Box of bits assembly of 1955 G80S

[Mick D]

Hi

Gudgeon pin bushes, 017317, are available as replacements, they are made of bronze originally I think.

Sounds like you have a PO bodge.

Regards Mick

[clive]

In defence of bodgers 🤔, Gudgeon pin bushes that were of a silver coloured material (presumably not aluminium) were certainly around in the 80s/90s, I still have a new one still I picked up somewhere. I imagine they were a replacement item offered by someone when phosphor bronze ones were not so readily available.

If it is cracked it will have to go though.

[SPRIDDLER]

I'm pretty sure the the originals were phosphor bronze which is an orangey bronze colour.
When I needed to replace a timing side bush in my '54 G3LS a recently retired toolmaker chum looking for something to do made me one from aluminium bronze which he said is harder and a more yellowy bronze colour. It's still fine after 25,000 miles. Ali bronze was commonly used for ships' propellers as it withstood salt water corrosion better than phosphor bronze. Not a lot of people (want to) know that .

[56G80S]

The small end bush on my Matchless is a kind of aluminium grey.

I put it in ages ago.

Maybe another thing to get from AMOC Spares for when I get the relined barrel back with a new standard piston.

Johnny B

[RobC_LAPSED]

Thanks for the help. Can I ask for your opinions on the engine please?

It looks like that small end material is quite hard so I was probably wrong on that.
When I got this in the 80's the guy said he had sorted the engine. I assumed from the look of it that he had the piston, barrel and pushrod tubes off as some of this looks like it's been replaced. It had blue silicone sealer around the bottom of the barrel, maybe him! Why he would go to the bother of replacing that and leave a big end that is so tight and notchy, that when you get it in the notch near TDC it takes some force to spring it out of there! It has been stood for 40 years since then though. Inside the barrel is still nice and clean, Think I poured oil in the spark plug hole years ago.
He couldn't have taken the crankcase apart judging by the amount of sludge in the bottom! That was stuck together with a much older red sealer, not silicon. It has been apart in the past though, by the marks on the big end nuts.

So I'll need to get a new big end crank pin assembly from the club. I assume the the outer ring of the crank pin bearing presses into the con rod and the con rod should be OK? I've got the crank out but not apart as I don't have the tools for that. What I can see of the con rod looks OK, needs a new small end bush as mentioned.
I assume the paper gasket under the barrel needs to have a cut-out over the oil way to allow oil into the grove/ring around the inside of the barrel lip and through the 2 holes into the barrel?
I'm also a bit concerned about the step on the crankcase top. I read that you should bolt the barrel on first before bolting the case halves together. I'm not sure a paper gasket will seal that, the gap is about 8 or 9 thou one side when flush the other? Does that indicate that it's not a matched pair? If it's not, its been running like it for some time in the past by that sludge!

I read that the new crank pin needs to be pressed in with an industrial press rather than by just tightening up the crank pin nuts. So I'll need to get someone to fit the new crank pin, small end bush, ream that and clean the crank oilways etc. Does anyone have any recommendations for someone who does this, preferably in south Hampshire?

The drive side crank axle bearings seem ok. I tried to take them out to clean them but they didn't drop out with heat on the case, as has been written. I tried a light bash with a mandrill as well but I don't want to damage them, so I've flushed lots of petrol through them and then WD40 spray. That seems to have cleaned out the bits I could feel in there. There was a slither of what looked like a bit of a previous piston in the sludge, that sort of radius. So I've been cleaning all the oil ways etc.
The timing side bush does seem to have a bit of play in it so I'm guessing it's best to replace that?
The oil pump plunger looks pretty good as does the timing gears etc.
Any other things I should look out for?

Thanks, Rob.

[Mick D]

Hi

Those crank pin nuts have only ever been torqued, (they have never been undone), so the chances are that the person who last replaced the crank pin didn't correctly align the flywheels and hence the pinching.

I'd get the crank stripped by a reputable firm, (T & L Engineering), before buying any spares, (they may be able to recover the situation by inspection and aligning).

Regards Mick

[RobC_LAPSED]

Thanks Mick,

I'll perhaps try and ring T & L this week when I should be able to get back to looking at this again, see what they advise.

This is the photo of the top of the crankcases that I meant to attach!
Rob

[magnusk750]

Hi.

Basically we are doing the same thing, even almost the same bike. This autumn I started to put a basket case, 1955 twin, bought in 1987 together. I've got a thread about it in the Garage Projects section. I found your thread today. Just read it briefly, but I can already see there's useful info in it, will reread properly soon.

There's loads of info out about the different components of a bike, less about the frame and how to build a bike around it. If you don't already have, get yourself a set of Cycle thread dies and taps. Lots of fasteners can be had ready from the club and AMC classic spares but not all, I've spent many evenings in the shop making them with longer ones as blanks.

[Andy51]

The engine of my '54 G80 which I bought in 1976 had been rebuilt by Joe Francis a year or so previously. It had a silvery metal small end bush and I would imagine that Joe was using NoS stuff at the time. Andy