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Discussion Starter · #1 ·




Just pulled this one apart today. Stone stock, no mods other than 4 seat cage.
This is caused by lack of lubrication to the piston pin. The pin usually galls in the rod first. After the pin locks up in the rod, the only place it can pivot is in the piston. The piston doesn't like the extra abuse and in this case it disentigrated!

This is evidence that the stock rod is a pretty decent part. The rod gets a lot of bad mouthing over at RF but it really isn't the culprit usually. This rod is bent and twisted and it stayed in one piece.

The fix for this is two-fold.
1. Check the oil every day! Check it more often if you put a lot of miles on it!
2. Upgrade to a DLC psiton pin. DLC is "diamond like coating". It reduces friction substantially and basically prolongs the pin life even when there is a lubrication problem.

I put the DLC pin in all the engines I build. Money well spent. :cool:
 

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Ouch, ya that looks like it has seen better days!

Makes me want to go out right now and check the oil level.
 

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That sucks. Your really better off buying a used one. Then you can sell off all the good parts from you blown up one.
The only problem is your still going to be stuck with the same insides as the one you just blew up and that's the reason it blew up.
 

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The pin is about 90 bucks. It is coated so that the surface will not gall up. I'm sure Chris can better explain. I also highly reccomend a CP piston. :good:
I have the coated pin in mine. I give a report of my findings next tear down



 

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Discussion Starter · #18 ·
What is the cost of replacing the pin with the upgraded one you are talking about ?
The DLC pin (diamond like coating) is $88.50. The pin BiggJim has is for a CP piston. The stock pin is much longer than the pin used for CP pistons.
I have not checked to see if they make one for the stock piston. If they don't, you can have the stock Yamaha pin coated. I don't know the cost for that.
I don't know what everyone else charges to do a Rhino top-end but through Benchmark it runs on average of $450 labor. A CP piston is $225 regardless of bore or compression. Plus a few bucks for coolant and gaskets.
 
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