Flywheel weight?

Schwany said:

I have zero experience with a Manx cluster. I'll take your word for it. I am getting what Molnar refer to as a Standard 5-speed TTi gearbox sometime in the first quarter of 2024. I think the gearing is going to be a little on the high side compared with what I have in the older AMC gearbox, but I'll get use to it I hope.

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I ran stupidly high gearing with the Manx cluster. It seems to work well with closer ratios. The slow taper needles in the carbs seem to help. My bike corners faster than many others so I am going faster at the beginning of the straits. The motor does not need to be so strong to keep up. If you lose revs you are likely to use more throttle - the taper on the needles is there to compensate for loss of vacuum. On some bikes the taper might be too rapid - the slightest bit rich will cause loss of power. You probably would not detect it on a dyno. You need to have load which creates the need for throttle response when you have lost revs.
I learned a lot about jetting by putting two-strokes on methanol. My mate is about one month younger than I am. I have talked to him as lot about jetting. He has even put TZ350s on methanol. He pointed out that during the 1970s, every new model of bike from one maker, always had different needles and needle jets - to suit the required power characteristics. If you get the needle jets wrong on a two-stroke, often the motor will not even start.
If you are using Commando primary drive and rear hub, raising the overall gearing might not be so easy that you would try a lot of different settings. With my bike, it is much easier. Every time I have raised the gearing, my bike has become quicker - strange ?
When you use petrol as fuel. the jets are smaller, so the errors in jetting are even more significant

When I ordered my 6 speed TTI box from Bruce, he asked about ratios. I requested 1st gear to be the same as a Commando, and the rest evenly spaced between there and 6th. He said 'I know what you mean'. Your 5 speed TTI box probably will not have a stupidly high 1st gear.
The original Schafleitner boxes might have had a high 1st for push-start races, The bikes were rolling when the motors started. My friend's 350 Manx has a 6 speed in it, and I doubt it has a low 1st gear. It was a works bike in the 60s.
I cannot remember what the TTI is copied from. I don't think it was a Quaife.

Schwany said:

I have zero experience with a Manx cluster. I'll take your word for it. I am getting what Molnar refer to as a Standard 5-speed TTi gearbox sometime in the first quarter of 2024. I think the gearing is going to be a little on the high side compared with what I have in the older AMC gearbox, but I'll get use to it I hope.

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IMHO you can relax, I think you‘ll find the TTI 5 speed to be just perfect.

Original Manxes were only 4 speed, and were designed for a push start…. not a standing start… so not really a relevant comparison to 99% of us on here at all (sumthin Al keeps forgetting).

Gearboxes have followed a natural progression. For racing in the 1950s, 4 speed close ratio were the norm, with all 4 gears relatively high. With push start races the high first gear was good. When races became clutch-start the high first gear causes the bike to be slower to get going. With a Commando the problem is not so bad, if you are prepared to rev the motor to 6000 RPM on the start line and drop the clutch. I don't like doing that with a Norton box, if it gives up, the rider can be hit by a bike coming from behind. The 4 gears in the Manx cluster are perfect for a Commando, everywhere, except in a clutch start (motor running).
Most of you guys have probably ridden modern bikes which have 6 gears. I think you would find Moto GP bikes do not use road gearboxes - the internal ratios are probably closer.
The A grade riders in about 1960 rode Manx Nortons mostly with 4 speed close boxes. My mate was the top A grader in Victoria. His 500cc Manx had 5 speeds close, and the 350 had 6 speeds close.
If you ever ride a Gold Star BSA with the RR T2 gearbox, you will discover what the 4 speed race gearbox is like - Most Goldie owners get rid of that gearbox - except for the guys who race. First gear is the problem.

The last time I raced was the only time I have ever had my Seeley 850 really going, and I was very nervous doing it. I got a great start and the rest is easy. But I really did not believe the Norton box would cop that treatment. I know people have used Norton boxes in conjunction with 1000cc Vincent motors, but that is no real comfort. I only bought the 6 speed TTI box to complete the bike. I intend to use it one day, just to find out the potential - it should be even better than the Manx cluster. I get two things out of racing - I love the dogfights, and I love developing the bike. Winning races is not as important as proving the bike.

Andy Molnar must know where a 4 speed Manx cluster can be obtained at a reasonable price.

Nigel, you have made me feel very old. The stuff I talk about was current in the early 1960s. How many years ago was that ?
The Commando motor is very different from pre-1965. I never expected it to be good.

Fast Eddie said:

IMHO you can relax, I think you‘ll find the TTI 5 speed to be just perfect.

Original Manxes were only 4 speed, and were designed for a push start…. not a standing start… so not really a relevant comparison to 99% of us on here at all (sumthin Al keeps forgetting).

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Perfect will be welcome with open arms.

I do not know what Commandos race against overseas, but in Australia, oversize CB750 Hondas are the go. Rex Wolfenden builds most of them. At one time there were 14 of them racing. If you read the link I am about to post, it describes the handling of his bikes when accelerating on a lean. Rex is a decent person, and I once had a conversation with him about the size of this engines. He correctly pointed out, they are within the historic racing rules. He told me then that Nortons were the only bikes which gave him trouble in races. When his bikes are in corners, they usually follow each other at great angles of lean being very careful. With Seeley 850, I have turned tighter into corners and simple blasted past the leaders. If I accelerate when on a lean, my bike stays more upright and turns in the direction I need to go. Period 4 is a methanol class. In the link both Period 4 and Period 5 bikes are described. My 850 motor is slower down the straights than the 1100cc Hondas, but my bike is much quicker in corners. If you get onto the straights going 10 MPH faster, the other guys need much more power, to pass you 10 MPH faster towards the ends of the straights. The rider adjusts to the bike. With a Commando, you need to make it handle - more trail.

Isn't everywhere overseas from Australia?

The early inline 4's were terrible handling motorcycles.

I never followed club racing much and didn't road race so not up on any rules. I'm surprised an 850 twin runs in the same class as an 1100cc inline 4. I thought racing rules were the reverse (bigger displacement twins run with smaller displacement inline 4 powered bikes) like World Superbike was when Carl Fogarty and others were kicking butt on Ducati's.

I've never ridden a Seeley frame with a Norton twin engine in it. I imagine it would be fun. I don't consider them to be Commandos myself. I think of them as a purpose built race bike powered by a Norton twin engine. If I were 35 years younger I'd build one with the parts on my P11. I'd get all dead riding on the street if I built one today though, so isn't gonna happen.

I've forgotten what the heck this thread is about. Oh yeah, flywheel weight. Mines lighter, and I like it, but it's not in an 850.

Fast Eddie said:

IMHO you can relax, I think you‘ll find the TTI 5 speed to be just perfect.

Original Manxes were only 4 speed, and were designed for a push start…. not a standing start… so not really a relevant comparison to 99% of us on here at all (sumthin Al keeps forgetting).

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Yep, I used a 4 speed with Manx ratios in my Rickman from '76 to '79.

The 4 ratios were exactly the same as the 2nd, 3rd, 4th and 5th ratios of the typical Quaife 5 speed box used in race bikes at the time!

I pushed off in first, they pushed off in 2nd, they may have used 1st at certain hairpins, but not all.

For the additional cost, not only of purchase but of regular repair (broken lay and mainshafts, numerous gears and broken cases), compared to not taking the inner cover off in 4 seasons of racing, I figured I made the right choice.

In 2015 with clutch starts, TTi 5 speed for me!

As a road bike, the Manx box is the equivalent of a RRT2 on a Goldie, but with no kick start, rather you than me.

As for race classes, well, back in the day ('75 to '79) I rode both 750 and 850 Norton twins in the common 501 to 1000cc class and various open 175 (or 251) to 1300 or 'Unlimited' capacity classes.

As a classic, I have ridden a 750 short stroke in F750 and 1300 Classic (open engine format) and 1300 twins.

The bikes were reasonably competitive.

Riding my Seeley 850 is like playing a piano, you play it up and down through the gears. I never thought I could get it right. But it is a really good ride. I just did not know how to use it. What it can do in corners is not obvious and not something I would normally do, with my previous bikes. The rider adjusts to the bike. It can make you look like a real ace or it can destroy you.
I have come to really like the heavy crank, it is not a problem, but an advantage. That last time I raced the bike, I had 3 really good rides - up in the front bunch, in all of them.
When I was modifying the bike, I knew what I was doing, but arse still beats class.

It is a bit like that. The music was better in some ways. Historic racing began in October 1973 in Australia - that was the beginning of the end. It was well-intended but stupid. The guys who started it had never raced. It does not matter in which year a motorcycle was made - it is what it IS that matters. I would have loved to race against bevel Ducatis - but very few were ever raced.
Gowanloch used to race in Historic Period 5 - https://ducati-gowanloch.com/

acotrel said:

It is a bit like that. The music was better in some ways. Historic racing began in October 1973 in Australia - that was the beginning of the end. It was well-intended but stupid. The guys who started it had never raced. It does not matter in which year a motorcycle was made - it is what it IS that matters. I would have loved to race against bevel Ducatis - but very few were ever raced.
Gowanloch used to race in Historic Period 5 - https://ducati-gowanloch.com/

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You didn't miss much, most 750 nortons were quicker than most 900ss ducatis on the track.

hybridracer said:

You didn't miss much, most 750 nortons were quicker than most 900ss ducatis on the track.

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Australian road racing rules never presented the opportunity for anyone to experience that situation. Bevel Ducatis are in 'Period 5', Commandos are in 'Period 4' with cut-off date of 1972. The competition has always been idiocy. Big twins could be in a class of their own, mainly for development reasons. For a short time there was a one-make class for 883 Harley Sportsters - it did not last long. With historic racing based on dates the whole thing becomes pointless - creating the past is impossible. What happens with the Barry Sheene Memorial Trophy at Goodwood is probably as close as can be achieved.
The only time road racing really interests me is when the same TYPE of machines are racing.
We need to recognise what game we are in - ENTERTAINMENT !