Horsepower Increase

Does anybody have any ideas of the best, most reliable way to get a significant power increase from a 1992 R100R? I am trying to decide whether to invest in more power or a different bike. I love this bike's character, riding position, and reliability; I don't love having to thrash it to keep up with Neons. All suggestions that keep me from buying something like a ZRX-1200 will be greatly appreciated.
Thanks, Mike

Slap a turbocharger on it.

Try the C.C. Products 1050 cc kit.

You can get a little more HP with 40mm Bings, more with the large valve heads from the 1980's withe the 40mm Bings
Then 9.5 compression pistons and dual plugging.
Eventually you will ruin the bike.
Sell it to someone who likes R100R's

The BMW sport cam kit (336?) is always entertaining.

To put it bluntly, you're going to spend a whole lot of money to make this bike marginally only marginally more powerful.

KBasa said:

The BMW sport cam kit (336?) is always entertaining.

To put it bluntly, you're going to spend a whole lot of money to make this bike marginally only marginally more powerful.

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Like they say: "Speed = Money, how fast do you want to go?" I think with new carbs (forget 40mm Bings, get Del'Ortos), high compression pistons, cams, and a new exhaust you could achieve what you wanted.
Then again, for about the same money, you buy a really nice used Triumph Sprint ST*, with 100 hp stock AND have a second bike for when you're "in the mood for something completely different" as Monty Python used to say.

*or a myriad of other bikes with roughly the same performance.

mikea--so far this thread has attracted a bunch of naysayers, not me. The first things you can do to improve performance is to remove unneccessary items. The smog/pollution control stuff can be easily removed by a competent mechanic. Lose weight and gain midrange power by going to a no cat two-into-one pipe. If stock your bike is probably at 60-65 hp. Kbasa is right in that the max you will ever get out of this bike is 75hp. You can buy any number of Japanese bikes that are far superior in hp and you can get them cheap. But you have an airhead and there are many virtues in that. Good Luck with whatever you choose.

I have a '95 R100R and I am considering some of the same. I really like the idea of a snarling-mad Airhead so that is some of the appeal.
I have heard that Siebenrock is going to introduce a 1070cc kit this year, but I've also heard that with larger bores there could be issues with the thickness of the metal in the cylinder spigots. I don't know if theis kit will rely more on bore or stroke to get the extra displacement.
One thing that I have heard makes a great difference is to get the heads gasflowed. I do not know if gasflowing is the same as porting but from pictures I've seen it does appear to at least be a similar idea.
The stock exhaust on the R100R is already a 2-into-1 without catalyst. That bulky collector box is merely dead weight. I'm thinking of having a Y-pipe fabricated to replace mine. It would save weight and visually clean up that area and if done properly may well have better flow characteristics than the old collector.
Intake/exhaust issues can be complex but there are some points that will simplify that. I'm fairly convinced that the stock air filter setup is about as good as it gets. Less restrictive filters don;t cath as much particulate matter. Not an issue to a racer for whom it only needs to live through the race, but I'm sure you'd like to preserve your engine's longevity. You can cut holes in the airbox if you really think it needs less restiction. Aftermarket exhausts may save weight in addition to whatever benefit they may offer in reduced restriction. But remember that the exhaust needs a certain amount of restriction for scavenging to be effective, and that if you go to a 40mk head I think the exhaust size is different too and that could mean some expensive fabrication.
I have yet to decide just what I want to take on though. No hurry and I don't want to go as extreme as is possible.

Great replies all, guys. I meant to ask for a very reasonable HP boost with as much of it as possible in tne midrange. Companies like CC Products (San Jose BMW) have various parts and ideas. These range from big bore kits; these soung attractive (what about vibration?), to porting , valve, and general airflow mods. I'm sure some modifications are easier to live with, some a more bang per buck, and some probably are just marginal.
Seems like others are interested. Please keep the ideas coming.

mike

Anyone that thinks they can improve on the stock exhaust system is dreaming.

So is the guy that says to remove the air injection. The latter is a good idea, but that system uses up no horsepower.

Given that an R100R is not much of a long-distance machine since it has no fairing, a good performance upgrade could be a lower rear axle ratio. Better acceleration, less top end, of course.

>I have heard that Siebenrock is going to introduce a 1070cc kit this year

VEG-DUDE, YOU JUST MADE MY DAY!!!!!!
If you were here, I'd kiss you ON THE LIPS!

I'd never heard of Siebenrock, but I thought I'd take a spin around their website and lo and behold, they have the RIGHT seat for my R75. For TWO-HUNDRED THIRTY BUCKS, SHIPPED FROM GERMANY!!!!! WoooHooo, I'm dancing the "Snoopy Dance". I would have paid that on Ebay for a beat up POS than needed re-chroming and re-covering. If it only has a steel pan, I'll be in heaven.

BOY, I love this site!

VEG-DUDE, YOU JUST MADE MY DAY!!!!!!

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Glad to be of service!

If you were here, I'd kiss you ON THE LIPS!

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Ummmmmmmm, are you pretty?

But seriously,

If it only has a steel pan, I'll be in heaven.

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Are you restoring or otherwise going for "correctness?" If not a plastic or fibreglass pan could be advantageous as it won't rust. My coworker rides an R75/5 with a seat pan so rusted that I think he could fall through any day now.

So anyway, yeah I think we Airhead tweakers should keep each other posted about this Angry Boxer stuff!

>Are you restoring or otherwise going for "correctness?" If not a plastic or fibreglass pan could be advantageous as it won't rust. My coworker rides an R75/5 with a seat pan so rusted that I think he could fall through any day now.


Harrump! I restore bikes to ride! Actually, neither of my Rs have rust and they've lived a hard outside life in Utah and Colorado. The 75 still has a pretty decent "Inspection" sticker on it even. I just think the metal pans are more durable. I'm just happy to get the seat as my current 75 seat need both a cover and rails. It has an (incorrect) single rail seat on it now.

Now if I can just find the "seat removal" kit that takes the place of the hinges (so the seat can come completely off instead of just swinging up) I'll be ecstatic. Any Ideas?

power increase

I just checked out the Siebenrock site. They are offering a piston and cylinder kit with 9.5 compression. A&S BMW also has what appears to be the same kit.
What do you think of simply bolting on a CC 1050cc kit? Would this increase vibration too much or require re-jetting?
Does anybody have any experience with this?

>Does anybody have any experience with this?

Not me, personally. But I will take a WAG and say that in order to achieve the maximum benefit from the money spent you would DEFINITELY want to rejet, maybe even go up a couple of mm in carb size.
But to really optimize the increase in CC, you might want to do some head work and maybe valves. (Insert WideBMWs post here)

IMHO, slapping on a big bore kit and doing nothing else would be a very expensive exercise in futility. You'd get much better performance results from a really meticulous tune-up. As a matter of fact, I think you could probably achieve a better result cheaper if you just took your bike to a mechanic who knew what he was doing. Understand that when bikes leave the factory, they are set for a BALANCE of performance, economy, and reliability. If your desires include more performance at the expense of economy, to some degree that's a simple re-jet and exhaust away.

But like I said, I don't have any experience with this kind of work on BMW Boxers. My "conjectures" come from working on two liter BMW and 1275 BMC engines and all my experience there, the most significant increase in "stage one" mods like you're describing come from improving the flow. (Porting/polishing, jetting, and less restrictive exhaust. But you have to be very careful with the last, because less isn't ALWAYS more with exhaust restriction and a Dyno is pretty much required to do the work, which can make it really expensive.)

There isn't really any need to open up the ports on the heads...take a look at them and you will see that they already have a nice smooth finished design. Unlike most automotive engines that just have rough unfinished castings.

The stock exhaust can be improved on if you can custom fabricate a 2 into 1 that has about 100" of pipe before it goes into the collector. Have fun fitting all that pipe on the bike.

The 1050 kit will require jetting, but at least it's a tried and true setup.

You can also advance your ignition base timing until you begin to hear detonation at higher rpm. I've run about 6 degrees advance for thousands of miles without problems in the AZ heat. I haven't tried to find out how far I can advance it. The increased initial advance will provide more power most notably off the line but will help with the entire rpm range and it's cheap.