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My 750F2 project.

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Cb750r:
I know I’m not alone when it feels like a bike you’ve owned for a long time is an ever evolving, never ending project. Even if your end goal is closer to keeping a bike in stock trim unless you have it in a temperature controlled museum and never ride it, there’s constant repair or refurbishment.

I’m on a new major phase with my CB. I’ve owned it since roughly 2004, it was a poorly researched purchase and I got scammed. The seller slapped together a bike/motor with a hodgepodge of parts and the head gasket blew a day or so after I purchased it, then the engine itself blew up after I replaced it. Long story long there was high domed F2 pistons in a K5 head that had been also milled down below specs because the idiot had wire wheeled the head and damaged the surface. (Could still see wire wheel marks in the old head under close examination.)

I couldn’t afford a new motorcycle, let alone a high horsepower build, I rebuilt the motor with used head, cylinders, eBay, used con rod, new stock size pistons etc. I also discovered that the engine cases had previously lost a fight with the drive chain and was welded back up. Glad to report my collection of new and used parts did turn into a well functioning engine for many years and lots throttle cable stretching action. However I have had to deal with oil weeping from the case halves where the damaged case was repaired due to unperfect mating surfaces. I made various attempts of repair over the years with RTV but obviously it never lasted. Last winter I pulled the motor out with the goal of repairing and rebuilding the engine.

I originally attempted to repair the cases I had, and used some specialized aluminum epoxy to build up the case as well as re drill and heli coil a damaged thread near the area where I had over tightened it to try and reduce the oil leak. The repair is better than it was but I could still see light between the gap when I mated the upper and lower cases. So project sat… until I found a Cb750f2 "parts bike" for sale randomly on marketplace! I started on tearing down and inspecting the "new" motor that came out of the back of a motorcycle shop where it sat for many many years after it had rear ended someone and broke its fork stem. Carbs and exhaust robbed but otherwise just left for dead. The motor tuned over so was stored "properly" but the oil left in the pistons had left the chat in subsequent decades and this engine top end needed a rebuild, however the bottom end and the cases look great.

So I contacted Mike Rieck in the USA, and outlined my goal of wanting to build up just about the strongest street motor I could with stock F2 rods… Even though I had a good 410 core, due to shipping costs Mike sold me a good core and then went to work doing his magic. A full stage 3 port new valves and seats, and spec’d a mega cycle cam that he’s used on several bikes to much success. I ordered, a set of high domed 836cc JE pistons designed to retain compression ratio on the F2 heads….  And for insurance a set of Carillo rods! So much for the Stock rods as my self limiting measure!

I have my crank and and rotating assembly as well as my cylinders and pistons at the local hot rod shop for balance polish cylinder boring and ring gap filing.

I’m painting case halves and just rebuilt the oil pump, and have welded in a set of the frame adapters to give access to the top end with engine in frame.  Hope to keep a log of the progress here to share my progress

Cb750r:
Some expensive pictures: [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ]

Cb750r:
I swapped out the wheels, front forks and front and rear brakes, back in 2005. I used mid 90s Yamaha fzr600r. I weighed the old wheels with tires and rotors and combined the new wheels are 50lbs lighter than the old comstar setup. I had them powder coated just before I decided to pull the motor…

[ Guests cannot view attachments ]

K2-K6:
Very interested to see your build progress, I always liked the F2 and a friend still has his originally bought one.

Head work looks good, any more pictures of it from combustion side too ?

Laverda Dave:
Good to see an alternative sled being built, makes a nice change. I agree with Nigel, looks a very nice porting job.
What's all the white powdery stuff under the front wheel, snow already 😱

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