Commando with VFR750 Fork/brake Conversion

[richlandrick]

CoPilot AI and I have been chatting for about a week now, discussing the best donor front end for a 1975 MK3 Commando. It says the easiest and best conversion (for me) is to use the front end of a 1991-1993 CFR750R. The goals are improved fork performance and dual front brakes. I will need to get a new hub and wheel to keep the Commandos period appearance.

Has anyone here done this conversion? If so, got pics?

 

[t ingermanson]

What are the qualifying specs that make that fork particularly compatible?

 

[richlandrick]

The only part that needs to be fabricated is the steering stem. The rest are bolt-on donor parts or purchased ready to bolt up (custom hub). It allows for two or four opiston Nissin calipers without adapter plates. Try asking CoPilot. That AI is very stoked about the possibility. Humor.

It is affordable and relatively easy. Maybe less than a $1,000 for everything, but I don't yet know exactly how much the wheel hub will cost.

Four-piston dual front brakes with modern rotors and cartridge front forks with correct geometry for the Commando.

 

[Elfix]

CRF750r? VGR750? What the heck are those?

I could see perhaps a VFR750 front end….

And custom building a steering stem pretty much adapts ANY other set of forks insofar as the only connection to the chassis is the steering head. It would seem to me you are looking to match fork length and the trail created by the offset of the triple clamps.

 

[richlandrick]

Typo. Maybe someone can fix it. It should be VFR.

Yes, the trail and fork length matches. I know of the common donors used over the years and the new internals avaliable for the forks. I'm exploring options. And these forks and AI did not exist when the early mods using donors started. Matching length, trail, appearance (conventional forks), drammatically better fork and brake performance seem like good things. Since I have a MK3 I don't have to worry about the speedo drive.

 

[seattle##gs]

Some of the modern Triumphs have very nice front ends that are very retro. Should give you what you want and the classic appearance. Has anyone looked into this?

 

[t ingermanson]

My cursory searches have differing steering angles between the two bikes, even with the strange mk3 yokes. The steeper steering Honda has much less offset in its yokes, and smaller wheels, to arrive at similar trail numbers with the Norton. Keeping the Honda fork offset will create ponderous steering, which is maybe what you want?

Cognito Moto specializes in fork swap parts, makes spoked hubs to match later model forks, and will make custom yokes to spec. If you go with them for yokes and hub, it should be a bolt up affair.

As you can see in my avatar pic, I've done a Honda fork swap for stiffer steering, better damping, and twin discs, so I'm not just being a contrarian. I rode my bike with 45mm fork offset for a decade before I bit the bullet and machined some new yokes at the Norton's stock offset. I only regret not doing it sooner.

AI has steered me wrong a lot when looking for technical assistance. If the world continues on this blind path, we'll all be its slave one day (hooray?), but it's currently not as proficient with details as it's cracked up to be.

 

[Fast Eddie]

AI should be used as a way of doing a lot of data trawling quickly. But analysis of the data, and THE DECISION must most definitely still be dome by the human.

It’s just wrong SO often. Try it yourself on things that you already know, you’ll see.

I saw this recently…

 

[Madnorton]

AI should be used as a way of doing a lot of data trawling quickly. But analysis of the data, and THE DECISION must most definitely still be dome by the human.

It’s just wrong SO often. Try it yourself on things that you already know, you’ll see.

I saw this recently…

View attachment 124677

AI was not wrong, it answered the question. It was the question that was incorrect.

 

[Mark Savage]

AI was not wrong, it answered the question. It was the question that was incorrect.

Not really, AI states, “Edible comes from the Latin word edere, which means “to eat.” Anything that people can safely eat is described as edible”.

Oh, wait…

 

[richlandrick]

Some of the modern Triumphs have very nice front ends that are very retro. Should give you what you want and the classic appearance. Has anyone looked into this?

I'll check, but they don't come up in the searches. CoPilot told me they will not work, but it lies.

 

[MichaelB]

My cursory searches have differing steering angles between the two bikes, even with the strange mk3 yokes. The steeper steering Honda has much less offset in its yokes, and smaller wheels, to arrive at similar trail numbers with the Norton. Keeping the Honda fork offset will create ponderous steering, which is maybe what you want?

Cognito Moto specializes in fork swap parts, makes spoked hubs to match later model forks, and will make custom yokes to spec. If you go with them for yokes and hub, it should be a bolt up affair.

As you can see in my avatar pic, I've done a Honda fork swap for stiffer steering, better damping, and twin discs, so I'm not just being a contrarian. I rode my bike with 45mm fork offset for a decade before I bit the bullet and machined some new yokes at the Norton's stock offset. I only regret not doing it sooner.

AI has steered me wrong a lot when looking for technical assistance. If the world continues on this blind path, we'll all be its slave one day (hooray?), but it's currently not as proficient with details as it's cracked up to be.

Looks like a great website and source..

 

[richlandrick]

All the comments about AI are about right in my experience. Sometimes it adds criteria I didn't want. And it often just seems to be lazy.

The VFR750F conversion will not work for me because the custom wheel hub would be too expensive. I'm still searching for the ideal candidate. The spoked wheel seems to be a big hurdle to get over.

 

[Fast Eddie]

All the comments about AI are about right in my experience. Sometimes it adds criteria I didn't want. And it often just seems to be lazy.

The VFR750F conversion will not work for me because the custom wheel hub would be too expensive. I'm still searching for the ideal candidate. The spoked wheel seems to be a big hurdle to get over.

Why are you so insistent on transplanting something?

Nothing wrong with doing that, but, unless you have a high level of knowledge and are a competent machinist with access to the required machines, it is likely to be quite a project.

Conversely, Norton forks bolt straight in, and generally speaking, don’t work too bad.

Upgraded aftermarket internals are easy to purchase and install if you want improved performance over the originals.

Jus’ sayin’ …

 

[o0norton0o]

1993 showa dampers are not externally adjustable for compression and rebound low speed damping response control, nor do I believe it has secondary shim stacks to handle high speed damping. The only thing you are getting with that swap beyond any currently available bolt on aftermarket norton parts is the dual disc brakes..... And as usual, that upgrade's performance superiority is most often used on a race track, not some public roadway...

I've been doing a commando fork modification project testing for a few years. The best fork internals for a commando on "public roads" is the Cosentino set without any doubt... The externally adjustable low speed damping and the secondary shim stack valves for high speed damping (pot holes, bumps, and such) give high performance AND a wide range of that performance on the variable quality of public road surfaces.


There are damper sets that split the compression and rebound duties into separate fork legs and allow for more specific tuning, but that same configuration does not have secondary shim stack valves to allow a wide range of performance that the variation of public road surface quality may require. The split compression and rebound legs design, without any shim stacks seems like a great race track set up where the track surface doesn't vary much and require a secondary shim stack to kick in on rough surfaces.. I've owned a set of Landsdownes and they worked OK on public roads. They certainly made the bike handle much better than the stock commando set up which seems very ponderous compared to anything else that I've ridden..

You could easily buy Cosentino's from NYCnorton and brake kit from Don Pender and be done with upgrading in a single afternoon,.... or you could build your own dampers, and be going on year 3 of experimenting and testing....

 

[richlandrick]

I'm not set on a whole new front end. I'm exploring options.

The 2006 CBR600RR cartridge fit inside the Norton Forks may be my best option.

As far as being a machinist, I owned Adventuretech, designed and produced parts moslty for V-Stroms for 20 years. I built my own CNC Mills and a CNC lathe. I still have the lathe. So I am interested in seeing the Kenny Dreer sketch that pops up in discussions about this subject. Anyone know where I might find the sketch or detailed instructions. AI will generate the instructions for me, but we all know how that goes.

 

[o0norton0o]

I'm not set on a whole new front end. I'm exploring options.

The 2006 CBR600RR cartridge fit inside the Norton Forks may be my best option.

No,.. the honda years are 99- 2004 so you can turn and thread the existing fork cap to fit the commando forks.. In 2005 the forks cap change it's shape so it's got a big void instead of material that needs to be machined.

Here's an early fork cap and a 2006. The later one has a big hollow, rather than solid aluminum that could be adapted to fit a norton fork tube.

I'll warn you now, that I just made my last modification a month ago to get a home made pair to work exactly right that I have been working on and testing for what is now the third year. There's a lot to learn to get it right.... I could write a book on it, or you could just read the book that I read. It's not Norton specific, but it's the book to read if you want to make your own fork suspension cartridge and develop an idea of what things you need to prioritize...

You should also visit this site: https://www.peterverdone.com/archive/highspeed.htm

Peter shows the different brands of showa 20mm dampers. The valves are different (6 ports) on the suzuki versions rather than the honda (8 port version) There are also versions with internal top out springs.

 

[acotrel]

Typo. Maybe someone can fix it. It should be VFR.

Yes, the trail and fork length matches. I know of the common donors used over the years and the new internals avaliable for the forks. I'm exploring options. And these forks and AI did not exist when the early mods using donors started. Matching length, trail, appearance (conventional forks), drammatically better fork and brake performance seem like good things. Since I have a MK3 I don't have to worry about the speedo drive.

You say the trail and the fork length match, but you might be comparing the two machines. If the donor machine has a different rake or front wheel size, the yoke offset from it might give a different result to the one which you might expect. Less yoke offset increases the trail. If the trail is slightly increased, that would be safer than if it is reduced. If you are using the Commando fork yokes, you would be safer. But I think most Japanese bikes have a non-taper fit in the top yokes - most Nortons have a taper fit in the top yoke. Less yoke offset decreases the trail and makes the machine more stable as you brake, but too much stability can suddenly cause the machine to stand-up and turn the wrong way. I laugh if I change something and the result scares me - you might not. I was lucky - when I had the wrong yoke offset , it caught my mate first, so for me - I was ready for it when it happened as I braked - I still almost ended-up on the deck.

 

[Madnorton]

The other issue is of changing the forks to something else is the availability of spares for those forks. At least Commando forks are still available with good spares back up and for 99% of owners ideal for the way the bike will be ridden. One of the 70's Triumph triples had a twin disc front brake that utilised a bolt up hub, maybe that will work.

 

[baz]

I'm not set on a whole new front end. I'm exploring options.

The 2006 CBR600RR cartridge fit inside the Norton Forks may be my best option.

As far as being a machinist, I owned Adventuretech, designed and produced parts moslty for V-Stroms for 20 years. I built my own CNC Mills and a CNC lathe. I still have the lathe. So I am interested in seeing the Kenny Dreer sketch that pops up in discussions about this subject. Anyone know where I might find the sketch or detailed instructions. AI will generate the instructions for me, but we all know how that goes.

If you have a lathe then it's dead easy to fit any front end to your bike
Over 25 years ago I fitted Yamaha fz750 forks to my commando,it was probably one of the best/cheapest upgrades I've done to my bike
The yoke offset is 40 mm so it has increased the trail and stability
I polished the sliders and the yokes
I made commando style clock holders and stainless headlight brackets to make it look more commando
The front wheel is from an apprillia pegaso and the caliper is a nissin 4 pot
The master cylinder is a 12mm grimeca from a scooter I found dumped in my local brook
It's an incredibly good front brake