Building a Scrambles G80 Bitsa

[Joker_Bones]

As I have ofen observed in the past, it's a matter of buying tools to make tools to mend tools... to do a job that you should probably not be trying in the first place.

Lol... I seem to spend a lot of my time doing just that.

[Joker_Bones]

I note some of the respondents did not fit the counter nut. The adjuster should be clamped in the crosshead to prevent what you describe.

Yes... the eye bolt type adjuster has a plain hole through the crosshead, so a nut is required both sides of the crosshead.

The other type of adjuster has threaded hole though the crosshead into which the adjuster screws, so I imagine a single nut is sufficient to clamp the adjuster to the crosshead.

[RichardS]

I'm finally making some visible progress with this project, but I've run into a somewhat odd problem with the clutch. I have an AMC late type bonded plate clutch with the requisite complement of 4+4+1 plates. The problem is that the pressure plate is nowhere near touching the outer plate even when bottomed out on the hub. There is somewhere around 0.150" clearance!

I know there are different pressure plates, but if I had one from a 350 suitable for the clutch with fewer plates then the pressure plate would be deeper and way clear of the hub. The plates are slightly worn (006-010" under size), but nowhere near enough to account for the clearance.

I'm thinking I'll probably just bung in a couple of extra plates, but it seems very odd.

Anyone got any ideas?

[RichardS]

Here's a dry assembly but starting to look better.
I need to take the chain case off again to tighten the sprocket nut properly and fit the foot rest too.
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The foot rests prooved to be something of a challenge. I have a pair of standard road bike ones, but they are nowhere near fitting - one is way too thick for the left hand side between the engine plates and frame and the other is too thin to fill the gap on the right and wouldn't clear the exhaust either.

In the end I fabricated some from heavy plate and pipe and welded a modern folding foot rest on the end. If I'd known the details before hand and had a jig to hold the parts in the right places it would have been an hour's work a side. As it is, I've been agonising over it for a month and cutting & shutting the various revisions to get the result near what I wanted.
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[Joker_Bones]

Good to see the progress...
I don't know what to say about the clutch other than there are two different arrangements for the clutch plates.
Earlier AMC clutches had the tangs on the friction plates facing outwards, later clutches they faced inwards. Earlier clutches had a friction lining on the inner back plate of the basket, later clutches didn't. Possibly a mismatch of parts?
I have heard the plain plates referred as thick or thin types, I don't have the measurments but 0.15" seems a lot to make up with thicker plain plates.

[dave16mct]

The latest clutch had 5 bonded plates.
Dave

[RichardS]

The latest clutch had 5 bonded plates.
Dave

Marvelous Dave! Thanks.
I thought I'd looked through all of the spares lists, but after your prompt I've found the '63-64 copy does indeed list 5 pairs and has a different center hub - guess that's what I've got. I have no idea of the provenance of the clutch, just and AMC unit I picked up at some point some decades ago, evidently missing a couple of plates, but until it came to use it, the omission was not obvious.


Cheers

[RichardS]

After assembling everything I found the steering lock was severely compromised, might be almost adequate fora road bike, but off-road no way. In retrospect it should not have surprised me as I always felt my Dommie was short of steering lock for in-garage manoeuvring, OK on the road obviously, but a pain in the car park. The Norton yokes have lock stops only just outside the bearing OD and I brazed a stop lug onto the front of the headstock before painting - the original behind and under the headstock was another detail amutation by the previous owner.

So, with no other choice I took the forks off again, cut the lugs off the yoke and made a half-moon kind of arc with new lugs at the ends, further round. Then bolted that to the yoke.
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The result works nicely with plenty of steering lock and still robust end stops.
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After that and having acquired a couple of extra clutch plates I could put the chain case on properly and move forward a couple of steps. Putting the rear chain on I promptly found how/why the frame lugs had been so badly damaged - the lower run of the chain permanently scuffs on the lug just inside the foot-brake and the top run drags on the swinging arm pivot boss. Even alloing for my non-standard collection of parts it is clearly an original problem.

I made nylon skids to go over the arm and frame and protect it in future. I may yet add a tensioner as well, but the syspension movement is not like modern trials bikes so it's probably over kill.
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With all that done I couldn't resist the temptation to start the engine and hear it run for the first time in 40 years. After a good 5 minutes there was still no oil return so I obviously stopped and investigated. I assumed there was just not a lot of oil in the nominally dry sump so poured another cupfull down the push-rod tubes and tried again (I had already put a cupfull down before the first start to lubricate the cams and, I thought prime the return). The additional oil served to smoke out the garage and half the street 'though the sweet castor smog was not entirely unpleaseant

I gave up and removed exhaust, gear lever and oil hoses etc to to access the pump ends (total PITA) and found nothing wrong, no blockages, pump oscillating as it should and finally the first traces of oil in the return line. The short story seems to be that the pump obviously doesn't pump air very well and with the sump near dry it took an inordinate amount of time and significant over-oiling of the sump to prime the pump and get the return to flow. The delay made worse by the fact that I have a filter in the return line which holds around 1/2 pt.

Finally, I got some return flow and another few minutes and the exhaust cleared to run quite sweetly. Happy days.
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I still have to fix the seat as the bare frame is a little lacking in comfort, and some other minor details to tidy up, but overall I'm resonably happy with it.
I'll see about registration next