starting problems

[judodave]

Hi, have been using my recently restored cb650z regularly, but it is a pain to start when cold. This is the first old style bike I have owned so understand it wont be the same as my previous bike a fireblade. The engine and carbs have been rebuilt but on starting it seems to be fuel starvation and fires up eventually after many attempts. I have heard that this model from new was a terrible cold starter, which probably explains the premature starter clutch failure history. Its a shame that honda withdrew the kickstart on this bike,any tips on better starting would be greatly appreciated. regards dave.

[K2-K6]

I'm not particularly familiar with the CB650 but most of this era Honda fours had quite a bit of throttle lift when the choke is fully activated, check it against spec to see if it's ok as they seem to need it to make it catch initially.

Useful technique is to give full choke and crank it for a while then switch it off for a few minutes then try it again and be ready to give it a bit of throttle as soon as it even coughs.

I'm always in two minds about using much throttle on a cold engine but it does seem to be built into these systems, so Honda must have felt ok about it.

[andy120t]

Mine starts on the button & first time with some choke - I balance the choke lever on the carbs but always get a pretty quick response.  Clearly it's been fairly warm this year but mine is living in a pretty basic shed (so engine isn't seriously cold) and hasn't given me any probs. starting at all.  (NB - brand new battery; carbs are GPZ600 rather than CB650 and have recently been fully cleaned through but no probs. at all with it firing up).

I If you are having fuel starvation thoughts then maybe there is a problem? Have you checked that the plugs are wet / petrol covered after the first attempt to start? Checked that all lines / filters are clear?  Fully cleaned all jets & passageways in the carbs?

[K2-K6]

You have a point there with the battery, it's worth using jump leads (if yours is not verified as strong) just to see the effect.

[judodave]

thanks all for the replys, I took the bike out yesterday and it started after 5 attempts this time with the choke only slightly out, after a couple of miles I can put the choke back in and the bike runs superb. when I got back, one of the carbs started overflowing, so I will clean through the jets again this weekend and see if I can improve the starting. regards dave.