crankshaft locking up

Anything related to Vespas... ask tech questions, post helpful info, or just read and learn.
Eddie15b
registered user
Posts: 21
Joined: Sat Jul 14, 2012 9:35 pm
Main scooter: gp200e
Contact:

i am restoring an old T5 classic and have taken out the engine
striped it and cleaned it up and using the scooter techniques DVD
replaced the bearings and cruciform
however when i put together the two halfs of the engine
and tighten up the bolts the crankshaft locks up and wont turn

any suggestions as to what im doing wrong?

as im sure the crankshaft itself is true
RGC GEOFF
registered user
Posts: 24
Joined: Tue Jan 05, 2016 8:08 pm
Main scooter: Vespa GTr BGM 190
Contact:

it could be one of the two masses that has moved if the crankshaft fell to the ground for example. Make sure the 2 masses of the crank are parallel. Use a comparator (crankshaft gauge ?)

Sometime it can just be 1mm move and you just need a copper hammer without rebound

Image

Image

Image
Built not bought...
Eddie15b
registered user
Posts: 21
Joined: Sat Jul 14, 2012 9:35 pm
Main scooter: gp200e
Contact:

okay thanks for that will have a look as the
engine has been lying in a box in bits for a good
few years and has been moved about a lot

can you pull in the crank too far on the bearing
on the main engine side? as when the halfs are bolted together
the crank web to engine casing gap seems lopsided
RGC GEOFF
registered user
Posts: 24
Joined: Tue Jan 05, 2016 8:08 pm
Main scooter: Vespa GTr BGM 190
Contact:

No you can't, but a possible issue is that your oil seal on the main bearing is not pressed enough and then it can block the crank.
Built not bought...
Eddie15b
registered user
Posts: 21
Joined: Sat Jul 14, 2012 9:35 pm
Main scooter: gp200e
Contact:

do you mean the big strange looking metal oil seal on
the main engine block side?
also is it ok to tap out the crank (gently) with a hammer
or will i have to get a dedicated extractor?
RGC GEOFF
registered user
Posts: 24
Joined: Tue Jan 05, 2016 8:08 pm
Main scooter: Vespa GTr BGM 190
Contact:

the oil seal must be absolutely its case absolutely flat
Image
Built not bought...
Eddie15b
registered user
Posts: 21
Joined: Sat Jul 14, 2012 9:35 pm
Main scooter: gp200e
Contact:

yes thats the one
i will get onto it tomorrow and see what i can find
thanks
Eddie15b
registered user
Posts: 21
Joined: Sat Jul 14, 2012 9:35 pm
Main scooter: gp200e
Contact:

stripped the engine down and i think your right with
the seal lip not being totally flush so its now tapped in flush
had a look at the crank and it seems to be true enough but its
not easy to be certain seen as the webs are different diameters
to each other
also made sure when i was drawing it into the main bearings
that it was square coming into the housing and was not rubbing
anywhere and have left it backed off a millimetre from
being fully seated to give me some room to play with

ill have to leave it for now till i get a new engine gasket as the
existing one ripped when splitting the engine...... :roll:
RGC GEOFF
registered user
Posts: 24
Joined: Tue Jan 05, 2016 8:08 pm
Main scooter: Vespa GTr BGM 190
Contact:

when you install your casing gasket use some grease so when you have to split the cases, the gasket is still ok ;)
Built not bought...
Eddie15b
registered user
Posts: 21
Joined: Sat Jul 14, 2012 9:35 pm
Main scooter: gp200e
Contact:

i did that as per the ST dvd but it still split....

all part of the learning curve i suppose

will update when a new gasket arrives
Post Reply Previous topicNext topic
  • Information
  • Who is online

    Users browsing this forum: No registered users and 5 guests