|
|
Post by walterp79 on Aug 31, 2024 16:20:15 GMT -5
Please can I ask a quick question? My petrol gets to my carb, so the petcock works and the pipes are open. I cleaned my jets very nicely, so the carb is clean. But the spark plug is still dry.
I rebuilt the top end because I blew it. So the only reason I can come up with(and actually Jack came up with this) is that it's not sucking petrol because the timing is out. But I went through this so many times now I can time it with my eyes closed.
I also replaced the oil pump so I took the flywheel and magneto off at some stage. Is it possible that I could've done something wrong there so that the timing is still off? That riff key is there, so it seems like everything falls into place?
Silly question. If I turn the flywheel and look at what the valves do,it takes two turns to complete a cycle. Should it be one? I am struggling. 😂
|
|
|
|
Post by aeroxbud on Aug 31, 2024 18:20:34 GMT -5
The full combustion cycle consists of two revolutions of the crankshaft. Hence the name four stroke. Two up, two down.
Have you tried sucking on the vacuum line to see if fuel flows out of the fuel line?
Is everything sealing correctly? With low compression it won't start.
|
|
|
|
Post by GrumpyUnk on Sept 2, 2024 8:57:16 GMT -5
Put a pencil down the spark plug hole, check the TDC mark on the flywheel to be aligned with the case mark. Check the sprocket on the cam chain to be aligned with the top of the cylinder head, large hole at the top(if not, rotate the crankshaft one complete turn and check again). If all lines up, your cam is in time.
If you don't have a compression gauge, replace the spark plug and attempt to crank the engine by hand using the kick start lever. You should be able to feel the compression-cause resistance as the piston is moved up in the bore compressing. If no noticed resistance, valves may not be seating. You need a few thousandths clearance on both rockers. Not much at all. Check that at TDC, or check when doing the above timing check.
You can apply suction to the petcock vacuum line attached to the intake elbow which should allow fuel to flow and fill the float bowl. The engine can run on float bowl content for several minutes, so you should have enough fuel to start and run after allowing fuel flow for a few minutes. You can also check flow by disconnecting at the carb, and collecting the fuel in a plastic soda bottle(clean and DRY). The fuel should flow without any restriction as long as suction is applied to the petcock vacuum line. If the flow is restricted or dribbles, your problem can be in the petcock or the plastic outlet tube inside the fuel tank.
tom
|
|
|
|
Post by wiscootsin on Sept 23, 2024 21:52:32 GMT -5
Please can I ask a quick question? My petrol gets to my carb, so the petcock works and the pipes are open. I cleaned my jets very nicely, so the carb is clean. But the spark plug is still dry. I rebuilt the top end because I blew it. So the only reason I can come up with(and actually Jack came up with this) is that it's not sucking petrol because the timing is out. But I went through this so many times now I can time it with my eyes closed. I also replaced the oil pump so I took the flywheel and magneto off at some stage. Is it possible that I could've done something wrong there so that the timing is still off? That riff key is there, so it seems like everything falls into place? Silly question. If I turn the flywheel and look at what the valves do,it takes two turns to complete a cycle. Should it be one? I am struggling. 😂 Do you have spark? have you tried removing spark plug, shooting starter fluid in it, putting spark plug back, and then starting? |
|
