Thanks Guys, and Sean, I don't know if I'm up for a race, I think you're a fair bit ahead of me with those two beauties, but I suppose we'll see. I'm really looking forward to both projects, CB750's are dead simple for me because I've done so many of them over the years and most of the parts I need are at hand, whereas I haven't had the pleasure of playing with a big air cooled Kwaka since my one and only Z900, so if I don't have a particular widget on hand, the project will stall until I can find one.
Wemoto in Japan are a great source for Z parts and quick to ship, I've already spent a small fortune on parts with them, so at least if I do get stuck I shouldn't have to wait too long.
Back to the K1. It was a stinker yesterday, temps hovering in the 90's, so too hot to play out in the driveway with the Swamp Rat. I've got a few health issues at the moment and one of them is dehydration, so I need to be careful on really hot days, so I decided to have a look at the spares that came with the K1, and put them away in the garage, then pull the top end down to witness the carnage that we're all expecting, after it dropped it's cam chain.
The first thing that interested me was the spare crank. I've got several cranks here, but none with so many holes drilled in the counterweights, anyone else seen one like this?
Wednesday K1 stripping 20 Nov 2019 by
Terry Prendergast, on Flickr
Anyhoo, I started the stripdown. As I said before, it looks like someone else has gone in, and I presumed, gave up due to the horrors that lurk within. I'd seen some early pics that the PO had posted on FB with pics of a cam in a milk crate, and there were some rockers in with the spares, so I assumed that there wouldn't be anything underneath the cam cover. I was pleasantly surprised to see that the top end appeared to be in order, apart from missing most of the nuts and bolts.
Wednesday K1 stripping 20 Nov 2019 1 by
Terry Prendergast, on Flickr
There didn't appear to be any excessive wear on the cam or rockers, which is interesting. On my first K1, which ate it's own top end due to silicon sealant being applied excessively by a "mechanic" who chose to slop silastic everywhere, rather than replacing gaskets. Some silastic had got sucked up into the oil jets in the head, blocking the oil supply, and the bearing end of my camshaft was chewed out so bad it looked like a cotton reel, the wiping faces of the rockers were all destroyed, and the cam tower bearing surfaces were all chewed out. By comparison, everything in this engine looks like it can be re-used.
Did I mention silicon? Yep.........
Wednesday K1 stripping 20 Nov 2019 2 by
Terry Prendergast, on Flickr
Wednesday K1 stripping 20 Nov 2019 5 by
Terry Prendergast, on Flickr
I'm guessing that this bike has been off the road for many years. Back in the day, silicon ruled, and everyone used it. I don't think any of this work has been done recently, because I doubt that anyone with access to social media and sites like this wonderful forum would still be ignorant to the limitations of using silicon sealants, like they were then. I say "They" because I learned the dangers of the stuff first hand as a 21 year old, so have always used "Honda Bond" or "Three Bond" etc, with a modicum of caution. So far, I haven't had any issues, apart from my first F2 rebuild when I used a "Loctite" case sealant, meant for gearboxes and not engines, and it washed out as soon as the engine oil got hot. No damage, apart from my broken heart as watched oil pissing out of the engine as it happily idled away......
Anyway, I removed all of the rocker gear and the cam and examined it, then moved onto the head. This was where I was expecting some carnage. I've got an F2 head in the garage that came with some spares, it looks like it dropped a valve and the actual valve guide, and the combustion chamber looks like a bomb went off inside it. The first "spoiler" though, was looking across the head, it looked like all of the valves were closed? If any were bent, they'd appear to be in the "open" condition. Hmmnnn. Anyway, I un-did the two remaining cylinder stud nuts, and whipped the head off.
Wednesday K1 stripping 20 Nov 2019 7 by
Terry Prendergast, on Flickr
Yep, no carnage. The combustion chambers showed no damage, apart from lots of greasy carbon buildup, but it was kind of disappointing actually, but the plus side is that I have yet another usable late model head to use on a future project.
The pistons were well and truly stuck in the bores, and I could see that the numbskull who'd done the previous top end strip (probably the same numbskull who'd slopped silicon sealant everywhere) had smashed the bottom fins off the cylinder block trying to extract it. I sprayed some silicon lubricant spray (because it was close at hand) into each cylinder and used a chunk of brass and my hammer to bash the pistons out of the cylinder block, and I did get them to move, begrudgingly.
Wednesday K1 stripping 20 Nov 2019 6 by
Terry Prendergast, on Flickr
Yes, the head gasket was on backwards, but I assume that only happened when he did the strip down, and not the build?
Wednesday K1 stripping 20 Nov 2019 3 by
Terry Prendergast, on Flickr
That was as far as I got, but I might sneak out today and do some more, I don't want to go too far, as I need to put the engine back together and away safely in the garage so I have the bench free for the Kawasaki build, which hopefully will be quick, I just want to weld on the missing frame sections, give the frame a squirt of paint, add all the new and used parts I've bought for it, and get my red plate. As time goes by, I will make it shiny, with modern forks, brakes, wheels etc, but it's easier to do it when the bike is registered, so it'll be done in stages.
I did take the opportunity to remove the clutch cover to ensure there was still a clutch in place, and was fascinated to discover a wasps nest under the chrome cover, complete with mummified wasp babies.
Wednesday K1 stripping 20 Nov 2019 4 by
Terry Prendergast, on Flickr
The PO must have had a wasp problem, because I soon realised that all of the "dirt" that was clogging the nooks and crannies in the outer cases, was in fact, wasp nest material. Anyway, no biggie, they were all long dead. I also took the opportunity to see if I could manipulate the shifter drum with some multi grips, as I need to do that on the Swamp Rat. No problems there, while the shifter assembly doesn't have the "oomph" to turn the shifter drum if it's stuck from sitting for so long, I was able to easily turn it with the multi grips, so the Swamp Rat will have it's gears sorted later today, or tomorrow, then I can think about finishing the wiring, and planning a shake down ride.
So that was about it. What was it that caused the cam chain to break? Well I'm not sure that it did break, to be honest. I reckon a PO (not the bloke I bought it from) just pulled the joiner link when he pulled it apart, there simply isn't any evidence of the kind of damage we'd expect, if a cam chain let go at any engine speed. I'll remove the barrels and inspect them for piston seizure, and check the oil ports in the head for silicon contamination, but I don't think I'm gonna find much.
I'm going to propose another theory in fact, that the bike was crashed, and then just used as a spare parts bike. Back in the day CB750's were everywhere, they were cheap, and if you paid more than a dollar per cc, you paid too much. The frame has some minor damage, the right hand side passenger footrest bracket has been damaged, so I wonder if this bike hasn't just been retired and cannibalised for parts, as there was a lot missing? Thee engine number (106XXXX) and frame number (112XXXX) seem too far apart as the engine would have been manufactured in late 1970 and the frame considerably later, so maybe the engine "spares" that came with it, are the guts of the original engine?
I guess I'll never know, and I don't really care, it's still a K1, my favourite of all the mighty CB750's. I'm looking forward to riding it.
