Piston problems Model C

pictures (or stories) of hideous injuries sustained by your ariel
M.Bagshaw
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Piston problems Model C

Postby M.Bagshaw » Sun Sep 15, 2019 8:23 pm

Rebuilt bike a couple of years ago, set of this morning on a run 18 miles in piston nipped up! Been running great, plenty of oil?
P1010781.JPG

JohnnyBeckett
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Re: Piston problems Model C

Postby JohnnyBeckett » Sun Sep 15, 2019 9:45 pm

is it Runing to rich and washing the oil off the boor or is the timeing out

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brenton.roy
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Re: Piston problems Model C

Postby brenton.roy » Sun Sep 15, 2019 10:56 pm

The pitting on the crown suggests it was burning really hot. Lean?
It's not easy to jet the mains as we tend not to ride at big throttle openings.
'51,'56 Squares, '48 VH, '27 Model C, R67/2, Mk IV Le Mans, '06 Super Duke and Ariel projects.

nevhunter
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Re: Piston problems Model C

Postby nevhunter » Mon Sep 16, 2019 12:29 am

Insufficient clearance It looks like. Perhaps the day was a bit warmer or your riding a bit more enthusiastic than normal. It takes thousands of miles to wear a bit of extra clearance on the piston and sometimes a piston will "grow " slightly. Don't file off the "heavily"dragged areas, they will already be undersize most likely. It's also a good idea to relieve under the lower ring and drill a few holes at an angle through the skirt. (NOT in the ring groove). A bit of two stroke in the fuel, doesn't hurt either. An egg cup to a tank of fuel is enough. Nev

john.whiting
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Re: Piston problems Model C

Postby john.whiting » Mon Sep 16, 2019 3:24 am

Insufficient,or deficient cam relief,if you ask me .....in fact it looks like the piston is just plain round ,with no taper,and no cam.....there was similar one pictured a few weeks ago,and I thought the same thing then........if you are going to use a round piston,give it plenty of clearance...like .006-.008........are both sides the same?.....the rod may be bossing in the piston and forcing it over.....ie crank not centred.

M.Bagshaw
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Re: Piston problems Model C

Postby M.Bagshaw » Thu Sep 26, 2019 9:26 pm

Thanks for your suggestions, but its none of the above, with the exception of perhaps being a little too enthusiastic!
Barrel being lightly honed then its back together for another go.


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