Topic: K0 motor/carbs ID confirmation

[moham]

Just picked up this motor for a future project. Bike was advertised as 1970 750, parts only, untitled. Talked to the guy a couple times and asked if he would sell just the motor. I ended up with the motor, carbs, oil tank. The rest of the stuff was in pieces, frame was painted with no vin tag. I didn't get a good look at the other stuff (wheels, forks, etc). I was interested mainly in the motor. The motor number doesn't look tampered with and there are a couple of numbers in the cases as well. I've got some pics below. Any thoughts as to what I've got for sure?

[moham]

Here's a couple more pics.

[ekpent]

Yep it looks like a late year K0 according to the numbers and the carbs are period also. Here is a timeline link if I can post it. Good find.    http://hondachopper.com/modifications.html

[moham]

Dig, ek, thanks for that link. It will help when I get the damn thing out of my car and into the shop. Only problem is it's about 35-below here. Run, don't walk, from car to shelter.

[ekpent]

I hear you Moham and feel your pain. O degree with no wind here across the "pond" and so much snow--may not ride till August !!! PS - Noticed your thread awhile ago in projects,good luck with it all.BRRRRRRRR

[moham]

Anybody else? What about the piston, is it odd that there are (seemingly) four valve reliefs (or at least some significant offset, refer to the picture above). Is this typical of the early 750s? What about the numerical markings in the case? I'll post some more/better pics later today. Motor mounts look ok but I haven't got to check the area around the drive sprocket for damage. Two small pieces of fin are bumped off but nothing crazy.

[scondon]

   I haven't taken apart a '70 cb750 motor before so can't say for sure, but "double cut" valve reliefs are typical I believe. It also appears that those pistons have a one-piece oil ring(bottom most ring) which would build the case that those are the original pistons for that motor.

   Those 4 cable carbs certainly date things as they were only available in 69 and early 70. Nice find

[754]

Nice score!!

Dont lick the motor, when you take it out!!

Piston is not what came in it. can you measure, might be big bore, looks like the right head.

Was motor apart, or did it have a chrome electric box under the carbs, notice top case bolts missing.

What are you doing with it? I notice you did not seem to want the frame, was it chopped?


On a hot day when you are riding it, you will always remember how cold it was when you got it...bbbrrrrrrr..

[moham]

Nice score!!

Dont lick the motor, when you take it out!!

Piston is not what came in it. can you measure, might be big bore, looks like the right head.

Was motor apart, or did it have a chrome electric box under the carbs, notice top case bolts missing.

What are you doing with it? I notice you did not seem to want the frame, was it chopped?


On a hot day when you are riding it, you will always remember how cold it was when you got it...bbbrrrrrrr..

Frame was untitled, painted and I didn't see the vin tag (appeared to be gone) so no way of knowing at this point if it's a legit frame. I'm probably going back for the rest of what he had, but my interest was mainly in the motor as these years I hear repeatedly talked about for their extra power (compared to later 750s). If he had title for the whole deal, it would have been a no-brainer for me but didn't really want the hassle of the title situation. In any case, my plans for it are sketchy at best right now as I'm headlong into a 550 project that is moving incredibly slowly due to job responsibilites. I realize I'm lucky to have the problem of too much work right now, but there it is. Gets in the way of motorcycles. That and playing Batcave with my son.

[scondon]

Nice score!!

Dont lick the motor, when you take it out!!

Piston is not what came in it. can you measure, might be big bore, looks like the right head.

Was motor apart, or did it have a chrome electric box under the carbs, notice top case bolts missing.

What are you doing with it? I notice you did not seem to want the frame, was it chopped?


On a hot day when you are riding it, you will always remember how cold it was when you got it...bbbrrrrrrr..

   Good to know the stock pistons weren't double cut. Axl has pics on his site of some of the big bore pistons of the day

http://www.satanicmechanic.org/bigbore.shtml

   There were a few manufacturers supplying "stock" replacement pistons in the early '70's(or so I'm told). I do have a NOS set from Rocky that are 4th oversize(62mm) and have double cut reliefs on the exhaust? side and utilize the single piece oil ring. This just for reference and not meant to identify your pistons, Moham.

[moham]

Here's some more on the K0 motor I picked up last week. The pistons measure ~63.95 at the apron. They have a stamp of "3.0" clearly marked on the dome. No other identifying marks that I picked up. So 3.0mm oversize? That's pretty hefty...

[moham]

On second glance, I guess that's only 811cc. In any case, the pistons are pretty worn, lots of scores and rubbing. Don't know if they are re-usable or not.