cub spitting and sputtering

jsfarmall

Member
I figured out its not in my carburetor. If my alternator is kicked in I cant run above half throttle, spits, sputters, coughs, and everything a motor shouldn't. If its not kicked in everything runs just fine. I can run the engine up, kick in the alternator and then it starts acting up. Suggestions?
 
Kicking in the alternator how in the world do you do that?? If the alternator is in fact causing you a rough running condition that says it is running way to lean or the alternator has way to much drag to it or is causing a weak spark. Does choking it hurt or help?? What does you spark look like?? You spark needs to be a blue/white and jump a 1/4 inch gap or more at all 4 plugs
 
A failed alternator can have output that can mimic points. Spiky wrong voltage when hooked into the ignition circuit in some way will do it. Have it tested, And show us how it is wired! Jim
 
Sound like the spark is getting weak when the alternator is cut in.

Try running a jumper wire from the battery + post to the hot (ignition switch) side of the coil. Now run the engine and see if it runs smoothly when the alternator is charging.

If it does look for an incorrectly wired ignition switch or alternator control circuit wiring.
 
First, what do you mean by "kicked/kick in"?
Only have two guesses, if you are positive that's the cause. First be sure its wired right (don't ask me, I don't know much about wiring) and right voltage for system(6v to 6v, 12v to 12v). The other thing check that it turns freely, not that it locks up (overwhelming the small engine, maybe?).
 
My battery wire is running to the hot wire on the starter. The #3 wire goes across to the battery wire. Then the #2 wire (left side blade sitting in driver seat) field wire I think its called, is hanging and when engine fires I touch to the starter wire which energizes the alternator then I take it off. Which is a time of about 1 or 2 seconds.
 
check flow of gas to carb. check compression. check ignition wires to see if they are copper or not. if not replace them. maybe adjust valve clearances.
 
The alternator should work that way, But if it is failing it can make problems for the ignition. The best practice is to have the alternator checked by a real Auto Electric store/shop. Not a high volume parts store. If you are still concerned, try this test. Hook up a separate battery to the ignition coil/ballast resistor and then start the engine with the normal ignition turned off, and then start the alternator. If it stays smooth, replace the alternator. Assuming it is a Delco 10SI alternator, the terminals will be BAT, 1 and 2. Bat to amp meter load side, #2 to Bat, and #1 to a idiot lamp (marker light Not LED) then to the ignition coil supply from the on off switch. (assumes it is coil and points, not a Mag. If a mag, no connection can be made from alt to mag. Jim
 
Sounds like you need to learn what is what on an alternator. I am guessing you have a Delco 10SI. It has a battery charge post then a plug with a #1 which is the excite and then #2 which is the sense wire. So again sounds like the alternator is dragging the engine down due to being bad or you have weak spark or carb problems. Like I asked what happens if you choke it some
 
Yeah got a battery. If it was too much of a load wouldn't it act up at low rpm too? Just strange it only does it when the alternator is working. When I don't have the alternator working the engine runs flawlessly. Even pulling a plow works perfectly. Surely that's more of a load than an alternator.
 
Maybe at the higher RPM the alternator has enough output that it back feeds through various paths that it shouldn't. Where at the lower RPMS the output is to low to cause a noticeable problem. All I know is electricity is force that goes by path of least resistance from source to ground. If that path happens to be feeding through ign. system it will go there, possibly causing problems with spark. I may be wrong, someone will correct me, we all learn.
 
Ran into the same problem on a green 2510. Changed alt.,fixed the problem. Guy said that it has never run this good before.
 
JS, assuming that this Cub has been converted to 12V, neg ground with a 12 coil or a dropping resistor in the coil circuit, I think the key is what the battery voltage is before the alternator is running, and after. Before should be about 12.6 - 12.8 with a fully charged battery, and about 13.4 with it running and charging. Also check the voltage across the coil with the points closed (ignition on, engine not running). It should be no more than 6.5v with a dropping resistor and 6v coil.

It's possible that the alternator internal regulator is bad and dragging the voltage down to where the spark gets weak, or the voltage is high enough across the coil that the condenser or coil is getting flakey.
 
Here is Farmall Bob's diagram that will allow you to wire your alternator so it does not have to be manually activated. Note, if this is a new installation, the fact you are not continuously supplying voltage to the exciter lead may be causing your problem. If you read note 4, you will see how to replace the warning light with a diode. Without the diode or bulb (one or the other) you will not be able to turn engine off.
05-12vAlternatorConv-rev4_22_08.gif
 
I have had the alternator checked and they said it was good. To my knowledge the coil is internally resisted. I believe my ammeter is bad so I'm goin to come up with a meter just to check things out and gonna try the diode. That very well could be the problem.
 
I don't have a diode yet, but I did stick the exciter lead to coil wire and it smoothed up and ran perfectly just now. I. Gonna try to find something around I can use.
 
Problem fixed. I just got a 1 wire alternator but still didn't work. Put a different coil on and worked beautifully.
 

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