Very Well Maintained Mower Won't Start


Old 04-03-07, 08:10 AM
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Very Well Maintained Mower Won't Start

I've got a three year old walk behind mower with a 6.75 HP Briggs
engine. It's called the MRS series, or Most Reliable Start.

Here's the model number:


Unlike most folks who neglect their mowers to death, I don't!
Halfway through and at the end of the grass cutting season I
do a complete engine tear down. All the engine components
are cleaned and checked for problems. When I stored my mower
last year it started easily with one pull.

I checked for spark with a spark tester. Spark is good. The primer
bulb is squirting gas into the carburetor bowl.

Before I start another engine tear down I was hoping someone could
tell me why my mower started so easily right before it was stored
for the winter. I've used gas stabilizer for years, so the gas should
be good. I'm really puzzled.
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Old 04-03-07, 08:27 AM
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Try a few drops of fresh fuel in the carb and see if it will try to start or even run a few seconds.
If it does you prolly got bad fuel, if not then you prolly do not have spark.
Sometimes the cable for the dead man bail gets stretched and if it does not release the engine brake assy far enough it will still still allow the coil ground to contact.
Sometimes you can hold the bail down, and move the lever it actuates by hand just enough.

If you still get nothing we can continue.
Old 04-03-07, 11:28 AM
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Hello Azis.

I can't remember how many years I've used gas stabilizer. I've never
had any problems with gas treated with a stabilizer.

I know I'm getting a spark. My spark tester shows a clean, normal
spark. In case anyone doesn't know what a small engine spark tester
looks like, just type "spark tester 19368" into Google.

What you call the "deadman bail" is also referred to as the "operator
presence control bar." The cable itself seems to be adjusted correctly.
If its too tight the bar won't retract all the way. Just to be sure,
I'll try moving the lever by hand as you suggested.

Sometimes I think its better to be uncaring or ignorant about mechanical
things. Many of my neighbors use their mowers until they won't start.
Then they put it out with the trash and buy a new one. I'm beginning
to feel like I should do the same. (Not really, but problems like this
are pushing me in that direction!)
Old 04-03-07, 02:09 PM
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I cant remember the last time I used stabilizer, oh wait, Never, and I personally have never had a prob.
I can not tell you how many hours I have spent troubleshooting outdoor power equipment, only to find out my inline spark tester was giving or not giving the correct spark indication. They will not detect a bad spark plug either. I don't use nor trust them! If you really want to test your coil, grab the high tension lead and rest the same hand against the block. Then spin the flywheel by hand, that will leave little doubt

Even if and when a spark is seen by grounding the plug to the case, it does not prove that it is doing so under compression. An inline spark tester is supposed to, but I already mentioned my feelings on that subject

It takes very minimal maintenance to keep nearly any lawnmower running until it rusts out. Since you had gone the extra and kept up, I was attempting to offer a few easy to check and quick yes or no's that Should show where the problem is.
If you have fuel and spark, you should have fire.
Assumptions rarely bring results.

Last edited by Azis; 04-03-07 at 02:20 PM.
Old 04-03-07, 04:55 PM
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Red face

Just a thought,if you say you tear the engine down completely,you may not had the flywheel bolt tighten enought,you may have a sheared flywheel key and now it out of time,even though you have a good spark.

Old 04-05-07, 05:21 AM
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After doing a few things, the mower started with one pull.

I purchased fresh gas. I poured last years stabilizer treated
gas out of the gas tank. Even though the carburetor was
checked for damage and cleaned before the mower was stored
for the winter, I repeated the process again.

If you work on your own car(s), I'm sure you check the spark
plug gap before you install each plug. When they started selling
factory gapped plugs for small engines most folks (including me)
stopped checking the gap. In almost all cases the gap should be
0.30". When I checked the gap on the new plug I had just installed
it was slightly off. Probably didn't make any difference, but I adjusted
the gap just to be sure.

All I know about gas stabilizers is that they've worked for me over
the years. I've never had a can of gas that's "gone bad" after
being treated with stabilizer. Maybe the gas had deteriorated.
I don't think I'll ever know for sure.

I just want to thank you guys. I was almost ready to junk this mower
until I posted on this forum.
Old 04-05-07, 06:51 AM
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Thanks for the update glad is was an easy fix.
I have never used stabilizer, mainly because I have never needed it. Have never heard of it being a problem either tho.
Proper storage is the best prevention. Keep it dark and cool and it will last. Extreme heat for extended time, and extreme temp changes in short spans should be avoided.
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