1974 R75/6...My New Project

[Rchop]

This thread will document the entire build for my new R75/6.

This build will be a streetfighter, based on a 1974 R75/6. I have purchased a virgin R100 tank on eBay along with an R90/S seat and cowl. I will try to fit a later model sport bike front end to the original frame with modern dual disk brakes and controls. I have some 32mm and 38 mm Mikuni carbs ( whichever works best) and I will try to fit a disk brake rear differential. The lower engine has all new bearings, oil pump, chains and a polished crankshaft. The upper engine parts have all been renewed or replaced. The cylinders have been bored to the second overbore with new stainless steel pushrod tubes.

Here is what I have so far:

http://www.frsengineering.com/75-001.jpg

http://www.frsengineering.com/75-002.jpg

http://www.frsengineering.com/75-003.jpg

http://www.frsengineering.com/75-004.jpg

[Optimus Prime]

:peepwall:
:ricky:
:jump1:
:drif:

That sounds like a helluva bike.

[DJ Down Under]

Thanks Randy..I'm looking forward to it.

DJ

[DarthRider]

Can't wait to see it Randy...
I love hopped up airheads!

[Rchop]

Thanks guys, I hope your not in a hurry to see the finished project. I will be completing the engine and tranny here plus try to fit the new front end when I find it. All the rest will be done when I move the Illinois.

[Optimus Prime]

Thanks guys, I hope your not in a hurry to see the finished project. I will be completing the engine and tranny here plus try to fit the new front end when I find it. All the rest will be done when I move the Illinois.

I'll have to make a trip down to see it in person... I may even bring the checkbook...

[Rchop]

Thanks Jason, I look forward to meeting you when I move.

[Rchop]

I just bought this front end set-up on eBay. It's from a 2004 Yamaha R6 YZF.

http://www.frsengineering.com/d5_1.jpg

[DarthRider]

Thanks guys, I hope your not in a hurry to see the finished project. I will be completing the engine and tranny here plus try to fit the new front end when I find it. All the rest will be done when I move the Illinois.

Hey Randy, good motorcycle stuff takes time.
Hell, it always takes me a couple of years to even decide what my next bike will be...even longer to get it "properly fettled!"

[Rchop]

even longer to get it "properly fettled!"

I guess I could get it "properly fettled" if I knew what that means:eusa_eh:

[Bones]

Oh, this is going to be fun!

Jeff

[DarthRider]

I guess I could get it "properly fettled" if I knew what that means:eusa_eh:

"Fettled"...adjusted, tweaked, tuned, polished, lubed, set-up, made right, leaks fixed, will start, will stop, rubbed-on, Loctite'd, safety wired, aired up, and spot f**king on.

Or, look up "Fettled" in your Funk & Wagnals and you'll a pic of your BMW chop!

Now, get to work...

[Rchop]

Ohh...that's what it means:rofl: Ummm...Ok, back to work it is:eusa_whistle:

[Tassie Devil]

Good luck with the new project Randy.
I'll be keeping tabs on your progress and just hope my old girl doesn't get jealous.

Cheers,

JQ

[Rchop]

Thanks JQ, don't worry, in my book all airheads are cool :023: :icon_cool:

[Rchop]

I spent all day boring the inner races of the BMw bearings to fit the R6 steering head. Looks like it's gonna work. I just ordered all the parts missing from the front end I bought on eBay. I also got the brake calipers, discs and front wheel on eBay. As soon as I have the steering head mounted and the other parts come in, I will post some pics.
I found a pic the other day that shows the direction I'm going with this build...

http://www.rockerboxer.com/i//Michael_Stallmeister.jpg

It's the one on the left

[rivi]

Cool project!

I really like this one:

http://i97.photobucket.com/albums/l238/rivers_bucket/85618502-L.jpg

http://i97.photobucket.com/albums/l238/rivers_bucket/85618503-L.jpg

[Tassie Devil]

I like the direction you're heading Randy. You're doing good.

Rivi,
That's one sweet motorcycle...

Cheers,

JQ.

[DarthRider]

Rivi -
Attsa one tasty toaster tank!

[Rchop]

Damn...the last time I started this "Build Thread it got overwhelmed with everybody's favorite airhead pics. I changed the name to: "post your airhead pics" and restarted this one. Please, if you feel the overwhelming need to post pics of your favorite airhead...do it here: http://www.motorcyclistcafe.com/forums/showthread.php?t=1902&highlight=post+airhead+pics

Randy

[Optimus Prime]

I spent all day boring the inner races of the BMw bearings to fit the R6 steering head. Looks like it's gonna work. I just ordered all the parts missing from the front end I bought on eBay. I also got the brake calipers, discs and front wheel on eBay. As soon as I have the steering head mounted and the other parts come in, I will post some pics.
I found a pic the other day that shows the direction I'm going with this build...

http://www.rockerboxer.com/i//Michael_Stallmeister.jpg

It's the one on the left

Very nice. I really like the single sided (GS?) swingarm and the 2 into 1 high exhaust.

[Rchop]

Very nice. I really like the single sided (GS?) swingarm and the 2 into 1 high exhaust.

I will do the exhaust like that but the single sided swingarm is out for me. I'm stuck with the old style. I did just buy 2 R1 shocks like I used on the custom cruiser project. I really like those stock R1 shocks. The rebound and damping adjustments work really good. Hyperpro makes a wide range of springs for them so, I should get the ride I'm looking for. $100 on eBay for the 2 shocks and about $200 for the new springs. Pretty good deal for some good performance shocks...
http://www.frsengineering.com/0104.JPG

[DarthRider]

Man, using two "mono" shocks as "twins" on that project bike will really look cool Randy!
Can you adjust the damping low enough, now that it will be "doubled"?

Edit: If you are interested, I have a card at work for a spring winder in Oklahoma that will have, or will make, any spring you would ever need, 2 wheels or 4. They do lots of racing & hi-performance work.

[Rchop]

I really had to beef up the single shock to work with the custom cruiser Dave. They are made to work with some serious extra linkage with the stock setup. I'm just guessing but, from past experience with these shocks...they will work good in a dual setup without the linkage. If it's too stiff, I can always go with a lighter rising rate spring. The guy I have worked with at Hyperpro has been very helpful in the past but, I'm always looking for a new source. I will take your info for future reference.
Thanks, Randy

[Rchop]

More new parts have arrived...

R1 shocks for the rear, lightened flywheel from San Jose BMW, aluminum pushrods and Vortex top triple clamp.

http://www.frsengineering.com/75-006.jpg

[Rchop]

I have the BMW bearings fit to the R6 steering stem. Now, I have to shorten the steering stem to fit the shorter BMW steering head.

http://www.frsengineering.com/75-007.jpg

[Optimus Prime]

I have the BMW bearings fit to the R6 steering stem. Now, I have to shorten the steering stem to fit the shorter BMW steering head.

http://www.frsengineering.com/75-007.jpg

Hot Damn Randy, looking good. I really enjoy these build updates. Thanks.

[Rchop]

I just got some Ducati mufflers I bought on eBay. I plan on fitting them under the seat. I will have to totally remake the rear subframe to hold the new shocks and the mufflers. Here are some pics I have during the mock-up:

http://www.frsengineering.com/75-008.jpg

http://www.frsengineering.com/75-010.jpg

The rear view shows the stock size tire. I have a lester mag that I can mount a wider tire on that will be used for this project:

http://www.frsengineering.com/75-013.jpg

[Rchop]

I finally shortened the front stem to fit the R6 front end to the BMW steering head. Everything fits well now:

http://www.frsengineering.com/75-009.jpg

The new front brakes should have plenty of stopping power:

http://www.frsengineering.com/75-011.jpg

[Optimus Prime]

Fantastic. The underseat exhaust will look great. :eusa_clap:

[Optimus Prime]

I spent all day boring the inner races of the BMw bearings to fit the R6 steering head.
Professional interest: Are the bearings thru-hardened or case hardened? How much did you bore out? Do you have the bearing dimensional info and part numbers? I would be able to help get quality, correctly sized bearings for this and future projects if you're interested.

[Deans BMW]

Randy, check the wheel bearings carefully on the Lesters, that was the only thing that we ever had problems with on them. We sold a lot of Lesters.

[Markus]

holy cow! Nice work....keep us posted!

[DarthRider]

Professional interest: Are the bearings thru-hardened or case hardened? How much did you bore out? Do you have the bearing dimensional info and part numbers? I would be able to help get quality, correctly sized bearings for this and future projects if you're interested.

What a cool offer!

[Optimus Prime]

What a cool offer!
It stands for other cafe endeavors as well :peepwall: We've got some really "high end" enhancements, that usually only make it to the big OEM customers, that may be beneficial to very "extreme" applications. :028:

[kocook]

Randy, check the wheel bearings carefully on the Lesters, that was the only thing that we ever had problems with on them. We sold a lot of Lesters.I'll second that. Dean took the one-off extra wide Lester from his bike and put it on mine (1978). The bearings gave out a month or so later. Held out long enough for me to limp in. Could not remove the axle, so had to cut off the ends to ship back to SJBMW. Chris fixed it and they never gave me any more trouble.

Only disappointment was that a Kaw Z1 wanted to race as I was limping home. Since Chris had put this bike together, it would have eaten that guy's lunch. As it was, I had to suffer through him tormenting me because I wouldn't race.

After that, I hunted down every Z1 I could find in SoCal while I was stationed there. Was like shooting fish in a barrel, especially if curves were involved.

Of course, none were named Duhamel or Pridmore. I had already seen them ride the wheels off that bike. :)

Kent

[Deans BMW]

Kent, by golly now that you mention that, that was a one off lester rear wheel.

Those days owning that store was more fun....................and stress than ever could be described. It was like being on drugs with out a let up.

[Rchop]

Jason, the BMW bearings are 28mm inside and 52mm outside race diameter. They are German made tapered roller bearings. Just like you would find in car or trailer axle. The Yamaha bearings are 30mm inside and 55mm outside race diameter ball bearings. I don't recall (CRS) the make of either but I have heard the names of both before. The next time I take the front end off I will post that info.

The major question for me was: where to remove or add material to make them work together. I decided to take the 2mm out of the inside of the BMW bearings. That made the most sense, since:shog: the most extra material was there. These bearings never make a full revolution so, I wasn't worried about weakening them in this manner. The material was extremely hard and I had to use a diamond embedded 26mm diameter stone on a high speed die grinder to accomplish this.

It turned out to be a very good fit and I would recommend it to anyone with the patience to hand grind and measure, hand grind and measure, hand grind and measure...you know what I mean. I don't have anything that would fit in a mill that could cut the material. I think the only way to machine bore these bearings would be with some type of electrical discharge machine.

Thanks for your generous offer and I will remember it for future projects.

Randy

[Rchop]

Dean, I will be removing the bearings for powder coating. I will renew them then, thanks for the heads up. The wheels will be powder coated shiny black with a hand painted red pin stripe on the rim. Hmmm, wonder where I got that idea from:icon_cool:
http://www.yamaha-motor.com/assets/sport/base/logo.jpg

[Optimus Prime]

Jason, the BMW bearings are 28mm inside and 52mm outside race diameter. They are German made tapered roller bearings. Just like you would find in car or trailer axle. The Yamaha bearings are 30mm inside and 55mm outside race diameter ball bearings. I don't recall (CRS) the make of either but I have heard the names of both before. The next time I take the front end off I will post that info.
If the BMW bearings are from that area, it's probably one of two:
-FAG is the main German bearing manufacturer
-SKF is a larger bearing manufacturer, but Swedish by origin.

I did some digging and found a reference that these are standard 32028, 28 x 52 x 16 mm. I couldn't dig anything up online concerning a 30x52x16, but I'll look when I get to work tomorrow. I'll also attempt to find out if it is thru-hardened or case hardened.


The major question for me was: where to remove or add material to make them work together. I decided to take the 2mm out of the inside of the BMW bearings. That made the most sense, since:shog: the most extra material was there. These bearings never make a full revolution so, I wasn't worried about weakening them in this manner. The material was extremely hard and I had to use a diamond embedded 26mm diameter stone on a high speed die grinder to accomplish this.

It turned out to be a very good fit and I would recommend it to anyone with the patience to hand grind and measure, hand grind and measure, hand grind and measure...you know what I mean. I don't have anything that would fit in a mill that could cut the material. I think the only way to machine bore these bearings would be with some type of electrical discharge machine.

Thanks for your generous offer and I will remember it for future projects.

Randy

Bearing hardness is some of the highest you will encounter. 65+ on the Rockwell scale (http://en.wikipedia.org/wiki/Rockwell_scale) is not uncommon. The reason I asked about the way the bearing was hardened deals with the ability to bore out the bearing like you did. Thru-hardened is just like it sounds, the bearing is heat treated in such a way that the steel is a uniform hardness. However, removing material from a case hardened (http://en.wikipedia.org/wiki/Case_hardening) bearing could be bad and is not recommended. In your situation, I'm not too worried about the thinning of the cone race thickness as I'm sure you have enough experience with things like this to be able to tell if there's enough material still there.

I'll let you know what I find out tomorrow.

[Rchop]

SKF is it Jason. I still have the outer races in the box as I won't change them until the frame is powdercoated. The outer race says: SKF 320/28 GERMANY-S 15 010B The box just has a BMW part #

I also did some digging online and found that all the 30mm inside dia. bearings had a 55 mm outside diameter.Of course that doesn't mean they don't exist...I just couldn't find them.

Randy

[Optimus Prime]

SKF is it Jason. I still have the outer races in the box as I won't change them until the frame is powdercoated. The outer race says: SKF 320/28 GERMANY-S 15 010B The box just has a BMW part #

I also did some digging online and found that all the 30mm inside dia. bearings had a 55 mm outside diameter.Of course that doesn't mean they don't exist...I just couldn't find them.

Randy

Randy,

I've been doing some digging, but I can't find any TRB's with the needed dimensions. (tapers are the preffered bearing in this application) It looks like 320/28 bearings are thru-hardened, which is a plus. However, I asked about your situation to 3 of the more experienced bearing engineers around here and, to a man, they all said "no way in hell". :icon_cry:

I think if you have no other options, you may be able to get away with it. But they suggested first trying to mount a bigger stearing neck to fit a 30x55 taper or turning the front stem to 28mm in order to fit a new 320/28 bearing.

[Rchop]

Jason, thanks for your information. I would have to disagree with your "experienced engineers". These bearings are so overengineered for this application that removing the material that I did would not affect them in the least for this application. Considering that these are tapered roller bearings...the 2mm removed only comes close to the outside of the inner race at the very inside portion of the taper. Before cutting the new bearings, I sacrificed an old one to make sure I would have enough material left and then cut it apart to see what was there.
I wouldn't even think of doing this to those bearings when used in another application such as wheels. Remember, these bearings never even make a full revolution in this application. Looking at the new ball bearings in the R6 steering head, they are positively flimsy compared to these tapered bearings. If I had to chose between the 2...I would say that my modified ones will work just as good as the new ones.

I would bet my life on it:floet:

[Optimus Prime]

Jason, thanks for your information. I would have to disagree with your "experienced engineers". These bearings are so overengineered for this application that removing the material that I did would not affect them in the least for this application. Considering that these are tapered roller bearings...the 2mm removed only comes close to the outside of the inner race at the very inside portion of the taper. Before cutting the new bearings, I sacrificed an old one to make sure I would have enough material left and then cut it apart to see what was there.
I wouldn't even think of doing this to those bearings when used in another application such as wheels. Remember, these bearings never even make a full revolution in this application. Looking at the new ball bearings in the R6 steering head, they are positively flimsy compared to these tapered bearings. If I had to chose between the 2...I would say that my modified ones will work just as good as the new ones.

I would bet my life on it:floet:
That's music to my ears. :020:

Personally, I figured you had enough experience to know what was ok and what wasn't. And since you responded with no hesitation or worries about your current course of action, I'm confident you've got everything well figured out. I figured if you had any doubt, then my comments would have given you pause. Since it didn't, I'd say don't worry about it. The only thing I was worried about, personally, was the heat treat process of the bearing. Since it's thru-hardened, there aren't any issues there.

[Rchop]

Thanks Jason, I really do appreciate your input and I am always open for suggestions and critique.

[Markus]

Whatever happened to this project ????

[JCsman]

Whatever happened to this project ????

I'll bet it got "salted" away.:icon_redface:

RChop is busy with an LSR project, covered by another post.

http://www.motorcyclistcafe.com/forums/showthread.php?t=2894

[Rchop]

This project has been postponed until my shop is re-opened in Illinois. Probably mid 2008.

[Rchop]

Just a side note for Jason on this build. I did find a company that makes the conversion bearings that I need. I bought 2 sets, one for this build and one for the Bonneville project. They have worked out well... http://www.goallballs.com/home.asp

[Rchop]

I have brought this build back to life as a winter project. My biggest problem with it so far has been the rear tire size. After installing the R6 front end and wheel, the skinny rear wheel didn't look right. I think I have the problem solved and parts are being shipped. As soon as I get them and mock it up, I will post more pics.

Stay tuned...:pot:

[Rchop]

I didn't like the direction it was going in with the stock airhead rear end. I bought an R80 single sided rear end and it didn't have the look I was going for either. I finally came across this 2005 Rockster rear end for sale and I thought: this is it! Just got all the parts in and mocked it up with a 2006 GSXR rear subframe and a Ducati under seat exhaust. I think I finally found the look I have been going for on this build. The only other thing I will probably change is the front tire to a lower profile.


http://www.frsengineering.com/TS6.jpg

http://www.frsengineering.com/TS7.jpg

[isiahstites]

That looks great Randy! I like the use of the new modern BMW parts with the old BMW parts of yesterday.:041:

[AntonLargiader]

That's a great look! Very much what a friend and I have been looking for in our upcoming winter project.

With the swingarm centered in the frame and the final drive and wheel mounted, how far offset is the wheel centerline from the bike's centerline? The R1100 (or R1150 in your case) swingarm is not centered on the Oilhead, whereas the Airhead swingarm is.

Another option is to use an R100GS swingarm to keep the correct driveshaft length (and keep the wheelbase from getting out of control) but that will limit the wheel width. And you won't get the central monoshock effect.

[Rchop]

The bike is just in mock-up right now. Eventually it will be set in a jig and the correct measurements determined. The pic below shows the offset needed in my last build...

http://www.frsengineering.com/0015.JPG

As I said in the above post, I have already tried the single sided airhead swingarm and was not happy with the outcome or tire size. The longer wheel base will work just fine.

[AntonLargiader]

As I said in the above post, I have already tried the single sided airhead swingarm and was not happy with the outcome or tire size.
I didn't read that you'd tried a Paralever one. The R100GS swingarm is basically identical to the one you're using, except it has the shock on the side. Oh, and it fits. :) But it looks like the fit part won't be much of a problem for you. I'm all eyes to see how you make it work in the Airhead frame, though!

I agree, the R80 monolever swingarm isn't very exciting.

[Rchop]

It's still in the idea stage here.
The thought is to try to adapt an R1100S trans to the R75 motor. If that doesn't work, then the next step may be an oilhead motor. Lots of hoops to jump thru here but, that hasn't stopped me in the past.

[isiahstites]

Anton,

I am not sure how familiar you are with Randy or if you have ever seen any of his previous builds but he is a true craftsmen. Having worked under him for almost four years in my profession and also having been involved in several of his projects and him being involved in several of mine I have learned to expect nothing but the best from the man. He will make it work you can bank on that.

Scott

[DarthRider]

I'll stomp grapes for a ride on this one, Rchop !

[Ed K]

Looks kinda like Speed Triple mixing it up with a BMW!

[AntonLargiader]

Any progress on this one?
:ear:

[Rchop]

Any progress on this one?
:ear:

Not yet. I don't think I will be back to this bike until this summer. Too many things going on right now. I just put the LSR bike on the rack to tear it down and get ready for Maxton.