JD LA135 Smoked on Start

[Rosher18]

I just love it when things fix themselves.

Richard

That just means it's mad at you for not dropping everything to fix it, and that the problem will come back with a vengeance right as you're about to start a big project that heavily features the previously-working piece of equipment. :laughing:

 

[Rosher18]

A little more info on this very old thread. I've been able to recreate the smoking issue by leaving the choke on for too long after startup.

I happened to connect the dots this past weekend and connected my father in law's compression tester to each cylinder. The right cylinder (when seated on the mower) read around 130 psi and the left only showed 90. This concerns me because of the earlier - mentioned burned oil on the rocker box side of the left head cover. What do I do now?

 

[Richard001]

Typically you would want the compression to be + or - 10% of each other. So it looks like you have a problem on one cylinder.

Did you remove both spark plugs and open the throttle to wide open when you did the compression test?

Also, when you do this, make sure that the plugs are connected to the plug wires and the base of the plug is connected to ground. Some of the electronic ignition systems don't like to have the stray voltage flying around.

Richard

 

[Rosher18]

Thanks Richard! I think I got lucky this time around because I cranked it with the throttle closed and with the plugs disconnected and ungrounded. I say I got lucky because I then mowed and fertilized some pasture after the test for about an hour.
Going forward I'll be much more cautious about grounding the plugs, and I'm hoping a full throttle test will give more accurate numbers.

 

[SandburRanch]

To the best of my knowledge, being the engine speed is controlled by a constant speed governor, the throttle plate will usually on most engines be wide open at cranking RPMs no matter where the throttle lever is positioned.

With the compression differential, I would check my valve lash work once more to make certain I didn't screw up and cause the de-compression to fail on that cylinder. That's just me.

BTW, my LA135 occasionally smoked on start up from new. In the about 260 hours I owned it probably smoked 8-10 times but always corrected itself. I like that self fixing term.

 

[Rosher18]

Update, my battery was quite weak, and it's possible I had less cranking power on the second test than the first. Plus my brother in law noticed the tester I used is really leaky, so I'm gonna throw those results out for now and re run the test soon. Still have dark discoloration on the top of the left head as you sit on the mower. New battery cranked the thing like I've never heard before!

 

[tomplum]

Just to group together some thoughts: It would sound to me too like the lash procedure should be checked. When I see large compression difference in this engine , I usually expect to find a push rod off. With that being said, I would guess that they are on , but quite possibly you were not setting the valves in the correct position? On this engine you need to know that the valve lift is comparable on all 4 valves, the valve guides protrude from the head comparably on all 4 valves, the rocker studs are tight and that lash is set 1/4" past TDC once the intake valve closes. I use .004 and 006, though some will use the .003 and .005. The original problem with the difficult crank would be due to the compression release not working- which is likely affected by excessive lash at the intake valve. I can assume that's why you adjusted the lash.

 

[leonz]

I wish my LA115 fixed itself!!