Andover Crankshaft now available

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Apr 15, 2009
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I had often commented that Andover has just about every Commando part except the crankshaft. Sounds like that has changed. I also suspect that shipping will cost as much as the part itself.

https://andover-norton.co.uk/en/shop-details/23406 750
https://andover-norton.co.uk/en/shop-details/23703 850

Andover Crankshaft now available
 
One piece, but not any details about weight
Pretty pricey considering what a Molnar crankshaft goes for
 
From Andover Norton:

750 = 10.790 Kgs (23.78 lbs)

850= 10.840 Kgs (23.89 lbs)
 
One piece, but not any details about weight
Pretty pricey considering what a Molnar crankshaft goes for
2 i looked up quick


ebay

vs
 
Should get a 9.000 rpm redline , now , then .

Well . . . . Wonder what it WOULD be good for ?

Short Stroke ( 80 m.m.) was 8.000 7 in toonin notes says the redlines 7500 with the norvil / W&S valve springs .

AS the valvegear maybe good for 8.000 , like in a 500 Domiracer & S stroke , one'd think this Opens a Few Doors
in the Go Gettum game .

Andover Crankshaft now available


Knactually , the presumption Is it'd run truer . As In less WHIP . So youd figure 7.500 might be o.k. with a carefully built ( hand fitted / finished - polished & clearanced )
IF the Cam & followers would hack it . :(
 
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8000 RPM in a standard stroke 750 is kind of frantic. I would imagine those $825US Norton short stroke engines spun up quick. 130mph in the straights on a mile oval. Well, that's what I read somewhere anyway.

If I can get over my fear of the RGM belt drive in my 750 flying apart, I'll see if I can get the Molnar crank to spin to 8000 RPM for a couple of seconds this summer.
 
I was talking to Dave Coates at Kempton recently about a (very) short stroke motor he and a talented engineer (RIP) built back in the day. They modified their own particular combination of components, and he said he should write down the combination, which I encouraged. He says it would rev to about 9k and “flew”. He tried to buy it back many years later, and thinks it may still be around somewhere. It had a big bore kit as part of the setup.
 
I wonder what they do about sludge buildup, or if it even has a sludge trap?
 
I wonder what they do about sludge buildup, or if it even has a sludge trap?
Wondering the same thing. I would love to see more pictures - maybe I'll bug them for that or @Madnorton will oblige and tell us all more.

This would be a good topic for Ashey's weekly YouTube videos - he did one several months ago but with little detail as they had just received one:
 
How many have seen sludge build up in a 3 piece crank to the point it covers the oil holes feeding the shells. It was considered and seeing as the 3 piece crank has nothing like a dedicated sludge trap it was deemed it was not needed, modern oils and filtration on most of the bikes also mitigates this decision.
For those that feel they need one then they can easily machine an aluminium core insert that will act as a trap like those fitted to Triumph cranks apparently.
The hole through the journals is straight through, this eliminates any stress raisers under the area near the journals. Looking at the drawings it seemed Norton spotted this late on in the life of the Commando and placed a note on later drawings where the drilling should stop. The crank comes with two knock in plugs that are secured in position with grub screws.
 
How many have seen sludge build up in a 3 piece crank to the point it covers the oil holes feeding the shells. It was considered and seeing as the 3 piece crank has nothing like a dedicated sludge trap it was deemed it was not needed, modern oils and filtration on most of the bikes also mitigates this decision.
For those that feel they need one then they can easily machine an aluminium core insert that will act as a trap like those fitted to Triumph cranks apparently.
The hole through the journals is straight through, this eliminates any stress raisers under the area near the journals. Looking at the drawings it seemed Norton spotted this late on in the life of the Commando and placed a note on later drawings where the drilling should stop. The crank comes with two knock in plugs that are secured in position with grub screws.
Thanks for that - pretty much answers all my questions.
 
When you can get your bike to flick into a corner while braking, then immediately accelerate flat out all the way around the corner and up the next straight, you will not need a light crank. You will need smooth power delivery and higher overall gearing. Then watch out for the guys you pass as you leave the corner. If they move sideways and get in front of you as you are about to pass, you have a problem - the speed differential can be too great. It does not matter if your overall acceleration rate is slower, because you accelerate for much longer. The other guys really have to fly to pass you before the next corner. Then the process repeats. There are many ways of skinning a cat. Light cranks and peaky power can be very stressful. I like an easy ride. I have done both.
A Commando-engined motorcycle is different from the norm.
If you are like me, you would believe your motorcycle could not handle like that - festina lente !
Increase the trail - it is dangerous to do that with a peaky bike with a light crank.
 
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My first racer had a 63mm stroke 500cc motor which was made from 650 Triumph parts. If I ran it low-geared, I would only have to blink to get a crash. A short stroke, light crank Commando engine might be better, but probably not much. Everything happens too quickly and you would need to be a genius, especially with separate exhausts. You would have to relie on beating the others after getting out of the corners. - Difficult !
Seeleys come out of corners much faster because they can accelerate earlier..
 
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8000 RPM in a standard stroke 750 is kind of frantic. I would imagine those $825US Norton short stroke engines spun up quick. 130mph in the straights on a mile oval. Well, that's what I read somewhere anyway.

If I can get over my fear of the RGM belt drive in my 750 flying apart, I'll see if I can get the Molnar crank to spin to 8000 RPM for a couple of seconds this summer.
With your light pistons and longer rods it will certainly spin to 8000RPM. I've had my stock crank (with radiused PTO shaft) up to 8200 just for a short test of the light pistons and longer rods. Having said that I don't recommend putting that kind of strain on your motor. I've done it so you don't have to. The stock 89mm stroke powerband drops off before 8000 anyway.
 
With your light pistons and longer rods it will certainly spin to 8000RPM. I've had my stock crank (with radiused PTO shaft) up to 8200 just for a short test of the light pistons and longer rods. Having said that I don't recommend putting that kind of strain on your motor. I've done it so you don't have to. The stock 89mm stroke powerband drops off before 8000 anyway.
đź‘Ť Alrighty then. I can skip that test.
 
Dave Coates’ tuner was Nelson Harring, who was tuner for top speedway rider Les Coffin in west country, UK. Also mentioned in Speedway Tuner book.
 
I have a set of 850 crankcases which were cracked by a kid who used to rev his motor to 8000 RPM. It would have had the low balance factor. My crank is balanced to about 72 %. I use a set rev limit of 7000 RPM. however I often see 7300RPM on upchanges. The motor feels as if it would have no problem revving to eight. I don't want to find out the hard way, that it will not cop 8,000 RPM. In any case it is fast enough without going there. My gearing is absurdly high, but that is where the performance seems to be. While the motor is pulling hard, it is happy. In a race, I simply flicked the bike into a corner while braking, then accelerate smoothly and very strongly around the corner and right up the next straight. The bike is slower than others in a drag race up a straight, but it comes out of corners at a much higher speed. It is a very easy ride. I just needed to watch out for the front guy in the corner as he reaches the end of the corner. They don't usually move sideways, but the speed differential was significant. When your bike handles and pulls like that, you don't need to be the fastest down the straights. Smooth power delivery is important - jerky can make things very difficult. I have a 2 into 1 exhaust system.
I hope what I have posted helps others to get their Commandos going faster - just be careful and patient - a crash does not help anybody. The joke is the Commando motor is fast enough - I would have thought that was impossible.
 
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With the increased trail on the steering, the Seeley stays more upright in corners and I sometimes lost traction at the rear wheel as I accelerated in corners. Most other bikes were up on the high line at full lean and very tyre dependent. It is a strange way to race, but easy.
 
With the increased trail on the steering, the Seeley stays more upright in corners and I sometimes lost traction at the rear wheel as I accelerated in corners. Most other bikes were up on the high line at full lean and very tyre dependent. It is a strange way to race, but easy.

Andover Crankshaft now available :confused:

 
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