Why won't my Honda CBX750 run properly?

Q. I’ve just got an ’86-reg Honda CBX750, it had blowing header pipes which I’ve fixed. My problem is that when I try to ride it after letting it warm up the middle two cylinders splutter then cut out.

I give it two minutes and it starts up fine, but won’t take any load.
Dave Wood, Bournemouth

A. Unfortunately it sounds like you may have bought a bit of a pig in a poke. The bike is now 25 years old, so things do start to go wrong, it’s inevitable. Are you sure it’s the two middle cylinders and not one? If you decide to keep the bike, then check the coil for cylinders two and three as well as the HT leads and plug caps.

If the problem isn’t there, then check the twin pulse pick-ups as they used to be one of the fewfaults this bike had back in its day. Also check the plug connector from the main loom to the coils (check for corrosion and continuity), as it is a separate piece of loom.

Drain the carb float bowls into a clean bowl to see if there is any water or debris in there too. If there is there could be water in the fuel tank as well. Check the vacuum pipe from the fuel tap is fitted securely and not split or leaking.