G75
08-04-2003 | 12:39 AM
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From: CORPUS CHRISTI,
TX
G75
Have a G75 that will not stop. Barrel is closing all the way. Stop is backed out. Our club requires the engine be killed with the transmitter. I checked for leaks didnt find any. I put a piece of hose over the carb, ran the crank up to comp. and blew into it while submerged...found air leaking badly thru front bearing....could this be the reason the engine will not shut down?
HELP!!
HELP!!
08-04-2003 | 08:33 PM
#2
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G75
If your engine runs well, I.e: has a good idle, top-end, and transition, then you really don't have a problem. That's all the manufacturer was worried about when the engine was designed. The carb really wasn't intended to be used as a shutdown device.
Usually, though, if an engine will not shut down when the throttle is closed, a carburetor air leak should be suspected. A leak at the front bearing would make itself evident by the fact that a lot of raw fuel is spraying out when the engine's running at high throttle levels. If you don't have the fuel spraying out, then the seal at the front of the engine's good.
On model 2-stroke engines, the front bearing almost always has nothing to do with the seal. The "seals" you see are just basically dirt shields to help deflect dirt particles away from the balls and ball races. The actual seal is made by a film of oil that forms between the crankshaft and crankcase forward of the carburetor. If the fit becomes too loose, then fuel winds up spraying from the front bearing. So that excess fuel doesn't build up there, a groove in the top of the crank tunnel allows the excess to be sucked back into the engine when the intake valve opens.
Again, the usual reason an engine won't quit when the throttle is closed is a loose fit between the carburetor body and the throttle rotor. Over time, this can wear, especially if it was on the loose side when the engine was new.
Usually, though, if an engine will not shut down when the throttle is closed, a carburetor air leak should be suspected. A leak at the front bearing would make itself evident by the fact that a lot of raw fuel is spraying out when the engine's running at high throttle levels. If you don't have the fuel spraying out, then the seal at the front of the engine's good.
On model 2-stroke engines, the front bearing almost always has nothing to do with the seal. The "seals" you see are just basically dirt shields to help deflect dirt particles away from the balls and ball races. The actual seal is made by a film of oil that forms between the crankshaft and crankcase forward of the carburetor. If the fit becomes too loose, then fuel winds up spraying from the front bearing. So that excess fuel doesn't build up there, a groove in the top of the crank tunnel allows the excess to be sucked back into the engine when the intake valve opens.
Again, the usual reason an engine won't quit when the throttle is closed is a loose fit between the carburetor body and the throttle rotor. Over time, this can wear, especially if it was on the loose side when the engine was new.
