Topic: Captain Rats - CB750K1 Project

[SOHC4 Cafe Racer Fan]

Cant see the photos.  Dont know why............Gary

Same here. Just blank spaces.

[Retro Rocket]

Thats weird, the first pics i can see but the head pics have disappeared ....

[captain rats]

Will get some more photos up when I work out how to do it without clogging up the gallery here. I took those other photos off as they were getting annoying in the gallery.

Back to the project.

The engine I got which was supposed to be rebuilt and ready to bolt in is far from it. The tappets and rods were inside a rag taped onto the engine. I took the tappet cover off and then the rod holder and saw that at least one of hockey pucks was missing. I have ordered some and think it is worth taking the head off to see inside the barrels to make sure its been worked on.  The good news is that it looks clean and new and I have been enjoying working on and learning about the engine.

I have bought Honda mans book and a shop manual so am looking forward to getting into it. I am also lucky to have a spare engine to take parts from and also take apart and reference. I have a few questions to help me forward.

The kick start seems jammed, as in it won't turn the engine over, there are no spark plugs in the engine so its not compression, any tips to help me with that? Where do I turn the engine over with a wrench?

Seeing as the PO of my " reconditioned" engine hasn't marked the tappet rods and holders is this a real problem as they are supposed to match? I can take the holders, rods, and tappets off my other engine if they will work.

Is there such a thing as an 816 kit for these engines, the PO said thats what is in it but hasn't been reliable so far.

Thanks

[Retro Rocket]

Just measure the bore or piston and know for sure...

[captain rats]

Thanks rocket.

Can anyone else help out with some answers above?

[Retro Rocket]

Thanks rocket.

Can anyone else help out with some answers above?

810 or 811 {same thing} is the usual bore size in that range, never heard of a 816 {i doubt there is any such kit}, I've had 776, 810, 836, 850, 900 and i've currently got a 970 and 1000cc. Thats why i suggest measuring 
Turning the engine over from the stator side is the way to go, only a small bolt on the points side and its too small to put that much pressure on. Are you sure the engine isn't stuck in the bores...?  Not knowing what the PO has done, and it sounds like he has no idea about the engine bore kit if it has one, i would use Hondamans book and pull the engine top end off and check everything out first....

[captain rats]

Yeah mate, and thanks.

I'm gonna take that head off in the next day or two and take some measurements and photos.

[captain rats]

Wow. This thread sucks with the #$%*ty photo deletion.

That will/should change now.

Here is my engine. It was supposed to be complete, rebuilt and ready to bolt in and ride. Problem is it wasn't.




As you can see the engine is not complete and came with the rocker shafts and rockers in a pile taped in a rag attached to the engine. These need to be marked so you can put them back in the right place.



The hockey pucks were missing from the two centre holes in the head. I have ordered some from cycleX so that is not a problem.




Here is the engine with the head off. Good news is that it looks definitely like it has been reconditioned, obviously they didn't replace the pistons as the top is still carbonised not sure if that's a big deal. In the photos is grease or something around the piston as I got them moving in the bore no worries.




The head looks good, that is just black spray from the engine paint.


It measures 2.5" across the bore, any idea what that translates to?


Anything look dodgy or need replacing?
Also even with the pistons now moving in the block the kick start still does not move when stepped on aside from a few cms. Am I doing something wrong? Please tell me I do not need to split the case.

[Retro Rocket]

 2nd over size 63.5mm, Its Japanese, always measure in MM... 810-811 is 64mm so i'm not exactly sure what 63.5 is...

[captain rats]

Slowly moving forward.

What do people think of this sprocket? To me it looks a bit worn but I am used to working on bicycles and this would need replacing.

Is this worn out and should I be buying a new one?

[Retro Rocket]

That sprocket is absolutely stuffed....Worn out

[Vinhead1957]

Sprockets & chain as one they should all be replaced

[Retro Rocket]

Sprockets & chain as one they should all be replaced

+1, replace the chain and sprockets {both front band back} at the same time, also, don't throw that sprocket out till you put it next to a good one so you can see the difference, it will become obvious then...

[captain rats]

Great, thanks for the advice.

Are people generally happy with the ratios on the factory spec?

If I am buying a new one should I consider a different ratio? Bike spec is 812cc, cx1 cam, basic street use and not much highway.

Is there a standard BCD you quote when ordering? Any after market recommendations?

Thanks again

[captain rats]

Finally fixed up my photos, sorry about that.

Have some good news. My order from cycle X is on its way and should be at my house tomorrow, even better is that i have the day off from work and can get into hopefully closing the engine up.

I have stripped it down a bit more and tidied up some of the wiring that was a bit old and tatty. I also took heed of some advice found on the forum here and water blasted the old engine and frame. The engine is coming out and i will be rebuilding it in case i need to swap it across. I at least want to see wht was wrong with it and fix it so it is running. That way if the needs arises i will have a back up.



Does anyone have advice on the sprocket question I posted above?

I am running a 18t x 48t on standard tyres ATM. I am going to go with the firestone champion deluxe tyre ( i know they handle like sh!7) which are a bit taller but how does this gearing sound to the enlightened?

Anyone running that cycle X CX1 cam and what is that like, any real difference?

[70CB750]

Per Hondaman I run 17/48 on my K0. It makes it lively in our area of mostly small roads. For longer trip or extensive expressway I would consider 18/48 to ease up on the rpms. 

[captain rats]

Thanks, that seems like the way I will go, I will be commuting on it so lots of start stops.

Had this show up, great book. Thanks hondaman, now some of my stupid questions will be answered without annoying the forum.

[captain rats]

Took apart my spare K2 engine today. The bottom end is stuck so I am checking it out and using some spares from it. Because the bottom end is stuck I could not undo one of the can gear bolts.



I ground down an old ring end spanner until it was thin enough to fit between the holder. Will hang onto this handy tool.

[captain rats]

So a fair bit of water under this bridge.

A few questions elsewhere (they seem to get answered a bit quicker off the project forum..

I got a deal on a K1/K2 bike with a rebuilt engine and lots of nice parts, it was all in bits and missing some of the cool K1 stuff like gauges, seat and rear mud guard.

Anyway I am up to putting the electrics in my bike, I removed the old wiring harness and installed a new CMSNL part. It is real nice.



I am going to put in the rebuilt engine I got from the other bike, its a K2 engine with a 836 wiseco kit in it. It was built at a shop so should be a good goer.

In the meantime I am trying to wrap up the rebuild on the K1 engine. It has been a pain in the ass. The guy sold me a rebuilt engine that really was not. It had no rubber seals in the oil return passages and I decided to replace the top end and rebore the cylinders. First thing I did was get Hondamans book, great resource and due to his advice put heavy duty studs from APE in it. I also got a webcam CX1 the milder one for it.
I rebored the cylinders and got a 811 wiseco kit from Chewie (good bloke). I have a standard K1 head with a little cleaning up it didn't leak from the seals and it is straight.

I had a question regarding the compatability of the standard head on the 811 wiseco kit. Is this going to work or is the compression ratio going to be too high?

Here is a photo of the head before I cleaned the carbon off it.

[SOHC4 Cafe Racer Fan]

The stock head should work but as everyone including Hondaman says, you will get better gains with a port job.

[captain rats]

So I cut my frame today to make way for my engine. It was a bit nerve racking and seemed wrong to be doing it but I am already finding such a great modification. If I had an OG K1 or earlier then I would be reluctant but I think the small cuts mean it can be refixed if someone cares that badly later. I will be swapping engines, cams and re-tensioning heads frequently so it is a worthwhile thing to do.



I made my cuts here, 100mm to the first cut, 280 to the second. I think they can most anywhere but this seemed like the best place for me.



I really like Franks kit, it is well made, is tight and most of all can be re-welded without sourcing more material. I think they run about $140.00 or so. His SOHC username is "754" if you want some.



My cousin helped me wrestle the engine in. Still tricky even with the space and extra pair of hands. This is a re-coed engine from a shop that bought with a stalled café project bike. It will be good to hear it fire up. It is still a ways off that but this step seemed like a decent hurdle to overcome.

[immortal]

Very nice project, you have inspired me to pull the cover off the 71 CB750 I have on the side of the house. Its just sitting there waiting for me.

[captain rats]

Very nice project, you have inspired me to pull the cover off the 71 CB750 I have on the side of the house. Its just sitting there waiting for me.

Thanks mate. Get stuck into it.. Its great fun!

[captain rats]

Woke up at 3am and couldn't get back to sleep. Went out the garage for some "quiet" work, no power tools etc.

Got a bit more done. Wheels in, forks on with new air caps, bars on rear shocks on just wanted to mock up the position and see the direction and if I like it. A few changes needed.



I am not happy with the rear Koni shocks, they sit too high and look #$%*. I have a pair of Cycle X (11.5 eye to clevis) but the eye bushing is too small to fit over the shock mount. I checked their website they reckon they are all the same?

Anyway, another question. I am left with one engine bolt that baffles me, the front lower through bolt that I have left over looks a tad short, see pic, is this how it is supposed to look? I have nothing left over and nothing else even resembles that length.




Got annoyed at the old lady so spent the rest of the arvo in the garage. Got the carbs on, coils on and exhaust mounts on. Man I cant wait to get that MotoGPwerks pipe on and scare the locals cats back to spinsterville.

[krusty]

Is the front wheel in temporarily? Seem to remember the disc being on the other side?