Re: Matchless 350 G5 piston and rings.

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
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Re: Matchless 350 G5 piston and rings.

Postby ajscomboman » Tue Sep 15, 2020 6:21 pm

Rangy65 wrote:No problem Rob but it has to be modified its not a direct replacement.

It is almost, the mod merely involves easing the edge of the skirt by 1/4" to ensure it clears the flywheel. A very quick job and nothing involving the crown or ring groves etc.

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Re: Matchless 350 G5 piston and rings.

Postby Andy1730 » Tue Sep 22, 2020 9:46 pm

Hi all ..I'm having a problem with the build found out it needed new valves so ordered a pair for a 1960 350 G5 and what I had delivered was totally different from what was taken out of the head the valve stems were lot thicker and the valve heads were larger diameter now im not sure if I have a 350 or if it has had a different top end fitted..The valves I removed are...Inlet shaft 7.10 mm head size 41mm and it's 113mm long..exhaust valve is..shaft 7.40mm..head size is 31mm and it's 103mm long..I have measured the stroke and it's is this consistent with a 350 or if not what model etc..these are approx sizes so apologies if I'm a bit out..Also I was given two gearboxes one is smashed inside and the other is missing 3 gears and the selector forks so I'm needing a gearbox..Many thanks Andy
Last edited by Andy1730 on Tue Sep 22, 2020 9:49 pm, edited 1 time in total.

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Re: Matchless 350 G5 piston and rings.

Postby clanger9 » Wed Sep 23, 2020 7:12 am

Hi Andy,

Welcome to the wonderful world of Lightweight parts.

Your best source of info is this (scrappy) scan of a later parts list that shows most of the variations: ... o_1966.pdf

This is the "Dead Sea Scroll" of Lightweight spares. Rob has been asking for years if anyone has a better copy of this list, but nothing has turned up so far...

There are two exhaust valve types for the 350: the early one (042033) is the same as the 250 and has a narrow stem. The later one (042868) is shared with the 250CS and CSR and has a fatter stem. Both are the same diameter.

There is only one type of inlet valve for a 350: 044002. This is a bigger diameter and is shared with the later 250CSR and the head has a 1 1/8" inlet tract. 250 (non-CSR) heads have a smaller inlet valve (044032) and 1 1/16" inlet tract.

The two head variants (i.e. "250" and "350/250CSR") are physically the same size, so it is possible for an engine to get mixed up over the years.

Lots of good info in this thread: viewtopic.php?f=16&t=23809

I probably have the gearbox parts you need, so send me a PM.
1989 Moto Morini Dart 350
1993 Ducati 750SS


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