A customer of mine sent me this e-mail looking for an answer to this problem.
I thought it might be a leaking centre gasket, taking in transmission oil into
the cranking chamber. Anyone have any ideas on what's going on here?
Go to this website for pictures of the mess.
http://www.redmtnmarineaz.com/cota-mess.html1974 Montesa Cota 247 21M12797. Last season, I had my first real problem since purchasing this bike in 1978. The idle started to “hang up” during an event more and more frequently until at one point, the throttle stuck wide open and I had to quickly kill the motor. Inspection at home revealed a sticky, light brown, glue-like material coating the throttle slide (especially cylinder side) causing it to stick firmly in the carb body. Further inspection followed the sticky coating down through the intake manifold. I pulled the head and cylinder in horror to find the goo coating everything, practically gluing the piston to the cylinder. The piston rings were stuck into the grooves. I had to use lacquer thinner to get everything clean, nothing else would budge it. I even poured some into the crank chamber, agitated and inverted the bike several times until the thinner came out relatively clean and clear. Prior to this nightmare, the bike had sat for a couple of seasons without use so I just chalked it all up to maybe gas that had settled into the crank chamber and gone bad? That was until this season. I had cleaned and reassembled everything after that episode last summer and put it away properly in the fall; ran it dry, drained gas tank, drained float etc. At the start of this season, everything was fresh. I used a supreme gas mix with Golden Spectro as I have for thirty-one years. It ran great for a couple of hours of use and then it happened; the idle started to hang, and then the throttle stuck open again. Sure enough, inspection has revealed the same thing is happening again. What is going on? Where is this stuff coming from? Could it be sucking gear oil into crank area? Could the inside of the fiberglass tank be dissolving? Primary side seal bad? I am at a total loss. The ONLY thing that I’ve done differently in the past few years is I tried using Bel-Ray air filer oil (blue, sticky stuff) but I can’t see how that would do anything. Please help me, this is driving me crazy.
Any help, suggestions or ideas would be greatly appreciated. Thanks, Matthew
