Bike Weights and Weighing

Little Honda

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I have read differing views on the following method. Bathroom scales under front wheel, back wheel on block same height, balance bike with steady hand on handle bar after pulling upright from slight lean on wall. repeat for back wheel. Add two totals. The question is, can the result be true?
If u check yr bathroom scales by say 5, 10, 30 kgs plus all weights, each time u use yr scale for yr bike, u will
know the deviation factor or "bathroom-factor". What I found out by weighing my Norvin: It had the same
weight distribution, like my Honda RC31 (650 Hawk), which - in my opinion - is the best road holding bike
in the 60hp class. These bikes have a lighter front wheel load, than rear, and this seems to be for the changing
load with braking. If u study modern superbike tests, like BMW 1000RR, Honda CBR1000RR, etc. , they all have
heavier front wheel loads. I asume, that this is for compensating the aerial lift at speeds over 140mph, to keep
these bikes steady at full throttle on the motorway. As we do not have this kind of lift with our bikes, they
should not have the same weight distribution, like modern Super Bikes, to submit an enjoyable ride at lower
speeds, even on track. In other words, a good Vincent, on road or on track, should have abt 40% load on the
front and 60% on the rear. Original brakes in good nick are fine on a Comet, but will need some improvement
on the front with twins.
 

Little Honda

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I bought 2 sets of el cheapo bathroom scales, the old school type with the rotary needle, make up some simple ramps and wheel the bike on. Hold the bike upright with your fingertips on one bar end and read the scales.......On my current single racer the front was 65.5 kg's and the rear 64.5 kg's........that's near enough to 130 for me.......With oils, no fuel.
Try again with rider on.
 

Little Honda

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Impressed Greg. Makes it 10kg lighter than a standard Manx, with all the fancy magnesium engine parts and throughdrilled bolts. Still some 15 kg heavier than a Yamaha TZ though.
A modern MotoGP racer has a minimum weight of 157 kg.
The 500cc single cylinder ohc Moto Guzzi works racer of 1939 weighs 90kgs at 47hp.
 

greg brillus

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I am surprised a Manx is that heavy........Mind you i only read the other day that a Manx engine is 35 Kg's on its own.......In spite of the majority of magnesium parts the engine is quite bulky. When I removed the ESO 500 engine on the scales it showed 30 kg's, this including the oil pump and magneto, plus the special sump I made for it. Because my racer is completely striped down at present, I will carefully measure the weight of the main parts as it goes back together....... I know on these bikes the 2 wheels generally come in at 30 kg's the pair, and this is difficult to do anything about. The modern belt drives save a considerable amount of weight, especially on a twin, I think when i built the twin racer years back the weight saving over the stock primary drive and clutch was at least 3.5 Kg's. I think a Comet engine is around the 30 kg mark as well........anyone know for sure.......
 

oexing

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Would you believe that these BMW RS 54 dohc twins were about 10 kg lighter than the Manxes ? Well, handling was a bit special which many racers never really got used to. My guess, the wheel base was a tad too short for these speeds. Nevertheless Walter Zeller gave the Manxes and MVs hard times. The engines were more successful in sidecar racers with decades of world championships.

Vic
BMW-Rennsport-RS500-Type-256-Left-Side.jpg
 

Mike 40M

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Wonder what I miss, having Norton engines in all four Nortons?
One problem with the AMC box is that it's a short distance (not much meat) between layshaft bearing and the sleeve gear bearing. Make them prone to crack when abused.
 
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davidd

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I think a Comet engine is around the 30 kg mark as well........anyone know for sure.......

Greg,

I weighed the completed engine for Dave Tompkins racer and it was 95 lbs. It had a new BT-H ignition on it. My racer was 280 Lbs. Dave's racer I believe is in the 285 lbs. area. I don't have any titanium on mine. Dave has a lot on his. The Godet racer is 267 Lbs. with a lot of titanium and magnesium cases.

All the casting weights are different amounts, so you cannot be very precise from one bike to another, but I think 275 to 285 lbs. is a good target for a Comet racer.

David
 

Monkeypants

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A couple of years ago I had my 850 AMC trans apart for replacement of the layshaft bearing, which was about to fail completely.
After a good look around in there I decided to take things a little easier in the future. No more powershifting!

For something that was originally designed to cope with 20 HP or less, then marginally upgraded, it does amazingly well. There is a limit though, and the stock 850 Norton seems to be about it. That might be about the same torque output as a stock 1000 Vincent, or a smidge more.
The 850 Norton is a torquey motor.

There is the TTI that will slot right in- expensive but by all accounts an excellent product.

Glen
 
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Monkeypants

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Greg,

I weighed the completed engine for Dave Tompkins racer and it was 95 lbs. It had a new BT-H ignition on it. My racer was 280 Lbs. Dave's racer I believe is in the 285 lbs. area. I don't have any titanium on mine. Dave has a lot on his. The Godet racer is 267 Lbs. with a lot of titanium and magnesium cases.

All the casting weights are different amounts, so you cannot be very precise from one bike to another, but I think 275 to 285 lbs. is a good target for a Comet racer.

David
I am surprised a Manx is that heavy........Mind you i only read the other day that a Manx engine is 35 Kg's on its own.......In spite of the majority of magnesium parts the engine is quite bulky.

I was surprised to read that the magnesium Manx engine is 28 lbs heavier than the aluminium 500 Dommie engine.
This was one of the reasons that Doug Hele wanted Norton to put more money into development of the twin for racing. They ignored his logic.

Re the TTI box fit on a Commando. A friend recently fitted one to his Maney 920 Commando. It required a few minutes with the die grinder to go in. A bit of steel on the cradle had to be removed.

Glen
 
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