wrist pin

[thrownchain]

Is anyone else having issues with wrist pins being more than a push fit? I've gotten some that are extremely tight. What's the cure?

[viclioce]

I put my last one in the freezer to contract it a bit. Went right in! Victor

[Bullfrog]

While I do not know the precise recommendations for piston pin fit with Wiseco pistons, I do know that you are playing with trouble if the piston pin is tighter than an "easy thumb push fit" with pin and piston at the SAME ambient temperature if you are using an OEM ART piston. (Cool pin and warm piston is specifically NOT recommended for ART pistons . . . I don't know about Wiseco's.) Piston pins tighter than an easy thumb push fit with ART pistons will often result in seizure.

The old school method of "fixing" a too tight in the piston situation was to use an adjustable reamer to ever-so-slightly enlarge the pin hole in the piston (while maintaining straight hole walls). "New school" method is apparently to use abrasive strips wrapped around a mandrel (flapping end fashion) to enlarge the pin hole abrasively. Thorough cleaning afterwards is required.

Ed

[taber hodaka]

A thumb push is a must and I have been having trouble with a new pin and and old ART piston. You also need a finger push to help align the pin with the upper rod bearing. I must confess I used the adjustable reamer on the last 125 wombat. ----------------Clarence

[Bullfrog]

. . . and I have adjustable reamers in the basement for both the 100's and the 125's (old school )

Ed

[Joe Ormonde]

I made a simple tool . I took a 12mm pin, roughed it up with a sanding drum and drove a Bolt Extractor into it. Then you use a Tap wrench to turn it round and round and in and out. Takes time, and cuts REALLY slow. Works for me! Joe.

[Bullfrog]

That would be a slow method, however, you would be assured of a smooth, straight, perfectly aligned re-sized wrist pin hole . . . and no worries about residual abrasive particles. Interesting!
Ed

[Joe Ormonde]

Because you start with a 12mm pin, you really can`t go wrong. You just keep at it until the new pin slides in smooth and that`s it! Slow BUT safe! The factory ART pistons clean up quick. The older Wiseco pistons take a lot more time. Be sure to use plenty of oil. Joe.

[viclioce]

Got any pics of this tool, Joe? Would like to see it! Victor

[Joe Ormonde]

When I figure how to post photos I will. Just a long stud that fits tight in the pin will work too. Trust me: some of the best tools are Home Brewed ! Joe.