Molnar flywheel for the Mk3 - anyone interested?

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mdt-son

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A suggestion was presented to Andy Molnar about offering his steel flywheel in a Mk3 ready version. Bobweights would be as per Mk1/2. He agreed, but requires a minimum order of 5 pcs, as he doesn't want to increase his stock of parts. Who would like to join me in a group order? I will guarantee fulfillment, but a 20% deposit will be required.

Best,
Knut
 
How is the Mk3 Flywheel different? That said I have really only worked on Mk3's so I have concept of what else is out there. Seems to me that getting a Mk3 drive side would be worth it, as if you eat the PTO on a crank you are out to dry trying to find a reasonable MK3 crank.
 
Well, yes, but this thread is about the flywheel.

Norton Twins Steel Flywheel

Norton Twins Steel Flywheel Commando Atlas Dominator Dommi Racer Dommiracer Domi Domiracer 650 750 850 920 cc 650cc 750cc 850cc 920cc 89 mm 89mm stroke Featherbed Feather Bed
www.tga.co.uk

- Knut
 
What advantage is there in a steel flywheel, if the balance factor has not been raised ? Do cast iron flywheels fly apart? A lighter crank in a Commando is probably of no advantage. When I first saw the crank in my 850 motor, I did not believe in it. However in combination with the close ratio gearbox, it is excellent. With a wide ratio gearbox, every upchange is too slow - the revs drop too far, and the heavy crank recovers too slowly. It affects the vacuum in the inlet port when you have more throttle with less revs - throttle response suffers. In that circumstance a quicker taper needle is used in the carb, which affects power output as the revs rise. A light crank tends to make a bike less rideable, it requires more rider concentration.
I use the following combination - heavy crank with 72% balance factor, close ratio gears, 30mm inlet ports, with the leanest possible needles in the carbs. The bike is as good as any other in a 1960s road race class, if not better.
 
Last edited:
acotrel said:
What advantage is there in a steel flywheel, if the balance factor has not been raised ? Do cast iron flywheels fly apart? A lighter crank in a Commando is probably of no advantage.
Click to expand...
1. No correlation between material and BF.
2. Yes, unfortunately.
3. In road racing, a lighter crankshaft brings advantages. Look at Steve Maney's cranks. Strength-wise, a lighter flywheel brings benefits irrespective of application.

- Knut
 
mdt-son said:
1. No correlation between material and BF.
2. Yes, unfortunately.
3. In road racing, a lighter crankshaft brings advantages. Look at Steve Maney's cranks. Strength-wise, a lighter flywheel brings benefits irrespective of application.

- Knut
Click to expand...
I'm interested if the flywheel is lighter so that the MK 111 flywheel spins up faster , like a 750 .
 
Torontonian said:
I'm interested if the flywheel is lighter so that the MK 111 flywheel spins up faster , like a 750 .
Click to expand...
I have no information on the 750 flywheel. The TGA flywheel is almost 30% lighter than a stock 850 flywheel, see the advert.
The important parameter for spin-up and faster retardation is not weight but rather mass moment of inertia.
For a plain disc of given OD, moment of inertia is proportional to weight of course.

- Knut
 
mdt-son said:
Well, yes, but this thread is about the flywheel.

Norton Twins Steel Flywheel

Norton Twins Steel Flywheel Commando Atlas Dominator Dommi Racer Dommiracer Domi Domiracer 650 750 850 920 cc 650cc 750cc 850cc 920cc 89 mm 89mm stroke Featherbed Feather Bed
www.tga.co.uk

- Knut
Click to expand...
Thank link doesn't work for me.
Tried TGA from Google - also doesn't work.
Maybe Andy has problems with his website?
Cheers
 
maaseyracer said:
Will it hold an idle or is this a race only item?
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I am confident it will hold an idle. You know, the crank cheeks possess mass moment of inertia too, so even if the flywheel has less moment of inertia (say, -20%), the overall figure will be much less, maybe -5 to -8%.

- Knut
 
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maaseyracer said:
Will it hold an idle or is this a race only item?
Click to expand...

Yes and no.

I have a Molnar crank in my 750 engine. The complete crank is 3 lbs lighter than stock and my engine will hold an idle with 35mm FCR carburetion or any carburetion I would put on it. Does it spin up quicker than a stock 750? Considerably. Would it get to the top of Dyno Hill faster than a stock 850? Heck if I know. ;)

Forgot to mention my pistons are also lighter than stock and I have long rods too.

Not an 850, but that shouldn't make much real world difference.
 
mdt-son said:
A suggestion was presented to Andy Molnar about offering his steel flywheel in a Mk3 ready version. Bobweights would be as per Mk1/2. He agreed, but requires a minimum order of 5 pcs, as he doesn't want to increase his stock of parts. Who would like to join me in a group order? I will guarantee fulfillment, but a 20% deposit will be required.

Best,
Knut
Click to expand...
yes i am interested
i had been looking into his flywheel for my mk3
 
When I built my 850, I looked at the crank and immediately decided it could never be any good for racing. I corrected the balance factor to suit high revs and still built the bike. That was in about 1980. In about 2002, I had moved to Benalla, and my mate still had a licence, so we decided to try the Seeley 850 -just out of interest. The next year I rode it at Winton and it was hopeless everywhere. Fixed the brake, changed the gearbox and tuned it. It turned out that the heavy crank is not an issue. Norton had a lot of racing experience, and I have come to the conclusion that the Norton twin was an alternative approach. The 650ss was an excellent motorcycle.
I never believed in my Seeley 850, but now I do. Where I can get on the gas really hard with that, is ridiculous and probably dangerous. One of the most frustrating things about road racing is the amount of care which is needed when you are up high in a corner at full lean - it is difficult to accelerate without crashing. With the Seeley, I can flick it into a corner and accelerate flat out from beginning to end on the low line. With a light crank, that would be hazardous - been there done that.
I don't know if I am a good rider, I just ride the bike to it's limit. I usually ride a slow bike against much faster bikes. It is more fun that way. But the Seeley 850 is different. I really like it, and I never thought I would.
 
Torontonian said:
I'm interested if the flywheel is lighter so that the MK 111 flywheel spins up faster , like a 750 .
Click to expand...
The lighter 750 crank doesn't seem to translate to revving faster when in gear, at least with the 750s I've ridden with.
When we are passing or pulling up a long hill the 850 has had a bit more oomph than the two 750s I've toured with.
The heavier crank might make an 850 rev up a fraction slower in neutral though.

Glen
 
My first race bike was a Triton with a short stroke 500 cc Triumph which was made out of 650 parts. It had a light 63mm stroke billet crank. My Seeley 850 is far superior. To race the Triton, I always had to be 120% on top of it. The heavy crank creates a difference which can be managed. The throttle response of my 850 motor is much safer, and it's power is much more usable. It spins-up just as quick as my 500 motor ever did, but it does not get stupid.
Most guys tend to follow each other in corners, usually up on the high line at full lean, and they are very tyre dependent. While they are doing that they are usually trying to go faster - a light crank does not help that process. If you watch MotoGP these days, most passing is done by slipping under other riders in tight corners. On the straights and sweeping curves, it is usually a procession. You do not see much passing when they are at full lean.
 

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