1971 Single sided swingarm fastback (2011)

I asked the question and the only swingarm I could find similar to what he is using was a hawk 650 gt that had the top mount ,all the other were link based for the vfr's.Either way he has done a great job of it.If you use a hawk swingarm you can convert the spindle to take the VFR wheel.

Would this mod add a little weight?
Although it's alloy, it looks to be a very substantial piece. The Triumph Daytona 955i with single sided swingarm weighs 7 pounds more than the same bike with a double sided swingarm. Both are monoshock and both are alloy, so its all in the swingarm design necessary to hold up from one side only.

The beefiest stock Commando swingarm is the MK3 version. It weighs just over 8 lbs, surprisingly light for such a rigid piece. The flimsiest Commando swing arm is only a few ounces lighter but is a lot flexier.

I'm looking for ways to cut Commando weight. A single sided swingarm is a consideration but its looking like it might actually add to the stock number.
There is also the monoshock to consider. Is the monoshock lighter than two standard shocks?

Glen

motoalchemist said:

Hello all,

so this weekend I finally got the bike done to the point of taking it out for a ride. It was only a series of 4 or 5, 15 minute rides, but i wanted to check things as there are so many "one off" parts on this bike. Overall the motor is strong, no major leaks and the CR carbs are very nice, but still need a little fettling..

The seat is very comfortable, but the riding position is "different" . The bike ran very smooth and strong, and I am completely stunned at how well it is handling so far. I have had the bike up to about 45 miles and hour and have taken a few residential turns at 30.bike response well and true, so wobble or confidence killing movements, holds its line and goes like a norton. One thing I did learn is you must keep balls of feel on pegs while making aggresive turns, my big feet drag if I dont. Which gives me more reason to upgrade the rear spring for my fat ass and to raise the rear of bike for a bit more clearance.

over all I am extremely excited at how well this bike is running and handleing. I wil post a vid as soon as I can get someone to tape me.

Click to expand...

The bike is a fascinating amalgam of new and pre-millenium components.
What is the final wheelbase on the bike, looks 60+ ish?

What is the intended end use for this bike ? Surely function dictates form ? When developing a bike it is normal to progress from point A to point B, testing all the way. When you do a lot of changes at one time, you end up riding a bike which might be radical and can more easily bite you. That rear tyre size might be too big for the motor - you have to get heat into it to make it to work properly, if you are going to ride the bike fast. Also you need to think about how that rear end affects the frame rake as you accelerate out of and brake into corners - you seem to have added a lot of length. I suggest it might be wrong to believe that because something is modern, it is necessarily better. In the end, it is how the bike performs against others during competition which is the measure. 'Because I can' is never a good reason for doing anything. I suggest it is never wise to speculate about the effects of changes you make to a bike - take it and test it as you go.
My own bike handles extremely well. It has been developed progressively over several road race meetings, however I think the result has been more by good luck than good management. Bike handling is not a continuum from old to new - motors which give over 100 BHP dictate a whole new ball game. What applies to a Manx Norton's handling does not apply to a MotoGP bike.

acotrel said:

...'Because I can' is never a good reason for doing anything'...

Click to expand...

:shock:

Interesting project, I monoshocked my Commando back in 94, using 89 Yam 600 wheels forks and swing arm, also put an extra Iso underneath the engine and a Norvil head steady to help with the slightly longer wheel base.

Bike rides really well, my Son an Ex Classic Racer rode it round Cadwell and was very complementary on its handling.

Hope yours is as pleasing as I found mine to be .

good luck
Chilly

Please understand, I was not trying to rain on your parade. I've built quite a few racing bikes and I am always very careful, the first time I ride them after making major changes. I've been bitten a few times. What you are doing is radical rather than progressive, so the risks are greater. A friend of mine once said 'every time we fall off, we could be killed'. I never really think of it like that - however he is probably correct, especially if you don't know how to get off safely at speed.

murraycod0 said:

I asked the question and the only swingarm I could find similar to what he is using was a hawk 650 gt that had the top mount ,all the other were link based for the vfr's.Either way he has done a great job of it.If you use a hawk swingarm you can convert the spindle to take the VFR wheel.

Click to expand...

sorry I have been out for awhile, but it is a VFR 750 swingarm, bone stock. I originally was going to use a Ducati swingarm back when I started project, in the mid 90s, but they were too much money back then.

I suspect weight would be in excess of stock by quite a margin. I have a Ducati owning friend who has two magnesium single sided swingarms, but they retailed at AU$15,000 each at the time some years ago. I suspect that the two main driving forces behind single sided swingarms are the "cool" factor and wheel changes. Oh, except that you cannot have a centrestand on a single sided swingarm bike, which leaves......

Fullauto said:

I suspect weight would be in excess of stock by quite a margin. I have a Ducati owning friend who has two magnesium single sided swingarms, but they retailed at AU$15,000 each at the time some years ago. I suspect that the two main driving forces behind single sided swingarms are the "cool" factor and wheel changes. Oh, except that you cannot have a centrestand on a single sided swingarm bike, which leaves......

Click to expand...

...only “wheel changes” (using a dead leg)

Fullauto said:

I suspect weight would be in excess of stock by quite a margin. I have a Ducati owning friend who has two magnesium single sided swingarms, but they retailed at AU$15,000 each at the time some years ago. I suspect that the two main driving forces behind single sided swingarms are the "cool" factor and wheel changes. Oh, except that you cannot have a centrestand on a single sided swingarm bike, which leaves......

Click to expand...

My '96 VFR750 had a factory centre stand that I used to do wheel changes! And an exhaust designed to swing out of the way.

Pity they didn't design the downpipes with the same maintainability in mind!

motoalchemist said:

sorry I have been out for awhile, but it is a VFR 750 swingarm, bone stock. .

Click to expand...

are you sure? i had a close look at it awhile ago & matched up with hawk 650 gt like this post also indicates
https://www.accessnorton.com/Norton...ed-swingarm-fastback.7750/page-11#post-100401

https://www.accessnorton.com/Norton...ed-swingarm-fastback.7750/page-10#post-100399

a pix of your swingarm

https://www.bikebandit.com/oem-parts/1991-honda-hawk-gt-650-nt650-swingarm/o/m151581sch14270

https://www.accessnorton.com/Norton...ed-swingarm-fastback.7750/page-10#post-100397

https://www.ebay.ca/sch/i.html?_fro...A0.H0.TRS5&_nkw=hawk+650+gt+swingarm&_sacat=0

Does the rear end finish up at the same ride height ? The amount of squat is affected by the amount of suspension travel and as you accelerate, effects the frame rake and thus the trail at the front wheel. Perhaps, you also need more fork travel ? With some bikes, minor changes can set you up for a catastrophe. I would be very careful the first time I rode the bike after it has been modded. Pick somewhere you can crash safely.

Because something is used on modern bikes, that does not necessarily make it better. Between old Commandos and moderns, there is no continuum or natural progression. The first road race mono-shocks appeared on TZ750s in the early 70s. At the same time there was a TR750 Suzuki with a Harris twin shock frame, which was better. The Japanese factory canned it and it ended up with Rod Coleman in New Zealand. Pat Hennen rode it with success in Australia.

acotrel said:

Because something is used on modern bikes, that does not necessarily make it better. Between old Commandos and moderns, there is no continuum or natural progression. The first road race mono-shocks appeared on TZ750s in the early 70s. At the same time there was a TR750 Suzuki with a Harris twin shock frame, which was better. The Japanese factory canned it and it ended up with Rod Coleman in New Zealand. Pat Hennen rode it with success in Australia.

Click to expand...

Its funny you mention Pat Hennen. He work with me todayat SFO airport......but you are right about modern bike parts making it better.

acotrel said:

Does the rear end finish up at the same ride height ? The amount of squat is affected by the amount of suspension travel and as you accelerate, effects the frame rake and thus the trail at the front wheel. Perhaps, you also need more fork travel ? With some bikes, minor changes can set you up for a catastrophe. I would be very careful the first time I rode the bike after it has been modded. Pick somewhere you can crash safely.

Click to expand...

Hello,
well, I was able to get some more mles on the bike. I did install a heavier rate rear spring to help with the sag. The bike does have some more figeting to do. At this point my stock commando 750 handle much better than this bike. But at this pint the bike has become more of a conversation idem than anything else.

84ok said:

are you sure? i had a close look at it awhile ago & matched up with hawk 650 gt like this post also indicates
https://www.accessnorton.com/Norton...ed-swingarm-fastback.7750/page-11#post-100401

https://www.accessnorton.com/Norton...ed-swingarm-fastback.7750/page-10#post-100399

a pix of your swingarm

https://www.bikebandit.com/oem-parts/1991-honda-hawk-gt-650-nt650-swingarm/o/m151581sch14270

https://www.accessnorton.com/Norton...ed-swingarm-fastback.7750/page-10#post-100397

https://www.ebay.ca/sch/i.html?_fro...A0.H0.TRS5&_nkw=hawk+650+gt+swingarm&_sacat=0

Click to expand...

Hmm, wow, you might be right. I was told it was VFR750 when I bought it in the mid 90s, back then the internet was not quite as full of info and I had no other reason to not question what it was......kind of blown away at this point.

Hello, I have had some time to put a few hundred miles on my "special" The bike is fast, CR carbs stock engine with a few internal lightening mods.
Handling is still not quite there, the front end I think ive sorted after about 4 different oil viscountcies tried. The rear end i had shock rebuilt with new charge and fluid and a very heavy spring. But mostly The bike has become just a bike that get compliments. The idea I had 20 years ago to make a super norton have fizzled

@motoalchemist wow! That looks absolutely stunning!

Kudos to your engineering work, and especially your vision!

Very cool - must be fun just watching other riders react to the details.