B&S 12.5HP I/C engine turning over a lot before starting


Old 03-08-13, 08:57 AM
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Join Date: Mar 2013
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B&S 12.5HP I/C engine turning over a lot before starting

Hello, I have just found this great site, looks very helpful.

I have a problem with My lawnmower\lawn tractor, its a Husqvarna LT125.

It was running fine last year and I started it once about a month ago and it started OK for having been sat up for about 5 months or so.

Last weekend it wouldn't start, I thought it was the battery since it hadn't charged all winter, so I connected it to my car battery with jump leads and it started OK after a little turning over.

I cut the lawn and then the engine started to loose power and eventually cut out under load. It never did this once in the year If had it. I took it it and cleaned the air filter and spark plug, it started fine with just the battery and seemed to be running great for a while, then the same thing, it cut out under load, at this point I suspected poor fuel not I had put fresh fuel i but there was some in there from last year. When I disconnected the inline fuel filter I saw it was blocked straight away so I replaced it and filled with fresh fuel.

The engine would not start with the battery , just cranked and cranked, it did this for maybe 5 tries before the battery started to fail.

I connected to my car battery again and continued trying to start, eventually I could hear it trying to fire just as I stopped turning the key, a few more tries and it fired up and started running.

Finished cutting the lawn with no loss of power and all was well, no I have tried to start it a couple more times and each time I need to hook it up to the car and its takes a lot more cranking than it used to by far, last time it only started after I stopped choking it (it always used to need the choke).

So question,

Why has it become harder to start since replacing the fuel filter.

Thanks in advance for any help
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Old 03-08-13, 09:26 AM
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Sounds like some trash got dislodged and is now in the carb. A piece is probably stuck in the needle area, allowing the carb to flood a bit which is why you have to start with the choke off. A carb cleaning is in order.
Old 03-08-13, 10:27 AM
Join Date: Sep 2009
Location: USA
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I'd agree you probably need a good carb cleaning.

I'd flush whatever you had in the gas tank out now too. If it clogged the filter earlier, just adding fresh gas won't clean it.

Pull the float bowl off, make sure it's clean, and let some gas flow through the carb while the bowls off. It MIGHT just clean the float valve enough for it to work.
Old 03-09-13, 02:53 AM
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Join Date: Mar 2013
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Thanks a lot for the help guys, now, being a novice, is there a risk of damaging the carb while cleaning it, do I need special carb cleaner?
Old 03-09-13, 05:43 AM
Join Date: May 2006
Location: Iowa!!!!!
Posts: 3,728
There's a lot of good aerosol cleaners out there. You can get them in Walmarts and all auto parts stores. A can of Gum Out or OReilly's does fine. Or you can do a soak cleaner from NAPA. In your case the aerosol should take care of it.

If you have something that's lodged in the float valve, you have more than a varnish problem, so plan on dismantling the carb.

If you're new to that sort of thing, a camera would come in handy to take pictures before taking it apart, step by step. It makes reassembling a lot easier and gives you a reference for doing it. Also if you have problems you can post a picture of what you have here and someone can guide you through it.
Old 03-11-13, 02:29 AM
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Join Date: Mar 2013
Posts: 4
Thanks again for your help, I have ordered some carb cleaner and I'll give it a go.

I have flushed out the fuel tank.

My Engine is Briggs and Stratton 286707 0454 01, I'm going to scour the net for a good how guide for removing and cleaning the carb
Old 03-11-13, 11:53 AM
Join Date: Sep 2009
Location: USA
Posts: 485
A few tips:

1. Before removing the float bowl, using a permanent marker draw a line so that you reinstall it the same way. Some have a flat portion on them, not all.
2. Take pictures BEFORE you remove the carburetor. Make sure that you can see all the linkages CLEARLY.
3. Be careful not to bend any linkages when removing them.
4. Don't crank down any mixture adjustment screws, just turn them lightly until they stop (so you don't score them) then back out as required for initial adjustment.
5. Look into the fuel tank. Is it clean or do you see "shadows" moving along the bottom? Is it metal? How about rust. If in doubt, flush it out. Drain the gas out of it completely and dispose. You can always flush some drygas through the tank and drain it to help get rid of any water or other debris.
6. Before you hook the fuel line up to the clean carb, flush it out. Older fuel lines can deteriorate and rubber particles can get into the carb. If it's doubtful, replace it.
Old 03-11-13, 02:04 PM
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Join Date: Mar 2013
Posts: 4
More good advice, thanks very much, the inside of the fuel line does look a bit rough, I'll replace it.

To be honest I don't feel confident taking off the carb and replacing it, I took a look in the local ads and found someone who works on these machines, he will clean the carb for 25 he says he has and ultrasonic carb cleaner? so I think thats what I am going to do next weekend.

Tonight I tried the engine and it took a little while to start but not has bad as it had been, I let it run for a little while and then tried it again, this time there was a loud bang like a gun and it started up, I turned off and started the engine twice more, both times it started perfectly.

If the engine is flooding should I be turning off the fuel each time If finished with it and let the engine cut out, would this stop it flooding?

Last edited by Julrose; 03-11-13 at 02:26 PM.

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