CB750 K5/6/7

[Brett72]

Hi, thought i had better move to a proper page and away from the newbies intro page and start a thread purely for my resto. Its a big task i have taken on especially knowing that there is lots of parts missing and working out whats not there!!
Still lots of fun tinkering in the garage and playing on the net searching for bits. Not 100% sure wether or not to try and go as near to original as possible or because the engine is one year different from the frame go for a cafe/unique look and just make something i like.

[Brett72]

just some of the photos as i go. I have a k6 engine but the carbs are from a K7. will they fit and work?

[Trigger]

Look for a K1 to K6 set of carbs. They are better carbs and think the K7, K8, F2 PD carbs are only a match for the heads with the larger valves or, i could be wrong. Nope, thinking about it the early carbs are much more user friendly 

[Brett72]

Thanks Trigger. Might see if anyone has a set to swap/px

[Brett72]

Evening, i have just taken the pistons off and have noticed that on numbers 1 and 4 the rings are fully compressed. Any tips how to get them off? They are soaking at the moment.

[Nurse Julie]

Evening, i have just taken the pistons off and have noticed that on numbers 1 and 4 the rings are fully compressed. Any tips how to get them off? They are soaking at the moment.

Having seen him indoors, Trigger, come across this problem on customers engines quite regularly, I think the answer will be buy new pistons. They are usually compressed due to corrosion and therefore are of no further use to man or beast, or engine.

[Brett72]

 :'(Thanks for the good news Julie. If i am lucky they will release in the potion i am soaking them in lol

[Nurse Julie]

:'(Thanks for the good news Julie. If i am lucky they will release in the potion i am soaking them in lol

I'm sure they will release Brett, it just depends on how much piston material the rings bring with them 😢😢😢

[Trigger]

:'(Thanks for the good news Julie. If i am lucky they will release in the potion i am soaking them in lol

From your picture, your pistons are part the point of no return and the bores will also be rusty and need reboring 

[Brett72]

Thanks Trigger. The potion brought all the pistons up a treat and they were in great condition apart from one ring that i could not get off and slightly damaged the piston . I am having trouble deciding how far to go with the engine. So far the top end is in bits and will get a full service, valve seats and pistons, bored or honed. The bottom end feels really smooth and there isn't any noticeable horrors that i can see. What are peoples thoughts? Should i continue to strip it all the way down or just rebuild the top and try and get a running machine? Open to suggestions.

[Laverda Dave]

If the engine is already out of the frame and the head is off I would open it up to check everything is ok and also to renew the chains. If the pistons are rusty chances are something else will be as well and you don't want to be pulling that lump out twice

[Rozabikes Tim]

If the engine is already out of the frame and the head is off I would open it up to check everything is ok and also to renew the chains. If the pistons are rusty chances are something else will be as well and you don't want to be pulling that lump out twice

Double ditto

[Brett72]

Cheers gents. I think that is the way i am going to go, just dubious on how much money i will put into this project. Will just have to drip feed without the missus noticing lol. Any advice on the best place to get parts around the UK?

[Trigger]

All depends on your budget.
First i would make sure that the head is K6 and not K7/K8 as, you bought the bike in bits.
Any short cuts on these old 750 engines can bite back big time 

[Brett72]

Trigger, are there any easy ways of telling the difference between k6 and k7 heads?