cota 247 hot and cold

[chapelfarmer]

Hi Can anyone enlighten me? My Cota 247 (1979) was restored about 10 years ago by somebody extremely expert but with whom I have since lost touch. It has had pretty gentle use since but is regularly exercised. Today I ran it for about 20 minutes and then died. It normally seta's first kick. After about 10 minutes resting it started again and ran happily for another 10 minutes. Then repeated the process. It was almost as if it was overheating but it's been a cold day and it wasn't doing much work. There was plenty of fuel flowing. The bike has an electronic ignition (with a small square red kill switch if that rings any bells). Can anyone suggest where to start hunting? I should add that the bike has had very little maintenance, in fact I've barely changed anything other than the oil in the time I've had it.

Many thanks

John 

 

[misscrabstick]

When it dies whip the plug out and see what sort of spark you have, also well worth checking the fuel tank breather, a blockage could make a vacumm in the tank that would stop the fuel flow into the carb, it would recover after a short while only to repeat when the vacumm built again.

[section swept]

As already indicated, old fuel, evict spider from tank breather. Your red kill switch shouldn’t ring any bells?but you could make sure it’s not shorting out. Anything left over a period of time will succum to deterioration, so a thorough check of the air filter and pipe work down to the carb is needed. There may be crud in the tank and crud in the carb float bowl (probably the fault you have). Oil seals will harden and bearings will corrode when left standing especially crankshaft bearings main and big end. Oil can build up in the crankcase and cause issues. A trick I learned from a Greeves Works rider could be the answer. Watching in the pits at Houghton Conquest, I couldn’t understand why when he’d got the Challenger running (numerous kicks) he’d then lay the bike right over onto one did and rev the nuts off the engine. Then he’d  swap sides and do it again...”clears the oil out of the crankcase” ...seemed perfectly reasonable to me then. I have always done this on any of my two strokes, amazing the difference to throttle response it makes. Oh and he won his race that day to?

[keychange]

I had similar experience with my 247 years ago - in mine the idle speed also increased -  appeared to be running lean but after many many hours and $$$ on the carbie I realised the timing  was slightly too advanced and that was the issue.  After no luck with depth guage I used paper timing disk - see attached and had no problems ever since.

timing.disc.pdf