Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

Briggs Stratton Head Pressure


MHConst's Avatar
Member

Join Date: Feb 2007
Posts: 1

02-21-07, 06:02 AM   #1  
Briggs Stratton Head Pressure

I have a MTD yard machine Briggs & Stratton 14.5 HP/42" Cut. When trying to start the engine, it cranks over in slow spurts as though the battery is dying. It can't get enough starter speed to start. When I take out the spark plug and crank the engine it cranks fine at full speed. I have been told that the engine has a valve in it that releases head pressure during start up, and that the valve is stuck. The mechanic wants $400-500 to repair it. He said he has to open the crank case.

 
Sponsored Links
Azis's Avatar
Visiting Guest

Posts: n/a

02-21-07, 07:49 AM   #2  
Azis
Posted By: MHConst I have been told that the engine has a valve in it that releases head pressure during start up, and that the valve is stuck. The mechanic wants $400-500 to repair it. He said he has to open the crank case.
Compression release uses the exhaust valve to relieve compression during start-up. The mechanism is in the crankcase however I think it failing is rare.
I would start with a good strong battery. Post the model #'s of your engine and or mower and specs can be provided to check your valve clearances.
I think for Briggs .004 Intake, .007 Exhaust should get it.

 
backyardwonder's Avatar
Member

Join Date: Jan 2007
Posts: 105

02-21-07, 02:51 PM   #3  
Just a comment - If an owner happens to put a tablespoon of oil in the cylinder to prepare for post season storage, as often suggested in the manuals, the first startup can be very difficult due to the increased compression provided by the oil.

Usually, a couple teaspoons of gas into the cylinder in enough to thin out the oil and allow compression to drop to normal.

 
gardener321's Avatar
Member

Join Date: Dec 2006
Posts: 180
SC

02-21-07, 06:29 PM   #4  
Need to know: Overhead or L head engine?
OHV Compression relief, can not raise the intake valve enough to bleed off some compression on start up if valve clearance is excessive and valves must be properly adjusted.
L head: the little device on the cam that raises the valve breaks or the spring does and you don't get the benefit of hissing of a little air on start up, Which after successive start attempts could overheat the starter motor.
To sum it up, the OHVs are notorious for this and need periodic valve lash adjusting.
In either case, if the little flipper on the cam is damaged, I don't remember it being serviceable and in that case you would need a new cam. That is why the mechanics quote seemed high.
I believe in nine out of ten cases, valve adjust will fix you right up.
Customer two weeks ago same problem, wanted a new starter. Adjusted his lash and he was tickled pink to get off will one hour labor. Want to hear what you find

 
cheese's Avatar
Forum Topic Moderator

Join Date: Jul 2001
Posts: 16,565
GA

02-21-07, 07:44 PM   #5  
This would be an ohv engine, and I agree...you just need to adjust your valves. There are some Briggs engines known to have bad compression release mechanisms on the cam, but most of the time this is not the case. A simple valve adjustment is probably all that's needed. $400-500 is pretty darn expensive even if it does need a new camshaft.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
paoylin1's Avatar
Member

Join Date: Nov 2008
Posts: 5

11-06-08, 05:24 AM   #6  
Posted By: gardener321 Need to know: Overhead or L head engine?
OHV Compression relief, can not raise the intake valve enough to bleed off some compression on start up if valve clearance is excessive and valves must be properly adjusted.
L head: the little device on the cam that raises the valve breaks or the spring does and you don't get the benefit of hissing of a little air on start up, Which after successive start attempts could overheat the starter motor.
To sum it up, the OHVs are notorious for this and need periodic valve lash adjusting.
In either case, if the little flipper on the cam is damaged, I don't remember it being serviceable and in that case you would need a new cam. That is why the mechanics quote seemed high.
I believe in nine out of ten cases, valve adjust will fix you right up.
Customer two weeks ago same problem, wanted a new starter. Adjusted his lash and he was tickled pink to get off will one hour labor. Want to hear what you find
Hi,
New to the site, but I have a problem similar to this. I have the L engine and noticed that I can't adjust the valves. exactlly how do you remove the compression for the engine to start? would replacing the cam be difficult?

 
Imtiaz's Avatar
Member

Join Date: Jun 2010
Posts: 1
OK

06-15-10, 07:52 PM   #7  
how to adjust L Head valves for compression release

Posted By: cheese This would be an ohv engine, and I agree...you just need to adjust your valves. There are some Briggs engines known to have bad compression release mechanisms on the cam, but most of the time this is not the case. A simple valve adjustment is probably all that's needed. $400-500 is pretty darn expensive even if it does need a new camshaft.
hey cheese, can you please explain how to adjust the L head valves so that i get the compression release on my tecumseh engine. i have the same problem as many do of engine is hard to spin due to compression lock up. engine model # VLV55 501029A. appreciate very much.

 
BFHFixit's Avatar
Forum Topic Moderator

Join Date: Jun 2007
Posts: 1,759
KS

06-15-10, 09:48 PM   #8  
Not to speak for cheese but, on Lhead engines, there is no "adjustment" for lash, valve clearance is changed by grinding the valve stems.

 
Search this Thread