teflon wrist pin buttons

I am building dirt bikes for my kids for Christmas and time is running short with one YZ 80 with go. I bought a engine kit a while while and today I split the engine cases and installed the rotating assembly. Slapped it back together, and discovered the little end of the con rod is different. E36 M3. Check the part number for the kit. It's the wrong year. Double E36 M3. Ok still a week and a half till Christmas, get the right kit. Nope, unobtainium. E36 M3 berkeley. So I want to keep the new bottom end as its together now. I can reuse the old piston in the short term but I need to match the con rod bearing and wrist pin. That means enlarging the wrist pin bore slightly. That will be easy but I will not be able to use the circlips. Rather than remachine the slots I thought to use Teflon buttons. I have no experience with them. Are they a press fit? Loose? machined to match the piston curve? Long and short is can I find some Teflon and make some buttons and if so, how?

Thanks

Most of the full floating wrist pins I've dealt with are just semi spherical caps that are semi snugly pushed onto either side of the pin. The ones on aircraft generally I can just push out along with the wrist pin with a finger. The caps on those engines didn't fit into the wrist pin either from what I remember. It's been a number of years though.

Oddly I found a link to a thread we had a while ago about Teflon buttons.

Air cooled VWs use Teflon bushings all the time; pretty much look like little mushrooms with stems that fit inside the pins and domed tops.

Hey thanks for the link. My questions are answered. Except, any oiling issues with plugging off the ends o the bore?

If there aren't any holes in the wrist pin for oil, then the buttons shouldn't affect oiling.

I'd be concerned about the ports (especially transfer ports) and if the buttons would catch on the edges.

The sharp edges of the ports may shave down the buttons or catch on them if any air trapped in the wrist pin pushes out on them as things heat up.

Pretty simple motor. I think just the main port with no power valve.

Yes as others have said they are tight fitting mushrooms but before you go trying to fudge it together what year piston do you need to do it right? and are you sure the pin height is the same? many times they change the wrist pin size along with a change in pin height to keep people from making this same mistake and crashing the head or have the piston sit below deck.

I've got BOXes of pistons in stock still from my home based shop long closed up...but I still buy left over inventory to sell from a couple dealers.

When they came out about 30 years ago, I saw some Harley motors built with them. They failed. As in not there anymore and the wrist pin walking out into the cylinder wall fail. Maybe they are better today, as with the way they were working out then, I can't see why anyone would have them anymore otherwise.

http://bacomatic.org/~dw/engine/BOSSbtns/bossbtns.htm

bearmtnmartin wrote: Pretty simple motor. I think just the main port with no power valve.

I would double check, to make sure none of the ports will interfere with the buttons.

Even the simple 2 strokes have ports at the bottom of the cylinder to move the air/fuel from the crankcase to the cylinder.

Most of the time those ports are on the side of the cylinder where the Teflon buttons might contact.

Maybe drill and insert a pin across the end of the wrist pin (not through the wrist pin) and then pene the hole over so the pin can't come out.

I have the motor apart on the bench. I just can't remember the port arrangement until I go out and have a look. If there are ports on the side then it most likely won't work, so thanks for pointing that out.

I have the help of a pretty amazing machinist so I am going to run the parts over tomorrow morning to see what he thinks.

44Dwarf wrote: Yes as others have said they are tight fitting mushrooms but before you go trying to fudge it together what year piston do you need to do it right? and are you sure the pin height is the same? many times they change the wrist pin size along with a change in pin height to keep people from making this same mistake and crashing the head or have the piston sit below deck.

This right here, don't get ahead of yourself.