hot starting

[Z1B Alan]

i have a z1b which is totaly standard aside from being fitted with z1r carbs
my problem appears to be a reluctance to start when warm/hot.
when cold the bike fires up first prod on the button, any simple checks i could do to try to find the problem carbs have been balanced, ignition timing is spot on (electronic) valve clearences all checked, plugs cleaned and gapped any ideas folks

[Pigford]

Assume shes spinning over normal speed (not sluggish s/motor).
Zeds being air cooled tend to get a bit hot, so fuel vapourisation is not uncommon. The fuel evaporates from the carbs, thus emptying them a bit, so sometimes need a few turns to prime 'em again
Other than that, could be electrical Coils could be breaking down, as electrics experience more resistance with heat, especially windings in coils, alternators, starter motors, etc.
Sorry this don't narrow it down much

[uk kev]

I have some questions to try to help find the answer...

1. is it hard to start when warm on both the side and center stands.
if it is only hard to start after being on the side stand this is due to fuel migration.

2. is it hard to start on both the kick start, and the button.
if it is easier to start on the kickstart when warm, this is spark related, as the coils are getting more power from the battery than when using the button.

3. have you tried using the choke when warm.
if it starts on the choke when warm, this is a fuel starvation problem caused by evaperation.

[Z1B Alan]

thank's UK KEV have only just got the bike on the road so i will investigate further your suggestions and post the results, any further ideas welcome

[ROZZER]

Put some petrol in it yer tight wad! Works a treat.

[rickm]

Holy thread revival Thought I'd start a new thread until I saw this one, which has some relevant info already.
I have a (mostly) hot starting problem too.
This is a standard 1000j, dynatek ignition, new HT leads, new lithium battery with big CCA, Delkevic exhaust, valve clearances checked and carbs balanced. The coils are relatively new replica standard type I think, and presume the starter motor is original.
When hot, the engine seems to struggle to turn over on the button. It's just sluggish and like the battery is low (but it's not). It doesn't like much throttle, and seems to start easier without any throttle initially. If anything, the hot idle is a little high (~1200rpm). I had to bump it earlier today, and then it started straight away.
I'm thinking this might be the starter motor (bloody expensive !) or maybe the coils breaking down?
Any thoughts / suggestions welcome.

[Al]

As mentioned above 'hot soak' is a real problem under certain conditions. Its just the 'volatile fraction' wandering off leaving incombustible material behind. Sometimes helps to use choke even when warm!! Sometimes not. The starter cable and its co-responding earth cable are highly suspect on bikes of this age. Replace them and their terminations with larger cross section multi-strand copper cable available in both cases, from places like Vehicle Wiring Products and many others.
http://www.vehicle-wiring-products.eu/
It would do no harm to overhaul the starter motor and there is a lot you can do; New base-plate and brush kits or just new brush kits alone are readily available from places like Electrex World.
https://www.electrexworld.co.uk/acatalo ... s_720.html
Clean the commutator with a wrap round of 1200 paper, carefully examine it to see none of the individual segments are 'bridged', (clear where necessary), examine the front face to see its not 'tracking', wash everything in new white spirit or old petrol, dry thoroughly and reassemble carefully. Ensure it still has a mm of end float. Dont over-tighten anything and replace the cable fixings (at the stud) with a pair of stainless washers and a stainless 6mm nut.
The screw / bolt that holds the earth return cable into the RHS back of the crank-cases will be frothy with scale. Take it out, clean it, treat it, and replace with a suitable (possibly stainless) alternative fixing and ensure a good contact at this location. Electrex World do a decent starter solenoid to replace yours if there is any doubt. Had one for about four years as the original is either NLA or about £90!!!!
AL

[rickm]

Great advice, thanks Al.