Rebuilding an F750

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

Rebuilding an F750

Post by Ericandchi »

Greetings,
I thought it would be interesting to start off this section with a photo of the first US F750 built by my father.

Over the next few months, the pics I will be posting are from a current project that represent the realization of a childhood dream. It all started a few months ago when we came into possession of an original never used factory frame that was "pulled from the dumpster" almost 50 years ago by the late Todd Schuster.

I will post more pics and information about the project as we move forward.

Regards,
Ericandchi

First F750
First F750
Frame found
Frame found

johnlacko
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Location: Toms River, New Jersey
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Re: Rebuilding an F750

Post by johnlacko »

Eric, I look forward to progress photos of the rebuild. I had heard that Todd saved one or two frames from the dumpster. Here is a photo of my own project. This is one of two frames known to have been built in 1973. The design was commissioned by Helmut Dahne (his bike - frame #1, is the second photo), and made from 1mm aircraft tubing. He is the one who identified what I have. My frame was supplied by BMW to Gus Kuhn in the UK, who were racing BMWs for a few short years back then. It was sold off around 1976 and turned into a street bike. With the help of Helmut, who has been great about answering questions and supplying photos, I am rebuilding it back to period specs. jl
A4F48408-20C6-4219-A181-66C02EEE2EF3.jpeg
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Last edited by johnlacko on Mon Feb 08, 2021 8:07 am, edited 2 times in total.

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Ericandchi
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Re: Rebuilding an F750

Post by Ericandchi »

Some background on how this project got started. My dad had a life long friendship with Todd that started with the building of the original Butler & Smith BMW race bikes and continued through their work at Team Honda in California. I met Todd when I was around 5 years old (50 years ago), my memories of him are likely similar to others who knew him. He was loud, yet very kind and always willing to help those around him.

Over the years my dad had mentioned that Todd had some of the old stuff hanging in his garage. When Todd passed a connection was made with Reggie Parsells, the person who Todd left his estate too. Along with the assistance of another local BMW fan, John Smeltz, we expressed our interest in some of the old BMW stuff. Reggie knew of my dads friendship with Todd and agreed that we could have the following items. When I met Reggie to pick up the parts, I promised him that I would do something meaningful with this stuff.

The list of items I received included the following:

1. One original never used BMW factory race frame
According to my dad 4 frames where delivered 2 of which were made into racers. At this time one is in the Barber Museum and last I knew the other was owned by gentlemen in Florida. Some years back it was up for auction, but didn't sell. I am not certain if the same person still owns it. As noted in this thread, I now posses one of the four frames. We do not know where the fourth frame ended up

2. One original C&J frame that my father had built in the US.
This frame was clearly built up into a bike at some time since it had a complete swingarm, rear sets, triple clamps, fairing stays, Krober ignition boxes and some other bits. The frame appears to have been modified at some time, but we don't know who did this work. Additional bracing was added under the tank from left to right and a diagonal brace fore/aft. I don't believe the bike was ever raced after these mods were made since they were unpainted. We don't know which of the two original bikes this was, but there were several guys that raced both of them. We have no information on where the other frame/bike ended up.

3. An original factory aluminum tank
The tank was modified to fit on the above modified C&J frame. Unfortunately weather took it's toll on the tank and there is a significant amount of pitting (more on this at a later time). The original fuel cap was on the tank, it's in great shape, just needed new o-rings.

4. Two original seats (#59 and #84) and the original mold
Both seats are in excellent condition considering their age. The mold is the original that my dad made. This might come in handy should we need to make a new seat.

5. One set of Ceriani forks
These are in excellent condition and even had oil in them

6. One brand new "inside exhaust" fairing and mold
In the past my dad had commented that Todd had the original molds for the fairings they had made. What we did not expect was to find a brand new fairing inside the mold that had never been used. Later bikes used a Harley XR750 over the exhaust fairing, but this one is truly an original made from the mold my dad build.

7. Tank for Rob North framed BMW F750
The tank is crushed in on one side, but retains the original paint. We aren't sure which of the two Rob North framed bikes this came from, but we know that the one in Barber Museum and the one owned by Irv Seaver BMW in California both have good tanks on them. This tank is now displayed in my shop along with one of the seats.

I'll put a few pics in a follow on post.
Last edited by Ericandchi on Wed Feb 03, 2021 6:06 pm, edited 1 time in total.

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Ericandchi
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Re: Rebuilding an F750

Post by Ericandchi »

Pic of C & J frame with the tank on it.

C & J Frame
C & J Frame

Pic of the seats and a Rob North framed tank
seats and Rob North frame tank
seats and Rob North frame tank

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Ericandchi
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Re: Rebuilding an F750

Post by Ericandchi »

After my wife and I collected the frames and other bits from Reggie this summer we headed to my dads to "drop the stuff off". Upon our arrival my dad asked, "What are you going to do with this stuff, make a coffee table or do you really want to build a bike?" I knew this was not going to be an easy task but indicated that I'd like to build a bike. A few days later my wife and I headed back to Texas...leaving all the stuff at my dads for him to mull over...!

Dad and I had some discussion back and forth. My initial thinking was that we should try to build up the C&J frame since it had actual racing pedigree. This would mean sourcing a lot of parts and machining an R75 crankcase and cylinders to make a narrow (small block) engine. Dad liked the idea of starting with the factory frame since it was essentially new except for some surface rust. As dad started to look closer at the C&J frame it became clear that it was too far rusted to build up a safe bike. So the decision was made for us, we will be using the factory frame. Knowing that we'd be building a bike that didn't have racing pedigree we take some liberties. Essentially we are building a custom bike that will utilize the old parts we have and some modern bits. If some day in the future I decide to build up an original engine, I'll drag out the C&J frame so see if it can be salvaged, but for now, this is the path we are going on. A custom F750 (eh, er, well 860) built by the man who built the original ones. What more could I ask for.

Dad agreed that he would start on the frame and as soon as I could get up to his place I would do the engine. However, due to covid I've held back from traveling by plane to his house. He's gotten first shot so a few weeks after he gets his second I'll head up there and start on the engine, unless he starts without me. Bottom line, dad's essentially done all the work to date. My job so far is to bankroll the project.

As we started to put the plan together here is what we've decided for the big ticket items.

1. I bought a 1982 R65LS that is/was in excellent shape to be used as a donor bike. The engine on these bikes is already a "short block" so we'd have a good basis to work from. Well also use the ignition and starter motor. We are too old to be push starting the bike so we won't be cutting the top of the engine off. As a result I've already modified the aluminum tank to cut off the lower part. We are also using the triple clamps and forks instead of the Ceriani forks.

2. We will be installing an 860 big bore kit onto the R65 engine. We haven't decided if we'll use the R65 heads or some others that we have. That decision can come later, I think we'll start with the R65 heads.

3. I sourced an R75 front hub which has already been laced up with 17 in rims. We are using a custom set of dual disks with Brembo 4 piston calipers that were "left over" from one of the Team Honda superbikes. The rear has also been laced with a 17 inch rim. The race swing arm is actually a bit narrower than the stock ones, so using smaller rims actually will let us put a slightly wider tire on the rear.

I'll post pics as we make more progress, but here are a few of it in it's current state.

Front End
Front End
Rear End
Rear End
Overview
Overview

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Ericandchi
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Re: Rebuilding an F750

Post by Ericandchi »

The aluminum tank modifications to cut the bottom off are finished. There were many small corrosion pit holes that needed welding. I spent several hours cleaning up the welds and sanding the whole thing to 400 grit. Next I' need to fill it with water to see if there are any leaks. If there are I'll weld them shut and go from there. I've worked around the original stickers, figure if they survived this long I will keep them. I sanded a sample spot to 600 grit and then polished it, the results are good so that is how I will finish it.

In process tank
In process tank

stwilliams
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Re: Rebuilding an F750

Post by stwilliams »

I think I may have some original stickers in that size that is on your tank. Tell me the diameter in millimeters and I can check. I got a bunch of stickers of varying sizes from an old BMW dealership. I know you are trying to save the originals, but in the event you can't, or they get damaged I "may" have some new ones.

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Ericandchi
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Re: Rebuilding an F750

Post by Ericandchi »

Logo is 80mm...as measured by attached pic.

Logo
Logo

johnlacko
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Re: Rebuilding an F750

Post by johnlacko »

Eric, I can't tell if the photos went out with my PM, so here they are again, just in case.
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Ericandchi
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Re: Rebuilding an F750

Post by Ericandchi »

Making progress. Dad finished front brakes, just waiting for me to get master cylinder. I finished sealing and polishing tank, just waiting for new decals to be delivered.


Front Brakes
Front Brakes

Tank
Tank

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