New gas cap won't close

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htown16

htown16

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If you fit a new ceandess gas cap and you can't get it to close here is the problem. The spacer between the cap and the plate with the rubber ring is too long. The one the right is from the old cap and the one on the left from the new. Simply swap them and problem solved. Actually found this out on my BSA but same principal on the Norton. Lets not turn this into a rant on pattern parts. Sometimes they are all you can affordably source and you gotta deal with what you have. Hope this helps someone out.
New gas cap won't close
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Too long or possibly too hard?


Please no "That's what She said" jokes ;)
 
Too long, similar hardness. It wasn't missing latching by much, maybe an 1/8 of an inch.
 
I have a question on caps as i need to purchase one.... the filler neck has a small diameter inner horizontal face. Above this is a larger diameter horizontal face..
Does the cap have two sealing plates one for the small inner & another for the larger outer
Or dos it only seal on one???
 
My Ceandess cap seals across the top face... all good if the rubber washer is the correct material and the tank is baffled (I had a repro which wasn't.. lap full of 4 star if filled too much!)
Matchless wing nut types as per P11 seal on the lower face//
 
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If I understand your question olympus, one is the top of the tank and the other is the top of the welded on bung. It only seals on the bung top surface.
 
EstuaryBoy said:
My Ceandess cap seals across the top face... all good if the rubber washer is the correct material and the tank is baffled (I had a repro which wasn't.. lap full of 4 star if filled too much!)
Matchless wing nut types as per P11 seal on the lower face//
Click to expand...
Not sure I agree with that...the Ceandass cap on Commandos and other bikes/cars (Triumph TR6. Jags etc) all have the same design. There is a vent to allow pressure to equalize as fuel flows out the tank via the petcock(s). Any sloshing of fuel up at the cap needs to be fully sealed at the large diameter lip seal. That sealing force depends of both the spring (to a lesser extent) and the rubber tube piece (to the greater extent). When my original cap was leaking at anything above 3/4 full tank, I renewed the rubber tube bit with fresh fuel hose (large seal was already new)....the amount of force needed to clip the tank shut has gone up considerably and it has solved all the leaks from slosh, even when tank fully topped up.
 
If the rubber seal is not 'poison petrol' proof (ie: 'cheap' copies) they can (and do) distort and stretch, so no amount of pressure or force will get a good seal when metal meets metal (been there... had that!)
On the unbaffled tank, I pushed a length of supermarket petrol can nozzle into the filler neck.. no more leaks :-)
 
From what I'm reading a genuine Cesndass cap is the way forward... but even with this leakage can occur..
It seems a pity no one has looked at designing an seal system to use both the small & large diameter seal faces
 
I'm sure genuine Ceandess are fine (mine is no problem at all), but 'pattern' parts or spares may well disappoint, but we all know that anyway :-)
 
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