A little lean at the top end?

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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StephenG80
Posts: 264
Joined: Sun Apr 30, 2017 10:42 pm
Location: ARGYLL UK

A little lean at the top end?

Post by StephenG80 »

Took my '54 -G80 out for spin having sorted out the mag timing and also fitting a brand new mono block carb sourced from AMOC spares. Went really well, but after a quite a hard climb at large throttle opening for a about 3 miles on A roads - maintaining about 50mph, when throttling off completely and running under no power entering a 30 zone, the engine died, a blip of the throttle brought it back straight away - just wonder if this might be due to her getting too hot due to being a bit lean at wide throttle openings? Spares supplied a carb with correct slide, jets , needle etc for the bike - should I put the needle up a groove, any suggestions?
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Expat
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Joined: Thu Nov 12, 2015 2:22 pm
Location: Tennessee, USA

Re: A little lean at the top end?

Post by Expat »

Hello Stephen,

I was concerned how my G3 was running so did a 'plug chop' ie ran at full throttle for 1/4 mile or so then cut the engine, coasted to a stop and took a look at the colour of the plug.

You want to see a nice chocolate brown colour. Very pale or white plug ceramic insulator would indicate a weak mixture.

I ended up reducing the main jet size as there is an air filter on the bike.

You could raise the needle but personally i would do a chop first. :)

Regards,

Steve
Keep shiny side up.

These are my principles, if you don’t like them, I have others. (Groucho Marx)
Mick D
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Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: A little lean at the top end?

Post by Mick D »

Hi

How's the running at idle? maybe the idle is a little low and rapid deceleration was enough to momentarily starve the engine - try screwing in the throttle adjusting screw a little.

Regards Mick
StephenG80
Posts: 264
Joined: Sun Apr 30, 2017 10:42 pm
Location: ARGYLL UK

Re: A little lean at the top end?

Post by StephenG80 »

Thanks Mick and Steve - I'll look at both those aspects. :beer:
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