Rebored cylinder - new piston clearance (tolerance) - SS180
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SS180, Sprint 150
Joined: 03 May 2011
Posts: 43
Location: Croatia
Mon Jan 23, 2012 2:52 am quote
I need to bore the cylinder on my SS180 and I want to know the recommended bore dimension for "Pistoni Gol" piston size 62.6 mm.

I currently have Pistoni Gol 62.4 mm. Measuring on the top of cylinder (undamaged by piston rings), it is bored to 62.55 mm. I guess someone before me has bored to Nominal (62.4) + 0.15 (recommended for PX).

As far as I know (did it before on other Vespas), It should be about 0.15 mm on top of piston dimension on the bottom (measured 62.3 mm) - 62.45 mm. Please correct me if I'm wrong.

Does anyone have clearance dimensions for SS180? Thanks.
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'64 Motovespa 150S (177) , '66 Allstate SF, '65 VBB, '66 180SS
Joined: 27 Mar 2013
Posts: 866
Location: S.Salem, NY
Wed Sep 30, 2020 3:22 am quote
8 years later...
I , too, would like to know the answer to this. I am seeing numbers from .004 to .007. Just go with .005 ?
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'64 Motovespa 150S (177) , '66 Allstate SF, '65 VBB, '66 180SS
Joined: 27 Mar 2013
Posts: 866
Location: S.Salem, NY
Wed Sep 30, 2020 1:28 pm quote
.004
Enthusiast
Vespa 125 VMA, Vespa SS 180
Joined: 14 Feb 2018
Posts: 75
Location: Minneapolis, MN
Wed Sep 30, 2020 5:16 pm quote
I went .004 over when I had my SS180 cylinder rebored. It runs great. The ring gap was .38 mm, so I think I could have gone a little less, maybe .0035. But I would not go more than .004.
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GL, PK, PE200 with hack, Sears Rust Badge
Joined: 24 Apr 2012
Posts: 993
Location: Deep in the heart of Texas
Thu Oct 01, 2020 6:00 am quote
Calling Gickspeed!!!!! Calling Jon Gick???
I asked Jon this same question with a couple msgs. He was reluctant to respond but I called him, too. He told me he does this for a a living and did not really provide a direct answer. I told him my measurements and he said to go with what you got and that turned out to be WRONG and too tight. Guess he was upset I asked a question about something he made money from. I was in shock because of the advise provided to him on this forum and the business sent to him from this forum I'm sure made him money more then a few times. Reminds me of a graveyard sometimes.....take in but will not give out. He's not like that all the time but with that question he was to me. But all the time he can get free advertising on this forum.

Hope you can get a correct answer from somewhere. I think between .003 to .0035 maybe the range for clearance.
Good luck!
Addicted
'64 Motovespa 150S (177) , '66 Allstate SF, '65 VBB, '66 180SS
Joined: 27 Mar 2013
Posts: 866
Location: S.Salem, NY
Thu Oct 01, 2020 10:57 am quote
According to the factory service manual for the GS160, which is basically the same motor as the 180SS with a smaller bore, the size stamped on the piston is the exact size of the bore and the piston is sized accordingly. So, a 2nd OS piston stamped 62.4 is sized to fit a 62.4 mm bore. Easy ?
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