Vintage moped case seal overhaul

#1
I have a vintage 1958 dated Rex Monaco 2-stroke moped in good working condition but which is very slowly leaking oil from the gearbox. The chances are that it never had any seals replaced in its working life (it still had it original spark plug when I got it) and since it isn't one of the mainstream or classic brands the chance of finding an original or reproduction gasket or seal set for the engine case is slim to none (and I have tried).

One though was to cut out a gasket manually from sheet of appropriate gasket material but I was also thinking of using a curing sealant like Curil or Curil T to do the job. Any recommendations?



The manual 3 gear shift took a bit of getting used to but it's great fun for pootling about in the valley.
 

Tyk

War Hero
#2
Personally I'd stay well away from the sealing compounds, especially with a vintage engine and gearbox you really don't know how the compounds will react with the metals, nor how any that got loose inside the casings would screw things up.
I'd be looking for suitable gasket materials and researching the original approaches they took, it may even be possible to find templates online. That or the old expedient of careful tracing and then cutting out with a sharp Stanley blade.
 
#6
Trace out the old one using a cornflake box, cut carefully, Get your sheet of material, gasket paper, cork sheet, felt sheet, whatever, lay flat with the cut out over it and even more carefully trace and cut the gasket to fit. If the old one disintegrates, you will have to do a rubbing of one side of the box using paper instead of tracing round the old one..
 

skid2

LE
Book Reviewer
#9
I'd go old school with the gasket set. You don't want it to be too sealed, it may not be able to breathe properly. ( or leak)
 
#11
Lots of the old gaskets were cork. All the one on my tractors are. I use a cork tile and hand press it on to get the outer shape and a scalpel\craft knife to fashion the inside....
 
#15
If you are going to be a good mechanic you've got to put away childish things. One of these things is using gasket cement everywhere. Gaskets are made to expand just a little when oil hits them. This makes a good, oil tight seal. If your sealing surfaces are smooth and you have a new gasket, you simply do not need gasket cement. A real sign of an amateur is lots of slobbery gasket cement. So do you put the gasket on dry? No, you use plain ordinary wheel bearing grease. I use grease on all new gaskets except the ones that come from the factory with a special coating already put on. The grease serves several functions.
To make a gasket simply lay a piece of gasket material on to the part, like a clutch cover or cylinder. Take the ball end of a Ball Peen Hammer and tap along each edge gently. You will find this cuts the pattern of the part into the gasket. It helps if you have a set of hole punches too. If you are careful you can make a fairly complicated gasket. It can take quite a bit of time. All in all, just buy them.

Taken from Dan's Motorcycle Gaskets may be of help
 
#17
Trace out the old one using a cornflake box, cut carefully, Get your sheet of material, gasket paper, cork sheet, felt sheet, whatever, lay flat with the cut out over it and even more carefully trace and cut the gasket to fit. If the old one disintegrates, you will have to do a rubbing of one side of the box using paper instead of tracing round the old one..
Other breakfast cereal boxes are available.
 
#18
Thanks for the advice Anglo. I am a tinkerer not a trained mechanic, hence my dipping into the fountain of knowledge that is arrse.

I'm still stumped on the proper thickness to use.
Reassemble it without the gasket, obviously the outer casing will be slack. The max spacing between the case and the body is the minimum thickness you need for the gasket, without changing the bolts.
 
#19
Thanks for the advice Anglo. I am a tinkerer not a trained mechanic, hence my dipping into the fountain of knowledge that is arrse.

I'm still stumped on the proper thickness to use.

Thickness depends if any shaft spacing needs to be taken into account, best you find a motorbike workshop and talk to the old bloke who works in the back,or talk to the local motor bike gang, they will tell you the best repairer in the area. most of them will give you good advice
 
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#20
Thickness depends if any shaft spacing needs to be taken into account, best you find a motorbike workshop and talk to the old bloke who works in the back,or talk to the local motor bike gang, they will tell you the best repairer
in the area
Its a moped, theyll take the piss....
 

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