Knocking noise in Linhai 250cc. By jburd (Read 2,833 times)

[jburd]

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.

[JR]

We do have a complete valve adjustment tutorial in the tech section if you need it.

JR

[4950cycle]

I wish it was just a snap ring !

[jburd]

OK so it's been a little while but I finally got the time to work on it some more. I adjusted the valves and put it all back together. It starts right up like never before so I know the valve adjustment is good. I still cannot get the fan to kick on. I have "burped" it multiple times. I opened up the radiator cap with it stone cold and the fluid was all the way to the top so I know I have all the air out. I jumped the wires that connect to the temperature sending unit and the fan kicks on so it's not the fan. It could be the temperature sending unit. However I happened to notice that if I turn it on with the Radiator cap off, there is not fluid circulating but the temperature gauge is hot. Thought that could be either the thermostat or the water pump. Also the knocking in the engine seems to be in the back left under the air filter. That's where it is the loudest. Do any of you have any ideas? I'm really getting a sick feeling with this thing and fear that I've possibly toasted my scooter. If you guys could help me figure this thing out, I'd be the happiest man in the world.

[alleyoop]

Can you clarify:
On the VALVE adjusting STUD that you say moves in and OUT. DOES it move in and out within the ROCKER arm itself or are you saying you can MOVE the WHOLE rocker in and out. If JUST the Adjusting STUD moves in and out in the ROCKER ARM then the ROCKER threads are stripped OR the Stud itself is stripped.
Alleyoop

[jburd]

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.

[jburd]

Alleyoop, the whole rocker arm moved in and out. I can tighten the stud down. When the spacer is in there, the rocker doesn't move. When I remove the spacer than it rocks in and out.

[scooteraddict]

Sept 16, 2012 19:02:24 GMT -6 jburd said:

OK guys, I think I might have found the knock. I took the outside cover off the magneto coil (where the oil stick is) to see if I could figure out what that piece was to. When I opened it up I found the small gear at the top above the magneto rotor just sitting in there loose. It was connected to the gears but wasn't fastened to anything. (see the attached pic) I turned the engine over by hand and I'm pretty sure that's what the knocking is. That gear was jumping all over the place. I tried that little piece I posted earlier that fell out the bottom in the center of that gear to see if maybe it went there. Doesn't fit. Anyways I thought I would at least post this and see what you guys think. I'm really hoping someone can help me here. I'm desperate to get this thing back on the road.

The reason the gear is loose is because the shaft for this gear is in the cover. You can remove the shaft from the cover and insert it in the gear and respective supporting hole on the other side. It is easier to do it this way then try to line it up with the shaft in the cover.

[jburd]

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.