14.5 HP Briggs OHV Hard Crank

[Argonne]

The folks I bought my place from reluctantly left behind the only piece of agricultural equipment they owned, their trusty 1999 Murray 42" riding lawn mower that they had named Norville. Norville looks pretty silly sitting amongst all of the equipment I brought to this place, and I really have little use for him, but I figure he deserves a shot at running once again, and with the big dogs, after heroically trying to maintain 17 acres single-handedly.

He starts hard. It doesn't look like a new problem due to the fact that the starter, solenoid, and battery look recently replaced. Feeling smug that I knew what the actual problem was that someone else had thrown a bunch of time and money at, I adjusted the valves. No difference whatsoever. When I crank, the compression stalls the starter on the first compression stroke. Starter gets hot, wiring on both sides of the solenoid get hot, and if I hand crank the engine the compression stroke stops me too unless I spend 5 seconds easing by it.

Is there anything that could be causing this besides a worn camshaft and/or a broken compression release (on the camshaft)? The part will be $80 and a few hours work for a mower I can live without, but I don't want to be looking at something large and red in my junk pile for years.

 

[alchemysa]

I had the same problem with a 17 hp single cylinder OHV B&S. It would not get past the first compression stroke.

The problem was the valve adjustment. I know you said you adjusted them but are you absolutely sure you got it right?

 

[tcartwri]

The decompression mechanism has failed. It holds the exhaust valve open for the first couple of engine rotations. Time to crack the motor open.

 

[Walt 2002]

The decompression mechanism has failed. It holds the exhaust valve open for the first couple of engine rotations. Time to crack the motor open.

Most likely the compression release on the cam has failed but the exhaust valve has no part in compression release and nothing holds a valve open for one turn let alone a couple. The INTAKE valve is cracked a few thousandths of an inch momentarily part way thru the compression stroke and can be detected by close observation IF working. You can probably find a good used camshaft with a little searching.

Walt Conner

 

[Argonne]

Most likely the compression release on the cam has failed but the exhaust valve has no part in compression release and nothing holds a valve open for one turn let alone a couple. The INTAKE valve is cracked a few thousandths of an inch momentarily part way thru the compression stroke and can be detected by close observation IF working. You can probably find a good used camshaft with a little searching.

Walt Conner

Ok, so I should be able to verify the functionality of the compression release if I closely observe the intake valve lifter during the compression stroke. Makes sense. Come to think of it, I suppose if I temporary reduce the lash to zero I could use a dial indicator to measure what is going on.

I haven't gotten deep into a small engine in about 20 years, so I'm tip-toeing into this. I have forgotten most of the general knowledge stuff, like how to remove that frigging pully from the crank without costing myself another 5o bucks, but we have the interwebs these days, so I'll just watch a few YouTube videos!

I had not thought of the used part angle. There are a dozen little shops around here littered with parts machines. I'll bet if I pull the cam and go on a search I'll come back with one for $30...thanks for the idea!

 

[Argonne]

I had the same problem with a 17 hp single cylinder OHV B&S. It would not get past the first compression stroke.

The problem was the valve adjustment. I know you said you adjusted them but are you absolutely sure you got it right?

Yea, I did it like 4 times, 3 by the book and once by cranking both down to about .003. The hard compression never went away.

 

[tcartwri]

Most likely the compression release on the cam has failed but the exhaust valve has no part in compression release and nothing holds a valve open for one turn let alone a couple. The INTAKE valve is cracked a few thousandths of an inch momentarily part way thru the compression stroke and can be detected by close observation IF working. You can probably find a good used camshaft with a little searching.

Walt Conner

Hey Walt,

Sorry but your out of line here. It is almost always the exhaust valve that's held open otherwise you get reversion back through the carb.

Without knowing exactly what motor he has we can only conjecture.

Argonne, make sure you have done the valve adjustments to the letter. The lifter has to be off the compression release when you set the lash.

 

[Walt 2002]

Hey Walt,

Sorry but your out of line here. It is almost always the exhaust valve that's held open otherwise you get reversion back through the carb.

Without knowing exactly what motor he has we can only conjecture.

Argonne, make sure you have done the valve adjustments to the letter. The lifter has to be off the compression release when you set the lash.

You are only adding to your obvious lack of knowledge here. By far the most B&S engines do and have relieved compression via the INTAKE valve. There are exceptions but the B&S 14.5 hp OHV engine is a 28 series engine and they all relieve by the Intake valve, no conjecture here. You need to study a Service Manual a little.

Argonne, I can send you a Service Manual for your engine IF you like, address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com

 

[Argonne]

I'll get the model number when I get home, but I am pretty sure it's the intake valve that the compression release is supposed to bump open. The camshaft gear engages the crank on the output shaft side (engine bottom), and I'm pretty sure the intake valve is the bottom valve evidenced by it's shiny aluminium pushrod. Anyway, the model number will end the conjecture, sorry I didn't post it up front.

 

[Walt 2002]

There is no conjecture. I have rebuilt dozens of these.

Walt Conner