Bike needs a lot of effort to kick over.

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Joined: Wed Sep 01, 2004 12:00 am

Re: Bike needs a lot of effort to kick over.

Postby SPRIDDLER » Thu Apr 04, 2019 8:24 am

Hi Scott. At this distance it's only guesswork (and it's a more or less 'unknown' engine) but certainly eliminate that it isn't only a g/box or clutch issue.
In my experience it's unusual for main bearings to seize, break up or become stiff. Likewise the big end unless (heaven forbid) the crank pin has broken. Bikes have still run with a broken crank pin. However, whilst the engine is still in the bike and before substantial engine stripping I would remove the oil pump plunger because its drive scroll on the timing side axle and the splines on the plunger (marked up pic below) can become worn or damaged and could cause jamming, a grinding noise or stiffness.

Also, while the engine is still in the bike examine the valve driving gears/cams. Note how the gears are lined up with the mark on their driving pinion before removing them.
It's unlikely but possible that the piston top is damaged and a ring has partially escaped from its groove but that's pure conjecture and obviously you will see that when you remove the cylinder barrel (AFTER stuffing the crank case mouth with rag to prevent any broken bits falling into the engine's nether regions).
EDIT - Check the magneto and dynamo for stiffness/grinding noise!!

Here you can find original Workshop and Owners Manuals, plus illustrated parts lists under 'Books'.

Here is an article on stripping and rebuilding a Heavyweight single engine which you will find a great help: ... hanics.pdf

I suggest you subscribe to this site (join the Club) as not only is your time as a 'Guest' limited but as a member you will have access to much more info and help.
I poke badgers with spoons.

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Location: KENT UK

Re: Bike needs a lot of effort to kick over.

Postby alanengineer » Thu Apr 04, 2019 11:49 am

check all of the chains for tension and condition before taking big bits off. Simple and quick. Must have a bit of slack in all three.

Dont forget the Christian's Archive for info

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Joined: Mon Jan 01, 1990 12:00 am

Re: Bike needs a lot of effort to kick over.

Postby bodgert » Thu Apr 04, 2019 2:32 pm

What primary drive ratio are you using A small engine sprocket makes it harder to turn Bodger


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