Flat top or dommed

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Flat top or dommed

Postby willowbedone » Mon Jan 07, 2019 6:56 pm

I've been looking though the g 80 forum and would like to know if my 1956 g80 should have a dommed or flat top piston

Thanks ian

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Re: Flat top or dommed

Postby spookefoote1956 » Mon Jan 07, 2019 7:21 pm

If you look on the feked site you will see that the 56 model was a change over year and the piston is different to previous years. I know this because mine is a 56 and it has a slight dome.

https://www.feked.com/jp-pistons-for-ajs-18-500cc-or-matchless-g80-500cc-1956-59.html

Cheers, Chris
हरे कृष्ण हरे कृष्ण
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!

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Re: Flat top or dommed

Postby willowbedone » Mon Jan 07, 2019 7:34 pm

Thanks Chris that answers my question I am in process of setting ignition timing Would you know if I measure from top of dome on piston or flat part on outside to set it back 1/2 inch
May sound weird but I think I've confused myself :headbang:

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Re: Flat top or dommed

Postby willowbedone » Mon Jan 07, 2019 8:37 pm

A rush of Blood 1/2 inch before tdc or 39% before
I think I'll return to the garage and time it in the morning

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Re: Flat top or dommed

Postby clive » Mon Jan 07, 2019 9:04 pm

willowbedone wrote:Thanks Chris that answers my question I am in process of setting ignition timing Would you know if I measure from top of dome on piston or flat part on outside to set it back 1/2 inch
May sound weird but I think I've confused myself :headbang:



Doesn't matter so long as you use the same point to measure the half inch from.
clive
if it ain't broke don't fix

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Re: Flat top or dommed

Postby spookefoote1956 » Mon Jan 07, 2019 9:05 pm

Just chuck your rod (ooer!) down the hole (ooh matron!) held against the thread. Find tdc then roll back 1/2". Don't worry about domes, just stick to 1/2" before.

Cheers, Chris
हरे कृष्ण हरे कृष्ण
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!

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Re: Flat top or dommed

Postby cfaber » Tue Jan 08, 2019 7:05 am

Anyone else see this and at first glance read Flat or doomed? :rofl:
Fix it until it's broken!

Otherwise how will
anything get done?

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Re: Flat top or dommed

Postby raffles » Tue Jan 08, 2019 7:23 pm

Only private Frazer
Tony

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Re: Flat top or dommed

Postby ajscomboman » Tue Jan 08, 2019 7:46 pm

raffles wrote:Only private Frazer
Tony


Wouldn't be referring to me would you Tony? :rofl: :rofl:

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Re: Flat top or dommed

Postby 56G80S » Wed Jan 09, 2019 2:21 pm

Is that Dick & Dom'd?

I'm an idiot and am only here for the money?

Johnny B

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