Stuck rings in two strokes

[David Lahey]

A side effect of the way modern two stroke premix oil works is that in trials use, piston rings can become stuck in their grooves, causing ring blowby, which causes loss of performance and uneven running.
I used to ride a fair bit at a property that had a big hill with mobile phone tower on top and importantly, a decent (very steep) track for the technicians to get to the phone tower. If I blasted up that track a couple of times a year on a trials bike, it never suffered from stuck rings. I didn't time it, but the motor was under sustained high load for probably 30-60 seconds. I don't ride there much anymore, or in sand dunes, so I've been experimenting with other ways to unstick the rings.
My first method was to pull the cylinder off, take the rings off the piston and clean the grooves and rings and reassemble. This worked well but took a while. Looking for an easier way, next time I pulled just the head off and with the piston near the top, squirted carby cleaner onto the rings and wiggled the piston until the rings moved freely, cleaned it up and put the head back on. That worked well too.
Today I tried something even quicker. I warmed the (TY250) motor up and had a test ride, took the plug out, moved the piston crown above the ports and squirted carby cleaner onto the rings via the sparkplug hole. I left it for a bit, kicked it over a few times, squirted the rings again, left it for a bit then kicked it over fast with the throttle fully open (to blow any remaining carby cleaner out of the cylinder). I then refitted the spark plug and went for a test ride. The result was a quieter motor, more power and running smooth again. The exhaust gas did smell a bit odd initially. I'm pretty happy with the results.

[Kurt]

Can't say i've had an issue with stuck rings but modern two stroke premix oils are generally designed for the high revving engines which run much hotter than a trials bike which spends 90% of its time idling.
I have looked up the flash points for many of the oils you can buy to try and find ones with the lowest flash point temperature in the aim of burning as much of the oil as possible.
The two I found that were the lowest plus easily available were:
Motul 710
LiquiMoly Offroad

[David Lahey]

Excellent. Thanks Kurt.
I can't see my riding style suddenly becoming wild enough to keep them clean so I'll give one of those a go.