105 piston

[600srad]

Hi Guys, i dont suppose any body either has a picture of their OS105 with the backplate off, or would be willing to whip their backplate of said engine and let me know which side the cut outs in the piston skirt face, either towards the opening or torwards the bearing.
Im having a total brain fart on this, i know the piston ring pin should be away from any ports, but either way seems to see this pin away from the ports.
Cheers Ian.

[waveydavey]

The tapered cut goes towards the bearing, the straight cutouts are towards the backplate.

[Kiwi64]

Hi Guys, i dont suppose any body either has a picture of their OS105 with the backplate off, or would be willing to whip their backplate of said engine and let me know which side the cut outs in the piston skirt face, either towards the opening or torwards the bearing.
Im having a total brain fart on this, i know the piston ring pin should be away from any ports, but either way seems to see this pin away from the ports.
Cheers Ian.

Just checking mine now !
image.jpg

[rachel]

Look at the top of the piston , crank nut is at 12 o'clock , piston ring pin is at eleven o'clock :-)
also remember to ensure slot in back plate is at the top , and always remove refit , the backplate with piston at tdc .

[bladeboy400]

Hey guys
I have two pistons let the ring retaining pin go now ! it has ballsed up the piston and ring this time and bounced on the top of the cylinder why do these keep letting go ? is it running temp? is the engine to lean allowing the pin to be loose?

[waveydavey]

No just badly designed John. I sent mine back to ripmax after the 2nd one went and they replaced FOC. I emailed Japan and Ripmax got in touch with me. I think what happens is that the con rod gets a little slop in it and the piston rotates slightly wearing the pin against the harder ring. The pin is a 1mm roll pin so is very thin. Peter the guy I dealt with was going to feed back the problem and I linked to some threads on other forums but I never heard anything.

Go for it mate, get in touch with Japan and Ripmax and give them some shit as they've never fixed this issue.

e-info@os-engines.co.jp

[bladeboy400]

yeah i have two regulators with ripmax at the moment Dave, the guy there is ok but os do not sell the diaphragms separately but they will refurbish at the factory ??? the guy at ripmax is helpful and going to send them straight to the factory, I think its absurd. what a waste of time. I think i will send the whole engine as it funned the head by pitting it, and the ring, i only changed them four weeks ago !!!

[waveydavey]

How old is the engine John, if you change the piston and ring make sure to change the con rod too.

[jwatts007]

Its more likely caused by them holes around the top of the piston...forcing fuel through them pushing the ring out in out shake it all about...and the pin gets hammered in...crap design I had it happen with the 90 HZ...
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