Go Back   Tech Support Forum > Automotive Center > Small Engines

12.5 hp Briggs & Stratton will not fire

This is a discussion on 12.5 hp Briggs & Stratton will not fire within the Small Engines forums, part of the Tech Support Forum category. I have a Briggs 12.5 hp motor that was give to me with a siezed up exhaust valve. I took


Reply
 
Thread Tools Search this Thread
Old 05-13-2011, 01:17 PM   #1
Registered Member
 
Join Date: May 2011
Posts: 4
OS: Windows xp



I have a Briggs 12.5 hp motor that was give to me with a siezed up exhaust valve. I took the motor partially apart to replace the valve and valve spring. I reassembled the motor with the cam and crank sprockets aligned per their marks. I have fuel, spark, air/exhaust, but the motor refuses to fire up. I have sprayed ether to see if it would fire off that, and have even sprayed ether in the combustion chamber and tried it that way. Still no fire. With the plug wire removed and engine cranking, I have a good spark. I have fuel inside the carb bowl and can feel the exhaust pumping out of the muffler. Does anyone have an idea what would keep this engine from firing?

__________________
dt21 is offline   Reply With Quote
Old 05-14-2011, 09:53 PM   #2
Registered Member
 
2and4StrokeTech's Avatar
 
Join Date: Apr 2011
Location: Arkansas
Posts: 63
OS: win XP SP3



How's the compression? Is the intake valve moving/seating?

__________________
2and4StrokeTech is offline   Reply With Quote
Old 05-15-2011, 02:15 PM   #3
Registered Member
 
Join Date: May 2011
Posts: 4
OS: Windows xp



I ran a compression test and have almost no compression. It also leaked down almost immediately. I'm assuming I'm going to have to replace the rings and lap/grind the valves too. Any ideas/suggestions?
__________________
dt21 is offline   Reply With Quote
Old 05-17-2011, 05:49 AM   #4
Registered Member
 
Join Date: Jun 2010
Posts: 375
OS: Vista Ultimate SP2 32 bit



What are the engine numbers? Model, type and code.

It's hard to get a compression reading from Briggs & Stratton because of the compression release. Check you valve clearence before you do anything else. Should be between .004 and .006 for both valves.
__________________
jrrdw is offline   Reply With Quote
Old 05-18-2011, 10:56 AM   #5
Registered Member
 
Join Date: May 2011
Posts: 4
OS: Windows xp



The engine is a 286707 type 0441.01 It's a vertical shaft engine with standard valve set up.
__________________
dt21 is offline   Reply With Quote
Old 05-18-2011, 11:43 AM   #6
Registered Member
 
Join Date: Jun 2010
Posts: 375
OS: Vista Ultimate SP2 32 bit



Set the spark plug gap at .060, that will simulate the spark plug being under compression and fuel conditions. Just because the spark plug fires laying on the head bolt or muffler doesn't mean it's sparking inside the combustion chamber.

Checking the valve clearance has to be done when installing a new valve. Check the clearance in between the valve tappet/lifter and the valve stem that sticks out of the spring. There must be clearance there when the valve is all the way closed and the piston is at top dead center on the compression stroke.

Does this engine have a cast iron sleeve in the cylinder?

With the numbers you just gave ignore the clearances I gave in the prior post, I thought this was a smaller engine.
__________________
jrrdw is offline   Reply With Quote
Old 05-19-2011, 10:35 AM   #7
Registered Member
 
Join Date: May 2011
Posts: 4
OS: Windows xp



I will check that valve clearance and see if that is the problem. It may take a couple weeks when I get the time though. I appreciate your help. Thanks!
__________________
dt21 is offline   Reply With Quote
Old 11-07-2013, 05:02 AM   #8
Registered Member
 
Join Date: Nov 2013
Location: pennsylvania
Posts: 2
OS: Windows 7 service pack 1



Have you checked that the fly wheel key way matches the key way on the shaft, the spark from the mag has to arrive at a specfic time. If off, it will never ignite when its suppose to.
__________________
jamez46 is offline   Reply With Quote
Old 11-07-2013, 05:06 AM   #9
Moderator Offline
 
Basementgeek's Avatar
 
Join Date: Feb 2005
Location: Ohio, USA
Posts: 11,553
OS: XP Pro SP3/Vista Ultimate SP2/Win7 64 bit



Hi and welcome to TSF jamez46

I assume they have it figured out by now as this is a two+year old thread.

BG
__________________

ASAP member since 2006

Four boxes keep us free: the soap box, the ballot box, the jury box, and the cartridge box.

Basementgeek is offline   Reply With Quote
Old 11-07-2013, 05:18 AM   #10
Registered Member
 
Join Date: Nov 2013
Location: pennsylvania
Posts: 2
OS: Windows 7 service pack 1



I had an atv that quit running on me, and even though I had spark at the plug end, I needed to find out is there was spark at the other end of the plug, which turned out that there was not. I simply used an allegator clip to connect the cathode of the plug to gnd, cranked it over and no spark. Changed the plug and all is well.

__________________
jamez46 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Briggs and Stratton 18hp VTwin
I have a Briggs and Stratton 18 hp Vtwin on my Woods 6180 mower and am having problems with oil sucking up into the air filter. I am using straight number 40 engine oil. I have it filled to the dipstick mark or maybe a little below. The mower has approximately 650 hours on it. Any ideas what...
Chevyman22360 Small Engines 3 07-16-2011 03:50 AM
briggs and stratton 20hp intec carb problem
dual barrel carb.....the engine starts on full choke, as you start to slide choke in rpms ramp up to a scary point. the throttle lever seems to give no response, at the engine when it is running the throttle/governer linkage is clear against idle screw. but if i take off choke it is like the thing...
prowler19762001 Small Engines 5 04-26-2011 10:33 AM
Briggs and Stratton
My Briggs and Stratton will start but not keep running.
Roy Allan Small Engines 2 04-05-2011 08:22 PM
briggs and stratton intermittent spark
i have a briggs and stratton motor fitted to a scott bonnar mower. the engine was new about 5 years ago and has not missed a beat. recently it has intermittently refused to start and checking the spark plug there in so spark. i cleaned and tested the spark plug with no spark.in the end i pulled the...
kowalskichris Small Engines 2 04-02-2011 06:30 PM
850 series briggs and stratton fuel problems
I have a poulan pro tilled that has a 850 series briggs. It is getting gas to the carb but not to the cylinder. You can pull and pull with no results. If u force feed the gas thru the carb by spraying it thru the throat of the carb then it will fire up and run u til it runs the gas out that u...
jmathews Small Engines 2 03-19-2011 03:45 AM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is on
Smilies are on
[IMG] code is on
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Post a Question


» Site Navigation
 > FAQ
  > 10.0.0.2


All times are GMT -7. The time now is 05:15 PM.


Copyright 2001 - 2014, Tech Support Forum

Windows 7 - Windows XP - Windows Vista - Trojan Removal - Spyware Removal - Virus Removal - Networking - Security - Top Web Hosts