hot starting problem

[Tom-madbiker]

right my bike has done 2500 miles since i got it on the road (about 6 weeks ago) and yesterday it started having probs when starting from hot but will start from cold easy have checked the carbs and it seems to have a spark but it is weak the coils are mounted on the top of the engine with spacers do you think that if the coils were dying they would be worse when hot

[Mitch]

Mrs R has had this problem... I ended up replacing both alternator and reg/rec - then problem was solved - so I'm not sure what the problem was, just know how to solve it... :cool:

[Taff]

The spark plugs look healthy round the end?
Might be reaching their sell by date if they came with the bike and you dunno how long they been on.
Or possibly check that the coil aint got a hardly visible split that is closed when cold, but grows as the bike starts to vibrate and open it up a bit.

[Mustang Boy]

Sounds lke it may be running lean.
On choke is ok so mixture good, then choke off when warm, too lean and therefore won't start!!
hope thats of some help.

Cheers'en.

[Tom-madbiker]

no it wont start even if i choke it but what i am suprised about is that it came on suddenly and the plugs are good they were new about 1500 miles ago

[shaggy696969]

What bike is it, Maxes are known for it , and thats down to bad earthing , on battery to frame, or at worst could be signs of heat seizing.

[Tom-madbiker]

its a kwak z750 of 82 vintage it will turn over but not fire till it coools down first i thought it was a vapour lock in the carbs i have one spare coil so i will swap over the one i think is suspect and see

[Mustang Boy]

just becausr the plugs are nw does not mean they will work!!
As i've found out a couple of times before :rolleyes:

Cheers'en.

[Tom-madbiker]

right it would not start even from cold just now so i bumped it down the hill and started first time maybe a lose earth ?

[scruffytrucker]

Coils.

They get weaker the hotter they get, especially old ones.

Have you left the ignition on without the engine running? If the LT circuit is closed for a period of time it can "cook" a coil and bring on the symptoms you describe.

Can you mount them in an airstream?

[Taff]

When it won't start, how won't it start?
Engine spins over but don't fire, click and nowt else from starter, chugs and spluts but wain't go...?

[Tom-madbiker]

the engine spins over but wont fire the coils are in the air stream but are mounted to the top of the rocker cover by long bolts and spacers as per photo

[Taff]

You sure its a hot/cold thing and not just a case of by the time it's cold the carbs have had time to fill up with juice again?
Looks like vacuum type carbs with a custom tank so probably custom tap, always troublesome.

[pyro]

Check the coil mountings, run an earth lead from the coil bracket to earth/battery and see if that makes any difference, although it does sound like duff coils.

[Womble_Lancs]

its a kwak z750 of 82 vintage it will turn over but not fire till it coools down first i thought it was a vapour lock in the carbs i have one spare coil so i will swap over the one i think is suspect and see

I suspect Taff et al are right, sounds like coils.

Grav or Big Pete are yer Z-men though :)

[dracken1]

doubt it but ensure the fuel cap is breathing ok, if however once running it keeps on running that won't be the prob.

[Tom-madbiker]

new leads have improved it no end think that was it bloody carbon leads back on good old copper leads but now it interferes with all my neighbors tellys when i drive it down the road :D

[teltwosheds]

If it runs better who care's about there tellys :D

[Tom-madbiker]

it ok cos they cant hear them anyway when i drive past :D

[bad toad]

it ok cos they cant hear them anyway when i drive past :D
old saying but loud pipes save lives!!

[Tom-madbiker]

good job i have loud pipes cos my horn is ****e its on o them halfords bicycle ones even the mot tester laughed but said he could not fail it cos it worked :D