New project, need some opinions

STEVE LANCEFIELD patented the canted motor Vs v i b r a t i o n principal , so we're told .



If your metickoless , you might keepup . ' period ' 7R brake , manx chassis , H.R.D. motorvation . In Sydney around 1970 .

Thisis from early 70s , maybe ' Big bike ' . A Californ eye A Combat Manx . ( you can see you could spead motor & box more . )


But this probably more like yours if a Slim Line . GRINDING EXHAUST PIPES helps you fall off . So see they dont .




If your filthy rich , just by a domiracer Chassis ,
Take it out to 920 . ( Cortina Pistons ) or sleeve & 960 . Ditto . fairly bulletproof , in a speedway outfit . Fairly STOCK ( Factory parts ) & it'd choke itself before it blew . 2 S cam .

Just realised how brave the OP is… starting a thread by openly inviting OPINIONS… on the INTERNET… !!

Should be dificult to grind them , like this .

'Dunstall' Norton 750cc 'Domiracer' Frame no. P7 6850 Engine no. 20 116603​

https://www.google.com/url?sa=i&url=https://cars.bonhams.com/auction/23600/lot/397/dunstall-norton-750cc-domiracer-frame-no-p7-6850-engine-no-20-116603/&psig=AOvVaw3HJfemxPomo8r9ZYtU_Lsk&ust=1720591866620000&source=images&cd=vfe&opi=89978449&ved=0CBIQjhxqFwoTCNiZlK2mmYcDFQAAAAAdAAAAABAn
A pile of silly pictures there . food for faught .


If you get OBJECTIVE , all the stars alighn and all the neccesary components gravitate to you , if left alone . Best is HILLCLIMB . So you can sit on the handlebars to stop it flipping .
and it can stand on its nose and still go into a corner , brakes locked up , and drifting . And can get the power on before , into the apex , so your powering out of it before youve gone into it .

Its Quicker , that way .

My project is based on a stock Atlas.

Click to expand...

If it looked dead stock , from 20 paces , you could tuck in the pipes & clean up everything , and say ' it's all standard ' ( just depends what you mean by ' standard ' . )

Olde Len had a Marroon & White wideline 88 , pinstripes , chrome , stock controls . With a Ex Race chopped H.R.D. Vincent engine in it . Pootle allong perfectly satisfactorally .

Sort of 50s Art Deco . Disquise or was it ? .

In the late 60s, in Victoria , Arthur Pimm used to race a 1000cc Vincent Motor in a featherbed frame in Allpowers A Grade races against the 500cc Manx Nortons. I only ever saw him win one race. He was a night-cart operator so had lots of money, and he was an excellent rider. The race he won was on the big circuit at Phillip Island. My first race bike was a modified Triumph motor in a featherbed frame - they always feel very big. My Seeley 850 is a much better thing to race. A Vincent motor in a featherbed frame would be horrible. These days Ken Lucas has one and he puts A-grader Peter Guest on it in Historic races - they win a few. But the races are different from what they were in the old days - the kids are now all mates. We were not.

Fast Eddie said:

Just realised how brave the OP is… starting a thread by openly inviting OPINIONS… on the INTERNET… !!

Click to expand...

Everybody's got one.

My opinion right out of my ass ....

Getting that featherbed frame from Molnar's shop to Seattle is going to be spensive. And that is only the beginning.

Edit: Leaning the engine forward may be your best bet for aftermarket or stock parts to complete your fueling and exhaust needs. You will have to use your creativity to make the engine plates to mount the engine. However, if I'm not mistaken you told me you had the tools to make engine plates easily.

Might be some creative thinking required to stand a Commando set of crank cases up straight in a Featherbed frame. If you have to use Commando primary covers you would have to relocate the mounting holes in either the inner primary or the drive side crank case. Sounds easy, but I don't think it is that simple. I have not done it myself, but have done a few things in my lifetime and that is my educated guess.

Yeah I'm full of crap.

Good to see Spencer back with all the historic images.

Fast Eddie said:

Just realised how brave the OP is… starting a thread by openly inviting OPINIONS… on the INTERNET… !!

Click to expand...

I think the OP will go with opinions that line up with what he already had in mind.

Glen

Schwany said:

Everybody's got one.

My opinion right out of my ass ....

Getting that featherbed frame from Molnar's shop to Seattle is going to be spensive. And that is only the beginning.

Edit: Leaning the engine forward may be your best bet for aftermarket or stock parts to complete your fueling and exhaust needs. You will have to use your creativity to make the engine plates to mount the engine. However, if I'm not mistaken you told me you had the tools to make engine plates easily.

Might be some creative thinking required to stand a Commando set of crank cases up straight in a Featherbed frame. If you have to use Commando primary covers you would have to relocate the mounting holes in either the inner primary or the drive side crank case. Sounds easy, but I don't think it is that simple. I have not done it myself, but have done a few things in my lifetime and that is my educated guess.

Yeah I'm full of crap.

Good to see Spencer back with all the historic images.

Click to expand...

Getting the motor positioned right might be most important.

Trial and error is all about building a bike and getting it set up right for each person, when I built mine I just did the opposite to my mate's set up, learned and improved from his mistakes and this was way before the internet, but I learned a lot and was lucky I got it pretty close to good and made small improvement as I went along, my Commando/Featherbed was the first bike I ever built and I was still young in my early 20s, but we all make mistakes, that's the fun thing about building your own bike and setting it up for yourself, not for anyone else.
I have had 44+ years of fun times on my Commando/Featherbed and it still amazes me in how good it is although it's showing its age, but that's the way I like it, a well ridden bike with a lot of hard miles on it and it still has more to give, it is now my play bike, my hotrod bike.
Building a bike from scratch is the most satisfying thing you can do and even better when it works out even better when on the road, mine has proved itself and even my good mate Don who got me into Norton's and Featherbed frames back in 1976 (I was 17 years old at the time) when I first rode his and 2 weeks later I rode my new 74 850 Commando out of the shop front door, he still can't believe it, we are still good mates.

Ashley

Heard back from Andy Molnar. If I want to use the alu primary with the 850 tilted motor then no center stand which is a must have. Also, the megacycle 56000 is off the table and will be sold with matching lifters. This will help fund the project. Also I have an excellent pair of new conti mufflers for Ducati if anyone is interested. These are real contis.

ashman said:

Trial and error is all about building a bike and getting it set up right for each person, when I built mine I just did the opposite to my mate's set up, learned and improved from his mistakes and this was way before the internet, but I learned a lot and was lucky I got it pretty close to good and made small improvement as I went along, my Commando/Featherbed was the first bike I ever built and I was still young in my early 20s, but we all make mistakes, that's the fun thing about building your own bike and setting it up for yourself, not for anyone else.
I have had 44+ years of fun times on my Commando/Featherbed and it still amazes me in how good it is although it's showing its age, but that's the way I like it, a well ridden bike with a lot of hard miles on it and it still has more to give, it is now my play bike, my hotrod bike.
Building a bike from scratch is the most satisfying thing you can do and even better when it works out even better when on the road, mine has proved itself and even my good mate Don who got me into Norton's and Featherbed frames back in 1976 (I was 17 years old at the time) when I first rode his and 2 weeks later I rode my new 74 850 Commando out of the shop front door, he still can't believe it, we are still good mates.

Ashley

Click to expand...

Many people do not seem to know the difference between a road bike and a race bike. With a road bike, you do not usually go around in circles with the corners repeating and arriving faster. As you do that with a race bike you are usually continually adjusting it. If you take a road bike and try to race it, you will always be initially slow until you 'improve' it. However it is possible to tune a motorcycle to a stand-still. What happens with race bikes can be very deceptive - often the faster you try to ride, the slower you become. It is a source of never-ending amusement.

acotrel said:

Getting the motor positioned right might be most important.

Click to expand...

You are correct captain obvious.

from our event last weekend, Pete McKenna's bike upright in a slimline frame

acadian said:

from our event last weekend, Jim McKenna's bike upright in a slimline frame

View attachment 115286

Click to expand...

Peter Mckenna . Won a prize/trophy . Best vehicle / new build .

worntorn said:

...
I would look at getting the lowest possible combination of rod and piston weight. That might be with a lightweight piston fitted to the stock rods.
...
You'll want to do your own research to check my numbers.
...
Glen

Click to expand...

Here is the correct comparison info for a build similar to Seattle’s:​

The JSM long rod weights for solid frame 850. 77 med C.R. piston presently in stock for long rod is 182 grms bare. With pin clips & rings piston total = 260 gr.

MAP piston for stock rod is 234 gms bare. With pin clips & rings piston total = 312 gm.

Stock rod small end approx 77 gms

JSM std JSM rod small end 106 gms or ultralight rod small end 95 gms for up to 70 HP

MAP long rod bushed small end 116 gms

Total reciprocating weight (causes vibration) JSM std long rod & piston = 366 gms (or 355 gms with JSM ultralight rods)

Total reciprocating weight (causes vibration) MAP piston for stock rod = 392gms

JSM 850 std med C.R. pistons for stock rods 255gms bare (lighter pistons available on special order).

Stock 850 Norton piston approx 315 gms bare.

Note that the longer rod significantly reduces vibration because the piston direction reversal is less abrupt than with shorter rods. The reduced rod angle during the power stroke reduces the side thrust on the cylinders, reducing wear/friction and increasing efficiency.

Vibration to be reduced by 1/3 (to ½) with the JS long rod setup compared to stock.

Note that the MAP pistons are too short and went too thin on the piston skirts which can cause them to collapse from .0035” installation clearance to .011+” clearance after running in, causing rattling and smoking as described at the link below (see post #34):

https://www.accessnorton.com/NortonCommando/forged-m-a-p-pistons.26197/page-2

A heavy bottom half of the rod isn't a great thing either- the whole assembly wants to go out thru the top just before it reverses direction.
I like the stock rods because they have the lightest small end weight and the lightest overall weight, plus... they are already in the engine, so they cost zero.

The idea of fitting a lighter piston to the stock rods seems a good one. I hope you continue with this.
I noticed that the MAP offers a very light piston for this purpose. It also is quite reasonably priced, as piston prices go.
It did not have the problem you mention above, in fact these MAP pistons worked very well long term for the fellow who posted about them.
The problem MAP pistons were the shorter lighter type for long rods, a different item, than the one I suggested. I mentioned both types in my post.

Glen

With a Commando engine - compared with a Triumph engine - the Commando has squish and at about 9 to 1, the Commando piston is flat top, not domed. With a Triumph at 9 to 1, lighter and taller pistons can be used which fit closer at the edges of the crown to give squish. They give a very noticeable power boost. A 500cc Manx Norton has a squish band which is full circumference. Steve Oszko's 350 Manx is an ex-work's machine. Inside the combustion chamber, there is a second squish band higher-up, which has been welded and cleaned-up to remove it.

worntorn said:

A heavy bottom half of the rod isn't a great thing either- the whole assembly wants to go out thru the top just before it reverses direction.
...
The idea of fitting a lighter piston to the stock rods seems a good one. I hope you continue with this.
...

Glen

Click to expand...

The big end of the stock rod weighs 343 grams. The big end of the JSM long rod weighs 326 grams.
Total weight of stock rod 420 grams Total weight of JSM ultralight long rod 401 grams, std JS long rod total weight 431 grams
Total weight of stock 850 rod and piston (one side) is 829 grams, Total weight of JSM std long rod and 850 light piston is 717 grams.

Lighter and lighter pistons for stock or long rods can be expensive depending on machining. Undercrown milling adds $30 to each piston. This lightens the piston by making the aluminum crown a consistant thickness.

Here's a forged piston without the undercrown milling


Here's a forged piston with the undercrown milling for the twisted valve pockets


Below is an aftermarket stock rod piston. Since the pin is lower there is a lot of dead aluminum weight between the pin and crown that can be removed with under pin milling as shown.


Forged pistons need the extra milling in order to be lightweight. But jacks up the price? Billet pistons are entirely machined (not forged) but they are not as strong. Forging shapes the metal along the lines of stress so it resists cracking. And what brand of pistons do you want in your Norton? American made or made in China? Lots of comparisons to make.

See link below about stock Norton D rod failure:
https://www.norvilmotorcycle.co.uk/techtalk35.htm

I have 3 sets of stock Norton al rods running at present. The Mk3 might have D rods. I read this post by Seeley 920 about a decade of riding ago and decided to worry about things other the rod failure. At the rate I'm deteriorating, I'm sure all three sets will outlast me and maybe the next set of owners too!

Off topic Sidenote- On the subject of "How long does it really need to last" and aging out-
I see ten Vincents for sale on the Spares Co. site. A few years ago it would have been 2 to 3 or sometimes none.
Prices are way down, naturally.

If I was going to go a step further with my 850 motor, I would buy Jim Scmidt's long rods and 12 to 1 comp. pistons. His pistons probably have slightly domed crowns to get the comp. But I doubt the crowns would be high enough to be adverse. I would also buy a programmable ignition system, and work on developing a curve for more torque. It is easy to get more power by revving the motor higher. But with a Commando engine, that is probably the wrong way to go. What I found with the 850 engine is it took longer to learn how to use it properly. It did not really go until I used close ratio gears to ride the torque. With close gears, the power never drops out the bottom. It stays between 5,500 RPM and 7,300RPM. The overall gearing becomes much higher.
With my first race bike, I had the opposite problem. I was always looking for ways to help it pull harder at low revs. It desperately needed 6 gears, and I never had much money to spend on bikes. I liked that bike, it was a thrill-a-minute, but deadly.