Sun Aug 07, 2022 3:27 pm

Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9A1T, V9B1T
Joined: 20 Jul 2018
Posts: 3904
Location: Staten Island, NY
 
Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9A1T, V9B1T
Joined: 20 Jul 2018
Posts: 3904
Location: Staten Island, NY
Sun Aug 07, 2022 3:27 pm linkquote
I'm having a strange problem installing the piston from this kit. Probably from the fact that I somehow lost the gudgeon pin circlips that came with the kit.

Luckily I had previously ordered many extra circlips after I lost ones on my malossi kit when they flew into the void of the universe.

I bought two thickness circlips at the time.. 1.17mm thick and 1mm (0.96 measured). Tried the thicker ones and noticed as soon as I put one side on and slid the pin in that those would be too thick and not able to get the second circlip in due to the thicker circlip installed pushing the pin over the slot for the second circlip.

Pulled that one out and installed the thinner circlip and it looked better with more room for the pin where I found see the slot for the second ring that time. But on install of the second circlip, it wouldn't seat into the slot because the pin was still just slightly blocking the slot and preventing the clip from seating.

Anyone with a vmc kit not installed yet, can you measure the thickness of your gudgeon circlips? Not sure how to proceed because I don't see circlips for sale except for the 1mm size I already have.

Only other thing I can think to try is to grind down the end of the pin a fraction of a mm just to get enough room to use the clips I have.
Sun Aug 07, 2022 3:43 pm

Addicted
Joined: 29 Nov 2020
Posts: 961
Location: Los Angeles
 
Addicted
Joined: 29 Nov 2020
Posts: 961
Location: Los Angeles
Sun Aug 07, 2022 3:43 pm linkquote
swiss1939 wrote:
I'm having a strange problem installing the piston from this kit. Probably from the fact that I somehow lost the gudgeon pin circlips that came with the kit.

Luckily I had previously ordered many extra circlips after I lost ones on my malossi kit when they flew into the void of the universe.

I bought two thickness circlips at the time.. 1.17mm thick and 1mm (0.96 measured). Tried the thicker ones and noticed as soon as I put one side on and slid the pin in that those would be too thick and not able to get the second circlip in due to the thicker circlip installed pushing the pin over the slot for the second circlip.

Pulled that one out and installed the thinner circlip and it looked better with more room for the pin where I found see the slot for the second ring that time. But on install of the second circlip, it wouldn't seat into the slot because the pin was still just slightly blocking the slot and preventing the clip from seating.

Anyone with a vmc kit not installed yet, can you measure the thickness of your gudgeon circlips? Not sure how to proceed because I don't see circlips for sale except for the 1mm size I already have.

Only other thing I can think to try is to grind down the end of the pin a fraction of a mm just to get enough room to use the clips I have.
Gimme a minute. I've got an extra in the garage...

True story:
Flung one of the clips into the garage nether. Ordered a new pair. Three weeks later a pair of the wrong diameter get delivered. Re-ordered pair got lost in transit in Frankfurt.

Took me 6 weeks to work out that flinging clip, which has now been found.
Sun Aug 07, 2022 3:58 pm

Addicted
Joined: 29 Nov 2020
Posts: 961
Location: Los Angeles
 
Addicted
Joined: 29 Nov 2020
Posts: 961
Location: Los Angeles
Sun Aug 07, 2022 3:58 pm linkquote
1mm x 16.5-17mm OD.

1mm for sure.
Sun Aug 07, 2022 4:16 pm

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '04 Ninja 250
Joined: 04 Apr 2013
Posts: 6233
Location: San Diego, CA
 
Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '04 Ninja 250
Joined: 04 Apr 2013
Posts: 6233
Location: San Diego, CA
Sun Aug 07, 2022 4:16 pm linkquote
I wouldn't hesitate to make that pin a bit shorter if the fit is so close.
Sun Aug 07, 2022 5:14 pm

Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9A1T, V9B1T
Joined: 20 Jul 2018
Posts: 3904
Location: Staten Island, NY
 
Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9A1T, V9B1T
Joined: 20 Jul 2018
Posts: 3904
Location: Staten Island, NY
Sun Aug 07, 2022 5:14 pm linkquote
Sounds like I'm going to have to grind the pin down cause my clips are thinner and still everything won't fit.

Thanks for the measurement!
Tue Aug 09, 2022 11:12 am

Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9A1T, V9B1T
Joined: 20 Jul 2018
Posts: 3904
Location: Staten Island, NY
 
Ossessionato
VSX, Stella 177, Stella 150, VNX1T, V9A1T, V9B1T
Joined: 20 Jul 2018
Posts: 3904
Location: Staten Island, NY
Tue Aug 09, 2022 11:12 am linkquote
Fix... grind the pin down slightly.


Original pin beveled ends.


grind the bevel down a bit.


here it is with still slight overhang on the clip groove.


clip still not sliding into the groove completely.


clip in the groove. Just the slightest section not fully seated. I might have to rip it out and give it another tap on the grinder to get the clips to seat with no issue. Just don't want to go too far and there be extra play inbetween the pin and clip.

Tue Aug 09, 2022 11:40 am

Hooked
Parmakit Primavera -74, Polini Primavera -68, Stock GL 150 -59, VMC 177 Bajaj Chetak 125 -95
Joined: 22 Jun 2022
Posts: 217
Location: Finland
 
Hooked
Parmakit Primavera -74, Polini Primavera -68, Stock GL 150 -59, VMC 177 Bajaj Chetak 125 -95
Joined: 22 Jun 2022
Posts: 217
Location: Finland
Tue Aug 09, 2022 11:40 am linkquote
I would not be too concerned about a gap between clip and the pin since there are no forces in lateral direction. Too tight would be an issue though as you pointed out and might cause the clip to jump out and ruin your cylinder. A small gap would also leave some room for slight expansion of the pin when the engine warms up.
Tue Aug 09, 2022 4:28 pm

Addicted
Joined: 29 Nov 2020
Posts: 961
Location: Los Angeles
 
Addicted
Joined: 29 Nov 2020
Posts: 961
Location: Los Angeles
Tue Aug 09, 2022 4:28 pm linkquote
"If I were you" I'd try to restore that bevel, rather than grinding more flat. Pin pressure against the C-clip will better keep it seated.

I can confirm there is (vibration?) pin pressure against that clip. I slightly bent a clip while installing, and didn't orient the ends in the direction of the piston travel as recommended (looked like your pic, pretty much). Piston rattle and tear-down later I found the clip barely hanging on. It was still there thank god, sitting outside of the groove.
Tue Aug 09, 2022 9:16 pm

Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 2187
Location: Siam
 
Ossessionato
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 2187
Location: Siam
Tue Aug 09, 2022 9:16 pm linkquote
I'd suggest stop using the grinder and use a hand file to finish it. The best would be a lathe.
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