O/T Kohler engine in Bobcat Skidsteer

btrc · January 02, 2005, 08:56:23 PM

I've got a question on a small engine and figured someone here would know the answer. I've got a little Bobcat 310 that has a 18 HP single cylinder Kohler engine. The gas tank developed a rust hole so I had to pull the engine out to replace the tank. I put it back in and it starts great but when I try to rev it up all I get is huge backfires. I thought it wasn't getting gas so I added a small electric pump but it didn't help. The only other idea I have is that it could be the coil or condensor as I remember having a problem like this on a garden tractor. Could that be? One other question problably not related to my running problem. There is a wire that comes out under the drive pulley on the engine. I don't know where it was supposed to go, anyone know?

Thanks a lot,
Bob

enjenjo · January 02, 2005, 11:06:07 PM

I believe that wire is for a kill switch. it may be shorting out the ignition. At least it is on my Kohler Magnum series engine.

Bruce Dorsi · January 03, 2005, 01:48:18 AM

Was the engine running OK before the R&R?

Did the engine lay dormant for a long period of time since it was last run? .....If yes, I'd bet on a lazy intake valve, hanging up in the valve guide. .....Kohlers were prone to this problem. .....Some oil added to the gas, along with some run time, should be all that is needed.

Electronic ignition or points-type ignition? ....I assume it is battery ignition, and is not magneto ignition.
.....You are correct that a weak coil or a bad condenser could cause the problem, but coils usually don't act that way when they fail. ....Usually, ignition failures cause hard-starting or no-start conditions, since these single cylinder engines either run or don't!
.....A bad spark plug can cause your symptom.
.....Sometimes, a bad condenser can cause the backfiring on acceleration, but that is not common.
.....If you have points, clean them thoroughly, and burnish them with dry brown paper (think, paper bag!) to remove any traces of oil or moisture. I have seen oil-coated points cause back-firing.

Another possibility, although a slim chance, is a valve seat that has loosened in the block, and causes a valve to seat erratically.

Another cause, which is highly likely, is a clogged jet in the carb nozzle. This creates a lean condition on acceleration, and can definitely cause stuttering. ....You should be able to open the carb adjustment slightly, unless you have a carb without a needle valve.
.....If you do not have adjustability, try increasing the engine speed very slowly, since these engines do not have accelerator pumps. If the engine does speed-up without backfiring, let it run for awhile, and the carb may clean itself.

Electronc ignition modules can fail in crazy ways on small engines, and can drive you nuts! ....A dealer may have a tester, if you suspect a bad electronic ignition.

If it is back-firing through the carb, it is firing while the intake valve is open. ...If it is spitting through the exhaust, it is firing while the exhaust valve is open.
.....If you did not have the engine apart, or alter anything, the ignition timing should not have changed.

I have not worked on an engine like yours, but I have worked on many smaller Kohlers, and the principles are the same.

Good luck!

btrc · January 03, 2005, 07:06:43 AM

Thanks for the replies. Yes, it ran OK just before I took it out, but there were a lot of times it didn't. I'm going to see if they make a carb kit for this and clean the carb up. There was all types of sludge in the fuel bowl. It's strange because it starts so well. I've tried bringing it up very slowly off of idle and it works a little better but then it starts messing up again.
Luckily this had been a record winter with no snow yet.

Bob

Dirk35 · January 03, 2005, 09:41:19 AM

We have ran a few of these on our puller tractors.

Everyone is correct: Backfires would indicate ignition problems. Buy new points, their cheap. Dont get them all greasy. Adjust them properly. Make sure you have a good coil. Make sure you have good wire connections.

Chocking down, bogging, stumbling of the engine on acceleration would indicate crud (rust particles stuck in the needle/seat) in the carb or a varnished needle and seat. I really doubt this would cause backfiring, but it is a good idea to take the carb apart and use a good carb cleaner.

Also, Stabil fuel stabilizer is a great product. The (the lawn mower shops and most of the pullers) say the Briggs and Stratton stabilizer is better, but I havent noticed any difference. Keeps you from having to clean the carb every few years after each winter season on you lawn mower.

40 · January 03, 2005, 10:20:57 AM

Bob....We have had a record mild Winter to this point but I'd hurry with the repairs if I were you....Looks like our luck is about to run out

btrc · January 04, 2005, 06:56:15 AM

Quote from: "40"Bob....We have had a record mild Winter to this point but I'd hurry with the repairs if I were you....Looks like our luck is about to run out

Your right Daryle, By the forcast your going to get dumped on tonight. We are only supposed to get 3-5 inches here. Just my luck, no show all winter and now I'm leaving Thursday night to get my car dwon in eastern Kentucky. Hopefully it (the bad weather) will be a ways ahead of me.

Bob

40 · January 04, 2005, 06:56:32 PM

Bob,Good luck with your trip! If you've got time to stop by on your way home....I'd love to check out your new ride! It's been snowing for a few hours already......the grandson is getting pretty excited.Tomorrow is supposed to be the first day back after Holiday break.....He'd much rather go sledding!!If the forecast is correct....we should have plenty of snow for that

Drive safe and if you need anything.....just yell!

btrc · January 05, 2005, 07:51:58 AM

I changed the coil and condensor and now it runs better than it ever has since I bought it. Just in time as we had a little snow yesterday (about 6 inches) and it just started snowing again, only harder. Daryle, as usual, your getting a lot more than we are here.

Bob

Mikej · January 05, 2005, 08:31:53 AM

I think I getting more than you guys too. :oops:

enjenjo · January 05, 2005, 08:35:44 AM

Quote from: "Mikej"I think I getting more than you guys too. :oops:

That's just bragging

I wouldn't be so sure.

40 · January 05, 2005, 08:48:15 AM

It snowed lightly for a couple of hours and then the storm split....half going South and the other half moving to our North....Just like Moses splitting the sea

We just have a skiff of snow and the 30 mph wind blew it all into the ditches.The weather report says we will not be as lucky with the next wave....up to 12" expected for later today and tonight.
Mike....Everyone is getting more than me....But, at my age...That's a Good Thing

Bob....Glad you got the cat up and running!

purplepickup · January 05, 2005, 11:01:30 AM

Quote from: "40"....Everyone is getting more than me....But, at my age...That's a Good Thing

Geeze Daryle, you're only 48. When I was that young I was getting more than both Franks combined.....then I got married :|

Amazing how a bunch of dirty old farts can turn most any post in the same direction, whether it's about a rear end, a front end, or fixing a bobcat before Mother Nature gives us 12".