Loss of compression

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Re: Loss of compression

Postby Rob Harknett » Tue Oct 31, 2017 10:55 am

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.

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Re: Loss of compression

Postby Bruno » Wed Nov 01, 2017 8:32 pm

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

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Re: Loss of compression

Postby g80csp11 » Fri Nov 03, 2017 6:20 pm

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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Re: Loss of compression

Postby Janet » Sat Nov 04, 2017 9:42 am

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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Re: Loss of compression

Postby g80csp11 » Sat Nov 04, 2017 11:43 am

only to happy to be proved wrong and corrected . always pay my dues eventually !

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Re: Loss of compression

Postby Bruno » Fri Apr 06, 2018 8:25 pm

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

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Re: Loss of compression

Postby SPRIDDLER » Fri Apr 06, 2018 8:56 pm

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....

viewtopic.php?f=18&t=23315&start=20
I poke badgers with spoons.

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Re: Loss of compression

Postby Bruno » Sat Apr 07, 2018 10:30 am

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

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Re: Loss of compression

Postby Bruno » Tue Apr 17, 2018 10:00 am

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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Re: Loss of compression

Postby Janet » Tue Apr 17, 2018 2:23 pm

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