Leakdown test - Crank Float
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Joined: 26 Aug 2009
Posts: 6

Thu Feb 07, 2019 11:24 pm quote
I've replaced the seals on my stock p125x, and while performing a leakdown test afterwards i was surprised to find a leak on the flywheel side seal However, there is some lateral movement in the crank. when it is pushed to one side there is a leak but pushed to the other it holds pressure well.

Should there be any lateral movement in the crank? if so, how much is there a tolerance? does this indicate wear in the crank web? any ideas?
does the clutch fixing bolt draw it towards the clutch side.

only thing different i have done this time is used a cork case gasket which is slightly thicker than standard.

Molto Verboso
2005 PX150 In a Love-Hate Relationship with a 2-Stroke Vespa Since 2007
Joined: 01 Sep 2007
Posts: 1805

Sat Feb 09, 2019 8:37 pm quote
Iíve never heard of a cork case gasket. Usually itís just brown paper, as in brown paper bag. Slightly thicker are the premium blue-green impregnated gaskets Piaggio uses in new builds and available on an unpredictable basis from some Euro parts houses.

A cork gasket sounds significantly thicker to me and could be the cause of your float and leak.
Joined: 06 Oct 2018
Posts: 111
Location: Gravesend, Kent, UK
Sun Feb 10, 2019 5:13 am quote
Lateral float
Hello Rendo.
How much movement? Can you measure it with a rule or just about with a vernier depth gauge.
The crank should be a tight fit in the Clutch side bearing. This is a ball bearing race. The flywheel side is a needle roller bearing and will allow the shaft to slide in and out.

Iím afraid itís time for a strip down.
Molto Verboso
2005 PX150 In a Love-Hate Relationship with a 2-Stroke Vespa Since 2007
Joined: 01 Sep 2007
Posts: 1805

Sun Feb 10, 2019 3:17 pm quote
As mentioned, float is the big problem here. A new, carefully installed clutch-side bearing should allow zero float. If the bearing is worn or improper procedures have been inflicted on that side, thereíll be a small amount.

How much float is the question here.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6951
Location: Victoria, Australia
Sun Feb 10, 2019 5:28 pm quote
Plenty of scooters run ok with the flywheel visibly moving across when pulling the clutch. However if it's leaking as well then it's a bit of an issue.
There is a flywheel seal available that is double-lipped which may help. It's on SIP but not sure of the part number right now.
Team Scooter Trash for Petfinder Foundation   Vespa Wasp Pin Badges   AF1 Racing Vespa Austin
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