Sun Sep 26, 2021 3:07 pm

Hooked
1964 Piaggio Allstate Cruisaire
Joined: 15 Aug 2021
Posts: 475
Location: York, PA
 
Hooked
1964 Piaggio Allstate Cruisaire
Joined: 15 Aug 2021
Posts: 475
Location: York, PA
Sun Sep 26, 2021 3:07 pm linkquote
Should be pointing down towards the exhaust port on a VNB5m - 125cc, correct?
Sun Sep 26, 2021 3:53 pm

Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '04 Ninja 250
Joined: 04 Apr 2013
Posts: 6217
Location: San Diego, CA
 
Veni, Vidi, Posti
'15 GTS300, '86 PX125EFL, '66 VBB, '04 Ninja 250
Joined: 04 Apr 2013
Posts: 6217
Location: San Diego, CA
Sun Sep 26, 2021 3:53 pm linkquote
Yes towards exhaust port
Sun Sep 26, 2021 4:04 pm

Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2922
Location: Rochester, Minnesota
 
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2922
Location: Rochester, Minnesota
Sun Sep 26, 2021 4:04 pm linkquote
If it's like most motors the exhaust side, shouldn't have a piston port on the exhaust side. Just in case it's one of those pistons with an arrow in the wrong direction.
Sun Sep 26, 2021 4:16 pm

Molto Verboso
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: 04 Jul 2011
Posts: 1336
Location: Tucson, AZ
 
Molto Verboso
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: 04 Jul 2011
Posts: 1336
Location: Tucson, AZ
Sun Sep 26, 2021 4:16 pm linkquote
Yes, towards the exhaust spigot but also another giveaway would be the ports matching on the cylinder wall and the pistons. Considering that the piston can only be mounted in one direction or another direction being 180 degrees then look at the ports besides the arrows.
Sun Sep 26, 2021 4:30 pm

Banned
2:6
Joined: 11 Jan 2007
Posts: 8217
Location: San Francisco
 
Banned
2:6
Joined: 11 Jan 2007
Posts: 8217
Location: San Francisco
Sun Sep 26, 2021 4:30 pm linkquote
I always put a sharpie mark on the top of the piston where the ring pegs are. If that mark overlaps a port then bad things will happen.

belt and suspenders...
Mon Sep 27, 2021 8:51 am

Hooked
1964 Piaggio Allstate Cruisaire
Joined: 15 Aug 2021
Posts: 475
Location: York, PA
 
Hooked
1964 Piaggio Allstate Cruisaire
Joined: 15 Aug 2021
Posts: 475
Location: York, PA
Mon Sep 27, 2021 8:51 am linkquote
Ok, I am still struggling with this concept, mostly due to the fact that I already reassembled the top end after a ring and stud job and can't physically look at the ports and the top of the piston. I didn't remove the piston. What I remember is that the the arrow was pointing up when installed in the scooter and the ring pins were on the bottom, toward muffler. This is a 2 port OEM cylinder.

I'm screwed and have to take it apart and flip the piston correct?
Mon Sep 27, 2021 10:24 am

Banned
2:6
Joined: 11 Jan 2007
Posts: 8217
Location: San Francisco
 
Banned
2:6
Joined: 11 Jan 2007
Posts: 8217
Location: San Francisco
Mon Sep 27, 2021 10:24 am linkquote
I'd pull the head off and confirm the arrow. if it is pointing away from the exhaust, then pulling the cylinder would be the next step.
Tue Sep 28, 2021 4:00 am

Hooked
1964 Piaggio Allstate Cruisaire
Joined: 15 Aug 2021
Posts: 475
Location: York, PA
 
Hooked
1964 Piaggio Allstate Cruisaire
Joined: 15 Aug 2021
Posts: 475
Location: York, PA
Tue Sep 28, 2021 4:00 am linkquote
I took the top end apart and sure enough, someone in the past 60 years put the piston in with the arrow facing up. Humorous note (it's funny now, after I cooled down), right next to the arrow was written "SCARICO". The Italian word for EXHAUST!

Tue Sep 28, 2021 3:39 pm

Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2922
Location: Rochester, Minnesota
 
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2922
Location: Rochester, Minnesota
Tue Sep 28, 2021 3:39 pm linkquote
On a 2 port motor, how misaligned were the two transfer ports? With no boost port to open up to the exhaust, wondering how bad it could be.
Tue Sep 28, 2021 4:30 pm

Banned
2:6
Joined: 11 Jan 2007
Posts: 8217
Location: San Francisco
 
Banned
2:6
Joined: 11 Jan 2007
Posts: 8217
Location: San Francisco
Tue Sep 28, 2021 4:30 pm linkquote
Christopher_55934 wrote:
On a 2 port motor, how misaligned were the two transfer ports? With no boost port to open up to the exhaust, wondering how bad it could be.
engine will run, exhaust is covered by the skirt...


but risk snagging the end of the rings in the exhaust port
Tue Sep 28, 2021 4:35 pm

Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2922
Location: Rochester, Minnesota
 
Ossessionato
2007 Stella 225
Joined: 02 Nov 2019
Posts: 2922
Location: Rochester, Minnesota
Tue Sep 28, 2021 4:35 pm linkquote
oopsclunkthud wrote:
engine will run, exhaust is covered by the skirt...


but risk snagging the end of the rings in the exhaust port
Ahh, wasn't thinking about ring ends.
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