Hey, all. Brand new to the forum, but have been slinking around here for a handful of years. Would like to start by saying thank you for All of the wisdom shared here that has helped me.
This thread will be about My CB750K4 project And I will do my best to provide picture updates of where I'm at in the process. I will definitely have questions about things along the way!
This bike came from Eastern Illinois a few years ago. My wife and I were living out there at the time and after we moved all of our crap to Eastern Iowa (good to be back!), I made another trip back to grab it. It had been sitting in a garage of a coworker since the late '90s. It was his buddy's who had passed away. I had first seen it three years prior, at which time he made a crack about me buying it from him and I scoffed in disgust at the monstrosity! Haha. I guess I finally convinced myself that it would be a good project and a piece of that part of my life that I could bring with me. Apologies, I've missed a fair bit of documentation prior to this.
At this time, my intentions are not to do a full restoration. I'm going to bring everything back to stock, put some super bike handlebars on it, replace everything I need to have a running, safe bike. Do some major cleaning, but limited painting. The tank is so beat up I don't think I'll bother trying to paint it. Maybe just leave it bare for a while And look for a nice patinaed replacement in the future. This will initially be a rat bike, figured I can always take the restoration all the way in the future sometime.
This poor ugly bastard. The most obvious things that made me cringe were the long fork tubes, windjammer, saddle and sissy bar. This bike is much older than me. Can someone tell me when this looked cool?? Ha! The other things were the hastily painted fins, foam pad hand grips, front brake hose extension that was held together with hose clamps, and the purple (plum?) Paint. From what I could see on the back of the side covers, it was a beautiful orange flake at one time. Once I started stripping the tank, I got some inside as to why he may have painted it. The tank is beat to sh!t. Lots of dents especially where the Honda emblems would be. Lots of Bondo. Almost wonder if someone didn't beat the crap out of the bike at some point which necessitated The body work! Or maybe he just took it in to get painted and the shop swapped his nice stock tank out with a beater. Besides all of that, the bike is pretty much all there and seems to be in fairly decent condition with 24k on it. Quite a bit of carbon and burnt oil on the Pistons / Chambers.
The spark plugs were basically welded into the head. Lots of heat and soaking allowed me to get three of them out, but low and behold I managed to twist one off leaving the threads in the head. I stripped the bike down and pulled the motor. Remove the head and cylinders. Took the head to a machine shop and had them extract the threads.
The following is probably not the"right" way to do things, but here's what I did. Piston skirts measured in spec. Cylinders appeared to be in good shape. Measured cylinder as best I could with micrometer and measured clearance between cylinder and piston skirt. Nothing "seemed" too out of whack. The rings were very worn and mostly frozen place with lots of carbon buildup. When comparing them to the new rings, you could visually see that they were narrower. The gaps were rather large when put back in the cylinder. I ordered a standard piston and ring set. The gaps we're pretty good on the new rings. I Hit the cylinders with a ball hone and replace them over top the new pistons and rings. I cleaned the head as best I could and lapped the valves. The seats looked kind of bad before, but lapped to a nice smooth gray. One thing that kind of haunts me is that I did not check valve guide clearance before putting everything back together. I assembled it all with a complete engine rebuild kit I got from NE. Cleaned mating surfaces as best I could and Copper spray on the head gasket. Got the head torqued down (re-tourqed 24hrs later) and installed the cam journals, cam, sprocket and rockers. Use the bit of red permatex under the box. Wiped excess away. Set tappet clearance. Oh, also replaced cam chain tensioner and roller. Everything seems to be moving in sync.
Now I'll hit you with some pictures in a few questions. Thought I'd show you my other old Honda. CB350k2. Before and after.
First question. I set the valve cover in place without a gasket just to keep dust and whatnot off of the top end. When I did this I noticed that the cover does not sit flush against the head. Further inspection found that the area that houses the tac gear is in contact with the middle bolt on the right cam journal. I realize I don't have a gasket in there, but there's like a .75 mm gap between the cover and the head. My fear is that when I do install the gasket, this will keep it from seating properly on that side. Is this normal? The journals are completely flush and pulled tight against the head, so I don't know what else would be causing this. Because there was plenty of aluminum there, I already ground a little bit away from the valve cover where the bolt was hitting.
Second question. It appears that the center of my drum stopper is worn. What causes this? Is it common? Also, what malfunctions could this cause if left as is? I'm not 100% sure what this part does.
Thank you for checking out this thread. Thanks in advance for any advice offered.
