750k engines

[ginger_jim]

Hi all  - im rebuilding an old K7 I bought in February and was wondering if there is any difference  between the K0 - K6 and K7 engines?  Many vendors list engine parts for all the K's except the K7?  For example -

Vintage Honda CB750K0 - K6 SOHC engine

Piston ring sets (4) @ Std size 61mm

Replaces 13011-300-024 ref only

NEW PARTS

So is there a difference?

Many thanks in advance for your replies!

[hairygit]

Yes, the K7 engine is basically the 750F1 engine, but with different carbs. Slightly higher compression ratio than earlier K's

[Bitsa (Ralph Wright - RIP)]

From what I can remember the k7 had different carbs,exhaust clamps,exhaust system which in my opion rotted quicker and was the last of the k series.Personally as a ex mechanic I thought was a bit of a wet fart.Soon after all the hype the f1 appeared and to be fair I did not think much of that,the history continues but op ions differ that's what makes us different.On lots of sites its the k0 to k6 that's still all the hype.Price also confirms that but to be fair if I could not have found what I wanted a k7 would have been surfice before they all disappeared.
Cheers
Bitsa

[steff750]

  yes most of the parts are interchangeable .(in "ye olde times" you never rebuilt a engine you bought a  bike for spares even then the the price of jap spares was very expensive) ive mixed and matched lots of parts over the years , like camshafts, carbs, clutch, starter motors.pistons conrods cranks,valves, rockers gear selectors, and gearboxs, early k0's  have smaller final drive bearings than k2-k7 so are not interchangeable,if anything i think the later engines got a bit better engineered as time went on, i have been told that you can put f2 pistons in early engines to raise compression although i ve used later pistons ive yet to try the f2 route? . its already been said by the time the later models came out they where well behind the other three jap companies ,and they where very dated by the end of thier run of almost ten years

[Bryanj]

Rings on there own don't fit, complete piston kits probably. Look up Motogrid and use there online parts fiche then check what other bikes use the same parts on the parts lookup

[ginger_jim]

What about Calipers?  My bike has the twin disk conversion but one of the calipers is a horror story as the piston and bleed nipple are siezed. 

[hairygit]

If they are both K7 calipers, yes they are different. The K7 used the same caliper as the 750F1 and the U.S. market autos, and are a pain to find in good condition, and the seals and pistons are much more expensive to find than the earlier type If the bolt heads that hold the 2 halves of the caliper together are hex head and are on the outside of the caliper, they're K7/F1, if they're allen head fitted from the rear, they're K0-6.

[ginger_jim]

Yeah ive been doing some research and have discovered the same.  Do you reckon that the calipers off the 400/4 are the same?
http://www.davidsilverspares.co.uk/CB400F-SUPER-SPORT-1977-USA/part_163403/
Dave silver offers stainless pistons and seals for them whereas they dont for the later model 750/4.

Hey I notice you are in Woodbury...if you are in Tiverton at any time and fancy a natter and tea let me know. 

[hairygit]

Sadly, 400four, 500four and 550four all use the same caliper, but 750F1 and K7 calipers are different. The piston and seals in the F1/K7 ares fractionally larger than the others, are a pig to find, and cost 2-3 times as much Also, for whatever obscure reason Honda spaced the bolts holding the caliper halves together about 4mm further apart than the rest of the range, which means you CANT fit a 400F etc caliper (no use trying a 500/550 caliper arm either as the 750 disc is bigger, so the caliper arm fouls the disc ) Dave Silver is currently testing prototype repro calipers for the F1/K7, but they wont be available until the end of the year. It would be good to meet up at some point, always good to meet fellow Honda fans!

[ginger_jim]

I suspected that it was too good to be true!  Anyway not to worry there are options available. 

Thanks for the posts :-)