Engine pushes back during starting

C

Commander Toasty

Member
:confused:

My engine fights turning over. It lugs back almost to a stop, then gives a healthy turn or two and starts nicely. Always been like this, and no matter what I do to the timing. I have tried seriously retarding timing way beyond what it should be but that has no effect, other than to hinder actual starting. No matter where I set my timing it still lugs back. This is not a problem with the starter as it will give me fast healthy cranking when the ignition doesn't cause a backfire. I have tried different throttle settings but that has no effect on the actual cranking. I've made certain I have plenty of battery power just as a test by doubling up with cables (6volt) and that didn't change anything.

One item - I have 'B' head. Is it normal that a higher compression head always has an issue like this?
 
Does it run real nice or just run? Does it labor when you give it the gas?
Sounds like firing order to me 1243
 
It sounds to me that the timing is advanced. The phenomenon you explain happens when you attemp to start the engine and have the spark handle down in the normal driving position. It may be that you have a "B" timing cover installed on the engine. This can be identified by an elongated timing pin boss instead of a round one. If this is the case your initial timing setting is too far advanced.

Tom Endy
 
Does it do this even if you crank with the ignition OFF? A combination of high compression and large inertial mass (Heavy flywheel+heavy counterweighted crank), as well as a weak starter motor will make this noticable. It actually is normal on all internal combustion engines, even if it is not noticable.

Here's why: When stopped, all cylinders bleed to atmospheric pressure. When you first start cranking you are trying to accelerate the rotating mass but encounter the first full intake and compression cycle on some individual cylinder. That compression bucks against the rotating mass. As you pass TDC on that cylinder, even if there is no ignition, the pressure helps to accelerate or push the rotating mass. Thus, the first 1/2 crank in a 4 banger is strictly bucked by compression, further rotation re-utilizes the energy from cylinders that have compressed gas, even if no ignition takes place.

More cylinders = less noticeable
More starter motor torque (NOT speed) = less noticeable
Higher compression = more noticeable
Increased rotational inertia fly/crank = more noticeable
The "square" of an engine (bore/stroke ratio) and bore/pin offset also have an effect

You may also be trying to fire an uncompressed charge on that first 1/2 turn. That would cause a pretty good resistive buck 'till things get turning.
 
I use the stock flat copper plug leads so it isn't possible to get the firing order wrong without something being seriously out of whack, and the engine runs quite nicely once started.
 
Commander Toasty said:
I use the stock flat copper plug leads so it isn't possible to get the firing order wrong without something being seriously out of whack, and the engine runs quite nicely once started.
Click to expand...

I've seen a couple of the repro distributor bodies short across internally, which could cause kickback.
 
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