OP
UTC

Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 368
Location: St. Catharines, Ontario
 
Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 368
Location: St. Catharines, Ontario
UTC quote
Hey all,
I have the pleasure of rebuilding my px125e bike. Again.

I rebuilt it once. It ran like crap and was so noisy. Ended up needing a new crank.

Opened it back up. Noticed the clutch side seal was out of place. Ok I thought, the crank is shot so it probably threw the seal out of whack.

Rebuilt it with an experienced vespa mechanic friend. He and I reassembled and he looked over and triple checked my work.

I took the bike on a trip and it ran fine. Until it didn’t. Turns out that I blew a clutch seal.

So now I’m wondering why?!?
Every bit of the internals of that engine are new. So why are these seals being damaged?

Could it be the rotary pad? I noticed that it was a bit worn. My friend didn’t really make any comments other than “it’s fine”.

Could the worn (ish) rotary pad have been a contributing factor to blowing out the clutch seals?

I really don’t want to rebuild it a fourth time......

Thoughts? Speculations?

Thank you.
@108 avatar
UTC

Ossessionato
V range 50s
Joined: UTC
Posts: 2413
 
Ossessionato
@108 avatar
V range 50s
Joined: UTC
Posts: 2413
UTC quote
Doubtful it’s the rotary pad… that only really effects how good your engine is running.

Assuming your engine is mostly stock and the bearings are in really good shape (no play)

For the clutch side seal, I’d look at this list:

1. check it’s the right type of seal for the engine. Rubber vs metal. If there’s a groove next to the circlip, rubber seal, metal seals if there’s no groove

2. If it’s a metal seal, does it need grinding down so it sits flush to the cases? If not, it’ll pop out

3. Double check the distance between the seal and the bearing after it’s installed. Using a feeler gauge, it’s suppose to have 0.5mm distance at least. Again you’ll be grinding oil seals if not.

My guess is incorrectly installed seals or worn bearings
UTC

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: UTC
Posts: 4605
Location: London UK
UTC quote
Once the clutch side seals have fallen out a few times, all the standard seal practices don't work. The casings become non round and the hole tapered. If the seal was spinning and bouncing around for a while it does damage which is hard to see or measure. However, the game is not over.
Loctite 638 is essential to fill the gap. Whatever cases they are use a full rubber seal. And in extreme circumstances of major bagginess, there are many ways of making metal retaining clamps to hold the seal in.
Blue corteco and brown BGM are the tightest fit. I've saved many casings from the scrap yard over the years.
OP
UTC

Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 368
Location: St. Catharines, Ontario
 
Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 368
Location: St. Catharines, Ontario
UTC quote
Thank you for the replies folks.

Ive used the blue cortec seals both times. Rubber seals is what came out of the engine when I rebuilt it the first time. New bearings were installed.

I’ll use the feeler Gauge next time around and even the loctite to be sure.

Thanks again.
N
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