Honda-SOHC

I like the sound of some of the 4 into 2 and 4 into 1 systems, but with stock pipes, I'm reluctant to make the change, even though it would increase my enjoyment of the bike.

No such issue with this bike. A decent price, if it has been put together properly, with money left over for sexy new pipes.

Mike, I replied to your PM. In short, masking tape pushed to a crisp edge with a Stanley/razor blade. Good crisp result, until you get a microscope on it!

I don't think a scotchbrite pad will be aggressive enough. May be wrong, but I would expect that to be a long job and lots of pads. 240 grit wet and dry, used dry, might be better, but the creases and corners will be tricky, if you try to get all the paint off. I found the dremel, used with the flexible extension head and a range of brass brushes, worked quickly, got into nooks and crannies and didn't damage the alloy. I then went over once with some wet and dry to key it. Took me 2 to 3 hours to do and another hour to brush clear all the little brass tines off the floor. You do go through the brass brushes in that job.

In my experience on other bikes, popping is due to lean running from something like a leaky carb rubber, or a leaky exhaust gasket. However the float bowl difference and the mixture screw setting you're running is suspect.

It's counter to other carbs I've worked on, but the US SOHC/4 forum ('Hondaman') is clear that turning the screw out further is richening the idle. His experience is, the screw comes into play after the fuel is atomised from the slow jet, so it meters the amount of atomised fuel that gets through the carb. Unscrew it and you allow more fuel in and it richens the idle / slow speed running. If true, it is not a pilot air screw, which like you, is how I had been approaching them. Hondaman ('Mark') was a Honda technician and has written a book on CB750 restoration, so I'm inclined to listen to him.

I think your K5 is like my K6: A standard carb, with standard exhausts and airbox should be at 1 turn out, give or take 1/8th turn.  So over 2 turns out is a lot! Possibly at the point the screw no longer has any affect. Mark made another observation, that old carbs = wear and he finds then, that 7/8ths out is more like the central screw position, +/- 1/8th.

You could well have a rich float level, made more rich by the screw adjustment. Maybe take the screw down to 7/8ths out and see if it reduces the popping? But the float levels should also be set to close to recommended and be the same across all 4.

How are you setting the float levels?

Four months ago I took the engine back to bare metal. I painted my cases with a light coat of etch primer, then 2 light coats of Simoniz VHT silver and then 2 light coats of clear engine lacquer. I was concerned about cooling, so I only applied 2 light coats of the Simoniz VHT silver to the cylinder barrel fins, no primer orr lacquer. I didn't oven bake any of it.

On the first wash, after a couple of rides, I noticed some paint coming off the cylinder barrel, but not the cases, when I towel dried it. So I've been blow drying ever since.

This week, having had about 20 heat cycles through the motor, I tested the fins and they now seem fine, no paint transfer. I expect, without the oven treatment, it needed a few heat cycles and some time to fully cure. I'm hopeful it'll be robust now.

When I first got my 750, the main case paint had been damaged by carb leaks and the previous owner had repainted with VHT, which would wipe off with any petrol on a rag.

When I worked on the engine, I wanted to repaint it. Although it was out of the frame, I only had the head and cylinder block off, so I couldn't put it in an oven!

I took it back to bare metal with brass brushes in a Dremel. Lightly scuffed it with 800 grit paper, to giive a better key. Then did a light coat of etch primer and left it a day to dry, light coat of VHT silver, left it to dry, then warmed up the case with an electric paint stripper on low, let it cool. This step took about an hour going over the case in sections. No idea if it achieved anything other than making me feel good! Then finally, I sprayed a light coat of engine clear lacquer. Let it harden for a couple of weeks, before it went back into the frame.

All was from aerosols. All in November/December, with a fan heater in the garage. Each time i made sure the engine case was at room temp (not hot), by gently heating with my paint stripper and the paint was kept in the house between uses.

It was a labour of love, for sure. Not quick. But, 1,000 miles in, so far it is standing up very well to riding and cleaning, much better than just the VHT. The odd stone chip off the front tyre. A lot of cleaning, due to winter muck. Still looks fresh. However, I did have an episode where petrol leaked from the carbs. A small area was damaged. Only the lacquer was affected and I cleaned it off, masked everywhere off and misted the affected area. Good as new.

That's the plug. I find they are fine for the first dozen or so times they're connected up, but they steadily get bent or loosened in the plastic and get more and more difficult to get a solid connection.

But I like the unit itself. Never a problem with the battery and also a very simple display.

The heated jacket doesn't touch the ignition switch. It has its own fused supply direct to and from the battery terminals. May just have been a coincidence it failed as I put the jacket plug in the socket. I don't generally believe  I coincidences! Wonder if the extra load causes a spike through the alternator / regulator. But, off topic.