how to increase r100 power

[Airhead Wrangler]

Originally Posted by RGregor

Just for curiosity, what's the basis for this statement?

I'm not sure what SS's basis is, but I'd agree with the statement. The bore to stroke ratio is well over square (94:70) and that by nature makes it an engine that is happier reving higher than lugging at low RPMs. The more over square an engine is, the more it depends on revs to make HP than torque. For a given displacement, a longer stroke will give you greater torque as the piston has a longer moment arm to turn the crank. With the same displacement, a larger bore (and thus shorter stroke) allows larger valves for better breathing as well as more piston surface area for combustion pressure to push on, but less mechanical advantage to turn the crank and thus lower torque. Since it can have larger valves though, it can breath better and rev higher. Since HP is a function of torque and the number of combustion events per unit time, over square engines depend more on revs to make HP than large amounts of torque. Square and under square engines by comparison depend more on big torque to make their power because they can't rev as high due to increased piston and rod accelerations due to the longer stroke as well as less ability to breath due to smaller or fewer valves.

[supershaft]

Originally Posted by RGregor

Just for curiosity, what's the basis for this statement?

Well, I started riding them in '75 when I was 14 but my dad put an end to that when he noticed I was grinding the rubber off the bottom of his brand new R75/6's foot pegs. I didn't ride them much but maybe around the shop after that until five years later when I bought my own. That was in '81. I have been riding the stink out of them every since. That and how they are made. Short stroke/relatively long rod. Pretty much everything about them says rev me except for their mile long pushrods. But most importantly, they just don't make good power until they are reved up a lot. Our shop was also a Moto Guzzi dealership. Overall, they are just the opposite. They are typically grunters. Other engines too. Not our airheads. I have pretty much never had any arguements on this subject or the other but there's always a first time.

[supershaft]

Originally Posted by Airhead Wrangler

I'm not sure what SS's basis is, but I'd agree with the statement. The bore to stroke ratio is well over square (94:70) and that by nature makes it an engine that is happier reving higher than lugging at low RPMs. The more over square an engine is, the more it depends on revs to make HP than torque. For a given displacement, a longer stroke will give you greater torque as the piston has a longer moment arm to turn the crank. With the same displacement, a larger bore (and thus shorter stroke) allows larger valves for better breathing as well as more piston surface area for combustion pressure to push on, but less mechanical advantage to turn the crank and thus lower torque. Since it can have larger valves though, it can breath better and rev higher. Since HP is a function of torque and the number of combustion events per unit time, over square engines depend more on revs to make HP than large amounts of torque. Square and under square engines by comparison depend more on big torque to make their power because they can't rev as high due to increased piston and rod accelerations due to the longer stroke as well as less ability to breath due to smaller or fewer valves.

That's the thing about airhead riders that I don't understand: Everybody calls the R65 a short stroke engine and the R100 has the EXACT same 'stroke'. 94x70.6 and 82x61.5. They both come out to 1.33:1 bore and stroke ratio. Yes, a R65 IS a short stroke but so is a R100!

[pommie john]

Originally Posted by Voltaire

I had to go back to 2009, # 269 was doing 1:11 lap times, he was 5th and the fastest was 1:06 on a 900SS.

I was surprised when he said 2.91 was not tall enough as my 3.0 wont hit redline in 4th on the same bit of the rising track.

I knocked 5 seconds off my previous best time with virtually no mods to the bike, so thats just me improving, I

can see a few more seconds coming that way....I'm pretty slow off the start and the first lap.

I can track the rest of the field on previous races and it would appear you plateau at some point as a rider...?

I did a bit of spectating and observed that nearly all the riders were turning in early on the hairpin...contrary to the

Super Bike school teachings of brake late, deep in, countersteer, throttle on......get on the gas asap.

The pre 89 Jappers are pretty fast in a straight line but some of cornering was pretty slow....I'm no expert but

thats where I think I make up my times on the high HP bikes.

Bummer about Super Bike School as I thinks its really worth while, following others around the track would have

taught me bugger all.

.......of course in the real world I ride an R65 and a Commando and there are cars coming the other way so I

don't worry about HP , butt, dyno, imagined or otherwise...

Did you see on Access Norton where one of the guys got all the Commando heads, flowed them on his bench

and posted up the charts.....showed that my Combat head was the worst.....only made power by the cam and

carbs.

I just had a look at a couple of Hampton Downs videos and I'm surprised that you'd need a 2.91 around there. It doesn't look as fast as Pukekohe. Just from a video, ( and I know it's a bit of guesswork, I'd fit a 3.0 .
The vid I watched was a 600 jap bike but it never seemed to get rally going in top gear.


If I ever get back to Pukekohe I'd have to pull my finger out. I can't remember the times but I think I was 1.11 or around there. Are the 2001 results online anywhere?

[Voltaire]

Originally Posted by pommie john

I just had a look at a couple of Hampton Downs videos and I'm surprised that you'd need a 2.91 around there. It doesn't look as fast as Pukekohe. Just from a video, ( and I know it's a bit of guesswork, I'd fit a 3.0 .
The vid I watched was a 600 jap bike but it never seemed to get rally going in top gear.


If I ever get back to Pukekohe I'd have to pull my finger out. I can't remember the times but I think I was 1.11 or around there. Are the 2001 results online anywhere?

Its not as fast as Pukekohe, but that's what he said.....I was running a 3.0.
I bought a set of big valve 1977 heads after Puke....then it was mentioned that the D port R80 heads are the better ones to start with.....got a set of these too...... head work on BMW's seems to be cloaked in secrecy.....

The BMW sidecar dropped a valve seat before even doing a lap..... and the ring lands were pushed together a bit.... Maxheadroom ( Nick) found a stock r100 head, swapped over the valves and rockers....carefully took the rings out...dressed the piston in the lathe.... and....

With this set up they managed a 3rd and a 4th...newish rider and different swinger.
I suggested they put it on the Dyno, disconnect one lead at a time and see which has more power.....
Apparently it ran the same but riders leg tended to blocked the carb

[RGregor]

Originally Posted by supershaft

Well, I started riding them in '75 when I was 14 but my dad put an end to that when he noticed I was grinding the rubber off the bottom of his brand new R75/6's foot pegs. I didn't ride them much but maybe around the shop after that until five years later when I bought my own. That was in '81. I have been riding the stink out of them every since. That and how they are made. Short stroke/relatively long rod. Pretty much everything about them says rev me except for their mile long pushrods. But most importantly, they just don't make good power until they are reved up a lot. Our shop was also a Moto Guzzi dealership. Overall, they are just the opposite. They are typically grunters. Other engines too. Not our airheads. I have pretty much never had any arguements on this subject or the other but there's always a first time.

I see, it's your experience.
Having started with an R75 (/5) as well I would guess it was not the experience with that, as reving a stock R75 won't take you very far. It simply doesn't like it.
So probably it's the experience with your engine.
That confirms my experience with duration cams (not the 336, but e.g. Schleicher 330): you get an engine that likes to rev high, but, compared to it's power at high revs, is a bit weak at bottom revs. Overall you get a mild torque boost, but over a wide rev range.

So far so good.
From personal experience I know that with the right cam and, most important, exhaust setup you can reach a torque level at or near the magical 100Nm/litre level.
Resulting in an engine that can be, that even likes to, but not necessarily needs to be reved to have fun.

I know better engines than this one but it will give you an impression of what I'm talking about.
http://www.advrider.com/forums/showp...1&postcount=41

What I want to say: IMO there isn't "the beemer". The variety of what you can get with different setups is that high, you simply can't lump them together.

[RGregor]

Originally Posted by supershaft

Our shop was also a Moto Guzzi dealership. Overall, they are just the opposite.

Compared to Guzzis beemers do have some disadvantages
http://harley.wolfcrews.com/misc/BMWc.jpg

[RGregor]

Originally Posted by supershaft

That's the thing about airhead riders that I don't understand: Everybody calls the R65 a short stroke engine and the R100 has the EXACT same 'stroke'. 94x70.6 and 82x61.5. They both come out to 1.33:1 bore and stroke ratio. Yes, a R65 IS a short stroke but so is a R100!

Maybe they just aren't good at maths?

[RGregor]

Originally Posted by pommie john

If I ever get back to Pukekohe I'd have to pull my finger out.

Where? Out of the nose (that's a spell over here to get fast)?

[alex117]

I wanted to go fast stop fast and go into the twisty bends at speed.
I had Roger Benett of Motoworks (bins?) build me a motor . He uses 97 mm J&N pistons big port big vale heads aka 77 rs, I use a 40 mm exhaust , 9.5:1 twin plug 336 cam the rest is stock. I can RAPIDLY ACCELERATE IN 4TH TO 100MPH SHIFT TO FITH AND IT KEEPS ON PULLING so far up to 135 mph and there is more to go.

Frame r90S 1974 is fully braced ala HPN style with diagonal side braces, R100R forks reworked with Race Tech valves and springs for my weight , very light Magnesium Wheels single front brake 310-320 mm? with 4 pot Brembo, Ohlins rear with proper springs for me

Ride like it is on a rail and superb handling. Stops on a dime . Of all my airheads I like this the best I can keep up with the guys on the sports bikes sort of but the bike is faster then me.

It has dramatically improved my ability on the road and was worth the time and effort to build.

[pommie john]

Originally Posted by RGregor

Where? Out of the nose (that's a spell over here to get fast)?

"Pulling your finger out" is an strange English phrase that means to do some hard work , to get on with something properly, to put in some effort.
I've no idea where it comes from.

[RGregor]

Originally Posted by pommie john

"Pulling your finger out" is an strange English phrase that means to do some hard work , to get on with something properly, to put in some effort.
I've no idea where it comes from.

"Nimm den Finger aus der Nase" ("take your finger out of the nose") is a german phrase sometimes referred to when talking about finding a means to increase speed.
I tried to find an online version of a cartoon from the german cartoonist Holger Aue about that topic, unfortunately couldn't find one.

[Uncle Pollo]

I love this thread. Lots of experience pooled togheter.

[supershaft]

Originally Posted by RGregor

I see, it's your experience.
Having started with an R75 (/5) as well I would guess it was not the experience with that, as reving a stock R75 won't take you very far. It simply doesn't like it.
So probably it's the experience with your engine.
That confirms my experience with duration cams (not the 336, but e.g. Schleicher 330): you get an engine that likes to rev high, but, compared to it's power at high revs, is a bit weak at bottom revs. Overall you get a mild torque boost, but over a wide rev range.

So far so good.
From personal experience I know that with the right cam and, most important, exhaust setup you can reach a torque level at or near the magical 100Nm/litre level.
Resulting in an engine that can be, that even likes to, but not necessarily needs to be reved to have fun.

I know better engines than this one but it will give you an impression of what I'm talking about.
http://www.advrider.com/forums/showp...1&postcount=41

What I want to say: IMO there isn't "the beemer". The variety of what you can get with different setups is that high, you simply can't lump them together.

No. I am not talking about my own bikes. I am talking about the hundreds of stock beemers I have rode from /3's up to the last ones. Can't lump them all together? Generally speaking you sure can. All of them are better off being reved up. At least the way they come from the factory.

[RGregor]

Originally Posted by supershaft

No. I am not talking about my own bikes. I am talking about the hundreds of stock beemers I have rode from /3's up to the last ones. Can't lump them all together? Generally speaking you sure can. All of them are better off being reved up. At least the way they come from the factory.

Well, I've not ridden hundreds of them.
But for all I know it's a matter of setup, not a natural law.
So at least for tuned beemers it's not a "must" but a "can".

For stock beemers, after thinking about it, I believe you're right.
They have to be reved to give power, having peak torque rather high.
Last time I rode a stock 2V beemer was at least 3 years ago (the year of the GS anniversary).
It was an R80GS Basic, right from BMW Classics, and it had literally no power at all.

EDIT: really stupid, I ride a stock R100RT from time to time. Probably forgot it as I don't connect it with Power ...