Leakdown test - Crank Float
Post Reply    Forum -> Not-So-Modern
Author Message
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: 1758

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: 58
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: 1758

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: 6594
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.
Rallies Europe 2016   Vespa Wasp Pin Badges   Cool Ass scooter seat cover
Post Reply    Forum -> Not-So-Modern
[ Time: 0.2212s ][ Queries: 23 (0.0363s) ][ Debug on ]