G80 Riding Impressions

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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G80 Riding Impressions

Postby Iron Head » Sat Nov 17, 2018 9:34 pm

Got a couple of hundred miles of riding on the ‘48 now and am very pleased with her. Managed to stop the float sticking and starting is excellent now. Although I’m running it weekly, wet-sumping seems to have disappeared. Amazingly my bottom end (or whatever) bearing rumble seems to have improved markedly but it’s probably just me getting used to it?!

Is the grease-filled Burman CP reasonably slow on changing - I don’t know what to expect from the box but it doesn’t like to be ‘hurried’ but changes perfectly under a more old school changing method.

Controversial, I believe, but I appear to be getting great results from running a long reach NGK iridium plug and great exhaust colour even with occasional blue smoke whilst the new rings bed in.

Bike is a joy to ride and much kinder to my back than my cafe racer-style ‘68 Wards Riverside 350!

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Re: G80 Riding Impressions

Postby Rob Harknett » Sun Nov 18, 2018 12:00 am

Grease will take a while to warm up. If your bike should have a short reach plug I would stick to that. Pistons can get holes burnt in them.

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Re: G80 Riding Impressions

Postby spookefoote1956 » Sun Nov 18, 2018 12:37 pm

Can grease be put in a B52 box and if so what sort and how do I know it's at the right level?

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Re: G80 Riding Impressions

Postby dave16mct » Sun Nov 18, 2018 3:18 pm

You can put grease in a b52 box. You need a semi fluid grease such as Castrol Spherol. You can warm it up and pour it in like oil or pump it in through a modified drain plug with modern grease nipple. I've got one if you want to borrow it. The level isn't critical, you can see when it's near the level plug.
But I would leave the straight 50 oil in. If it leaks, fix it. It's a much nicer gearchange with oil in. I did it a while ago and regretted it. I didn't like the slow clunky change with the grease.
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Re: G80 Riding Impressions

Postby Iron Head » Fri Nov 30, 2018 5:10 pm

Rob, I've put a short reach NGK BR7HIX in the bike and I must admit starting is better and running is smoother vs the long reach. It's a while since I did the top end rebuild but it has a period Hepolite domed piston and the long reach might have been running a bit near to the piston crown during ignition. I measured with copper wire and the plug tapping in the iron head is definitely short reach length (i.e. 1/2").

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Re: G80 Riding Impressions

Postby robcurrie » Fri Nov 30, 2018 8:10 pm

Beware of fitting long reach plugs in ally heads designed for short reach - carbon could build up on the exposed end and might damage the thread in the head when the plug is unscrewed.

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Re: G80 Riding Impressions

Postby Pharisee » Sat Dec 01, 2018 2:40 pm

robcurrie wrote:Beware of fitting long reach plugs in ally heads designed for short reach - carbon could build up on the exposed end and might damage the thread in the head when the plug is unscrewed.

Rob C


And vice versa... Put a short reach plug in a long reach head and you will get carbon build-up in the lower threads in the head. If you then screw in the correct long reach plug, it will probably jam and damage the lower threads in the head.

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Re: G80 Riding Impressions

Postby clive » Fri Dec 07, 2018 10:36 pm

But you are unlikely to damage an iron head as should be fitted to a 48 single! Mind you i could not guarantee that a long reach plug in a head designed for a short reach plug would be clear of the piston.
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Re: G80 Riding Impressions

Postby spookefoote1956 » Sat Dec 08, 2018 11:53 am

I do quite a good G80 riding impression. I sit on the end of the sofa with my lid on and a fan going full belt in my face. Throwing hot Cazzy R into the fan completes the impression. The only breakdown I experience is a mental one!
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Re: G80 Riding Impressions

Postby Iron Head » Sat Dec 08, 2018 4:23 pm

Changing tack slightly regarding this bike has anyone else experienced a modification whereby the crankcase breather has been diverted via a flexible pipe and then a short length of copper oil pipe into the back of the primary chain case? It’s a crude modification, but as an idea, seems to work quite well with any oil generated directed onto the primary chain.

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