!979 R100RT more power for side car rig

[Lornce]

Originally Posted by caponerd

I know.

But I just can't bring myself to mess with mine. I bought it just over 10 years ago this summer. It needed a lot of minor work due to neglect, but since that time, I've replaced tires every couple of years, changed the oil every 3000 miles, lubed the final drive splines every time the back wheel was off for a new tire, and filled it with gas every 150-180 miles. And I check the valves every once in a great while. I've only adjusted them three or four times in 60,000 miles.

This bike is like the Toyota Tercel of motorcycles. It's never failed me. This is what's great about airheads, they're simple and as long as you at least check the basic stuff, they just do what they're supposed to do.

I admire you guy's interest in obtaining more performance out of them, but compared to my Aprilia (which happens to be down for yet another weird electrical problem) riding an airhead is like driving an old 1300cc VW bug.

I know what you mean, but to be honest I was mostly motivated to improve the engine's efficiency/fuel economy when I began to modify my GSPD. Low compression ratios are antithetical to good fuel economy.

Originally I was just trying to make it as efficient as any pre-'78 airhead. It bugged me to run out of gas after only 550 kms with a 35 litre tank. Managed to get it to 700kms per tank and considerable increases in useable torque primarily through porting/head/piston mods and increased compression (12:1).

The performance gains just grew from there.

[Airhead Wrangler]

Originally Posted by Lornce

Originally I was just trying to make it as efficient as any pre-'78 airhead. It bugged me to run out of gas after only 550 kms with a 35 litre tank. Managed to get it to 700kms per tank and considerable increases in useable torque primarily through porting/head/piston mods and increased compression (12:1).

The performance gains just grew from there.

How can you run anything but race gas at 12:1 in an airhead? Yikes. Maybe I missed it, but do you have a writeup somewhere of all the engine work you've done on your bike?

[supershaft]

Originally Posted by Lornce

Most of what I know about airheads I've gained from 28 year's of fiddling with the things and the generous guidance of a few knowledgeable friends. Not google. fwiw.

If you'd care to share with us how you realised 33% additional power and at what RPM's you achieved these gains from your airhead, I'm sure you'll find a ready audience here. I'm really not interested in joining you in a mud fight.

Personally, I've currently got a high-mile GSPD that's faster and better handling than an 1150GS. While the second claim's not hard to achieve, the first took a bit of effort. It was worth it, and it ain't over yet. If you'd care to know anything about the mods I'm happy to tell you everything I know.

Don't take my word for the performance claims. Check with some of the other riders on the board.

Now, tell us all about your bike?

I already have told you about my bike. I have already mentioned everything I have done to it power wise. I guess you do realize that 15hp is a 30% gain in power for many a liter airhead that I have seen dynoed when I worked at San Jose BMW. If you don't think I could get something along those lines with an exhaust, airbox, Dell's jetted to the tits, 336, and ports that I tried to mimic the best of what I have seen Kenny Axtell do to airheads, I don't know what to tell you other than meet me for a ride if you live around the bay area. I will buy you more than one beer if you can outrun me and ask what you are doing spitting out the same old crap I have heard about 336's for decades that myself and friends have proved time and time again just ain't so.

What about telling me that I claimed a 336 alone got me 33% more power?
Did you re-read my posts for real this time? What about all the other bogus crap you were throwing at me? What about constantly changing what you claimed you wrote when it has all been right there for us all to see the whole time?

It's obnoxious.

[Lornce]

Originally Posted by Airhead Wrangler

How can you run anything but race gas at 12:1 in an airhead? Yikes. Maybe I missed it, but do you have a writeup somewhere of all the engine work you've done on your bike?

There was a fair bit of info in my rebuild thread that basically explained all the mods that had been done and how they worked. I'll have to re-link some threads in my sig line.

Yes, 12:1 seems high for an airhead, but with the correct combination of parts it's achievable and manageable with pump gas. The key to manageable high cr's is effective squish turbulence. Stock airhead combustion chambers have virtually no squish turbulence, one of the reasons they run such low cr's. (gross oversimplification).

[supershaft]

Originally Posted by caponerd

Don't want to butt into the dispute between Lornec and supershaft, but my R100RT runs about 65 mph at 4000 rpm. This is according to my GPS. My final drive housing is stamped 32/11, but according to the various listings I've seen, I should be doing 70 or above with that particular ratio.
Which leads me to suspect that someone's installed different parts in my bike. Fuel economy has never matched what everyone tells me to expect either. I get anywhere from 32 to 48 mpg depending on riding conditions.

Ok. I'll quit pretending, I do want to butt in:

What's the point of arguing about cam specs for these things?
They'll never put out the kind of power that's commonplace these days for any of todays bikes over 500cc, so why worry about it?
My son's Ninja 500 (everyone calls it a "beginners bike") can easily walk away from my R100 (it's seen a gps certified 125 mph with only a front sprocket change), and probably could manage to pull away from all but the most radiacally tuned racing airheads.
Let's not even bring up what my Aprilia will do to any of them.

I resisted the notion for years, but let's face it guys, these are old, air cooled engines, and we'll never see them perform like modern bikes. If that's what you're looking for, give it up and buy a modern bike.

For starters, tires make such a big difference with speed per rpm. I followed the graph with two ratios that I am very familiar with and that one was high and the other low.

I don't need my old airhead to perform like a new sport bike. I do, however, enjoy the extra very reliable power to be cruising along with traffic on 5 at around 100mph and when some nimrod in his kitted 180hp Honda Civic thinks he has one up on me I can punch it without downshifting and leave him behind. The extra power is fun other places as well.

I don't think it would take a radically tuned airhead to outrun a stock EX500. I think my bike will. I worked at a Kawasaki dealership that was racing an EX500 punched out to 650 with some seriously flowed heads and whatnot. That thing hauled but I still think Chris's Wrecking Ball could take it at least on top were all that extra torque starts pulling!

[supershaft]

Originally Posted by caponerd

I'm really not taking sides here supershaft, I've read a few posts you've made in other threads, and I have a fair amount of respect for your knowledge. But I've also read quite a few of LorneC's posts as well, and I think he's also pretty knowledgable.

I suspect there's more than a little poorly worded stuff here that's causing a huge misunderstanding.



This quote, taken by itself, does suggest that you're saying the cam was entirely responsible for the 33% horsepower gain. Dellortos, and the cam? Probably a completely different story, although I'd really like to see dyno charts on that. 33% is a big gain.
You know what they say about horsepower and $.

Thanks but read what I said before and after that sentence. That sentence is saying that that kind of HP gain IS possible with stock CR. I HAD already mentioned the Dellorto's. I nowhere before or after that sentence claimed that those gains were from the cam alone. I can't tell the WHOLE story in one sentence! If I were claiming that entire gain on a 336, don't you think I would have been making a bit more of a fuss about such a miraculous outcome! Let's get real! Do I have to start by saying the Earth IS round!?!

I wouldn't print my dyno chart even if I knew how. I cant tell you how many totally BS dyno charts I have seen on the idiotnet and no one even raises a eyebrow at the fact that the graph lines are obviously misplaced on the chart for the torque/hp junction being at the wrong rpm! One guy had a chart and the hp on one side of the graph and the torque on the other were in different scales! Printing it on the idiotnet don't make it fact either! Besides, dyno charts can very easily be just as much about the dyno and its operator as it is about the engine!

[Lornce]

Originally Posted by supershaft

I already have told you about my bike. I have already mentioned everything I have done to it power wise. I guess you do realize that 15hp is a 30% gain in power for many a liter airhead that I have seen dynoed when I worked at San Jose BMW. If you don't think I could get something along those lines with an exhaust, airbox, Dell's jetted to the tits, 336, and ports that I tried to mimic the best of what I have seen Kenny Axtell do to airheads, I don't know what to tell you other than meet me for a ride if you live around the bay area. I will buy you more than one beer if you can outrun me and ask what you are doing spitting out the same old crap I have heard about 336's for decades that myself and friends have proved time and time again just ain't so.

What about telling me that I claimed a 336 alone got me 33% more power?
Did you re-read my posts for real this time? What about all the other bogus crap you were throwing at me? What about constantly changing what you claimed you wrote when it has all been right there for us all to see the whole time?

It's obnoxious.

Well, actually you didn't tell us anything about what you'd done to your bike in this thread (the only thing I've had to go on re. your bike). I did just discover a little more about your bike from another very interesting thread dealing with stoic ratios, and that was telling.

Raised port floors caught my attention. I bet you a donut that looks a lot like a tube framed Buell Thunderstorm port. Now we're getting somewhere. That's a clever trick and it works, as you know.

And yes, I'm aware that late model boxers barely crack 50rwhp. I actually asked you in that stoic thread if your own small port bike cracked 45rwhp in stock trim.

So yes, given the mods I'm now aware of, that's an entirely reasonable claim. 60ish rwhp, well done. A bit sad when 80+ is possible, but we'll just leave that alone for now.

And I'd love to go for a rip around the penninsula with a fellow airhead enthusiast sometime. But we'll just have to wait and see who buys the beers.

[supershaft]

Originally Posted by Lornce

There was a fair bit of info in my rebuild thread that basically explained all the mods that had been done and how they worked. I'll have to re-link some threads in my sig line.

Yes, 12:1 seems high for an airhead, but with the correct combination of parts it's achievable and manageable with pump gas. The key to manageable high cr's is effective squish turbulence. Stock airhead combustion chambers have virtually no squish turbulence, one of the reasons they run such low cr's. (gross oversimplification).

Wow! I knew you could say SOMETHING that I would agree with.

How are you measuring your CR?

[pommie john]

Oh yeah, one more thing about RPM and gear ratios. I used to run a genuine BMW tacho on my race bike...it was err... less that accurate!

[supershaft]

Originally Posted by Lornce

Well, actually you didn't tell us anything about what you'd done to your bike in this thread (the only thing I've had to go on re. your bike). I did just discover a little more about your bike from another very interesting thread dealing with stoic ratios, and that was telling.

Raised port floors caught my attention. I bet you a donut that looks a lot like a tube framed Buell Thunderstorm port. Now we're getting somewhere. That's a clever trick and it works, as you know.

And yes, I'm aware that late model boxers barely crack 50rwhp. I actually asked you in that stoic thread if your own small port bike cracked 45rwhp in stock trim.

So yes, given the mods I'm now aware of, that's an entirely reasonable claim. 60ish rwhp, well done. A bit sad when 80+ is possible, but we'll just leave that alone for now.

And I'd love to go for a rip around the penninsula with a fellow airhead enthusiast sometime. But we'll just have to wait and see who buys the beers.

Late model? I have seen many a decent running /7 that would barely crack 50hp.

BMW raised the port floors in '88. Not enough but it was a start.

If and when I ever find an airhead that can keep up with me, the first thing I am going to do is raise my compression. In the meantime, my 60ish hp bike has out motored MANY a claimed 80+hp machine. If you live in the Bay area, let's get started!

Still, what about all the crap you were shoveling my way. WTF over?

[Lornce]

Originally Posted by supershaft

Wow! I knew you could say SOMETHING that I would agree with.

How are you measuring your CR?

185 - 190lbs measured cold.

[Lornce]

Originally Posted by supershaft

Late model? I have seen many a decent running /7 that would barely crack 50hp.

BMW raised the port floors in '88. Not enough but it was a start.

If and when I ever find an airhead that can keep up with me, the first thing I am going to do is raise my compression. In the meantime, my 60ish hp bike has out motored MANY a claimed 80+hp machine. If you live in the Bay area, let's get started!

Still, what about all the crap you were shoveling my way. WTF over?

Shovelled crap? Honestly, I think you might have been confusing info posted in other threads. There wasn't any info in this thread about your engine mods. It made your arguments look like a shell game until I figured out you might have been confused about what you'd posted where.

Unfortunately I live in Southern Ontario. Would love to ride around the penninsula again, but it's probably not going to happen anytime soon. But that's better for you cause I'd kick yer butt.

Have fun, you live in an awesome part of the world.

[anotherguy]

Compression at 7.5-8:1,small turbo running 7-8 PSI boost with a stock cam. Do this on a mechanically solid engine and it will do exactly what you ask.

[supershaft]

Originally Posted by Lornce

Shovelled crap? Honestly, I think you might have been confusing info posted in other threads. There wasn't any info in this thread about your engine mods. It made your arguments look like a shell game until I figured out you might have been confused about what you'd posted where.

Unfortunately I live in Southern Ontario. Would love to ride around the penninsula again, but it's probably not going to happen anytime soon. But that's better for you cause I'd kick yer butt.

Have fun, you live in an awesome part of the world.

Look, I had mentioned the Dellorto's in this thread and NEVER mentioned that those gains were from the cam alone. YOU DID! I was trying to make the point that I got those gains with the cam, the ALREADY mentioned carbs, and STOCK 8.7:1 CR AND who knows what else since I never specifically said that those gains were from the cam alone. YOU SAID THAT! NOT ME! The CR that you called "lawnmower compression" and that it would be a waste of time. I caught you out on that among MANY other things and then you create this diversionary issue of me claiming something I did not claim. I am not confused and you need to read more carefully AND stop making up your own points to argue with.

Your swift boating has worked. We have spent all this time going around and around about something I never said and you have not answered ANY of my questions about your erroneous 336 info and the BS. STILL no quote of me saying what you said I said? How hard can it be? I guess pretty hard when it doesn't exist. Stock CR, stock ignition, before I put the Dell's on it had stock slightly rejetted stock 32mm carbs. READ! MY point was and is countering what you said about 336's and stock CR, ignition, and carbs. NOT that my ultimate power gains were from the cam alone! YOU INVENTED THAT! If you were confused, you could of at least asked instead of the BS.

[moorespeed]

for what its worth I would go with a 308 cam in a road going sidecar, unless I was looking for more than 70bhp at the wheel then I would pick the 336. but the last batch of 336 cams are all bad the lobes on the right hand cylinder are not ground properley and are destroying the cam followers. this problem goes back over a year and we are talking hundreds. I found the problem 3 weeks ago and bmw germany are looking at it. lets hope you all have old stock.