The building of my vintage racer

[bill42]

No, I meant a dyno at the wheel like the ones you have used. If the dyno you are familiar with showed R100's having low 50hp numbers at the rear wheel then it seems 20% driveline loss is indeed accurate. That really is a lot of loss just for a wheel 2 feet away! The driveshaft to right-angle gearing must take up a bunch of this power. I have heard people predict over the years that while a driveshaft is a nice pleasing design it really is not providing the driveline efficiency of a sideways engine that uses a chain drive with zero right angles. Perhaps this is an acceptable loss one must live with to get the benefits of an air cooled boxer with cylinders out in the direct air path

Originally Posted by supershaft

How much actual hp at the crank? I know of no one that has measured the power at the crank other than the factory. I suspect there rating is a bit high but they don't stretch the truth near as much as many manufacturers. At least here in the states I think the only airhead rated that high was '77 RS's half way into the '78 model year? I think a US '81 R100 was rated at 67?

I don't think our drive line eats up 20%. Oil alone makes a big diff but . . . . It's close! Different dyno's read different figures. It all depends on the dyno AND operator. The dyno I was around that dynoed a lot of airheads you were super lucky to get 56hp. Most were from 48 to 54hp and that's R100's.

[Voltaire]

There are a couple of Guzzi's in the class I race in....they fly and are quite similar in layout....maybe the induction tracts are better.....
The Guzzis are so fast in fact they can keep up with the Commandos

I picked up a set of original Norton reverse cone mufflers, going to try them instead of the home brewed 2 into 1 with the Taiwanese muffler ( that has no internals).

[supershaft]

Originally Posted by bill42

No, I meant a dyno at the wheel like the ones you have used. If the dyno you are familiar with showed R100's having low 50hp numbers at the rear wheel then it seems 20% driveline loss is indeed accurate. That really is a lot of loss just for a wheel 2 feet away! The driveshaft to right-angle gearing must take up a bunch of this power. I have heard people predict over the years that while a driveshaft is a nice pleasing design it really is not providing the driveline efficiency of a sideways engine that uses a chain drive with zero right angles. Perhaps this is an acceptable loss one must live with to get the benefits of an air cooled boxer with cylinders out in the direct air path

My whole point is that 20% makes sense IF the factory claims at the crank are accurate. That is a HUGE if.

Of course a chain is more efficient. Belts are more efficient than chains by most accounts.

[supershaft]

Originally Posted by Voltaire

There are a couple of Guzzi's in the class I race in....they fly and are quite similar in layout....maybe the induction tracts are better.....
The Guzzis are so fast in fact they can keep up with the Commandos

I picked up a set of original Norton reverse cone mufflers, going to try them instead of the home brewed 2 into 1 with the Taiwanese muffler ( that has no internals).

For some reason Guzzi's RUN. They always have IMO. And they weigh a ton!

[chasbmw]

I agree withh SS on this one

[pommie john]

Originally Posted by supershaft

How much actual hp at the crank? I know of no one that has measured the power at the crank other than the factory. I suspect there rating is a bit high but they don't stretch the truth near as much as many manufacturers. At least here in the states I think the only airhead rated that high was '77 RS's half way into the '78 model year? I think a US '81 R100 was rated at 67?

I don't think our drive line eats up 20%. Oil alone makes a big diff but . . . . It's close! Different dyno's read different figures. It all depends on the dyno AND operator. The dyno I was around that dynoed a lot of airheads you were super lucky to get 56hp. Most were from 48 to 54hp and that's R100's.

I have seen an airhead engine run on a crank dyno. I was there when Jim Cray was testing his first race engines. It was running 105 bhp before the clutch caught fire. ( The dyno pick up was off the clutch friction plate splines)

[supershaft]

Originally Posted by pommie john

I have seen an airhead engine run on a crank dyno. I was there when Jim Cray was testing his first race engines. It was running 105 bhp before the clutch caught fire. ( The dyno pick up was off the clutch friction plate splines)

Wow! I think that is the first I have even heard of anyone but BMW AG dynoing one at the crank. Well, close to it! I could be wrong but I am thinking the clutch catching on fire threw off the reading a bit (on the low side!).

[noman]

thx mr beast!
i'll be hitting as many of these as i can (they're very close).

[FreeTheBeast]

Iron & Air showed my bike on their Facebook page.


They may do a short feature on the bike in an upcoming edition. Iron & Air is in Concord, New Hampshire which isn't far from me.

[Wirespokes]

Originally Posted by moorespeed

more compression in a race engine only gives extra power up to a point, after that the engine just starts to get harsh. and as for twin plugs, i have never seen any gains, so i stick with single plug even on my bored and stroked engines.

How do you prevent predetonation?

[bmweuro]

Originally Posted by Wirespokes

How do you prevent predetonation?

On a race bike? Octane.

[bmweuro]

Originally Posted by FreeTheBeast

Well, the first race weekend is over. The bike had issues. The shifter arm was moving on the gearbox shaft. I wasn't able to shift the bike very well on Saturday, but I got through my only race that day. I came in a solid last place. It was probably because I hadn't tightened down the set screw well enough. So, in an effort to sort that out, I tried to remove the shifter arm. It came off half way and then got stuck. It took a bit of work to get it either back on or get it off. Finally got it off the shaft.



I believe the banging and cranking on the shaft really fouled up the alignment inside the gearbox. Sunday morning I put back on the shifter arm nice and properly. I thought I was all set and ready to go. Set off onto the track to find I couldn't shift the bike into 3rd gear. I could only use 1st and 2nd. Bugger! I was done. I wasn't going to tear into the gearbox there at the track. I will try to find a 5 speed gearbox. I have a 4 speed one in there now. And with the 5 speed gearbox, find a newer clutch and flywheel.

I was quite disappointed Sunday morning, but I got over it. I will chalk it up to experience. I was still able to learn a lot about how the event is run. I had a fun weekend all the same, although racing would have made it more fun. Next race is a one day event on 11 June. I'll return from watching the Canadian Grand Prix in Montreal the evening before and then get to the track, which is 30 miles from my home, to do my own racing.

For pictures from the whole weekend, click on the photo above. It will take you to the gallery.

Originally Posted by SJ BMW

The /5 shift lever is held by a tapered bolt, I have never seen anything else work to hold the shifter on the shaft. I would change the design to be like the stock piece or you may miss the next race too...

Chris

I thought I would update this. I have had them on my own /5(with a 4 speed) for a while without any problems. The 8mm set screw seems to hold just fine as long as the shift arm is in the right position to make sure the set screw is hitting plat on the shift shaft.

[FreeTheBeast]

A friend of mine was testing out some lenses at the track during the last races. He threw together this video...

[noman]

mr beast, many thx for providing the hillclimb dates. took my duc over to okemo and watched the gang today, am and pm runs. much fun in the paddock too. met a guy named "marcus", and we chatted about his bike's mods. a clean build for sure.

a great day of racing, followed by a long twistry ride home on my 900ss, a perfect day.

[FreeTheBeast]

I hope you enjoyed it Noman. We certainly did. Marcus is a character, no?

Click on the picture to go to the photo gallery from the event: