in a machanical bind! need a genius

I have decided to get my1994 XR600R up and running for a freind. the upper end seems to have run dry. replacing the cam, valves and the valve cover are not such a big deal. but the problem lies with a small amount of scaring on the inside of the upper ring of the connecting rod. the bike is not worth the money to tear it down to the crank. Any thing more than the upper end would have to be done by a machanic. I am hopping someone can help me with a solution in fixing this problem without tearing it down to the crank.

here is a photo.

This may not be the best thing to do, but I'd probably take some fine emery paper, smooth out the rough stuff, polish it up, and call it good.

I'm thinking that it may also be possible to bore it out and machine a sleeve on a lathe to press in.

That engine needs a new rod and most likely, crank bearings.

Yup, new rod.

You could run it on a pin hone to polish it up for a short term, but it really is toast.

Besides, you have to DX it to hone it, so you would replace it then anyway.

You might want to post this up in the XR650 would be interesting to see what the gang has to say there....

You could have the small end honed and bushed, but that would require the crank to be removed.

I had the same problem on my 150cc 4T scooter. I used a fine sand paper (fine water sand paper) of number 1200, then I polish it so long that the piston rod went in smooth and clean with no slack. I put new piston rod in piston and rings and put the motor together. After half of year scooter still runs great and strong and he runs up to 10000rpm. :moon: I think you should think about if it's worth to change the rod, or simply do as I did and see what happen :p:busted:

That piston pin bushing/bearing is shot, obviously, but what you should be thinking about is the rod bearing, the piston pin does not rotate 360 degrees like the crank pin end of that connecting rod, so it goes without saying that if the pin bush is scored the crank end is probably destroyed. The piston end is splash lubricated from the crank end runoff, so it was run out of oil for a period probably. Tear it down is my two cents worth

No good, its badly galled. If you try to hone it to clean it up, you will have too much clearance. You are going to have to "crack the case". Big task.

It looks nasty but.. measure it.(or should i say have it measured)

Iv'e done some that looked that bad but measured in spec,so together they went and ran forever.

Like someone said,it's not like the lower end.It dosn't spin.

Al bakers' or Powroll would put a bushing in them years ago.. but i'm not sure if they still do?

looks toast to me, since you have it this far apart, just finish the job right the first time...otherwise...... how much for the bike?

Does it use a roller bearing there? If it does then a new bearing is not going to last very long. If it does not use a bearing, just the piston pin slides into it then it might last quite a long time.

Assuming the rest of the engine is ok.

I had the same problem on my 150cc 4T scooter. I used a fine sand paper (fine water sand paper) of number 1200, then I polish it so long that the piston rod went in smooth and clean with no slack. I put new piston rod in piston and rings and put the motor together. After half of year scooter still runs great and strong and he runs up to 10000rpm. :moon: I think you should think about if it's worth to change the rod, or simply do as I did and see what happen :p:busted:

Im still debating on the practicality of just touching up the rod and seeing what happens. the crank had plenty of oil. there was just cloging someware to keep from getting oil to the head. I could be compleatly wrong butt dos'ent the pistion itself spin on the pistion wrist pin. if this is the case wouldent the pistion turn on the wrist pin if it was slightly bound by the connecting rod connection

take a hold of the piston end of your rod with one hand and turn the motor over with the kick starter with the other hand. If you are looking down into the case you can see how the crank pin rotates 360 degrees in the large end of the connecting rod. Now if you were to put the piston pin and piston back together temporarily with the small end or upper end of the connecting rod you could then rock the piston back and forth. That motion, actually a little less is all the movement a piston pin makes while the engine is running, that is why splash lubrication is sufficient for the piston end of the rod. I kinda doubt that you had a plugged passageway to the head when your pin bush is so damaged, you had low or no oil, or an extremely dirty oil filter in order to damage the engine so completely.

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