Refit a complete scott engine

'Ever taken an engine out of the frame in pieces, then found it won’t go back in reassembled? If it’s a Scott, don’t give up…'

 Rick’s old Rex Acme; ripe for restoration or best left alone?

Rick’s old Rex Acme; ripe for restoration or best left alone?

I had some bad news today: the completely original 1925 Rex Acme I used to own has changed hands again, and I’m told the new owner intends to restore it. I hope it isn’t true; after decades of unspoilt bikes being rather grotesquely described as “ripe for restoration” by restorers looking for an easy concours win, popular opinion seems to be that originality is better preserved than sandblasted away. But at what point is preservation and restoration one and the same? If you ride a rusty bike through a couple of winters it’s likely to get rustier however handy you are with an oily rag. I guess a bike like the Rex Acme is now so rare that it is possibly the only one left unrestored. It is also not a bike you would be likely to commute on during the winter, leave outside in the rain all day or park under a canvas cover at night. If your classic is a practical bike for today’s roads, restoration may be essential to keep it that way – but the older the bike, surely the less this really applies. I used to think cutting frames to build choppers was the ultimate one-way street, but frames can always be retubed; the thing you cannot ever replace is the original factory finish. Restoration wipes away history like chalk from a slate and I think we owe it to future generations to interfere as little as possible and avoid making restoration the automatic default for every old bike that comes our way.

 

Wobbles and washers

Having stripped the primary drive of his 1970 Bonneville, Ken Adams has a few queries. First, he’s concerned that the clutch is free to wobble quite a bit when disengaged. ‘Also,’ he asks, ‘which way round does the bronze face on the thrust washer go? Facing the clutch or the bearing hub?’ Yes, it’s perfectly OK for the clutch to wobble when disengaged. If it didn’t, I’d recommend checking standard ¼in x ¼in bearing rollers haven’t been fitted instead of the shorter Triumph ones. These clamp everything up and cause a lot of problems. With the correct bearings the chainwheel/basket is effectively floating once the pressure of the plates is relaxed and the primary chain keeps it in line. The bronze face on the thrust washer should run against the polished area on the back of the chain wheel. It faces out from the centre line of the bike. Originally these washers had ears located in notches on the clutch hub, but these were done away with.

Sticky subject

Gary Williams has conflicting advice over whether it is OK to use 10W40 motor oil, rather than 10W40 motorcycle oil, in his restored 1971 Honda CL350. “The only difference I can see is that a bike clutch runs in engine oil, but I have had no trouble,” he says. Honda’s recommended oil grade was originally 20W50 in the ’70s, but by the ’80s they were specifying 10W40; being thinner it’s better able to get to sensitive areas when the engine is cold – particularly the overhead cam and its bearings. The concern with oil is that, over the years, additives have been reduced or removed to prevent damage to catalytic converters. Modern motors are designed with this in mind, but there’s a possibility that older engines can suffer. The API (American Petroleum Institute) administers a sort of British Standard grading system for oils with an alphabetical change for each new standard. ‘S’ denotes petrol engines and API-SA dates back to pre-war times. API-SM was the first without the zinc-phosphorous additive. API-SL is often recommended for older motors. But as this is now an obsolete grade, it isn’t common in the car world. Fortunately it’s less of a problem with bikes; Silkolene Super 4 is a 10W40 oil graded API-SH. Various ‘classic oils’ also avoid the additive problem, but unbranded supermarket oils without any API rating could be almost anything – avoid them.

Winter layup

Antony Hunt has a Morini engine he wants to store and asks: ‘Would it be a good idea to remove the pushrods?’ I’d say so; Tony’s point being that, on anything other than a single, one valve will always be open. The only way to ensure they are all closed is to remove the means that lifts them: the camshaft on an ohc four, or the pushrods in this case. You could just remove the one on the open valve, but removing all lets you turn the crank over every so often without having to return to the same place. Pour a bit of oil into the inlet and exhaust ports first and turn the engine to get it on the valve seats and prevent furring up around the closed valves. Drain any dirty oil, replenish with clean and pour some into the bores. Block the ports – rubber stoppers or globs of bath sealant are better than rags, which soak up moisture. And don’t forget where you put the pushrods…

 Triumph clutch thrust washer fits between the hub and chainwheel

Triumph clutch thrust washer fits between the hub and chainwheel

Bouncy Triumph

Graeme Curtis is still getting to grips with his 1962 Triumph T100SS. His forks top out easily over bumps and he’s heard they can be converted to the later shuttle-valve type. But it’s not so simple. Shuttle valves were a ’68 update of Triumph’s ’65 fork, with different dampers and stanchions in more or less the same carcass. Your 1962 fork is a completely different design. The only conversion I know of for these comes from the pre-’65 trials world, where the outside diameter of Bultaco (or similar) fork sliders are turned down on a big lathe until they become a sort of giant aluminium fork bush that is pressed into the Triumph slider. In effect this clads the Bultaco fork in a Triumph skin, thus fitting relatively modern suspension without breaking the rule that the forks must be ‘outwardly standard’. I suggested heavier-weight oil (SAE 30 usually sorts them out) but Graeme told me that, having removed the top nuts, he found the damper tubes that should be attached are missing, along with the corresponding bottom tubes in which they telescope. These are crummy things and easily bent, but they’re necessary. Graeme’s ringing round for a set.

Wiring worries

After replacing nearly every component, Leslie Sparrow still can’t get a charge out of his BSA C15. He’s wired it as per the manual but questions why the purple output wire from the rectifier goes to ignition switch terminal 13 instead of the ammeter. Is this the problem? Digging through my old Lucas books provided the answer. As well as confirming Leslie’s wiring is correct I found a diagram showing the internal connections of the complex switch. It reveals that in the ‘on’ position terminals 12 and 13 are joined, sending the DC current to the ammeter. It sounds like this connection may have failed – check this first.

 

How To

refit a complete scott engine

Ever taken an engine out of the frame in pieces, then found it won’t go back in reassembled? If it’s a Scott, don’t give up…

  1.  Whichever way I tried, the completed engine was obviously bigger than the window in the frame. Before removing the top end once again, I decided to phone a friend.

1. Whichever way I tried, the completed engine was obviously bigger than the window in the frame. Before removing the top end once again, I decided to phone a friend.

  2.  Long-term Scott owner Colin Heath had the answer. Jack the bike up into a wheelie position. Lay the engine on its back – the flat side rails will now clear the cylinder block.

2. Long-term Scott owner Colin Heath had the answer. Jack the bike up into a wheelie position. Lay the engine on its back – the flat side rails will now clear the cylinder block.

  3.  The top rear engine mount should just pass through the frame mountings for the bottom lugs without removing the gearbox, allowing the engine to pivot 90° into position.

3. The top rear engine mount should just pass through the frame mountings for the bottom lugs without removing the gearbox, allowing the engine to pivot 90° into position.

  4.  Fit the long front bolt to support the engine weight, then line up and fit the two rear mounting studs and spacer. There – not so difficult after all. Thanks Colin!

4. Fit the long front bolt to support the engine weight, then line up and fit the two rear mounting studs and spacer. There – not so difficult after all. Thanks Colin!

 
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