SY250 - cutting out

[Husie200]

Hi all, hoping someone can point me in the right direction. Recently bought a 2002 SY250 for me to use while my son gets to grips with trials on my Sherco. First outing, it ran great from cold for about 20 mins or so, but when hot and under load, loses power and gets progressively worse until it cuts our almost like it has run out of petrol. Removed the carb and had it cleaned in an ultrasonic bath and set up, so i know the carb is ok. Out again at the weekend and still exactly the same problem. As i mentioned, it only happens when really hot and under load when climbing hills etc.

Any pointers on what to look at next? Coil or HT lead breaking down under load, fuel starvation etc?

New to Scorpa's so not sure if this is a common problem.

Thanks for any help.

Edited January 14, 2019 by Husie200

[misscrabstick]

So when it's cold and running fine remove the plug and look at the spark, observe how fat it is and the colour, when it's messing about remove the plug and repeat the test compare the spark with the previous result, although rough it should give you a yes no on it being ignition related, I would fit a new plug anyway.

Also check the fuel tank breather is clear, if blocked you could be getting a vacumm in the tank which will mess with fuel delivery to the carb, this has happened to me, it will stop the bike annoyingly after 10 to 20 minutes, after a rest the bike goes again as air manages to slowly bleed into the tank allowing it to flow again.

 

Edited January 14, 2019 by misscrabstick

[Husie200]

Thanks for the reply. Forgot to mention it has a new plug and the spark 'looks' to be ok. The tank breather sounds feasible, i'll give that a try. It seems to run ok when on the flat, but as soon as you put it near an incline, it starts to sort of 'miss' and then completely cut out as soon as the throttle it turned.