920 On the road. Hoorah!!

My nine month rebuild of the MK2a is complete & one or two of you expressed an interest in the finished article. I have been out for three short rides & it's just come up to four hundred miles. Sorry I can't post any pics as I don't have a camera or i phone. Maybe later!
The mods include Maney cases, barrel, & crank. JS rods & 920 pistons, re used PW 3 cam.re used Trispark, Fullauto head reworked by Jim Comstock, TTI 5 speed 'box & lots of chassis changes. I hope this does not sound like the bragging list of a man with too much spare cash. To build this, my dream Commando, I had to sell another bike.
The bike is running like a dream. Whilst I run it in the 32mm Amals have been pressed into service, but when it's done another four hundred miles or so It has an appointment with a Dyno. A CNW manifold & a pair of 33mm Keihin round slide smooth bores will then be bolted on to see if they are any better than the Amals. Not sure if they will be as the Amals are great.
One or two points of interest so far: the engine seems smoother the before perhaps due to the JS parts. The light weight crank is fantastic. It is really responsive & revs (only up to five thou. at the moment) for fun whilst remaining perfectly tractable & idling perfectly at 1000rpm. The head, which I criticised for being poorly finished at the price in a previous post, is as promised not porous unlike the Norton item, which is nice. The DS crankcase is the stronger race version & machining the pr. chaincase to fit was easy. I machined the crankcase to take three screw in pillars on which to mount the alternator. If you are thinking about new crankcases this is, in my opinion a better option than milling away part of the crankcase to fit the pr.case. It would of course prevent you fitting an Alton electric start kit.
If any one is in the market for a new gearbox the TTI is superb. It took a long time coming but was well worth the wait. Beautifully spaced ratios (CR 5speed) & a really nice change quality. When it arrived it had been fitted with the wrong selector drum but they sent the correct item so I pulled it apart to fit this. It was a joy to work on & even easier than dismantling the AMC version. It's just had it's third oil change as recommended & the oil seems a lot cleaner now.
When it's been on the Dyno. we'll see what Mr Comstocks headwork has achieved & I'll post some more info.
Cheers,
Martyn.

Beg/borrow/steal a camera! Dyno slips will also be great to see (make sure they get the torque and HP to cross at the requisite 5252 rpm...)

Nathan

Martyn

You've put a fair shift in , I bet you don't let it out yer sight.



Top job
Cheers

Martyn, that sounds fabulous, good on yer!

Please do keep us posted.

Any reason why you've gone the 33mm round slide route over the 35mm flat slide option?

that sounds like a great machine best of luck with it ,,,,,,,,,,,,,,baz

I'm on edge of my rocking chair reading your delights Martyn. Relieved to know to lighten crank is also a delight. I am also wondering how hard its is to start. The 32 Amals are each rated to like 90 hp cfm mixture flow so may not gain anthing but pure top end by the 35's but I'd have to find out too or loose sleep dreaming of em. Change oil now and run er up near red line please watching out for tire spin or wheelie.

Tidy darts there Martyn. Do you work at British Aerospace by any chance? I worked there in the mid eighties and knew a guy with a few Brit bikes?

Thanks for the kind comments. Love the bike in bed photo. but if I tried that my wife would insist on a foursome. By that I mean with her beloved XKR...ooh eer! The CRs came at a very good price, that is, less than half the price of a pair of FCRs & although I have been in engineering all my working life I have never worked at BAC. Hobot, you need to get a seatbelt for that rocking chair.
I will try to post some pics soon.
Martyn.

Ok Martyn I'm holding on, barely, but ya knew that. My grinning muscles getting a work out re-reading your teaser post. No one mentioned dislocated ankles or busted knees so guess its a non issue, yea!

Congrats! Sounds like it should be a great package. Looking forward to the pics.

Ken

Matchless said:

...One or two points of interest so far: the engine seems smoother than before perhaps due to the JS parts....
Martyn.

Click to expand...

How about a photo?

Are the pistons medium C.R. or Hi C.R.?

Those Keihin round slides are one of the few options that will fit on a Nort.

Strange about the TTI box. I had the same experience of replacing the selector drum. I would have thought the AMC shift pattern would be the most commonly used by Bruce Verdon's customers. After I fitted my box, I tried to ride the bike and I didn't twig the shift pattern was reversed. I thought the extremely high gearing was my own doing, caused when I changed sprockets. As I rode the bike around the pits at Winton, got frustrated and gave it a big squirt. I wouldn't have thought the motor would pull such a high gear, I almost put the bike through the fence.