Topic: Engine part compatability - K1 bits to K7 crank case?

[Wannabe Racer]

I need some help please...
I bought a put together bits bin bike (own fault didn't check too carefully), and am slowly wading my way through the list of crap I'm discovering...

The major problem is that I have a piece of #$%* K1 engine (according to the serial number) that has had a final drive chain problem at some stage that has chewed up the crank case, behind the gear selector cover. The damage has been repaired with Araldite, and was leaking.
I have an old K7 crank case in good condition but I'm not sure if all the internals are compatible and transferable.

Has anyone else out there tried this kind of internals transfer or knows if there are any major snags I'm going to encounter?

I would really appreciate some sage advice on this one, please.

A despondent CB fan 

[754]

K7 trans has differences, and longer output shaft.
 Your parts may fit but, sprocket may hit or be close to seal area.

[Wannabe Racer]

Hi 754,
thanks for this.
Will a K7 gearbox fit the other K1 internals in the K7 crank case? I do have a spare k7 gear box!

[BPellerine]

the crank will fit,as will the other parts, what frame will you be using?the k7 has a longer output shaft which makes the final drive chain run out of line on a k6 or earlier frame.bill

[Wannabe Racer]

Hi 754,
I'm using a K7 frame.
I have a K7 crank case; gear box, barrels; Head & valve gear
The donor is a K1 (serial CB750E-109...)

My understanding is now that everything will transfer from the K1 to the K7 except the gear box... is that correct.
I take it that I should try and use as much of the K7 as possible?

Really appreciate your experience and knowledge, 754.

[Wannabe Racer]

I'm just reading around the subject of compatibility of different Mk parts...
It appears that the K0 to K6 engines are pretty much 100/% compatible. Is that correct?

So just what am I gonna need get get a working engine from the crappy K1 I have and the K7 bits I have?
I've not even split the K1 yet I'm just assuming I will need new pistons and rings, but this site https://www.cb750supply.com/products/4/engine/75/pistons-ring-sets seems to suggest that if I use K7 barrels the pistons won't fit...

The K7 and F1 engines seem to be the same engine... Is that correct?

This compatibility issue is getting to be a pain in the nether regions!

[PeWe]

You have a K7 frame and a complete K7 engine. What’s the problem?
Use this combination.

Forget the K1 stuff. Except if it has a good big bore cylinder and a good ported head that can be used on the K7 bottom.

[dave500]

ahh Araldite,is there anything it cant fix?

[BPellerine]

the k1 barrels will fit on the k7 cases,as will the head if you go that way,the k7 pistons have a small dome on them,and the rings are diff,than the k1,so you can use whatever you have the most parts on hand for.bill

[Jerry Rxman Griffin aka MuthaF'er]

The K7 and F1 engines seem to be the same engine... Is that correct?

Pretty much. Only very slight possible differences which are mostly not an issue. The output shaft with the 10mm offset in the K7 is the main difference. The other differences are non-issues. The piston crowns of the F probably provide a slight 0.2 bump in compression as I noticed in the K8 engine I put in a F0 frame. Cam timing is slightly different.

[Wannabe Racer]

Hi all, and big thank you to 754,  BPellerine and Jerry Rxman Griffin aka MuthaF'er for taking the time to help an old dullard 

Please forgive me, but my advancing years and limited IQ are producing the mother of all confusions...
RECAP:
I started with a K7 frame and in it was a K1 engine (that's a piece of crap!)
I have sourced an additional complete K7 crank case, head, barrels and gearbox (but nothing else)

So I think I get that I can transfer everything I have IN the K1 engine into the K7 crank case EXCEPT the K1 Gear box.

So using all available and compatible parts I will have K1 internals (except gear box) in a K7 crank case, K7 barrels and K7 head with K1 valve gear and it will all work... is that correct?

[BPellerine]

yes it will work.bill