Lawn Boy electric start, no start

Discussion in 'Mechanic and Repair' started by jeffco67, Aug 25, 2006.

  1. jeffco67

    jeffco67 LawnSite Member
    Posts: 19

    Found this one at the curb, have no info on what kinda life it's had. I believe it to be a 6.5 hp. I took the motor off the deck (damaged) and kept the controls, battery, etc also...

    I had this sucker running on the bench with no problems last summer, it would start and run easily. I found another LB mower with a torched motor but good drive and deck, etc, and started building a useable one with this electric start motor.

    Anyhow, it's all together and ready to go, just won't start. The battery is good, cranks strong, the blade stop/ignition kill switch works, I guess, insofar as with it depressed the engine cranks, let go of the plunger and it won't crank, starter relay is disabled...pulled all the connectors apart looking for corrosion, we're all good there.

    Still no spark, I'm a bit confused by what I see up top, there is the mag coil, which I pulled apart, cleaned up and gapped to .010" (is that right?), but there is another coil pickup winding opposite of the ignition coil, with a small white plastic dodad strapped to it with a ziptie...four wires total, two from the coil, two from the dodad...what the heck is that thing? I suspect the problem lies there, but I don't know what it is, much less how to test it...

    Also, any quick ohm meter tests for it and the ingnition coil?

    Any help appreciated!
  2. jeffco67

    jeffco67 LawnSite Member
    Posts: 19

    Forget it....tried resetting the gaps with two business card together, and it fired like crazy and is running fine ides what caused it to quit sparking in the first place...still like to know what that little white box and second pickup are for, exactly...
  3. lucforce

    lucforce LawnSite Member
    Posts: 223

    That is your charging system. It uses the magnets on the flywheel.
  4. jeffco67

    jeffco67 LawnSite Member
    Posts: 19

    I don't know why that didn't occur to me...thanks! For some reason I just assumed there was a charger you had to hook the battery to after use, I made one out of a 12v adapter to get it charged in the first place...if I'd really thought about how the wires were running, I might have guessed that...

    Thanks for the reply. Now I gotta go make a couple of holes in the deck for the battery hold down and cover...

    I haven't used a 2 stroke mower in a long long time, amazing how strong it is, and how far it throws grass from the chute...

    don't know the mix ratio do ya? i've got 32:1 in it right now...seemed pretty happy with that
  5. lawnboy dan

    lawnboy dan LawnSite Gold Member
    Posts: 3,712

    32/1 is correct
  6. jeffco67

    jeffco67 LawnSite Member
    Posts: 19

    OK, one more question.

    I'm pretty sure the charging system is working fine, at least I haven't run the battery down in many starts yet...I wondered outta curiousity what the output from that mag setup was...

    I assume that white plastic box with the two wires I spoke of is a sort of regulator/rectifier? If it's like the charging system on motorcycles, it's not good to run it unloaded (no battery), so I just pulled the battery connector apart far enough to expose the connectors with it running, and took a voltage reading. It showed about 12.6v, which is also the standing charge in the battery with the motor off...

    So against my better judgement I tried taking a reading directly at the connector while pulled apart, engine running.In this condition, I was getting about 18v outta the the question is, is the charging output (or lack of it) when connected just due to the battery's current state of slight overcharge (12.6v) and the reg is just leaving it alone? I'm used to car's systems, 13-14v charge is normal in a 12v system...

    Anyway, it works, so I'm not gonna argue with HOW it works...just wanted to satisfy my curiousity about it...thanks!
  7. Jim@MilkyWay

    Jim@MilkyWay LawnSite Senior Member
    Posts: 472

    1st, if I interpreted your post correctly, then your charge system is fine. And 3rd, when you pulled the connector apart, then you created a "open circuit" condition. In this case I am surprised that you only read about 50% over the expected(?) value of 12V.
    Your battery represents the "load" for whatever type charge system you have. With it removed from circuit, remember you pulled the plug apart, you can not trust what your meter tells you. As soon as the battery is reconnected, you will get a reliable indication of charge voltage. Further, the fact that you had a higher than expected open circuit voltage, does not mean that your charge system will overcharge your battery. Also 12.6Vdc is not even slightly overcharged for a healthy 12V battery.
  8. jeffco67

    jeffco67 LawnSite Member
    Posts: 19

    Right, I know a slight surface overcharge is correct for a battery, what I'm saying is that with battery connected, I'd expect to see 13-14.5 volts (if this were a car or bike) output from the charging system, not standing battery voltage (12.6v, same as when shut off), which in a vehicle would mean the charging system is dead, neither charging nor discharging, just doing nothing.

    I guess I am wondering what the setpoints of the reg are on this thing, does it pull back on charging output as long as the battery is over 12v? In a car or bike system, you are dealing with a vented, liqiud filled battery that can deal with a constant 2v overcharge by outgassing and venting, but this battery, being constructed the way it is, cannot, I would probably just burn or rupture...

    So I guess I just wanna know what is the spec for charging output on these, just curious on the one hand, plus I reset airgaps on both mags without a spec to go by, but I have good spark and good (?) output from the reg/rec, so I assume it's fine....

    Just couldn't understand the voltage I was seeing with it connected and running. Also would like to know if you know, like a car or bike, will you destroy the reg/rec if you run it unloaded for extended periods?

    Remember? The old bikes with kick start and generators you could ride without a battery (or with a completely wasted battery) in the circuit indefinitely if you wanted to, but once they went to multi phase mags with diode rectifiers, you'd burn the system if you did that for long...
  9. Jim@MilkyWay

    Jim@MilkyWay LawnSite Senior Member
    Posts: 472

    Sorry I have not addressed this earlier. Busy; you know the drill.
    I'm not real clear on at least one of your statements. I don't think out-gassing has a bearing on charge condition. Further, I'm pretty sure all mowers have lead acid batteries, and therefore your comments about "this battery being constructed the way it is" should cause you no concern.
    How long after starting did you check the voltage?
    When you engage starter, even if engine is a quick start, you are still "draining" the battery, a lot on hard starts, a little on easy starts. Well, the battery does take a few moments, to several minutes for it to fully charge, depending on condition of _all_ components in start and charge system.
    Therefore, if you check battery voltage immediately upon starting, it could read low without a problem actually existing. Make sense?
    As for running without battery being connected, I have no experience trying it, so I have no advise.
  10. jeffco67

    jeffco67 LawnSite Member
    Posts: 19

    I was just thinking, all lead/acid batteries produce hydrogen when they charge or discharge...that's the bubbles you observe forming on the plates and bubbling to the surface when you take the caps off an autmotive battery. Mixing with the sulfuric acid (the "water" in the cells), they produce Hydrogen Sulfide gas, an explosive mix, as well as pressure, which is why they are vented. Same with a motorcycle battery, or a lawn tractor.

    If you completely sealed a lead/acid battery, it would eventually rupture from internal pressure. It has to vent. There is no vent on this battery. It appears to be something along the lines of a large sealed 6 cell NiCad (6 two volt cells), and NiCads and others constructed that way typically can't take charging at the high rate you see in lead/acid batteries. They burn or burst.

    So, since I have no specs on the mower's charging system, and the recharging specs on the battery are unreadable, I can only assume all is as it should be, as it continues to work OK...

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