PDA

View Full Version : Exmark Navigator question


DLAWNS
09-12-2008, 09:18 PM
I recently demoed an Exmark Navigator at my local dealer. I noticed that when I would shut the machine off it would backfire almost every time I shut it off. I didn't think much of it because it was the demo unit even though it was a brand new machine.
I purchased that same machine about a week later and have now been using the machine for approximately a month. It has still been backfiring quite a bit but I always forget to ask my dealer why that would be happening.
What made me thing to post my question is that while I was cutting today a customer approached me with a question and when I stopped the machine it backfired and he nearly hit the ground because he thought he was getting shot at. Does anyone have any experience with this problem or any ideas how to stop this?
On a side note I was not the biggest fan of this mower when I demoed it last year but it has really grown on me as I have been using it. So if anyone has been on the fence about purchasing one and you have any questions about my likes or dislikes feel free to ask.

2stroke
09-12-2008, 09:21 PM
my Walker would do that same thing. if you are idleing it down it will backfire. try shutting it down at full throttle. thats what i do. no more gun shots.

DLAWNS
09-12-2008, 09:23 PM
Thanks for the quick reply. I was always told not to shut it down at full throttle as it is bad. I have no grounds for that belief, just what I've been told. If it's safe for the mower that's what I will do.

zak406
09-12-2008, 10:46 PM
The only time any of our walkers at work would backfire is when we were losing our engine... i doubt this is your problem but we also idle ours down before we shut off and have no backfiring problems what so ever. however i think you should get it fixed under waranty because that does not sound normal.

STIHL GUY
09-12-2008, 11:00 PM
i had this problem with the walk behind leaf blower. i started to idle it down before shutting it off and the problem was solved

nosparkplugs
09-12-2008, 11:06 PM
The Kohlers are notorious for backfiring all the time from less than 5 hours to 700 hrs, Our Scag Tiger Cub's did it, the Walker does it the only fix is to shut it down wide open throttle, only when I shut it down idling does it backfire. My Kohlers started backfiring with less than 5 hours of use so it BS, that "backfiring" is a sign the motor is "going" out.


To reduce Kohler backfiring:

1.) Always shut down full throttle
2.) use a high quality fuel & fuel additive

zak406
09-12-2008, 11:07 PM
The Kohlers are notorious for backfiring all the time from less than 5 hours to 700 hrs, Our Scag Tiger Cub's did it, the Walker does it the only fix is to shut it down wide open throttle, only when I shut it down idling does it backfire. My Kohlers started backfiring with less than 5 hours of use so it BS, that "backfiring" is a sign the motor is "going" out.


To reduce Kohler backfiring:

1.) Always shut down full throttle
2.) use a high quality fuel & fuel additive
excuse me no spark plugs but if you read my post i said i doubt this is your issue our engines went out at 1940 in hours in the walker im talking about (he never specified the hours on the exmark eather)

nosparkplugs
09-12-2008, 11:17 PM
The only time any of our walkers at work would backfire is when we were losing our engine... i doubt this is your problem but we also idle ours down before we shut off and have no backfiring problems what so ever. however i think you should get it fixed under waranty because that does not sound normal.

You said it yourself "is when we were losing our engine" no hours of use specified could be new or old??? I just stated the facts in my experience with Kohlers

b121774
09-12-2008, 11:21 PM
My walker started backfiring at 4 hrs! Dealer said it's normal.

ffemt1271
09-12-2008, 11:52 PM
mine did the same thing and had to choke it every time i started it.i started using pennzoil full synthetic oil and it doesn't backfire and i don't have to use the choke anymore unless it's really cold

Mowing Freak
09-12-2008, 11:56 PM
This was told to my dad straight from Kohler. They are to be shut down at half throttle or more. I know that goes against the grain but it does with me too. After doing this, I have never had one back fire unless I was trying to scare somebody! Too much backfiring could cause engine damage later too.

DLAWNS
09-13-2008, 09:32 AM
Hey guys, thanks for the replies. I appreciate all the responses. If anyone else has any input by all means lets hear it.

BarrFarms
09-13-2008, 10:18 AM
Seems like backfiring may have something to do with excess heat and uncombusted fuel? I usually idle mine for a min or two while im grabbing and starting the trimmer. This is supposedly good for the engine and it gives it a chance to cool off without load. This theory is adopted from the practises we use on tillage tractors, they are let high idle for 5-10 minutes at the end of the day (12 hr).

Beast12
09-13-2008, 02:21 PM
I have done extensive testing with these Kohler engines and the backfiring. We have them on a couple pieces of equipment (23HP on a Walker and a 25HP on a Vermeer stump grinder).

First, it is best to allow the engine to cool and an idle before shutting it down. Though this does not affect the backfiring.

DO NOT shut if off at full throttle. Instead idle it all the way down the move the lever up a little but so it just starts to rev higher (usually around half). Then you can shut it off. Our machine will NEVER backfire if you do it that way.

Good luck.

-Matt

huskres
09-13-2008, 04:22 PM
The Kohlers are notorious for backfiring all the time from less than 5 hours to 700 hrs, Our Scag Tiger Cub's did it, the Walker does it the only fix is to shut it down wide open throttle, only when I shut it down idling does it backfire. My Kohlers started backfiring with less than 5 hours of use so it BS, that "backfiring" is a sign the motor is "going" out.


To reduce Kohler backfiring:

1.) Always shut down full throttle
2.) use a high quality fuel & fuel additive

My Kohler has always backfired. Louder than hell. I always shut down at full throttle.

grassaholic
09-13-2008, 07:00 PM
I've had this issue with many different air cooled motors but mostly Kohlers. My method has always been to set the engine to idle and let it run for a min. or two before turning it off. This usually seems to eliminate the backfire. If you let the motor backfire enough, you will ruin the muffler and those are not cheap! If your looking to eliminate the backfiring all together, make your next purchase an EFI motor if you can and it will never happen again.

cutbetterthanyou
09-13-2008, 07:10 PM
I've had this issue with many different air cooled motors but mostly Kohlers. My method has always been to set the engine to idle and let it run for a min. or two before turning it off. This usually seems to eliminate the backfire. If you let the motor backfire enough, you will ruin the muffler and those are not cheap! If your looking to eliminate the backfiring all together, make your next purchase an EFI motor if you can and it will never happen again.

my exmark is 26 efi kohler and has backfired since new. i don't worry about it it has 1500 hrs so far so good.

Tadams
09-13-2008, 09:00 PM
I agree with every one that it is bad to shut a mower off at full throttle but my 27hp Kohler also backfires at idle. I asked the mechanic at the mower shop about it and he said that the Kohlers have a fuel shut-off solenoid in the carb that only works at full throttle. Therefore, if you idle it down it does not shut the fuel off which causes the backfiring. I had to replace the exhaust gasket on one side before I was told all of this.

DLAWNS
09-14-2008, 09:04 AM
Thanks again to everyone that replied. I'm going to show my dealer the problem and than start trying all of the suggestions that everyone gave me.

Liquidfast
09-14-2008, 09:40 AM
My Kohler has always backfired. Louder than hell. I always shut down at full throttle.


You may be one of the lucky ones. Just because you put a bullet in a gun and play roulette SUCCESSFULLY doesn't mean you should do it.



.

grassaholic
09-14-2008, 10:48 AM
my exmark is 26 efi kohler and has backfired since new. i don't worry about it it has 1500 hrs so far so good.
Wow thats pretty strange. That was one of the things I liked about my first EFI motor and all the others since. Theoretically when you turn the key to the off position the injectors should immediately stop spraying fuel. Maybe you've got a leaky injector?