Seeley Commando Which frame to choose

springer

springer

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Ok lurking-studying for a long time, it is time to start the project. I want to build a Seeley Commando bike mainly for quick street use, some track days also. Will build it using a replica Seeley frame and a mildly tuned Commando motor, medium compression and cam with emphasis on reliability correct and beautiful build, 4LS drum brakes , ceriani replica tuned forks maybe belt drive and the best transmission i can afford etc etc.
Trying to decide which frame to choose MK2 or MK3.
What do you guys think? I have in mind some pros and cons, just wanting to read opinions.
 
My Seeley 850 has the MK3 frame, most others including Minnovation , use the MK2 frame. Looking at the photos of other bikes, my motor is probably slightly further forward - which is probably a good thing. However a while back, Bill Horsman was riding Gerry Kooistra's MK3 Seeley G50 in our historic races and winning most in his class. He told me he could feel the front of the bike 'walking' as the frame flexed. I have never felt that, however I have a piece of well-gusseted chrome-moly tube in front of the motor where the 'ladder' usually is on Mk3 frames.
 
Thank you for the reply, forgot to write, the replica i am going to use will have a removable front down tube (or tubes) for the front norton motor mount. Other than that, i believe the MK3 was the "racing frame" back in the day or was it the evolution of the MK2 or MK1?. The MK2 is very beautiful and in my eyes more conventional, also it makes difficult the use of some exhausts mostly under the motor exhausts.
 
springer said:
Thank you for the reply, forgot to write, the replica i am going to use will have a removable front down tube (or tubes) for the front norton motor mount. Other than that, i believe the MK3 was the "racing frame" back in the day or was it the evolution of the MK2 or MK1?. The MK2 is very beautiful and in my eyes more conventional, also it makes difficult the use of some exhausts mostly under the motor exhausts.
Click to expand...

My Mk3 frame is genuine 1966 Seeley and was always intended to be raced using a Commando motor. I think the head steady mounts are different from some others There is a natural progression in the frames, however they all have the 27 degree rake on the steering head. To my mind the Mk2 is a better frame, but as I said - I think my motor is a bit more forward. It does have a substantial affect on the handling, if you can get the motor even an inch further forward, Also the Mk3 is probably slightly lighter than the Mk2. I don't think it really matters - all of the Seeley frames are much better than any Featherbed.
 
In the beginning , the MK2 for me was the way to go, the look of the MK3 is growing up on me now and i ve talked with a frame maker and he claims that the removable front down tubes make the rigidity similar to the MK2, i believe this is something people used to do also back then right? You say there is a natural progression but you think the MK2 is a better frame? i don t get it. Or did the MK2 appear after the MK3?
 
Quoting from another forum thread:
From Colin Seeley's own book, photos and facts. Mk1 and Mk2 Seeley bikes were only ever for AMC single cylinder power, except for the prototype Fath four. Mk1 was prototyped in 1966, and raced mostly in 1967. Mk2 was least used, prototyped in 1967 and raced in 1968. The Mk3 came out in 1969. Gus Kuhn racing bought a AJS7r and G50 powered pair of Mk3 Seeley bikes to race for the 1969 season. This was the frame with no front down tubes. During 1969 Seeley and Kuhn worked on a prototype with a Commando twin engine, which got onto the track late in 1969.
 
Hi Springer

On the road the MK3 is a nice ride. Don't go overboard & fit wider tyres cos they don't work. The frame will fracture the top tubes between the headstock & the head steady. This area needs tying up really well. You can feel the front end walk especially when used on the road. I ran mine without the original clamp on front engine mount tubes big mistake went after about 6,800 miles. The frame was rebuilt with a better brace between the top tubes for the headsteady. If you look at the piece on the Redfern frame Roy told me it never failed as a 750 but the 850 pulled it apart.
MK2 handle great but they do look more traditional. If you want the best handling frame have him make you a MK4
All the best Chris
 
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The MK2 is a more conventional frame and might be better for a road bike. Most race circuits are relatively smooth these days, so a Mk3 frame probably holds up better in racing than it would on public roads. With a Mk 4 frame, I think the lower frame tubes go around the motor, so a Mk 2 or a Mk3 might be easier to work on when you are adjusting the carbs. With a road bike, that might not matter much - because once you get it right, you would usually leave it alone. With a race bike, you are always at it.
Also, the original Seeley frames are made from chrome-moly tube, I don't know about the copies. If they are not, the Mk2 might be better than the Mk3. The Mk3 is more stressed.
 
Chris said:
Hi Springer

On the road the MK3 is a nice ride. Don't go overboard & fit wider tyres cos they don't work. The frame will fracture the top tubes between the headstock & the head steady. This area needs tying up really well. You can feel the front end walk especially when used on the road. I ran mine without the original clamp on front engine mount tubes big mistake went after about 6,800 miles. The frame was rebuilt with a better brace between the top tubes for the headstart. If you look at the piece on the Redfern frame Roy told me it never failed as a 750 but the 850 pulled it apart.
MK2 handle great but they do look more traditional. If you want the best handling frame have him make you a MK4
All the best Chris
Click to expand...
Thank you Chris, this is excellent info. How about reliability and strength of the MK4, or the MK2, do they brake too? My intention is to make a mildly tuned 750 Commando motor but then again who know later what i ll be searching for...
 
acotrel said:
The MK2 is a more conventional frame and might be better for a road bike. Most race circuits are relatively smooth these days, so a Mk3 frame probably holds up better in racing than it would on public roads. With a Mk 4 frame, I think the lower frame tubes go around the motor, so a Mk 2 or a Mk3 might be easier to work on when you are adjusting the carbs. With a road bike, that might not matter much - because once you get it right, you would usually leave it alone. With a race bike, you are always at it.
Also, the original Seeley frames are made from chrome-moly tube, I don't know about the copies. If they are not, the Mk2 might be better than the Mk3. The Mk3 is more stressed.
Click to expand...
Great info, the frame will be made with reynolds 532 mainly i think and bronze brazed or welded. this is going to be mainly a road bike with mild track day use a few times a year.
 
Hi Springer
The MK4 is good, for hard road use the full loop MK2 is probably the strongest.
However I love the look of a MK3/4
There are so many great frames for Commandos. I'd build a Dunstall spine frame a North a mono. I really liked the Mantis frame that was used for hill climbing.
God there's no hope for me!
All the best Chris
 
If it were me, I’d stick to the full loop mk2. I know the others work fine, but a pre unit engine as a stressed member just doesn’t quite ‘feel’ right to me.

(Note: no science, specific engineering knowledge, or even personal experience was used in creating the above statement)
 
Fast Eddie said:
If it were me, I’d stick to the full loop mk2. I know the others work fine, but a pre unit engine as a stressed member just doesn’t quite ‘feel’ right to me.

(Note: no science, specific engineering knowledge, or even personal experience was used in creating the above statement)
Click to expand...

I would have thought that with the MK3 frame, the motor would be pulled slightly sideways by the transmission . However my engine plates are 8mm aluminium and show no signs of cracking. In Featherbed frames, even 10mm aluminium engine plates have been known to crack. Perhaps the greater rigidity of the Featherbed frame arrangement is a factor ? (if it cannot flex, it breaks ?)
 
I think engine plates, and engine mounts, and frames crack in featherbeds when things are not perfectly aligned and enthusiastic lads ‘make it line up’.

At least that’s why mine broke when I were a lad !
 
Usual trick is to use cardboard and scissors with the motor carefully supported in position in the frame, then cut the engine plates out of aluminium plate with a jigsaw. Then take a piece of 3/8ths round steel and turn a point on it and slide that through the holes in the frame and engine mounts, to mark the plates for drilling. That way no bolts have to be forced in on an angle.
 
Yeah, but if you’re not starting from scratch with all new stuff, there’s limitless opportunity for misalignment with a 60+ year old frame, mix n match 60+ year old engine and trans cases, and ‘who knows how good they were in the first place’ unknown origin engine plates!

It’s a wonder they work at all really !!
 
I have only ever made my own engine plates when building old bikes. It is rare that the positions of the main mounting holes on the two sides need to be different from each other. The frame would have to be a horror. I usually drill two holes in both plates then bolt them together and drill the rest of the holes through both plates. I would not like to buy ready-made conversion engine plates. I don't think they would ever be right.
 
After all answers and my search through the net and discussions with my pals, i am leaning towards the MK2. I like the looks of it, it seems stronger and probably goes better with the period look i will try to accomplish with Brake drums instead of discs, although marginally historically correct for the Commando motor. My plan is for a mildly tuned road-track day bike with modern suspension internals. I d like it to be as reliable as possible, unfortunately vintage racing in my country is practically non existant so it will have to serve for Sunday rides too.
I will keep the thread posted as soon as i decide and maybe do a little write up as my project progresses.
 

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