I was doing a bit of spirited trail riding on the beloved '97 Techno today. Bike started popping and then would start revving out with the throttle closed. By some miracle it got me back to my trailer.

Seems like it must be an air leak. Did what my knowledge would let me which basically meant giving the bike a really good clean... Re-sealed the reed stack. Drained the oil which looked whiter than it should be although the coolant level seemed fine? Took the water pump impeller cover off as I think some piece of magnesium is supposed to rust out, didn't see anything? The left side crank case always gets covered in spooge but I can't tell for the life of me where it's coming from.

If my problem is crank case seals are these seals that can be replaced by me rather than needing to press the crank out? Help greatly appreciated!

Before doing anything else pressure test the engine. You just need to make blanking plates for the inlet and exhaust and fit one with a tubeless valve. Pressurise the engine to between 5 and 10 PSI and see if the pressure drops, look for bubbles in your coolant or air coming out of the gearbox breather.

If engine seems pressure tight try giving it a decoke, sometimes this revving with throttle close is caused by glowing carbon in combustion chamber or exhaust port.

What heat range is your plug, if you ride a rials bike harder than normal you should go up a grade or two.

Thank you so much for the reply. To my amazement the bike fired up today and seemed to run fine.

The thing that caught my eye was the de coke of the exhaust. The mid pope is chock full of the stuff and I had never ridden the bike wide open on those trails before. The fact that the bike is running ok today makes me think that is the problem. I'll get that sorted and see how she does. I would never have thought if this so thanks again!