MK3 Restomod

This is a thread about rebuilding and modifying my 1975 Commando MK3. It was my street bike for many years, and I've finally got around to building it into my idea of the perfect Commando. I posted some details on straightening and modifying the frame here


and I'm now in the process of mocking things up to see how my ideas are going to work out, and to get some measurements for machining parts.

These two pictures show the frame and swingarm with empty crankcases installed. That let me check the steering head angle and swingarm droop angle with the lower frame tubes horizontal. In that configuration, the rake is 26 degrees, and the swingarm has 7 degrees of droop. Those are the numbers I expected, but it's nice to be sure before I start machining the fork yokes. I'm planning get 3.75 to 3 " of trail, still not sure exactly what I want. I'm using a set of Ohlins (conventional) Superbike forks, which have 43 mm diameter stanchions, and require wider separation that the stock Norton forks. Because I steepened the steering head angle, I'll need less offset in the yokes, and I'll also need them a bit wider because of the diameter of the sliders. I'm still not decided whether to make new yokes, or weld inserts into some Yamaha yokes, and re-drill the stem holes for more offset. The latter would be quicker and easier, so I'll probably go with that.


These are pictures with the Quaife 5-speed gearbox and electric starter bits (Old Brits kit) in place. Because I'm using Maney cases for the 1007 cc engine I'm building, and a crankshaft with pre-MK3 configuration, I'll have to do some machining on the cases to fit a MK II style alternator, and probably a modified MK 11 primary cover. Preliminary measurements indicate that I will be able to move the gearbox over a bit to the left, and still make the Old Brits starter work. On my old PR race bike, I moved the gearbox over almost 1/4", which gave me clearance for a wider tire. In this case, I don't think I can go that far, but it does look like I can still move it over a significant amount. On the PR, I had room for a really wide rear tire, but for this street bike, I'm only looking for a little more room.





That's it for now. Next step is to machine cases and then check everything with the belt drive installed. Then it all comes apart for final painting and assembly.

Oh yeah, before someone catches it, yes, I do have the shocks installed on the wrong sides. The pre-load adjustment knobs will be on the outside, not the inside.

Ken

Ken, I think there are quite a few of us here who also consider this to be the dream Commando. I'll be tuned into this one, thanks for sharing.

Glen

Yes I agree, the bike is looking great. I wish I had the skills to do something like that !
sam

Hi Ken

Lots of ways to customise a Commando & everytime I look at modernising I come up on the same areas.
Swinging arm, engine plates. Your neat box section I love. Ludwigs alloy swinging arm & engine plates are just exceptional & are on my dream/wish list.
OIl tank or lack off. I like Jeans tope tube conversion but there is a lot of work to it,ie filler neck, altering the petrol tank etc.
Front end I have decided 43mm BMW forks with one off yokes, modern but not over the top.
Light weight wheels & discs I keep coming back to spoked wheels.
Engine I believe the bigger the better, drive is what it is all about.
Thats the thing about Commandos. What you can do to them is endless & stock bikes are lovely as well.
Great work Ken keep it up.

Chris

Great stuff - I look forward to seeing more!

Ken,
How does the QPD starter system work, I take it there is no engine sprocket sprag ala stock Mk 3 ?
sam

trident sam said:

Ken,
How does the QPD starter system work, I take it there is no engine sprocket sprag ala stock Mk 3 ?
sam

Click to expand...

Yes, I'm interested in this also. I've never seen this one. Do you have to cut the cover to fit around it?

This looks like an awesome build. Keep the info coming.

Holy moly that's good looking! Looking forward to the build.

dennisgb said:

trident sam said:

Ken,
How does the QPD starter system work, I take it there is no engine sprocket sprag ala stock Mk 3 ?
sam

Click to expand...

Yes, I'm interested in this also. I've never seen this one. Do you have to cut the cover to fit around it?

This looks like an awesome build. Keep the info coming.

Click to expand...

Hi Sam,

it's an Old Brits starter, not QPD. Very similar, and clearly derived from the original QPD and later Kenny Dreer designs, but a little better engineered.

The Sportster starter has a Bendix drive, which engages a ring gear on the back of the clutch drum. No sprags, etc. I'll eventually post some pictures that show the details. It does require cutting the primary covers to fit around it, but since it uses a belt drive, that's not much of an issue. I would have considered keeping the MK3 starter system with a Dynodave starter motor, which I've been using on the bike for quite a while, but can't do that with the Maney 1007 crankshaft, which doesn't have the MK3 style extended mainshaft. I'm also not really sure the stock sprag would hold up as well with the larger engine. I kind of like the idea of getting rid of the sprag.

Ken


In my case, since the original bike is a MK3, I've got to sort some things out still. I'd like to use the heavy duty Quaife 5-speed, but it's set up for a right side shifter. That means I have to decide whether to find a good way to convert to left side shift as on the standard MK3, or go back to the earlier right side shifter. I've become used to the left side shift on all my street bikes, with only the race bikes still having right side shift. If I go back to the stock Norton gearbox instead, it's pretty straightforward to adapt the earlier primary cover to the stock MK3 crossover shaft for the left side shifter. It would also be pretty simple to do the same with a custom primary cover, if I go that direction. If I go with the right side shift, then I have to fab some brackets and linkage on the left side for the rear brake system. Decisions, decisions.

Thanks for info Ken.
As an aside, there was a Commando for sale on evilbay UK recently, an import from the US that was fitted with a QPD starter and belt. The bike was semi choppered but was up for a good price of GB£5000, it had obviously had a lot of money spent on it, and really wouldn't have taken that much to sort it out, of course I didn't have the 5 grand :roll:
Good luck with the rest of the build, I'm looking forward to seeing the finished article.
sam

Very cool. I think getting rid of the sprag is a huge step in the right direction. Terrible design in my opinion.. Cant wait to see more about your project Ken, cheers

worntorn said:

Ken, I think there are quite a few of us here who also consider this to be the dream Commando. I'll be tuned into this one, thanks for sharing.......Glen

Click to expand...

+1 lookin' good Ken and I will also "tune in" next week for more of your "regularly scheduled" posts :mrgreen:

I mean no offense to others here with on going builds .... but this one is way cool .... go for it Ken .... lots of interest for sure... a real beauty so far ...
Craig

A stand out attribute of these electric starters is the gearbox output support as with the Maney outrigger. And of course, no god awful spragg. A real bonus! The installation seem a bit exhaustive though.

I'd be interested to know how the combination of your new steering geometry with the isolastics makes the bike handle. Are you using 18 inch wheels ? I've often thought of playing with a standard commando and the slight disconnect between the handle bars and the pivot puts me off.
Looks like an excellent build - keep up the good work.

Your 26 degree rake on the steering head is the same as a 70s TZ350 which had 18 inch wheels and a shorter wheel base. So, if you use a similar yoke offset, your steering/handling should be slightly on the stable side of neutral under acceleration and stable under braking. You don't have the peaky power characteristics of the two stroke, so you are unlikely to get a hi-side, however to my mind the isolastics are an unknown factor. You should have enough travel on the rear end to be able to tailor the handling to suit your riding style. The spring rate, damping and pre-load on the rear shocks are important. If the bike feels bad in the front, it is usually the rear end which causes it. If you are using 19 inch wheels the handling might be too quick.

Thought I'd better add an update so you all won't think I'm slacking off! Actually, I have been, but at least I'm making some progress. This is a shot of the crankcase and bits on the bench. The crank was balanced by Steve for 78% using Carrillo rods. I'm using Don's (madass) steel rods instead, and also using the engine in a Commando, not a rigid mount, so I'll probably do a little re-balancing. I normally run 62% BF, but might move that up to 70% or more for this engine. Still have to sort that out. At the moment, I have a different issue. I used new old stock FAG bearings that I had on the shelf, which are standard clearance, and Steve recommends the looser fitting C3 bearings. Now I know why. After I took this picture, I installed the inner races on the crankshaft, and encountered a bearing fit problem. With the tight fit of the outer race in the crankcase, the bearing tolerances are used up and the crank will not fit into the case. The timing side fits, but not the drive side. I pulled the inner race off the drive side shaft, and it still won't fit into the installed bearing. Must just be the tight fit of the outer race in the crankcase. I also pulled the inner race off the timing side, and it will slide into the bearing, but just barely. Looks like I'll have to order some C3 bearings. I've read about this problem for several years now, but this is the first time it's bitten me. Live and learn.



Ken

A little more progress. I've spent a lot of time lately just fitting engine, transmission, and primary parts, trying to sort out how to make it all fit. I did move the gearbox over 1/4" to the left. I had to do that to clear the custom swing arm. I'd forgotten that when I raced my PR with this swing arm, I had moved the gearbox over for more tire clearance, and the clutch basket will not clear the pivot in the standard location. No real problem, just some time needed to figure out how to make it work. Using the Commando primary covers is now not an option, so I'll be making my own. Because I'm planning on using a larger front pulley, I need a custom mount for the alternator stator. I've sorted out how I plan to do that, using an intermediate mounting plate similar to the stock MK3. I drilled the crankcase in the MK3 4-stud pattern, and installed Timeserts. I plan to use standoffs over studs to position the intermediate plate, to which the stator will be bolted. Kenny Cummings sent me some pictures of something similar that he fabricated for John Magyar's (Danceswithshrapnel) Seeley framed 1007, and I liked the idea. I'll be mounting the Sparx 3-phase alternator instead of the Alton that Kenny used, but I'm doing it in a way that will let me switch to the Alton if they become available in the future. This is a shot of the crankcase after fitting the Timeserts. Now I can get on with assembling the engine.



We had some good painting weather recently, so I also got started on restoring some side covers that were in pretty sad condition. I'm setting the bike up as a Roadster, because I like the seating position better than its original Interstate configuration. I'm also converting my other MK3, the one my grandson rides, from Interstate to Roadster, so I'm working on two sets of sidecovers and two new EMGO tanks. So far I've done an epoxy primer to seal the covers and provide a good bond, and then several coats of high fill polyester primer. Lots of sanding and filling left, but the worst of the fiberglass repair is done. The tanks need a little cleanup grinding on some of the welds before priming, but look good otherwise. When I have everything finished to suit me, I'll either paint them or send them to Brent for paint, or maybe one of each. I'm looking at a flashier paint job for the grandson's bike, and I really like the quality of Brent's work.

Any how, this is my extensive paint studio, followed by a shot of the sidecovers hanging from my custom drying rack.





Ken

Thank you for posting Ken. I am glad to see that you are getting around to putting you dream bike together.
Hope to be down in your neck of the woods within a couple months. I will have to stop in and make sure your fridge is the right temp.

Shade tree mechanics are happy mechanics.