Terry

Actually Greg you are probably correct but the manual is not that easy to figure. Looks like the WU connects and pulls the SV open for cold, then releases them for hot, so shorter cold/longer hot seems more likely from closer inspection. The key in any case is to check whether the SV's are being lifted when cold and set down when hot, which is easy enough to visually spot.

Some of the originals...

If the bike is "struggling to reach fast idle" when first started then I doubt you have any coolant flow issue. When the bike is cold the wax unit will also be cold, and at that time is will be in it's cold extended position. If there was any coolant blockage the unit would be slow to reduce the fast idle back to a normal warm speed. I would be taking a look at the wax unit and the movement of the starter valves to ensure that the starter valves are being held open when cold. If the starter valves themselves are out of whack that won't be helping.

Somewhere I may even have a copy of the original installation instructions! The reservoir was separated from the frame spar on some rubber mounts, and held in place with big hose clamps.

Just my opinion but I think that would be a Bad Idea. On an exhaust system the wrap gets hot and dries out, but on a frame I'd expect it will trap water and accelerate corrosion.

My cut and paste was direct from the 5G manual in the fuel section (chapter 5).

A locking rear brake is a sign that all is not well in the secondary master cylinder which resides on the left fork leg. Could be either the pushrod is seized or the compensation ports are clogged. You should plan on pulling this off and giving it a careful clean and possibly a rebuild kit, cleaning out the master cylinder reservoirs carefully and then giving the brakes a very good flush.

They do this in Japan...no carcinogens involved (actually I love the Rothmans colours).

I recall reading about such things back in the day when ram-air airboxes were first introduced. Maybe the ZX750? Anyway: carburetors deliver fuel through the jets based on the difference between the air pressure in the venturi (moving air hence Bernoulli's theorem of pressure dropping with increasing velocity) and the air above the fuel in the float bowl. If the pressure in the plenum varies due to ram-effect of changing bike speed, then the vacuum signal pulling the fuel through the jets will also vary. That could mean that jetting that works well at low bike speeds will be leaned out at high speeds (more ram pressure = lower venturi vacuum). So the pressure in the plenum should be equalised with the pressure in the float bowls, by connecting the float bowl breathers to a port in the plenum. Or so I read.

I think that was the peak of my sartorial eloquence in the 80's, and it has all been downhill since...I did have a big run of red/white/black bikes (CBX400F, VF500F) bikes so it all made sense. I spent a lot of those years chasing my best mate on a series of GPz900s and then the ZX-10 and ZZR1100, they were all great bikes, the 900 did like to get hot. I keep looking for an old not-too-molested CBX to buy and restore for laughs; these were basically the last new air-cooled in-line 4 that Honda made until the near current CB1100.

Amen to all that. The cam covers need very little tension from the bolts to seal and in fact the bolts in normal use are bottomed out on their shoulders so applying more tension won't compress the gasket any more if it is leaking. A much better idea (if you need to) is to replace the rubber washers under the hold-down bolts as these get squished over time and provide less compression to the gasket. I speak from experience, where I replaced the first the bolts, then the gasket, and finally the rubber washers to fix a leak. Only the last thing helped.

Good advice from Greg.

Those are some lovely pictures Calculon. I was lucky enough to own a CBX750F back in the day (1984?) from new and clocked up about 30,000km on it. This used the same basic engine as your CB750 but in a higher state of tune with a claimed 95 bhp, and in a chassis that wasn't unlike the first VF750F with 16" wheel and Pro-link rear suspension. Honda bought the CBX out as a bit of a stop-gap between the VF (which was getting lots of bad press for camshaft wear and dodgy cam tensioners) and the 86 VFR750. My recollection is a bike that sounded quite gravelly at low revs but went off with a great shriek when you got the revs up.

I used F4i forks, 954 calipers, CBR600RR 03 master, 6th gen triples and bars, F4i fender and the 5G wheel/axle/spacers on my 5G, was a great combination that gave me no issues at all. The only bit that did not align perfectly was the steering lock, and I used a couple of washers to lower the mechanism down from the top triple which worked fine.

Maybe the problem with the front brakes is not hydraulic. I've certainly been able to put a rear pad in slightly wrong and catch the backing spring, which kept pushing the pad off the disk and made for awful feel. I'd suggest you check some basics, that the pads springs are in the right place, the pads are correctly fitted and the sliding pins for the calipers are moving freely. It is quite correct that there is NO hydraulic connection between the front master cylinder and the rear so what you do with the pedal should not affect the brake lever. Pushing the pads against the front discs with the pedal will however affect how much movement is needed for the lever to start applying some pressure.