Hello all , I took the head off and the covers for the motor to Paint them after running the motor for about 1 month strait . After I painted them I reassembled all the parts , and now my 80CC motor wont run , does anyone have any suggestions ????
Compression Problems
- Thread starter Deiseldave
- Start date
try flipping the head gasket over you can usually get a second use out of it some times you cant depends on how crushed it is
DDave: Did you use a new head gasket when you reinstalled the head? Also, did you put the head on the cylinder in the same position as it was originally? BMF
I didn't use any new gaskets the one at the top is a metal gasket and the one at the bottom wasn't crushed so I reused it. is there a proper position for the piston and if so how do I reposition it
the aluminum one crushes when you torque it down it needs to be flipped if you want to use it more than once
is there an electrical and piston timing position so that the spark happens when the piston is in the most upright position. Or is it all pretimed??? for the 2 stroke 80 CC
DDave; It is important to position all parts, as when the engine was running; just in case there is a difference in something, such as a warped cylinder head. You didn't have the piston out of the engine did you? If you could make up a fitting that screws into the spark plug hole that you get compressed air into it, you should be able to find out where your air (compression) leak is.
About 15 years ago, I built my first small model hit-n-miss gasoline engine from scratch. When I completed it, it ran like a charm and does to this day. As a matter of fact, it runs so good, that I was afraid to take it apart and paint it! It still has my layout blue on many of the parts and it is going to stay that way because, if I take it all apart to paint it and it doesn't run afterwards; I am not going to be a happy camper!
Let's get that little engine running DDave! BMF
About 15 years ago, I built my first small model hit-n-miss gasoline engine from scratch. When I completed it, it ran like a charm and does to this day. As a matter of fact, it runs so good, that I was afraid to take it apart and paint it! It still has my layout blue on many of the parts and it is going to stay that way because, if I take it all apart to paint it and it doesn't run afterwards; I am not going to be a happy camper!
Let's get that little engine running DDave! BMF
the magneto is set with the timing key as long as the magneto hasnt been taken out and the key isnt broken the timing should be fine
on another note , Before this , when clutch was disengaged while bike was off the rear tire wouldn't move at all , now when I move the bike in the same way the rear tire moves and I hear the piston raising up and down , its like there is no combustion
well yall , ty for some of the advice . ill be back on after I try to fiddle with it more . I cant afford new gaskets right now , guess its my own dumb ass fault for wanting to paint it .... I just hope I can get it running again because of my back and knees. like I said this is my main scource of transportation .
so the engine turns over real easy with the rear wheel?
did you take the cylinder off when you painted everything?
did you take the cylinder off when you painted everything?
you can hear the piston moving and there's no resistance on the tire? You, my friend, have a major compression issue then, just check to make sure all the parts and gaskets are fitted tightly, and all the head screws are tight. If you have a spark, and there's a good amount of resistance, I might have suggested an air leak on the intake manifold (either at the gasket end or the carb end).
I've been having compression issues too, though not to your extent, apparently these motors should have around 100psi of compression from the factory, I just tested mine at 80psi. I thought my issue was bad port timing, turns out my ports arent even big enough, just weak compression (after porting, with a reed valve, shaved head, stuffed crank, and corrected transfers, these motors can hit 120-140psi), considering my motor feels about 2/3 as powerful as stock, I'd say an extra 20-40psi could make a rather substantial gain in power.
I've been having compression issues too, though not to your extent, apparently these motors should have around 100psi of compression from the factory, I just tested mine at 80psi. I thought my issue was bad port timing, turns out my ports arent even big enough, just weak compression (after porting, with a reed valve, shaved head, stuffed crank, and corrected transfers, these motors can hit 120-140psi), considering my motor feels about 2/3 as powerful as stock, I'd say an extra 20-40psi could make a rather substantial gain in power.
the motor was still mounted to the bike , pulled clutch cover off , drive gear cover off , and the magneto cover off to paint, with motor still mounted I pulled the head, and the cooling fins that the piston rides up and down in to paint . The piston layed in the air while I painted far away from engine. once paint dried , I replaced the cooling fins and guided the piston back into it and replaced the head and the aluminum gasket at the top of engine , then replaced the head. put the muffler back on , and the carb and tried to start it , and nothing . and yes the rear tire moves now and I hear the compression from the piston but wont fire up to run the motor.
Ok guys leave ur coments and I will check them in a few days , I have to get ready to go .. have a good night and I will try anything to get this running again , Im broke and outta work and I have been using this bike to get around to look for work , getting too old to pedal , bad knees and back . so all suggestions are appreciated.
