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Rebuilding an F750

All about BMW in racing can be discussed. Sharing of pictures, and other information.
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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

We had a slight change in plans over the past few weeks. I initially we were going to use a set of magnesium Brembo calipers from the mid 80s, but we have been unable to source new seals. Unfortunately we discovered this after all the mounting hardware was made. I located a new set of Brembo calipers which are now mounted. The brackets are actually a bit simpler, all that's left is a bit of polishing.

Front brakes
Front brakes

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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

Latest progress. Note the crankcase is a spare R90s. The engine we will use is still with me in Texas ready for rebuild when I get up to dads next month.

I ordered tires this week so soon it will be easier to roll around.

F750 in Progress
F750 in Progress

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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

We've made good progress in the last few weeks. I brought the vapor blasted cases up to my dad's so we could build up the engine and get it into the frame along with the transmission.

We temporarily put the carbs and tank on for fit checks, all looks good. We have a set of 38mm stainless headers that fit good too.

We evaluated the full fairing we have that was still in the mold...its pretty rough and will need a lot of work. The very first of the bikes actually had a small half fairing similar to a Norton or Ducati so we are thinking of going in that direction. Plus the engine is looking so nice it seems a shame to cover it up.

Engine in Frame
Engine in Frame

sherman980
Posts: 79
Joined: Fri Oct 27, 2006 3:00 am

Re: Rebuilding an F750

Post by sherman980 »

Eric,
Really enjoying your posts on this (re)build. Please, more pics if you can!
Thanks.
Chuck S.

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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

Here is a pic with original tank which I modified so we could keep starter motor. Note top of engine not cut off and we bought one of those 1 piece covers. Not sure how I feel about the cover...gives it a sort of vintage vacuum cleaner look. Seat needs some cleanup.


[attachment=0]tank_seat.jpg[/attachment]
Attachments
Tank and Seat
Tank and Seat

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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

Here is latest update.

Finally got a rear tire that fits (Mitas 130/70). Not sure how well it will perform, but gotta be better than what was available 50 years ago. I do have a set on my Grom and really like them so should be fine for starters. Shocks also came in and are installed.

New rear tire and shocks
New rear tire and shocks

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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

I had a rod of Titanium (6AL4V) that had been sitting on shelf for at least 30 years. We decided to use it for a rear axle. Note F750 swingarm is narrower than stock, hence it is shorter. It's also been drilled/threaded at ends to install bobbins for paddock stand.

New Ti axle next to stock steel
New Ti axle next to stock steel



Installed
Installed

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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

Some pics of fenders and fairing.


Front Fender
Front Fender

Rear Fender
Rear Fender

Fairing
Fairing

Werner1111
Posts: 86
Joined: Fri Dec 16, 2016 6:39 pm

Re: Rebuilding an F750

Post by Werner1111 »

Looking great! What are those flat slide carbs? What are you using for an intake manifold between the carb and the head?

I ask because I have some Mikuni TM38s on an R100s build. I had used a reducing rubber tube to b/c the OD of the Mikuni is smaller than that of the stock intake tube on the head. But, then the carbs would dance around because the tube moves around when the engine runs. I recently found a set of aftermarket manifolds with the same OD as the Mikunis so I could use a solid tube without any reducer, but have yet to install them.

Here's the current setup with the reducer.
Attachments
R100s Carb setup.JPG
R69 R90/6 R100/7 R100S R1150GSA S2R1000

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Ericandchi
Posts: 41
Joined: Sun Oct 09, 2016 10:11 pm

Re: Rebuilding an F750

Post by Ericandchi »

Carbs are Mikuni TM38 flatslides as you noted. Manifolds are rubber PVC couplers from local hardware store cut short as possible to minimize flex but not allow carb to touch head. After final installation carbs get safety wired to bike to protect from flying off should I somehow kick them loose.

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