Loss of compression

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Rob Harknett
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Posts: 11039
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Loss of compression

Post by Rob Harknett »

Bruno wrote:Hello,

An unexpected delay in rectifying the problems with my G3. I managed to shred the ends of my left hand thumb and index finger on a circular bench saw - very lucky to still have them and on the mend, but I've been 'digitally challenged' for the couple of weeks.

I will shortly resume clean up on the exhaust valve and get the top end back together. It is now moving nice and smoothly in the guide since removing the deposits. I think the build up may be related to the bike being run very rich by the previous owner - when I got the motorcycle it was running really badly, mainly due to the carb set up being far out.

Anyhow, I'll give it a go and report back in due course ... hope to catch a couple of warmer days for runs before the proper Scottish winter sets in.

Cheers, Bruno
Opps 50 years a wood machinist and never a scratch. Most of the time as a machine setter / supervisor. I had to make sure machines were properly guarded and operator made aware of all dangers. Then some fool cut the tip off his little finger. Guy said, there was a little gap I thought my little finger could go under, so I tested it. You don't expect anyone to do that with the machine running. Eventually we had to sack him as he was a danger to others.
Bruno
Posts: 48
Joined: Tue Jul 07, 2015 9:42 am
Location: ABERDEENSHIRE UK

Re: Loss of compression

Post by Bruno »

Hello Rob,

Sounds like he might have been a relative of mine!

No excuses ... I broke every basic safety measure and was very lucky to just damage a couple of digits which are on the mend.

I can even get my motorcycle gloves on now.

Cheers, Bruno
g80csp11
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Posts: 1091
Joined: Mon Jan 01, 1990 12:00 am
Location: WEST SUSSEX UK

Re: Loss of compression

Post by g80csp11 »

Bruno , if t turns out it was not the valve seat , send me you address so I can post you the
£1 I owe you !
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Janet
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Joined: Mon Jan 01, 1996 12:00 am
Location: EAST YORKSHIRE UK

Re: Loss of compression

Post by Janet »

g80csp11 wrote:Bruno , if t turns out it was not the valve seat turning , send me you address so I can post you the
£1 I owe you !
Corrected for you. ;)
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g80csp11
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Posts: 1091
Joined: Mon Jan 01, 1990 12:00 am
Location: WEST SUSSEX UK

Re: Loss of compression

Post by g80csp11 »

only to happy to be proved wrong and corrected . always pay my dues eventually !
Bruno
Posts: 48
Joined: Tue Jul 07, 2015 9:42 am
Location: ABERDEENSHIRE UK

Re: Loss of compression

Post by Bruno »

Hello,

I'm at last in the process of putting the top end of my G3 back together. However, I've discovered that 2 of the 3 different washers around the rubber gasket at the top of the push rod covers are missing and that the old rubber gaskets don't seem to be rubber at all - it's a hard, brittle black material like bakelite?

Probably explains why I've experienced some oil leaks around the push rod covers ever since I bought the machine.

Is this just a 'bodge' by a previous owner or were these gaskets made of this sort of material in the past? I've bought new rubber gaskets and sets of all 3 washers for the rebuild anyhow.

Cheers, Bruno
SPRIDDLER
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Posts: 7305
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Loss of compression

Post by SPRIDDLER »

It's not a bodge. The rubber collars do turn to Bakelite brittleness over time and leak.
This was answered on the Forum extensively a week ago.
Here's the link....

http://www.jampot.com/forum/viewtopic.p ... 5&start=20
I poke badgers with spoons.....from 2 metres.
Bruno
Posts: 48
Joined: Tue Jul 07, 2015 9:42 am
Location: ABERDEENSHIRE UK

Re: Loss of compression

Post by Bruno »

Thanks for this link Spriddler.

I've already received the replacement rubber gaskets, so I'll just fit them for now - but great insights into alternative leak free options.

Cheers, Bruno
Bruno
Posts: 48
Joined: Tue Jul 07, 2015 9:42 am
Location: ABERDEENSHIRE UK

Re: Loss of compression

Post by Bruno »

Hello,

Finally ... put the top end back together last night, good compression and started up 2nd kick. Nice to hear that steady, deep resonating thump again after several months!

Turns out that the head needed a thorough decoke and the both inlet & exhaust valves re-ground - there was a heavy build up of carbon deposits around both valves which was preventing them from seating properly and the tappet stems were a bit tight in the guides and needed some light cleaning to free them up again. Everything else was sound, so pretty straight forward in the end.

Just really glad to be back on the road and intending to join the Cairn 'O Mount run staged by the VMCC in Aberdeenshire next month ... maybe even get some decent weather?

Cheers, Bruno
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Janet
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Joined: Mon Jan 01, 1996 12:00 am
Location: EAST YORKSHIRE UK

Re: Loss of compression

Post by Janet »

Who won the £1 (she asks, hopefully)? ;)
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