View Full Version : Briggs and Stratton Engine Problem

07-01-2006, 11:54 PM
Hey everyone! I recently got a riding lawn mower from my grandma that I used to use until they just bought a new one. I went to start it and it starts, but once it gets going it starts vibrating and then once I engage the blade the motor just dies. This is a 12 HP Briggs and Stratton Power Built Engine. The model number is 284707. I was wondering what I could do to fix this situation to get it working again because the mower is in perfect working condition besides this engine problem. I appreciate any ideas that you may have and thanks for the help in advance.


07-02-2006, 11:00 PM
Could be anything from spark plug breaking down to bad fuel. Why don't you install a new plug ,then go with some freash fuel and a bottle of water dryer.If it does not straighten out you might need to clean your carb. and reset your gov. setting. Hope this helps. Georgeharry

07-02-2006, 11:25 PM
Mr. Jeff
I am afraid you are not supplying any specifically useful info. Does it "start vibrating" a little or a lot, is it vibrating because engine is cutting out or what. An engine does not normally get 'unbalanced' somehow and vibrate. And then, once started, is the engine _trying_ to pull the blades when you try to engage them, or is a safety switch killing power to engine? It is even possible a piece of garden hose is wrapped around the blades. Hey, I have seen it happen.These things can be determined by ear if you have some experience with mowers or other power equipment.

07-03-2006, 02:11 AM
Hey Jim,

Well today I first went to start the engine. So I started and it runs alright when the engine is running without the blade engaged but once i moved the lever to engage the blade the engine just starts losing rpm's and then just completely shuts off. And also while I start the engine I noticed that the mower seems to vibrate as I am driving around with it without the blade engaged and then once I engage the blade the engine shuts down.
Now today, I started taking apart some of the engine parts and then I noticed that there was some carbon deposits in the combustion chamber. Could this be a problem related to the blade not engaging or could it even be something with the pulleys? I am giving everything a good cleaning now and I will keep you up to date on how the progress goes. Thanks for the replys.


07-03-2006, 08:17 AM
Sounds like you have a operator presence safety switch (seat or deck engagement) acting up killing the engine. As for the vibration it sounds like a flat spotted drive belt or a bent stack pulley on the engine. Check the drive belt by looking at the edges of the V part making sure the V doesn't get skinny'er at any point. Mower numbers could be of help with the switch problem. It doesn't sound like you have a problem with the engine.

07-03-2006, 05:42 PM
I sometimes assume too much, but it does not hurt to ask. Have you tried pulling the blades through by hand?
With a 12 horse engine, I assume there are at least two blades. Make sure all the pulleys and all the blades turn as you spin one. Restrorob is most likely dead on with it being a operator presence switch; but what if...?
You should use the same logic to assure that all belts and pulleys turn 'normally?' all the way back to motor.
Maybe you should go make us a audio recording of some kind and let us hear it.:clapping: :drinkup: :usflag:
I have honestly pondered trying that very thing on a Kaw that I suspect is going south on me right now. You see, I have been running power equipment for a lot of years, not in a shop, just my own stuff. Well, this racket that I hear coming from one of my Kaw,s defies description.

07-03-2006, 05:51 PM
Oh, I just thought of what it sounds like!
When I first start it, and until it has run at WOT for a few minutes, it sounds like it has a rat, deep inside the round thingie, chewing on the crank stick.:laugh: :laugh: :laugh: :laugh:

07-03-2006, 06:04 PM
LOL :laugh: , but tonight im going up there to check about that operator presence switch tonight and also when I was up cleaning the engine this afternoon I noticed the the drive belt is starting to wear away so it needs replacing. But I realized I have a record feature on my cell phone so tonight I will record the sound of the engine and post it tonight. I will keep you updated on the progress. Thanks for the replys.


07-03-2006, 06:47 PM
.... As for the vibration it sounds like a flat spotted drive belt....

Well, it looks like Restrorob nailed it again. There is little to no difference between belt flat spots and missing V material.
If you do try, it will be interesting to see what you are able to record and then pass along as a sound bite to the forum. Can you actually do that?;)

07-03-2006, 10:27 PM
Hey I did record it on my cell phone, but the quality is horrible and it sounds like a fish tank. But the good news is that the engine is totally fine. The mower is fine now when the blade was engaged and I actually was able to cut, but when the mower is in motion about every 20 seconds the mower seems to stop and then go again and the engine seems to slow down and then go. This happens even when the blade is not engaged so I am thinking it may need a new drive belt. This is really the only problem and then just few minor ones which are no problem to fix, but does this sound like a drive belt because the belt looked worn and a little frayed in a few places? Thanks for the replys!


07-03-2006, 10:47 PM
ALWAYS replace a belt with even the slightest irregularity. The only exception I allow, is when the flat side has a little 'rip' and no idler is involved. By rip I mean a little fray in the back fabric. If the belt has cracks, toss it, if it has flat spots, toss, missing v material, out-a-here. Also, get down really low and study your under carriage _closely_. You may have a 'hidden' belt that you have never noticed.
Unfortunately, 20seconds is too long an interval for a 'skip' due to a belt IMHO. A belt will not take that long to cycle through.

07-03-2006, 11:00 PM
Whoops sorry i meant every 5! I had 20 seconds on my mind because that clip was 20 seconds long. I guess I better read over my posts even harder now. Sorry for the mistake.