Author Topic: Misfiring Briggs & Stratton 17HP Single OHV  (Read 14829 times)

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Offline Scott P.

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Misfiring Briggs & Stratton 17HP Single OHV
« on: June 14, 2014, 10:13:56 pm »
I am stumped. I am working with a 17HP OHV single Briggs, model 311707.

It will start up and idle fine but if I try to rev it up it will misfire and then pop out of the exhaust if I get off the throttle. Sometimes it will eventually come out of the misfire but it still feels like its not very powerful in the higher portion of the RPM band. (See video below)

Here are some things I have already tried to fix the issue:
-Fresh 93 octane
-New spark plug
-Checked and set valve clearance
-Checked and set ignition coil clearance

Current mods:
-Throttle pedal installed in place of the original throttle lever
-Stiffer spring installed on the governor

Some things I noticed...
-When spinning the engine over I noticed that the intake valve seemed to bump open and close a tiny bit after its normal cycle. I don't know if this is some sort of feature for this engine or if something weird is going on with the cam?? (See video below)
-It appears this motor was originally equipped with the solenoid on the carburetor fuel bowl but when I got it the solenoid was gone and the bolt holding the fuel bowl on looked a bit odd,  it was threaded on the outside to and had a small allen set screw inside it. I ended up replacing the fuel bowl, gasket, and bolt and the bolt supplied with the new bowl was just a plain bolt. I am not sure if the original bolt was special or needed?? (See pictures below)

Anyone have any ideas? Does this carb need modification to get anything over stock mower RPM??



Valve opening video: http://youtu.be/fDKIyyLohwg








Offline crazycraftsman

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #1 on: June 15, 2014, 12:29:36 am »
Sounds like the carb has sum junk in it.clean it real good and blow air throw all the holes.  The valve bumps up because it hitting the compression release mechanism on cam .  :)
Owen
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Offline Scott P.

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #2 on: June 15, 2014, 12:40:45 am »
Ahh yess the compression release.

Thank you for the insight Owen, the carb is one thing I didn't go through because when I pulled off the bowl it looked pretty clean. I will order a rebuild kit and go through it thoroughly.

Would you reccomend I get this?..... http://eccarburetors.com/store/needle-jet-kit.html

Offline Rooster

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #3 on: June 15, 2014, 03:08:29 am »
Stop over revving that stock flywheel. That's a good way to get dead!!
Bert stole my cookies!!
 I think he used them to bribe Ed into something naughty?

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Offline Scott P.

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #4 on: June 15, 2014, 06:02:32 am »
Oh really? Is it common for these flywheels to come apart? Does anyone make a scatter shield?

Offline crazycraftsman

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #5 on: June 15, 2014, 11:20:06 am »
I would just clean the carb and get it running proper first. That adjustable jet from ec works great. I would get the billet flywheel if you are going to be reving it over 3800. And what rooster said !
Owen
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Offline birdman_express

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #6 on: June 15, 2014, 02:38:38 pm »
Does anyone make a scatter shield?

Scattersheild is a way to get hurt. Do Billet Flywheel, or leave the GOVERNOR on.
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Offline Scott P.

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #7 on: June 15, 2014, 03:35:51 pm »
Which flywheel do I need?

Is it this one? http://www.arcracing.com/servlet/the-602/ARC-Billet-Flywheel-AVS/Detail

I don't believe my motor is AVS though.

Offline Scott P.

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #8 on: June 15, 2014, 06:40:48 pm »
So I pulled the carb off and started taking a look at things. I think I may have found a problem. The emulsion tube/main jet assembly that is screwed into the bottom of the carb appears to have not been screwed in all the way. From the looks of things when everything is assembled the fuel gets into the carb through a small port on the side and it was blocked by threads.

I am going to rebuild the carb, install the needle jet kit from EC and report back.

Blocked??


Screwed all the way in

Offline crazycraftsman

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #9 on: June 15, 2014, 07:39:24 pm »
Yes it's a non Avs . So make sure you order the non Avs flywheel. Can't believe it ran like that. The motor is kinda rare so don't blow it up. Lol
owen
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Offline Scott P.

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #10 on: June 18, 2014, 09:17:21 pm »
So my jet kit should be here tomorrow from EC and my billet flywheel is on order.

Can someone post up a picture of the throat of this style of carb? I am wondering if the emulsion tube is supposed to protrude into the throat of the carb?

Has anyone tried swapping over to the cast aluminum intake elbow? Is there any power gain from it? Looking at it compared to the plastic one the entry angle to the head is a little straigher.




Offline cycloneracer

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #11 on: June 18, 2014, 10:06:07 pm »
Use the plastic one...............
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Offline Scott P.

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #12 on: June 18, 2014, 10:13:01 pm »
Use the plastic one...............

Oh yea? How come?

Offline cycloneracer

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #13 on: June 18, 2014, 10:25:12 pm »
Keeps carb cooler.   



Smoother flow to head. 


Paul Krueger

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Offline Scott P.

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Re: Misfiring Briggs & Stratton 17HP Single OHV
« Reply #14 on: June 19, 2014, 12:05:18 pm »
I got my adjustable jet kit.

When I screw the tube into the bottom of the carb, it is supposed to be installed until it bottoms out right?

I ask because I notice atleast 1/8" protrudes into the throat of the carb. Is that the way its supposed to be?

 

anything