Yes, it has nipped up on the gudgeon pin by the slight scoring and discolouration. Check the new pin slides through easily. If it doesn't, you can coat it with metal polish and slide it about in the eye until it frees off. You need to be careful not to get any in the crankcase and clean all traces away before final assembly. I have an air cooled 500 down, awaiting the rebore, which was much more seized, in fact I couldn't get the pin out in one direction as bits of piston are welded to the pin, on one side.

 

So I mic's out the "Connecting Rod Small End I.D." and it looks like I'm in spec - I have .748- ... definitely less than service limit (Spec is 0.7488 - 0.07496 - Service Limit 0.751).

The bearing on the bottom end feels tight & smooth; especially up/down. I checked the "big end side clearance", I got a .016 (Spec is 0.002 -0.026 - Service Limit 0.03).

Inside the crankcase looks real clean ... just some minor sludge.

At this point, I'm thinking top-end. I'm not seeing any reason to crack the case. I'm still puzzled as to what caused the cylinder/piston damage ... previous owner must have ran with no oil.

 

Check to see if he had the oil filter in backwards??

 

It was in proper; but, didn't look like it had been serviced in a loooong time.

 

I know it's a long shot and you might not even have the quad anymore, but I was wondering if you ever figured out what the issue was? I just bought one not that long ago and it's making the same sound yours was, if you remember what the issue was I would greatly appreciate it

 

It was piston seizure as is shown clearly in the pictures, but when you have the head off you must check rockers, valves and seats too. Often, running a bike short of oil, will cause wear in more than one component.

 

Thank you, guess it's time for a rebuild.

 

The sound was the piston skirt slapping the cylinder wall. Both the cylinder & piston were toast .. as pictured. I bought it this way, so I can't say for sure "how" it happened - but, I suspect that it ingested water.

I rebuilt the top-end and all was well afterwards. I still have the quad & it runs well ... issue I have now is that it "smells" like its running rich, but its fuel injected. It also only seems to only want to run on "reserve". New petcock, fuel pump, & entire throttle body later - and, I still have the problem.

 

Ahh ok. I guess that's where I'll start off looking then. Thank you for that, probably saved me a couple hours of searching and digging through the engine. Good luck with your new problem.

 

"it "smells" like its running rich"


It is just possible that the engine temp sender is telling lies, so the ECU thinks it needs choke all the time. Check plug colour, black and sooty and it is running rich. Regarding the running on reserve, as you know, all the fuel tap does on reserve is pick fuel up nearer the bottom of the tank. If fuel runs out of the pipe going to the filter/pump canister when the tap is ON the bike should run with it like that.