Seized up

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Seized up

Postby willowbedone » Sun Apr 22, 2018 6:18 pm

Last week whilst enjoying a forty miles plus run my g12 it tightened up I had to pull in the clutch coast to a halt let it cool down then it started and runs fine It was the hottest day this year But surely this should not have happened Any idea as to why please The engine was really hot When I stopped

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Re: Seized up

Postby Rob Harknett » Sun Apr 22, 2018 7:19 pm

Any history??? Was the bike OK prior to this particular run?? Does it have manual AR you are not accustomed to ? Simple fault may be timing. A bike will run a bit hot retarded, at correct timing, once warmed up the AR lever should be set fully advanced. Also if retarded speed would also be slower.

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Re: Seized up

Postby Duncan » Sun Apr 22, 2018 7:47 pm

A couple of possible thoughts:

Has the bike been re-bored with insufficient clearance?

Has the petrol tank been relined with a product that is breaking down, this can block fuel taps and the carb leading to lean running as can a blocked filter on the carb, also failing tank sealant can block jets as the fuel evaporates .

Could there be an air leak on the carburettor flange?

Is the ignition timing correct and the grade of spark plug correct, what colour is the sparkplug?

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Re: Seized up

Postby MalcW » Mon Apr 23, 2018 9:36 am

You probably did this first, but as well as the excellent suggestions above, another thing to check is that you have sufficient oil, and it is circulating OK. How fast were you going at the time?

Malc

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Re: Seized up

Postby willowbedone » Mon Apr 23, 2018 6:50 pm

Today I removed the sump bung expecting the worst But no swarf or metal just clean oil I checked the carb jet needle possition and set it as per workshop Manuel (it was one notch to low ) The bike started ist kick runs sweet and done 30 odd miles with no problems

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