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45" parts, and hello!.

Post Thu Aug 14, 2014 3:22 am

Posts: 3
Hello, I just realised I had not replied to you, rude of me, apologies. Have actually been out riding much of the summer, until the home made belt drive flew to bits!
The story of the belt drive is that when the bike was first built (20+ years ago), they were no belt drive kits for 45s so a standard tapered machinery belt drive front pulley was used, with a tapered spacer to go between the big female taper and the small 45 crankshaft sprocket shaft taper, a poor engineering solution but it did last for a few thousand miles.... It flew to bits as I was riding it recently so I got an original 45 sprocket and turned it back on the lathe to get the right spacing to keep the belt in line, with a protruding register in the middle, turned a corresponding female register in the pulley and bolted the two together. Seems to work fine. The clutch end is something I bought at a jumble somewhere I think (was a long time ago) and uses long round allen-headed screws in the drum, which has 68 HTD teeth on the outside, as the locating points for the outer edges of the plates and a Triumph boss and hub that fit onto the Triumph gearbox. I think the springs and outer plate are Triumph but a Norton three spring is reckoned to be better by some 'experts'. It never slips or drags though! The outer of the drum has 68 teeth and the front pulley has 36, with 1:1 top gear, and a 20 tooth gearbox sprocket and 43 tooth on the rear with a 4.50 X 16 tyre, this gives 78.48 mph at 4500 rpm. I am going up a tooth on the gearbox sprocket as it will pull it. I generally cruise at 60-70 now (4000 rpm is 62.46mph). The belt is a Contitech HTD 1040 8M (8mm pitch) (with the half round teeth NOT the square or trapezoidal teeth, the HTD profile is much better). You can buy pulleys for about tenner from or other places on the web. You can buy a 64 tooth or 72 tooth pulley from them for about £50 and turn it out and shrink it onto your existing clutch drum. I use 30 mm wide belt which seems plenty strong enough for what is a mildly stroked and tuned 45 motor and it is often blathered in oil and does not seem to mind. They are available in 20, 30, 50 and 85 mm width. Most big twin people seem to think they need very wide belts but they just get in the way of your feet as far as I am concerned! Ridden properly, the 45 has very nice smooth power delivery and is not hard on the driveline. The mnistake I think a lot of people make is that they think because it is a sidevalve, it should be 'ligged' at low revs. Actually, I find that the engine design works best at 3 - 5,000 rpm. Have a look at belts at: ... HTD_en.pdf
Give me an email at if I can help at all.
Oh, the Indian CHief 1940 back wheel has worn out now and I have a Harley wheel with disc brake but need a 3/4 inch axle/spindle to get back on the road, if you have have lying about?!

Post Tue Aug 19, 2014 1:20 pm

Posts: 19
Excellent and comprehensive info, thanks very much.
No joy on the spindle I'm afraid. On a similar note, I've owned a couple of Indian Chiefs, never did get on with them, much prefer my 45".

Post Wed Aug 20, 2014 10:39 pm

Posts: 1654
My 45 conversion has a similar front pulley, I'll find some images of it and post them for comparison.

Agree entirely about ridiculously wide belts. They belong on potato graders and coal mines. Mine has a Tony Hayward 30mm belt which was originally marketed for Classic racers, Nortons and Triumphs making 50bhp plus. These sort of units have been widely used in classic racing for years and work very well. The actual belt came from an industrial catalogue because if the length, but it's the same spec.

Also, agree about not "slogging" sidevalves. The old BSA sidevalves will run quite smoothly at virtually nil rpm, nut they aren't making any power at that speed. There's a fast Norton 16H that appears at the VMCC occasionally and its power band is very narrow. The 45 needs to be flexible to cope with its considerable weight and dreadful 3-speed gearbox, but the transmission is also structurally weak and flogging it at low revs does no good at all.

I'm firmly of the opinion that the 45" twin represents the optimum size for a bike if this type. Indian also had great success with their 45s, BSA built an ohv V twin in tne 1930s which was highly regarded if not a big seller. BSA showed, as Indian did, that a 500cc twin is just overweight for its power output and too expensive.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Wed Aug 20, 2014 10:49 pm

Posts: 1654
Oh, and Norton/AMC clutches are far superior to BSA and Triumph ones. I have used them on grasstrack bikes for years and they give no trouble at all, and this us on bikes making 45-50 BHP and making frequent clutch starts. You can tune them so they are JUST slipping when you drop the clutch at 6000rpm, and they take it and go on taking it.

The Jawa 3-spring clutch is based in Norton units, to the extent of usung the same plates and springs. The later 6-spring version isn't really any different; it is easier to fine-tune and the springs last longer and give a lighter action, but that's the only real difference. I use Jawa fibre plates these days, because you can get them easily and they were cheaper than Norton ones, and they are designed to run in air; but I have one bike with Norton repop plates and it has been in use fir donkeys years like that. I should probably fit some new plates!
Shoot, a man could have a good weekend in Dallas with all that stuff...


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