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So if some of you have seem my posts over the last couple months, you would know my JCL MP250a scooter has been out of commission for a little while. It's a long story that I won't tell here. Long story short I got everything back running and have had my scooter out on the road quite a bit the last several days. It's seems to be running great. I have noticed however that my idle is running at about 3000 rpm's. When I sit at a light I can feel a slight jerking forward like it wants to take off. It seems to me that before it broke down, the idle usually ran around 2000 rpm's but it's been awhile so I'm not certain. During the process of fixing it I did do a valve adjustment so I was wondering if that would possibly affect the idle speed. Does anyone have any idea about this and if the idle is too hight, is it easy to fix? Sorry if this is redundant and answered somewhere else. I couldn't find any post that answered this.

It took a little convincing but I finally got the water pump off and from what I can tell the shaft going through the engine seems to be fine. I actually started the scooter and ran it for about 20 seconds and the shaft was spinning. In looking at the water pump, what I think is the issue is the impeller seems to be spun off the shaft in the water pump. I can spin the shaft without moving the impeller and vice versa. I think all I need to do is get a new water pump and I'll be back in business.

Here's the background. I have had a lot of issues with my JCL MP250A scooter overheating and I have yet to solve it. I have "burped" it more times than I can count. The coolant level has not changed in the top which to me means I have the air out and am "burping" it correctly. However it stilll overheats. I jumped the wires coming out of the temperature sensor in the bottom of the radiator and found that the fan works fine. I then concluded it's got to be the thermostat or the water pump. I did happen to notice that if I had radiator cap off while it was running, none of the coolant seemed to flow at all even when the scooter was hot. My conclusion was maybe my problem was the water pump. I removed the cover from the water pump to reveal the little propeller inside which at first seemed difficult to turn. With the cover off and the scooter cold, I started the scooter and noticed that the propeller didn't turn at all. If I primed it and started it spinning by hand, it would continue to spin but if I stopped it, it would not start on it's own. First of all, is that normal and am I on the right track? Granted I didn't leave the scooter on very long as I didn't want to overheat it with no water in there. I'm assuming the water pump is my problem. Secondly, I removed the two 8 mm bolts that hold the back of the water on but I can't get the water pump to even budge. Is there some trick to actually getting the entire water pump off? Any help would be greatly appreciated.

So I talked to a local mechanic and he said the knocking is more than likely a crank bearing that has gone bad and will require a new crank shaft. I won't know until I take the motor off. So I'm going to head in that direction and see what happens.

I've followed JR's instructions to a "t" and it appears to be fine as far as the fluid goes. When the engine is hot, the tubes on both sides of the radiator cap are cool so that's another reason I think I have water flow issues. As far as the knocking in the engine, I have a feeling after checking on youtube that it might be the crankshaft bearings that have gone bad from it overheating.

JR - thanks for the clarification on the piece. It makes me breath a little easier. I just hadn't seen it before on oil changes. As far as the clearances on the exhaust, I set it on .005". When I have the spacer in place, there is no play. When I take it out, then the rocker moves up and down off the spring. It could definitely be possible that the crank is not in the correct position. At this point anything is possible. I will readjust it and see what happens. Now as far as the gear, I feel a little dumb and actually busted out laughing because the shaft that holds that gear in place is on the inside of the magneto cover with a snap ring on it. The reason it was moving free was because I took the cover off and didn't see that shaft. I think I'm going to re-do the valve adjustment and put it all back together and see what happens. I've checked everything I can think of and maybe the knock indeed is that exhaust valve. At least I've learned a lot in the process. Thanks for all the tips guys. I really appreciate it. I hope I'm able to give back to the forum for all you guys have helped me out so far. I will keep everyone posted on the progress.