I have a Troy Bilt Bronco riding tractor, about 6 years young, with a Kohler Courage 20 (19hp) engine that is extremely difficult to start in temperatures below 40F. This is a persistent problem.

What is happening

When it is cold outside, I try to start it with choke on and the starter will spin the flywheel very well but it will just spin and spin and spin some more until I smell gas.

In contrast when it is warm out, I start the tractor and it starts in about 10 seconds of spinning.

I can get it started easily if I spray starter fluid into the carb but my father in law told me I will kill the tractor if I do that.

Once it is started it runs beautifully in all weather and even with old gas.

Some Info about the situation

  • Battery is about 3 years?
  • Oil is 10w30 per engine manual specifications
  • Battery when fully charged is showing 13.4v on my volt meter
  • Starter is only a year old (that obviously wasn't the problem)
  • Replaced carb gasket earlier this year because engine was dying when going up hill. Noticed there wasn't a good seal and the gasket paper that was on there was ripped. Engine ran exceptionally better after I changed the gasket paper.
  • Gas in the tank is almost 3 months old

Some things I tried

  • I jumped the battery to my car when it was running. This has moderate success but it is still damn stubborn.
  • I sanded all the battery contacts and starter contacts
  • I replaced the starter a year ago when I last ran into this problem. No difference.
  • I tested the spark plug and it makes pretty blue sparks on the engine block when the starter turns
  • Carb gasket is less than a year as stated above

Some things I thought to try?

  • Replace/clean the starter relay? I am hesitant to do this. It is a cheap part but was mounted in such a ridiculous location that I have to remove 20 parts just to get to it.

  • Tighten the choke linkage? I read somewhere that if the choke plate doesn't close completely this can cause a cold weather starting problem.

  • Bring the battery inside overnight to warm up? Is the battery just cheap? It has always had this problem since the battery was brand new.

  • Drain the gas and try fresh gas?

Any other ideas that you guys would consider? I sold it to a guy who gave me some money down on it back in October but the weather was warm and it ran perfectly. I am afraid he will back out of the deal when he comes to pick it up and we can't get it started.

  • 2
    If the starter spins the flywheel with no issues, why do you think changing the relay or heating up your battery will help? Adjusting the choke linkage is a good first start.
    – cory
    Nov 21, 2016 at 20:34
  • 2
    Yes avoid the starter fluid in the small engines it can cause damage. Use WD40 instead of the starting fluid works the same just less "BANG". And as Cory stated look at choke first. Small engine chokes may be closed all the way or open a very small amount based are carb type. Nov 21, 2016 at 21:29
  • @spicetraders I would think that since Wd 40 is oil it would gunk up plugs and stuff with residue Nov 21, 2016 at 23:27
  • @maple_shaft It is a very flammable substance. Search some youtube videos on WD40 fires. It also is a fine oil content and functions more like a topend lubricant. Been using for years especially on hard to start low use items like a chainsaw or for me a mower. Nov 22, 2016 at 2:26
  • 1
    @cory Thanks the choke plate was not closing the whole way. I adjusted the carb and the choke cable and it starts perfectly now. Nov 22, 2016 at 18:15

1 Answer 1


This does not sound like an electrical problem to me. Let me break down the issue a bit and see if we can come to some conclusions.

  1. The engine starts fine with starter fluid. This tells me that it is consistently generating a spark. Hence, we can rule out electric systems, except the possibility of a weak battery.

  2. You are turning the engine for a substantial period of time. You wrote that during the summer you turn it for 10 seconds and it starts. I'm assuming that means you are turning it longer than that during the winter. This tells me that your battery holds enough juice to turn the motor plenty fast enough to get it started.

  3. The battery is generating 13.4v of electricity. This sounds like a healthy battery. Confirms #2.

Up to this point, we've basically ruled out the electrical system. The one thing that would tell me it could be still is that the mower starts better if it is attached to a car battery. I'll come back to that.

  1. The spark plug is clean. This tells me that the carburettor is basically adjusted correctly for normal running. Starting could be a different matter.

  2. The motor starts after substantial cranking. This tells me that the engine is not flooding; rather, the engine is getting either insufficient fuel to actually start the engine or insufficient compression.

For me personally, having evaluated the facts given, I would narrow you down to two different possibilities with a possible third:

  1. Insufficient fuel delivery in the low-speed jet. Quite possibly, you are due for a carb cleaning, and possibly and adjustment on the low speed jet. You could try, just for the experiment, backing out the low-speed jet screw by, say, half a turn, and seeing if it starts better. Just remember any changes you make and put them back as they were if you don't do a full adjustment!

  2. Insufficient compression. It is just possible that as the engine turns over, it gradually starts to seal the cylinder better as the oil coverage increases. A compression test should validate/reject this possibility.

  3. It is vaguely possible as well, as you suggested, that the fuel is too old. I have had that issue on numerous occasions, however, usually the symptoms are starting and then shutting down and refusing to start until the engine is cool.

Coming back to the boost with a car battery: whatever the case, having it connected to your car could generate an extra boost of power that you shouldn't need to start the tractor that would give it a slightly higher compression. Whether it be inadequate fuel or inadequate compression, this extra boost could set you rolling.


Check your compression and run a carb adjustment/cleaning/rebuild.

  • 3
    Hallelujah! I know others suggested as much in comments, but I DID get it to start in less than 3 seconds! I followed your advice. I adjusted the carb slightly, but I also noticed that the choke cable was not closing the choke plate the whole way. I tightened this up too and with both adjustments it seems to run gloriously now even though it is freezing outside. Nov 22, 2016 at 17:47
  • Great to hear! Glad you got it going!
    – anonymous2
    Nov 22, 2016 at 18:05

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