Can a base gasket delete affect the ignition timing?

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stihldragon

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I still have the gasket, and it's in reusable condition. It pops hard when you pull the cord, almost pulling it from your hand, which makes me think it's the timing. This is rebuild I'm doing on a bg65

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What you're feeling is the increased compression. 10-15% can make a big difference if it's a saw you're familiar with.
 

Yes retard opposite of advancing timing. Dropping the cylinder, the piston will travel farther before the ignition fires. Maybe 1 degree on a saw no big deal. More noticeable would be the port timing and possibly the port open duration depending on the engine.
 
Yes retard opposite of advancing timing. Dropping the cylinder, the piston will travel farther before the ignition fires. Maybe 1 degree on a saw no big deal. More noticeable would be the port timing and possibly the port open duration depending on the engine.
Wow, had to think about this. The spark would still occur at the same number of degrees before TDC but because the piston is slightly higher in the cylinder, the spark would effectively occur slightly later in the compression stroke. The ignition timing wouldn't change but the spark timing would need to be advanced to occur at the best time in the cycle. I agree - never thought of it this way.
 
These saws would be much easier to mod if they had a removable head. Then we could add gaskets to increase port timing (poor mans port job) then cut the head back to stock or higher compression. On snowmobiles we slot the pick up on the stator or use different timing keys on the flywheel to adjust ignition timing. On a saw you could slot the mount holes in the coil to adjust timing.
 
Well I think deleting the base gasket will actually advance the ignition timing,the spark plug will be closer to the piston when the spark fires,making the flame front hit the piston a little sooner,but will probably not even alter actual timing even 1 degree,or make much difference in timing. so if you delete the cyl.gskt. you will gain some compression and slightly advance timing,however you are also lowering your ex. and transfer ports,(loss of max. power)getting less duration and power which is why I don't use this trick much,except low-comp. Poulans.
 
These saws would be much easier to mod if they had a removable head. Then we could add gaskets to increase port timing (poor mans port job) then cut the head back to stock or higher compression. On snowmobiles we slot the pick up on the stator or use different timing keys on the flywheel to adjust ignition timing. On a saw you could slot the mount holes in the coil to adjust timing.
Filing the key is a fast and easy way to change timing.
 
Yes,good mod,some saws like a little ignition advance boost. I like keyway mod best,slotting the ignition module is not easy to do safely,filing thru the laminations of a coil can "fray" them,reducing output voltage.
 
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