got my ty running great, only problem after about 2 hours use it starts missfiring then stops, no spark, change the plug and off it goes again no problem for about another 2 hours, iv got the mix right by the colour of the plug, its just had a rebore and crank seals, exhaust is a new wes system so not blocked, dont think any electrics are getting wet as the only wire to the coil is covered in silicon sealant so is the plug cap, anyone got any ideas!!!!!

I would try changing the condenser and the points at the same time.

Or better still, fit electronic ignition from http://www.tytrials.co.uk/

are you using good quality 2 stroke oil ?

Sounds a bit obvious, but are you sure the plug isn't whiskering?

Especially after a rebore etc.

try using that shell v power petrol and good 2 stroke but not silkolene ideally putolene ,i had exactly the same problem on a cr250 i used to own and it just about drove me daft until i was told to try this and it cured it completely and plugs lasted for ages

Just a thought, I had a similar fault, I thought it was the plug but in the amount of time it took to push the bike back to my car and change the plug the engine had cooled enough for it to start, nothing to do with the plug it would of started even if I didn't change it. It was a fault on the source coil, fitted electronic ignition as mentioned by majesty.

Gday, second what Andy says above, also what colour is the "old" plug exactly?

Cheers,

Stork

right im using silcolene premix, useing the same mix in my lads ty80 with no problem,i have to carry a spare plug with me, as soon as it cuts out i remove the plug that ia a nice brown colour check if its sparking (not) change to a new one and off we go again go through about 10 plugs since the rebore so any muck has gome by now, could the condenser cause a problem like this as iv not changed that yet

Condensors can fail as they heat up, and work again once cooled down.

I would change it anyway.

Gday, it seems strange that a good coloured plug will not spark, but a new one will. What actual plug are you using? (Brand and number). If a new plug makes it go, I doubt the condensor is at fault, however it is old and a new one will be a good idea anyway as B40RT says.

Cheers,

Stork

I think the suggestion that it might be the condenser is based on the motor (and condenser) cooling while the new plug is being fitted. A test to prove/disprove this theory would be to try one of the old plugs again when the motor was cool.

I had the same problem,years ago,and it was the condencer.Try what feetupfun said.It will work with the old plugs when they are cold.New condencer and new points and your bike will run for ages again.

Chrs:Mike

thanks guys points & condensor are now on order, will let you know!!!!

Thanks guys points & condenser changed no problem since, so far got about 6hrs use out of one plug!! fingers crossed sorted