just had cylinder rebored but now bike wont run for more than a couple o minutes before it just dies. idles just fine for as long as you like but 2 mins after you start riding the engine just stops like youve hit the kill switch.restarts after a 5 mins but then stops when you ride.Sounds temperature related to me so i Removed the radiator cap and the water dosn't seem to be flowing through the rad. Mechanic checked the water pump and says its fine. anyone any ideas where to go next? its got me stumped.

Could it be something like the side stand switch engaging from the motion of the bike for some reason?
a small bump causing it to engage - maybe try cable tying it up and go for a ride to see what
happens to eliminate the possibillity. Does it cut out at certain revs or unpredictably?

sidestand cut out has been removed. Bike seems to cut out when moving at any speed but the faster you go the sooner it cuts out. as i said seems to be a cooling thing as it wont start at all straight after cutting out but leave it 5 mins and it fires up again but for less time before it cuts out again.

have you tried pulling the coolant tube from the cylinder head to check that coolant is reaching it and it has been bled
properly? it may have some air in there. It will hopefully piss out, so have a rag and container handy but let it flow
for a while to make sure no air is in there. I would have thought the temp light would have come on if overheating unless it's faulty. maybe worth giving it a visual once over also just to second check everything was attatched in the right place when the barrell and head went back on also. Did you replace the head gasket with a new one and fit it right way up?

you could try the inlet fuel valve on the carb, it may be partially stuck or blocked. This could well give a similar effect , as the fuel in the float bowl is used up , but replenished a rate slower than its being used , unless the bike is on tickover ,thus calling for less fuel.

Good lead from FMtB. Otherwise Electrical part short & overheating????

Could also be not enough flow from tank as crud in fuel filter? The tank has a filter inside as part of the fuel tap.

knackeredMk1 wrote:Good lead from FMtB. Otherwise Electrical part short & overheating????

Could also be not enough flow from tank as crud in fuel filter? The tank has a filter inside as part of the fuel tap.

yea good call NKMK1it sounds fuel, its just the cuts out like the kill buttons been hit

Not the classic 'petrol cap breather' blocked?
Stops the tank from allowing air in to replace the petrol flowing into the carb, creates a vacuum, and hey presto, no fuel flow.
take the cap off or leave it a while and its 'cured' for another 5 min run!
Fuel related probs dont tend to be quite so 'immediate' in the way they stop the bike.. and you describe it like just hitting the kill switch.
Old Brit bikes suffer with dodgy old electrics and its not unheard of for a coil to get hot and give up but be fine when cold...
Hmm.. curiouser and curiouser...
KK

" Tone" said like chorus in TV sit com "Cheers" where you bin , long time no hear
Coil would do it, quite rare now though, that sort of fault.

Hi Mike,
Had a short notice call up to Fraserburgh for work..and yes..thats a bloody long way from Cornwall! I just worked it out today..from the Monday night I set off, to coming back on the Sunday, I clocked 84 hours on the timesheet! Should cover the engine rebuild I spose...
Regards KK

A few more hours would have put you in A/R country, go on pop down to Lands End and back .