it on regular gas or outl He did say his grandson rolled it over so I am not real sure what is going on. Top of piston was destroyed because something got into it, just top of piston and inside head. It was not a ring, not sure what it was but it is embedded in top of piston, looks like a copper or brass piece. Anybody have any ideas?

 

could be it got the plug so hot it burned off the metal tab (for setting gap). seen that happen on sleds!

 

Hope it's not pieces of the brass shims or bearing cage from the big end of the rod. That would make a major knock but not for long. Did you check if that bearing was smooth & tight when you rebuilt the top?

 

I looked at it and I thought all the pieces where there. I think I am going to pull it back down and look again. I nee to find out how much play I can have in the side to side and up and down on the rod and the crank. I hope LT80(Jack) chimes in since he is the resident expert on these beasts.

 

I saw a picture of the connecting rod bearing and I think the piece lodged into the top of the piston may from the bearing cage. Looks like it may need crank and bearings. I need to do this at home in my garage as the guy does not have a lot of cash. Any pointers would be greatly helpful, like the steps I need to take to tear it down and put it back together.

 

Yes, Wiggle the rod sidways and up/down. If bad, I can usually feel the slop when wiggled up/down. Excessive sideplay usually means it'll mobve up/down. Bad..
OK, a Wiseco and a hone. But what is the exact clearance? They do slap around in there till it (piston) warms up and swells.
The head marks could be a broke reed too.
let us know how the rod is and we'll go from there. [img]i/expressions/face-icon-small-smile.gif[/img]

 

Well, got it back apart and when I pulled the head off you could already see new damage to the top of piston and a little in the head, small pieces of metal. Got the cylinder off and had a ton of play in the connecting rod. I believe the bearing cage has come apart. So I started pulling it all down and right now I am stuck on the flywheel. I am going to need to pick up a puller, one I have will not work. Any other pointers any one can help me with would be great. Thanks for the help so far.

 

Make sure you pull straight on the flywheel.
Rebuilding the crank is a pain. I recommend a new crankshaft.

 

He said he wants to replace the entire crank so that makes it easy for me. Going to replace the crank bearings and seals also. Made a puller at work today(benifits of working at an industrial plant), any other pointers. I have searched the site so I have some ideas. Thanks Jack so far.

 

Well, it came apart pretty easy, except for the stator assembly. The screws are thrashed, I did not think I was going to get them out. The connecting rod bearing cage is gone, only the rollers are left. Now time to order the parts and get her back together.