Restoring cb 750

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Alsproject

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Would like to get some advice. Just finished restoring my car and decided to start another project. I always had a passion for motorcycles, first motorcycle I had was a Kawasaki 250 dirt bike then later I purchased a new Honda CB 750 custom which I sold a few years later. My brother has a 1974 Honda CB 750 last ran about 35 years ago and was thinking about restoring it back to original, and I know it’s going to be a project. It has around 34k miles on it and ran good at that time. I know it will need carburetor work. Not sure if engine is seized yet, if I do get it started would it still be a good idea to rebuild it? Enclosed are some photos.
 

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If it gets running a compression check will give you an indication of some of the condition. There are still unknowns that you cant see...bearings, gears, timing chain, tensioner wheels, primary chains, valve guides, valve seats, seals etc. I dont like unknowns on my personal stuff. Good chance the tensioner wheels for the timing chain and primary chains are hard and ready to break apart. With the miles Im sure the valve surfaces have seen better days. More than likely some surface rust in the cylinders, could be worse if its stuck. Rings may be stuck again cant see it unless it runs then you can see if its burning oil or has low compression. To hard to say what condition it is in, alot depends on how it was stored and how it ran when parked.
 
It ran good when he parked it, was stored inside cold storage. The engine did turn over about 7 years ago. If I go thru with a complete restoration and I can have someone help me with the engine rebuild what do you think approximately the cost of a total restoration? Thanks
 
Hard to say, depends on condition of the bike as a whole and what type of restoration and what can be salvaged and what needs to be replaced. If you are going for a correct restoration its going to get expensive fast. Stock exhaust is well over $1000. Its been painted so going back to stock with decals will add up. Engine can be hundreds to thousands depending on what it needs inside, with the miles stuff wont be perfect and it probably could use a freshen up, all parts are available but it gets expensive. My performance big bore engines start at $5000 and go up from there. Complete stock can be $2000 to $3000 easy. Figure rebuilding caliper and master cylinder and hoses. new tires.
 
If an engine is seized I automatically disassemble the engine. I dont take any chances. With the head off it is easier to get the pistons unstuck using rust penatrant and or other means. If you are going to disassemble you can be a little more forceful in getting stuff to move.
 
Alsproject said:
What is the best way to unseize engine?
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I wouldn't tear it apart until you have no other options. Make sure the Trans is in N. Pull plugs, flood w penatrant, marvel mystery oil, wd, etc. Let it sit. Keep cking it, working it. These old bikes are pretty tough.
 
Thanks , let’s say if I’m able to get it running and with decent compression that it wouldn’t make no sense to overhaul it
 
You don't even have to have it running to ck compression. If u get freed up you can use the kick starter or use the starter motor. If u ck compression with carbs on, manual days to have throttle full. If u use the battery and starter if working , it's good practice to turn kill switch to off.
 
Double ck yourself when you do compression test. I almost tore my 750 down thinking the rings were bad in cyl 3, but all it was I didn't have the hose seated on gasket.
 
Like I said in the second post, very good chance by now that the tensioner wheels and guides are hard and starting to break apart. I have taken engines down with less miles that had wheels almost gone. Sometimes they go longer. At this mileage the valve guides start getting wear and seals get hard as a rock. If it sat in a moist environment good chance you will have rust marks in the cylinders where it was stuck. Compression is only part of the story on the condition of an engine.
 
In restoring a bike is it best to use the original parts if possible even if they have to be rechromed or go after market
 
The quality of chrome on repro parts is very variable, I'd go with rechrome original parts just had some done for my F1, I bought a set of Chinese crash bars and will be having them rechromed with my next batch as the chrome is already flaking, the guy I use completes to better than OEM and I know it will last.

Loki
 
Alsproject said:
In restoring a bike is it best to use the original parts if possible even if they have to be rechromed or go after market
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That's totally up to you. How much u want to spend, do u have a good chrome shop within a reasonable distance and price. Aftermarket sometimes can be a guessing game. I guess how visible the part is can be a determinate
 

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