Honda CB750 Cafe Racer Race Shift Conversion + Carburettor Adjustment | 33

Honda CB750 Cafe Racer Race Shift Conversion + Carburettor Adjustment | 33
In the last video when I finally got to ride my project cafe racer CB750 I found a few issues. So in this one I try to address them.
Things that I used:
Carburetor Synchronizer Gauges: ebay.us/g2cm5F
Motorcycle Auxiliary Fuel Tank: ebay.us/7aeVud
The first couple of rides on this project bike didn’t go as smoothly as I would have liked. But with any project you always expect some teething troubles. There seemed to be 3 main issues, but in reality they all came back to the one main issue. And that was that the bike would not idle well. It was inconsistent, it either hung, in that when you closed the throttle the revs took a while to fall back, or cut out altogether. This made the other problems seem worse.
The other two problems were centred around the gear shift. The rear set shifter didn’t work as well as it should. Changing up seemed fine, but when changing down the connecting rod seemed to snag and stop it clicking back positively. I had tried adjusting it a few times, but I still couldn’t get it right. The inconsistent idle made this seem much worse, especially trying to find neutral.
I decided that I would try to cut out the linkage altogether. It is quite common practice for race bikes with rear set footrests to put the gear change lever on facing backwards. This makes the shift pattern reversed, but this is quite easy to deal with. I bought a standard lever and fitted it but it was too long to be able to use with the footrests where they are. Rather than trying to move the footrest I decided to shorten the shift lever. Although it wouldn’t give the same leverage, it should still work quite well.
As this was a trial I decided to bolt the two parts of the lever together when I cut them. Overall I took around 5cm out of the lever's length. Eventually I will probably get the shaft welded, but only when I am really happy about the required length.
As the idle seems to be the biggest problem, I decided to synchronise the carburettors again, having the carbs working together makes the biggest difference to the running of multi cylinder bikes, so it is always worth doing. When I started the carbs were out of sync, so that would have been having some effect on the running.
I also decided to have a go at adjusting the air screws. On the CB750 carburetors the air screws adjust how much air is let through to the pilot jet when the bike is idling. I usually set these at the standard setting from the manual, and to be honest I have never managed to find anything changing when I have fiddled with them on other bikes.
Like my previous experiences moving the air screws didn’t seem to make any difference to the idle. In hindsight it may be that the carbs are not as clean as I thought, however I did run carb cleaner through all of the airways that the air screws use and they did seem OK.
However, the bike now idles quite well, but it doesn’t really want to start well when cold, great when warm though. But with the changed gear shift it all works quite well. Neutral is still a little hard to find, but I think this is more an issue of not having a light to confirm when you have selected it. It is quite a comfortable bike to ride and does seem to be becoming more useable.
Everything in the garden isn’t completely rosy. There is a strange phenomenon when riding along. At first I thought it was the clutch slipping, but it isn’t clear cut. Basically the engine note changes, perhaps sounding like the engine is picking up, even though the throttle hasn’t changed. Strangely it doesn’t really make an impact on how you feel the bike is pulling, and the rev counter doesn’t increase. I think I will have to take a few more trips out on it to try to find out what is causing it. Oh the joy of projects :)
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