Hard to start Craftsman 19.5HP 42" Riding Mower

[dart451]

Working on a Craftsman tractor, 917.270812,42e707-2631-e1 that's hard to start. Has a known fresh battery but mostly it barely clicks when you try to start it. Now, when I use my jumper pack, it will get enough oomf to turn over and start...runs great! I took the battery tray out to inspect the solenoid, all connections are tight, ground looks perfect. I was just working on a single cylinder briggs that had a compression release problem because the rockers were too loose but I do not think this twin flat head engine has compression release. I'm kinda steering for maybe a weak starter? Anyone have similar problems with these twins?

[RoyM]

That engine has a compression release, the intake valve clearance has to be .005"-.007" for it to work. Usually the clearance on these old L-heads closes up over time. I suspect a loose/corroded connection or a tired starter.

[bgsengine]

First, get a jumper cable set, and jumper from engine block ground directly to battery negative terminal and see if it cranks over better, if it does, then you wanna look for loose engine mountings, rusted or corroded ground connections between engine and battery.
if it makes no difference, then rather than trying to key start it, make sure you got clutch disengaged, everything in neutral, brake is set, and try jumpering positive direct from battery to starter post, if that improves things, you have a voltage drop somewhere on the positive side.. not as common as a ground problem... if none of that solves problem, and it otherwise starts right up when using the booster pack connected to your battery, then you have a bad battery.

[SUKI]

What ever happen to doing voltage drop tests? They pin point the problem quicker than guessing at it. It does sound either a dragging starter or voltage drop problem.

And opposed didn't have a mechanical compression release. At best it would had a ramp grind on the camshaft for ACR system.

[dart451]

Interesting! Never heard of a Voltage drop test...but found a video on it...I will check that out! Thanks.

[dart451]

First, get a jumper cable set, and jumper from engine block ground directly to battery negative terminal and see if it cranks over better, if it does, then you wanna look for loose engine mountings, rusted or corroded ground connections between engine and battery.
if it makes no difference, then rather than trying to key start it, make sure you got clutch disengaged, everything in neutral, brake is set, and try jumpering positive direct from battery to starter post, if that improves things, you have a voltage drop somewhere on the positive side.. not as common as a ground problem... if none of that solves problem, and it otherwise starts right up when using the booster pack connected to your battery, then you have a bad battery.

Tried that bgengine... with the jumper set...no difference...I'm thinking battery...the voltage has dropped down to about 10.5 again...

[bgsengine]

Tried that bgengine... with the jumper set...no difference...I'm thinking battery...the voltage has dropped down to about 10.5 again...

definitely a bad battery - if you can charge it up, and then drop it to 10.5 just from cranking it over, you likely have a dead cell in the battery. 10.5 volts is just barely enough to crank over a warm engine in otherwise good shape, provided that all electrical connections are clean and not dropping too much.. add in a bit of resistance from the various connections after they are "worn in" it isn't gonna have enough juice to crank engine over efficiently.

[Skywatcher]

Hi Dart

When going through 4th year heavy duty mechanic's training, we studied the electrical side of things. Our instructor taught us some very useful nuggets of information, one of which was: If there is a problem with an electrical system, the problem is most likely going to be in one of 3 places - the positive side of the circuit, the ground side of the circuit or the appliance itself.

BG gave you the tests for eliminating the first two by using jumper cables to completely bypass each side of the circuitry. These tests assume you either have a known good battery, or have an adequate 12 volt (12.8 to 13 volt) power supply connected to the system. Just because it's a fresh battery doesn't automatically mean it's good. Check the stand-by voltage on and do a load test the battery (battery tester very handy for this). Posting the year of manufacture of the machine is also helpful as it gives us an idea of how much time corrosion has had to work its way into the system (S/N of the unit or Code # of the engine).

The average voltage drop in an electrical circuit in good condition is 0.1 volt per connection. When you look at an ignition key switch, you see the two external connections, but you have to remember the two internal connections that you can't see. The same holds true for the PTO position sensor switch and the brake switch, plus the internal and external connections on the starter solenoid.

The starter motors on these old flat-head opposed twins are also known to wear out over time. Bushings get dry and cause drag, brushes and commutators get worn reducing the amount of current flow through the starter motor. Other things I've seen are broken or missing drive belt guide pins causing the belts to drag on the pullies making the engine harder to turn. All these things can add up to a slow or no crank condition. Start with the simplest things first and work your way through the diagnostics from there. All the best,

Sky