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Scotts Mower w/B&S Engine - Won't Start


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04-11-08, 03:04 PM   #1  
Scotts Mower w/B&S Engine - Won't Start

I have a Scotts mower with a Briggs and Stratton 6.5hp Intek Edge OHV engine. It worked at the end of last season but now when I try to start it nothing happens.

I put in fresh gas and changed the plug. Thinking it might be clogged, I even broke down the carburetor and everything looked spotless.

When I try to start it with the air filter off, I get a small pop and can see a flash. Once in a while I even get what sounds like a backfire but the engine never turns over.

Any suggestions are appreciated. . .

 
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04-11-08, 05:14 PM   #2  
Did you try grounding the plug wire or plug to see if it sparks, so you know which direction you need to lean toward? (fuel or spark)?

 
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04-11-08, 05:50 PM   #3  
Did you use the correct spark plug?

What gap did you use on the plug?

Try priming the engine with a little fuel and see if it will start that way, if so then there may still be a carburetor problem.

 
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04-11-08, 08:16 PM   #4  
Posted By: ecman51` Did you try grounding the plug wire or plug to see if it sparks, so you know which direction you need to lean toward? (fuel or spark)?
Since I was getting a flash out of the air cleaner base (when the filter was removed) I assumed a spark was present. Is this something you would still recommend I try?

 
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04-11-08, 08:21 PM   #5  
Posted By: AAWrench Did you use the correct spark plug?

What gap did you use on the plug?

I matched the replacement plug with the one that was left in at the end of last season. I did not, however, verify the gap. I'll pull it and make sure it'scorrect (.020 I believe).

Try priming the engine with a little fuel and see if it will start that way, if so then there may still be a carburetor problem.
Good suggestion. I'll give this a shot also.

 
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04-12-08, 04:32 PM   #6  
Follow-up

I spent the afternoon working on this again . . .

As suggested, I verified that the gap on the plug is right and I tried priming the engine but still no luck. In addition, I drained the fuel tank and refilled with fresh gas.

I tried to ground the plug and check for spark but it was impossible without assistance. However, after breaking everything down I get a louder "backfire" then I did before. (I'm assuming that the backfire isn't possible without spark).

Not sure if I'm making progress or just making things worse?!

 
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04-12-08, 09:40 PM   #7  
Have you tried an other new spark plug yet?? Sometimes they get carboned up & can't properly fire under compression. Try a new one again just for goofs... Roger

 
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04-13-08, 12:26 AM   #8  
Does it even have compression? It's beginning to sound as if you have an intake valve stuck open.

The mower was running fine when it was put up last?


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04-13-08, 07:58 AM   #9  
Posted By: cheese Does it even have compression? It's beginning to sound as if you have an intake valve stuck open.

The mower was running fine when it was put up last?
It worked fine when I put it away for the winter. When I pulled it out earlier this week I got nothing nothing. Now it's just a sporadic backfire.

What's involved in diagnosing a stuck intake valve?

Thanks for the continued help!

 
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04-18-08, 10:31 AM   #10  
Follow-up

Well I was finally able to spend some more time working on this. I tried grounding the plug and checking for spark but from what I could tell I got nothing!! So, assuming this is the problem where do I go from here? Replace the magneto?

I noticed that I never posted the model information. It's a 6.5hp B&S / Model 121682-0122

 
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04-19-08, 01:26 AM   #11  
Go with another brand new plug first off. Then if still nothing, make sure the deadman bar calbe is getting a full pull on the kill switch and engine brake assembly. If so, then remove the kill wire from the coil and check for spark. If still no spark, replace the coil.


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04-19-08, 05:09 AM   #12  
Thanks for the continued advice, Cheese!. I'll take another look today and post the results.

 
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04-19-08, 05:16 PM   #13  
Spent another hour on this. . .I am definitely getting a good spark. Strong and blue but still nothing. Absolutely no indication that the engine is even trying to turn over.

Sorry to keep dragging this one out but. . . any suggestions?

 
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04-19-08, 05:46 PM   #14  
You never said anything more about the compression suggestions. I also was leaning that way as I got deeper into the thread and all you have said up til now.

Like maybe when you shut it off working last season, a valve was open, and for some odd reason some crud in the cylinder either broke loose, from it drying out, or somehow else, and is now holding it open enough to lower compression and allowing combustion to go up that valve to cause backfire.

 
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04-19-08, 07:24 PM   #15  
Admittedly, my knowledge of small engine repair is limited which is what makes this forum so helpful!

As I posted, I'm not sure how to go about diagnosing a compression problem (stuck valve). Any direction would be greatly appreciated.

 
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04-19-08, 09:21 PM   #16  
You know how a lawnmower engine feels when you pull the rope....it has a compression stroke that is a harder spot to pull through then the rest of the time it spins. During this time you are compressing the air in the cylinder. Do you feel this resistance when pulling the pull rope? If not, you have no compression due to either a stuck valve or broken connecting rod.


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04-20-08, 08:41 AM   #17  
Thanks for the lesson, cheese! At least I'm learning something during this whole process

Anyway, I ran a test with the plug out and then with the plug in and there was little or no difference in the feel of the pull. It would seem that we're narrowing down the possibilities to a stuck valve or broken connecting rod? Any other possibilities or is this where my attention needs to be focused?

 
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04-20-08, 12:57 PM   #18  
Finally!

Once I started looking closely at the compression it was obvious something was wrong. I broke everything back down including both valves. Although they weren't sticking, I noticed 2 things:

1. The Cylinder Head Plate Gasket was deteriorated in multiple spots.
2. One of the Rocker arms didn't seem to be adjusted properly.

I replaced the gasket and put everything back together. Not sure if only one of these was to blame but there was a noticeable difference simply spinning the flywheel by hand.

Long story short, it fired on the very first pull!! A few more adjustments and it was running perfectly. Thanks for all the help. Now for the string trimmer!

 
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04-20-08, 11:49 PM   #19  
Great! I tend to think there was a valve problem involved here...especially if the rocker arm was out of adjustment.


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