TS 185 Intermittent Fault

[petestan]

Hi , Just wondering if anyone has any ideas on an intermittent fault on a 1981 TS 185. The bike will start and run fine for a while then all of sudden just cuts out , its definitely not fuel related but more like the ignition has been turned off . I tried a new plug but no difference so am suspecting coil, PEI ignition or magneto? Any one come across a similar problem before? When you leave it for a while it will start and run again , cannot see anything obvious.

[Two wheels good]

Well, here are a few suggestions but I've no experience of the model. It's 2-stroke right?

Fuel: Is the tank vent blocked? When it cuts out open the cap. Is there a whoosh of air entering.
Open the carb drain screw and check for fuel in carb.

Ignition: Is there spark at the plug? Check elec. connections are sound. (Does it have points?)

Maybe the engine is overheating and seizing: Will it turn-over when after the problem appears? Is there oil in the 2T tank?. (Maybe it's a fuel-oil mix?). Have you meddled with any carb screws?

More detail on these questions needed for further diagnosis.

[Warin]

Only happens after a warm up?
And will restart after a cool down?

Identify the ignition systems boxes ... and wait for the failure to happen .. then cool each box in turn using water .. if none of the boxes is causing it then magneto.

If magneto is the suspect them measure it (resistance - ohms) clod ... then once the fault occurs .. you are looking for a large change .. not just 20%. A large change will tell you that it is the magneto.

If it is one of the boxes .. check if it has a 'heat sink' (bit of finned metal) attached to it .. check that it is still bolted up? If that is ok .. then there is a heat transfer paste between the box and the heat sink .. that can dry out and may need replacement.

Good Luck.