Timing Advance?

ckswanecamp · Feb 9, 2011

I don't know how to time this motor properly, but I understand this much:

"Timing advance" refers to the number of degrees before top dead center (BTDC) that the spark will ignite the air-fuel mixture in the combustion chamber during the compression stroke. Retarded timing can be defined as; changing the timing so that fuel ignition happens later than the manufacturer's specified time. For example, if the timing specified by the manufacturer was set at 12 degrees BTDC initially and adjusted to 11 degrees BTDC, it would be referred to as retarded. In a classic ignition system with breaker points, the basic timing can be set statically using a test light or dynamically using the timing marks and a timing light. really, whats that?

My Motor:
http://forums.iboats.com/showthread.php?t=457972

I have researched this process long enough to understand that its complicated. Thats about all I really learned this far. Can the timing be as simple as setting the points gap to .020?

I don't understand where to adjust the postion of the piston, and in relation to what? theres no witness marks or such. Theres a key that is on the top of the shaft that flywheel joins to, and the high point where the points break contact fits in the same key as the flywheel, so everything seems rigid and i don't understand that process and where the allowance for adjustment is.

In addition, there is a curved plate that the parts list refers to as a "cam" which rides against throttle/spring on the butterfly. It is connected to throttle linkage from the tiller. This plate has minimal play for adjustment. So i am sure this needs to be brought into play.

I am gonna put this motor back together on sunday (13FEB2011) with the help of a friend who is a small eng mechanic. I got a complete gasket kit and an oil seal to replace. He's checked out the motor and tryed tuning it while it was running last week, but we're both unsure on how to get this thing to idle properly. she runs great at full throttle though. we figured it the timing advance. whats your take?

thanks for reading.

F_R · Feb 9, 2011

Re: Timing Advance?

You would have gotten a quicker answer if you had told us that is a Clinton.

Anyhoo, full advance is USUALLY set so the points break at a certain distance of the piston from TDC. Sorry. I don't know the spec. A guestimate would be 3/16" BTDC.

But that has nothing in the world to do with idle speeds. At idle speed, the carburetor butterfly should be completely closed and the speed is then accomplished by spark retard. The amount of spark retard is controlled by the sliding throttle/speed control on the front of the motor. Move it toward "slow" and it retards the spark. Move it toward "fast" and it advances the spark and opens the carburetor butterfly....till it is limited at WOT.

The point at which the carb just begins to open is referred to as "sync" and is fairly critical for mid-range performance.