Ready to Race Finally

Acotrel, no issue this end , it works in my favour to have the higher gearing at the outset, as I am running a Maney 40mm belt and a crank triggered ignition, that is set and I dont need to change any of that.
I am running a 21 tooth gearbox sprocket to my modified Commando drum brake, which I can change the ratios easily and quickly with out any need to go near the gearbox sprocket, which has always been the initial idea behind my hub modification.
I didnt go for the after market hub mod as I wanted to use as much of the original parts from the bike I had in hand.
As the rear hub mod allows the smallest sprocket of 44 teeth(original is 42) this now allows me to go up in teeth size(down in gearing) so now I know I can reach in excess of 130mph with the 44 tooth in 5th at 7100 rpm (if the track and conditions allow) and know I still can get plenty of punch using the lower gearing , as I said in the thread, I changed to a 46 tooth rear for the second day of racing and managed to keep the motor spinning in a narrower rev range and more drive everywhere which gave me the better placings. One of my own issues was I was still riding it as if it had a 4 speed in it!!!!!
Taupo was shortened for our weekends racing so never really got to stretch its legs on the longer track .
My biggest problem was the missed gear changes with the reverse pattern, now able to resolve that as I have the 1 up 4 down barrel selector sitting on y bench. (yes I do know about running a standard gearstick back wards etc, I needed to run everything I have bolted to the bike to see how it all worked, rearsets, linkages) Remember it has only been going for two weeks!!!
I am back to work though , so all efforts for the bike are on hold for the next moth
Regards Mike

Hi Mike,
great looking machine. Good to hear you had a good outing at Taupo. I have three final drives I run on the BMW and I use the lowest at Taupo as its got bugger all straights on it. I used the same gearing at Hampton Downs but it was far to low for the two long straights so currently running stock R90 gearing which gives good punch out the corners and I can get into 5th on the front straight.
To get used to Hampton Downs I recommend the Super Bike School method, stay in 3 or 4 and ride around lots of time without using the brakes.
Turn 2 and 4 seem to catch a few especially on cold tires on the first lap.
I run a max of 30 PSI but generally 25/27 enough to get a bit of stickyness and balling, works for me and the BMW is very stable.
Commandos generally kick my arse , but you expect that on The Bavarian Tractor....
Don't forget lots of water, sunscreen, wet weather gear and a gazebo.
I'm running in pre 72 Posties too so that should be interesting.
See you in October.

Thanks for the advice John, see you there.
Will try and get my set up done on the Friday as I am going to need as much practice as possible.
Regards mike

Thinking of dual disks with decent calipers?
Turn one at 200kmph is not the place to have these thoughts :lol:

Hi Jarred, make one like this
Regards Mike

Nice!

Thanks to you Dave for the brackets, I fabricated the bit in the middle, drilled out an old hexagonal barrel nut, welded a left hand thread nut one end, right hand thread nut the other , 2 x Heim joints with lock nuts and the end result is what you see in the pic.
you should market those base brackets!!!
Regards Mike

that be a Micheal Taglieri style head steady who figured out a way to do it with just a hack saw. Go out a break a leg eh.

Mike, bike is looking great, glad you are enjoying yourself with the racing. Sorry I didn't get to see the project while I was in NZ, looks like I'll have to return next summer. My Commando has stirred from its slumber, tweaked and cleaned for the All-Norton ride next Sunday in Perth. I've gotten one of those Gopro thingies, I'll be recording the run for posterity.

Mike, I had the same issue about the change direction with my TTI box. I'd ordered it thinking that it would come one up, five down as all the TTI boxes must be intended for racing. Bruce sent me the replacement selector drum, and it took me about 8 months to get around to swapping it over. I still haven't had the opportunity to try it again. I wouldn't have thought a commando could struggle off in top gear and still accelerate like a rocket. I almost put it through the fence in the pits at Winton raceway during my last attempt to practice with the new box.

Hi Ralf , thanks for that, pity you couldn't get over for the Barry Sheene meet on the 25th!!
Glad your bike is good and up and running, post some video/pics after your Perth ride. Yes the Go Pro is the shot for footage, have some good footage from the rally earlier in the year.

Acotrel, did find it strange on the first start up, although within 50 m up the road after initial start, realised I had the wrong shift pattern.
Had ridden many different bikes with different shift patterns and on both sides of the bikes, so wasn't to much of an issue, except when I raced it, made the odd dodgy shift when needed most!
Anyway have the new shift pattern barrel waiting on the work bench until I get home to fit on the 18th.
It did pull off in top, although i did need clutch slip assist as I stalled it twice before I realised the problem!!!
Regards mike

Corrective porting in the RH10 head to suit both sets of manifolds.

Great looking bike there and sounds like you're having a ball!
What size flat slides did you use? And what size manifolds (ie straight or tapered). I'm intending to get some JS flat slides and also have a RH10 head, so would like to know what you used and what you mean by 'corrective porting'.
Thanks in advance.
FE.

Fast Eddie, when I was in a state of readiness for my first start up, I didn't have any decent Amals available, I had 2 x sets of originals Amals off both my bikes, road and race, but neither of them were in the best shape to put on the race motor, be a waste not to get the full potential with worn carbs, so I used a set of JS motor sports 32mm flatslides to get me going, these were a spare set I picked up off another NOC NZ member for a very good price. The manifolds that they come with I had blended into the head to match the port entry exactly and are now a matched pair marked as such L & R.
i then purchased a set of new 32mm Premiers, blended the set of standard manifolds that were originally on this head and once again a matched set marked up as a L & R. Head ports were done as per similar recommendations by forum members on here, nothing off the floor, some widening approaching the valve pocket and some tapering of the valve guide, basic stuff really, and certainly not to radical , results have proved that it has enhanced the performance.
I will eventually be using a set of 34 mm Amal MK2's when they become available again
Hope this helps
Regards Mike

Thanks Mike that is very useful info, I was planning 32mm JS carbs with tapered manifolds too and with your feedback I'll certainly be sticking to this plan!
Interesting comments re the ports. The ports on my head have already been cleaned up by a PO, but not enlarged as such, as i don't know any better, I'll probably leave well alone, but I have a knowledgable Norton friend nearby (with the Omega pistons) so will take my head for him to look at today... Cylinder head that is... He's not a shrink!!
Rgds,
FE.

I use 34mm MK2 Amals with the ports tapered back to standard within 25mm of the gasket face. My motor is built with maximum pulling power across the whole rev range in mind, using higher overall gearing and close internal ratios to climb in speed. I start to worry if there is no lag after every up-change - it means the bike can go quicker if the overall gearing is raised more.
Good luck with your racing, I hope I've helped you.

acotrel said:

I use 34mm MK2 Amals with the ports tapered back to standard within 25mm of the gasket face. My motor is built with maximum pulling power across the whole rev range in mind, using higher overall gearing and close internal ratios to climb in speed. I start to worry if there is no lag after every up-change - it means the bike can go quicker if the overall gearing is raised more.
Good luck with your racing, I hope I've helped you.

Click to expand...

Hi Acotrel,
When you say the ports 'taper back to standard' do you mean 30, or 32mm?
Rgds,
FE.

It is a standard Mk2A 850 head, I think the ports are 30mm as standard ? It is quite a substantial taper, however over 25mm it is not too bad and the bike still pulls like a train, however running on methanol might make that deceptive. I did not open the ports beyond the first 25mm, simply blended the taper, so that the original gas speeds are maintained as much as possible. From playing with two strokes, I've got the habit of feeding the throttle on firmly, however I've never had a lack of response which might be attributed to the larger carburetors. I've fanged it pretty hard at times.

P.S. I 've just measured the ports in my spare head which is identical to the one on the bike. It seems I removed 2mm a side from the first 25mm of the port. And now I think about it a bit more, the ports were originally 30mm. They are still that beyond the first 25mm from the gasket face.

acotrel said:

It is a standard Mk2A 850 head, I think the ports are 30mm as standard ? It is quite a substantial taper, however over 25mm it is not too bad and the bike still pulls like a train, however running on methanol might make that deceptive. I did not open the ports beyond the first 25mm, simply blended the taper, so that the original gas speeds are maintained as much as possible. From playing with two strokes, I've got the habit of feeding the throttle on firmly, however I've never had a lack of response which might be attributed to the larger carburetors. I've fanged it pretty hard at times.

P.S. I 've just measured the ports in my spare head which is identical to the one on the bike. It seems I removed 2mm a side from the first 25mm of the port. And now I think about it a bit more, the ports were originally 30mm. They are still that beyond the first 25mm from the gasket face.

Click to expand...

Good info, thank you.
FE.

acotrel said:

It is a standard Mk2A 850 head, I think the ports are 30mm as standard ? It is quite a substantial taper, however over 25mm it is not too bad and the bike still pulls like a train, however running on methanol might make that deceptive. I did not open the ports beyond the first 25mm, simply blended the taper, so that the original gas speeds are maintained as much as possible. From playing with two strokes, I've got the habit of feeding the throttle on firmly, however I've never had a lack of response which might be attributed to the larger carburetors. I've fanged it pretty hard at times.

P.S. I 've just measured the ports in my spare head which is identical to the one on the bike. It seems I removed 2mm a side from the first 25mm of the port. And now I think about it a bit more, the ports were originally 30mm. They are still that beyond the first 25mm from the gasket face.

Click to expand...

You should not get any 'lack of response' with 34mms, you can run 36mms with no issues, guys with 1007cc are running 38mms. I didn't have problems with 36mm into 34mm ports....

I plan 34mm Mikunis on my 750 Short Stroke, but may go to 36mm Amal Smoothbores as I develop it. Some of the fastest Commando's I ever saw were Thruxton M/Cycles, circa '77, riden by Tony Smith/Tony Holland, they used 30mm ports and curved/tapered manifolds to 36mm at the MkII Amal, with very wide but fairly short bellmouths similar to those the Cosworth used. They had to be cut verticaly for clearance between each carb....

If you are restricted by rules, bore your 32mms to 33mm.....

I plan 34mm Mikunis on my 750 Short Stroke, but may go to 36mm Amal Smoothbores as I develop it. Some of the fastest Commando's I ever saw were Thruxton M/Cycles, circa '77, riden by Tony Smith/Tony Holland, they used 30mm ports and curved/tapered manifolds to 36mm at the MkII Amal, with very wide but fairly short bellmouths similar to those the Cosworth used. They had to be cut verticaly for clearance between each carb....

If you are restricted by rules, bore your 32mms to 33mm.....[/quote]

Tony Smith lives near me. He still rides a Commando on the road. He's a top bloke, so modest, but so much history. He's the guy I got my 10.25:1 pistons from, that I mentioned in my raising CR thread!
FE.