Just wondering if any of our heroic Lightweight 350cc owners had tried using one of the pistons originally fitted to an AJS/Matchless 600cc twin? I've found two mentions of this in the literature, and that one of these pistons will not only fit the G5/Model 8 but will provide a bit more power as they will have a higher compression ratio.
My reason for asking is that my Model 8 could really do with a new piston but they are not too easy to find, and are pricey.
Anyone had a go? And which model precisely is the 600cc twin mentioned?
Cheers,
Al
600cc twin piston in 350cc Lightweights?
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BigAl350
- Posts: 154
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- Location: BERKSHIRE UK
600cc twin piston in 350cc Lightweights?
Al Bolton, G4VSQ
1960 Matchless G5 (Off the road for now, maybe for sale?)
1960 AJS Model 8 (Just passed MoT)
1962 AJS Model 8 (Still lurking in a Devon shed in bits)
1960 Matchless G5 (Off the road for now, maybe for sale?)
1960 AJS Model 8 (Just passed MoT)
1962 AJS Model 8 (Still lurking in a Devon shed in bits)
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ajscomboman
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- Joined: Mon Jan 01, 1990 12:00 am
- Location: HAMPSHIRE UK
600cc twin piston in 350cc Lightweights?
Al
The info is incorrect. It's a '59' 7.5-1 comp ratio 650 piston that you need to use. You have to modify the skirt to clear the flywheeels and thats about it. I'm currently talking to Jim at JSL to see if T&L Engineering can look at modifying some of the existing GPM pistons in stock.
I'll keep you posted.
Rob
P.S. yes it does make them fly but make sure the big end is sound.
The info is incorrect. It's a '59' 7.5-1 comp ratio 650 piston that you need to use. You have to modify the skirt to clear the flywheeels and thats about it. I'm currently talking to Jim at JSL to see if T&L Engineering can look at modifying some of the existing GPM pistons in stock.
I'll keep you posted.
Rob
P.S. yes it does make them fly but make sure the big end is sound.
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BigAl350
- Posts: 154
- Joined: Sat May 22, 2010 4:32 pm
- Location: BERKSHIRE UK
600cc twin piston in 350cc Lightweights?
That's brilliant, Rob, and many thanks for the reply - more useful info for the Lightweighteers. I know I'd certainly be up for a few, though the G5 will need a new crank to cope with the awesome power unleashed...
Al
quote:
Al
The info is incorrect. It's a '59' 7.5-1 comp ratio 650 piston that you need to use. You have to modify the skirt to clear the flywheeels and thats about it. I'm currently talking to Jim at JSL to see if T&L Engineering can look at modifying some of the existing GPM pistons in stock.
I'll keep you posted.
Rob
P.S. yes it does make them fly but make sure the big end is sound.
Al
quote:
Al
The info is incorrect. It's a '59' 7.5-1 comp ratio 650 piston that you need to use. You have to modify the skirt to clear the flywheeels and thats about it. I'm currently talking to Jim at JSL to see if T&L Engineering can look at modifying some of the existing GPM pistons in stock.
I'll keep you posted.
Rob
P.S. yes it does make them fly but make sure the big end is sound.
Al Bolton, G4VSQ
1960 Matchless G5 (Off the road for now, maybe for sale?)
1960 AJS Model 8 (Just passed MoT)
1962 AJS Model 8 (Still lurking in a Devon shed in bits)
1960 Matchless G5 (Off the road for now, maybe for sale?)
1960 AJS Model 8 (Just passed MoT)
1962 AJS Model 8 (Still lurking in a Devon shed in bits)
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1608
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- Joined: Mon Oct 05, 2009 1:00 am
- Location: ESSEX UK
600cc twin piston in 350cc Lightweights?
Shame I can't use 2 X 250 pistons in my 500
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BigAl350
- Posts: 154
- Joined: Sat May 22, 2010 4:32 pm
- Location: BERKSHIRE UK
600cc twin piston in 350cc Lightweights?
Rob,
I'll probably have to rebore and replace the piston soonish - wonder if you ever got anywhere with JSL and T&L? Or an indication of what needs to be machined would be really helpful.
Cheers,
Al
quote:
Al
The info is incorrect. It's a '59' 7.5-1 comp ratio 650 piston that you need to use. You have to modify the skirt to clear the flywheeels and thats about it. I'm currently talking to Jim at JSL to see if T&L Engineering can look at modifying some of the existing GPM pistons in stock.
I'll keep you posted.
Rob
P.S. yes it does make them fly but make sure the big end is sound.
Edited by - BigAl350 on 26 Mar 2012 11:46:35 AM
I'll probably have to rebore and replace the piston soonish - wonder if you ever got anywhere with JSL and T&L? Or an indication of what needs to be machined would be really helpful.
Cheers,
Al
quote:
Al
The info is incorrect. It's a '59' 7.5-1 comp ratio 650 piston that you need to use. You have to modify the skirt to clear the flywheeels and thats about it. I'm currently talking to Jim at JSL to see if T&L Engineering can look at modifying some of the existing GPM pistons in stock.
I'll keep you posted.
Rob
P.S. yes it does make them fly but make sure the big end is sound.
Edited by - BigAl350 on 26 Mar 2012 11:46:35 AM
Al Bolton, G4VSQ
1960 Matchless G5 (Off the road for now, maybe for sale?)
1960 AJS Model 8 (Just passed MoT)
1962 AJS Model 8 (Still lurking in a Devon shed in bits)
1960 Matchless G5 (Off the road for now, maybe for sale?)
1960 AJS Model 8 (Just passed MoT)
1962 AJS Model 8 (Still lurking in a Devon shed in bits)
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beesy
- Posts: 62
- Joined: Mon Oct 06, 2008 8:47 pm
- Location: SOMERSET UK
600cc twin piston in 350cc Lightweights?
i'd also be interested in a spare piston ofr my model 8
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Don Madden
- Member
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- Joined: Mon Jan 01, 1990 12:00 am
- Location: USA USA
600cc twin piston in 350cc Lightweights?
Hmmm. I have several sets of 1959 G12 in 7.5 & 8.5 CR. Most are Covmoco & AE, both are Hepolite labels. Also a Mondial brand piston. Some are new, some good used, std & +0.020in sizes. PM me if interested. Cheers, Don.
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ajscomboman
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- Joined: Mon Jan 01, 1990 12:00 am
- Location: HAMPSHIRE UK
600cc twin piston in 350cc Lightweights?
Al
Sorry not progressed much with the pistons yet, the new parts service has taken much of my time.
To be honest you only need to grind the bottom of the skirt to clear the flywheels and this can be done by using the original as a template. I used masking tape, a scriber and a dremel with a coarse sanding disc.
You can only use 1959 650cc 7.5 CR pistons as the higher CR pistons have a dome that is too large.
Sorry not progressed much with the pistons yet, the new parts service has taken much of my time.
To be honest you only need to grind the bottom of the skirt to clear the flywheels and this can be done by using the original as a template. I used masking tape, a scriber and a dremel with a coarse sanding disc.
You can only use 1959 650cc 7.5 CR pistons as the higher CR pistons have a dome that is too large.