Murray engine troubles

handirifle · Feb 28, 2011

The Dougster said:
Go back and find out who had an engine and was willing to give it to you... Pay whatever it takes for him to ship it to you... Sheesh!

No way am I going to pay big bucks for an unknown engine. It may or may not be the same horse power, may not be in any better condition than mine was. Remember, this mower ran fine when I first brought it home. I have very little faith in used engines. I have seen too many lemons picked up that way and would rather try to fix mine or replace it with new.

The B&S repair guy says this is common with these engines, so any used engine might be just as ready as mine was to do the same thing.

Jim,
I will look again,to see if it is located somewhere else. I got this number off the cowling that covers the flywheel. So far it's the only one I have found.

Progress,
Last night, after studying the B&S web site and reading up on removing the valves on this engine, I made up a makeshift spring compression tool, and managed to get the exhaust valve out. So far I am very optimistic, since I discovered that about 75% of the lip the valve seat rests on, is still intact.

I took some pictures to give you an idea, and record what I chose to do.
I had already removed the valve, but placed it back in like it was when I pulled the head, so you could see what I saw.

First pic is what I saw when I pulled the head off at first.

Same shot, different angle. Notice how the valve seat is angled out, unevenly. It was sticking out on the left side, and resting down inside the plenum on the right.

Next, you can see the damage done when it came loose. In this pic, I have already dremmeled the area a little. There was some metal preventing the valve seat from going back into it's original place.

Next, is a pic of the seat removed and laying on the tire. As far as I can tell it looks perfect. The outer edge of the seat has zero marks on it, indicating no metal has apparently been removed from it, and it is not out of round.

Finally, after I cleaned up the recessed area, I tapped the seat back in place, and slipped the valve back in, to have a look see. It's still, suprisingly, a fairly snug fit. Not sure how much force was required when it was new, but I figure, when my friend Tig welds in the gap areas, I can leave a few extra .000" to make it a tighter fit still.

You can see on the lower left where the valve seat cut away material near the seat. I will get that filled back in too, and grind it smooth. Luckily, that will not have to be a machined surface.

My friend is supposed to come by tomorrow, hopefully, and if he does, I will post updates. I have to go to th B&S web site now and order their spring compressor and some new gaskets. So far all I need are head gaskets, and a gasket for the valve service area cover.

handirifle · Mar 3, 2011

Well, all attempts to obtain a Tig welder, by the friend, have fallen through, so I will look into other methods of repair, short of totally dismantling the engine to take it to a machine shop. That is my last resort, prior to completely replacing the engine.

Molerj · Mar 7, 2011

Not to be pessimistic, but I would be real suprised if you were able to repair this. Just my opinion but an educated one. If and that's a big if, it is able to be tig welded, then you need to have the seat cut & the valve lapped in to proper specs. BTW, I have never heard of anyone doing anything other than peening the old seat back in & as you have shown, there is too much damage for that to happen.

handirifle · Mar 8, 2011

Molerj said:
Not to be pessimistic, but I would be real suprised if you were able to repair this. Just my opinion but an educated one. If and that's a big if, it is able to be tig welded, then you need to have the seat cut & the valve lapped in to proper specs. BTW, I have never heard of anyone doing anything other than peening the old seat back in & as you have shown, there is too much damage for that to happen.

Moler
I have no experience welding alum, but there are a couple possibilities here. First, luckily, the seat is steel, and is a seperate piece of metal, and still in perfect condition. What I need is the repair of the 40% of damaged shelf that it sits on.
I'm not making any bold claims here, just explaining the ONLY options I have left. I just spoke to B&S customer service, and the engine they recommend as a replacement is nearly $900, and that's before tax and shipping. Just a little steep, for a $500 mower.

Honestly, I'm gonna play with my Mig (since the Tig deal fell through) and if that is a zero possibility, then there's some aluminum repair putty or JB weld. I have NOTHING to lose.

Let's see, I can trash the engine now, or "fix" it and hope it works, or worst case, it trashes itself again. I only hope I can patch it and get some use out of it before it goes bye bye. With it costing me $150 each time to get my place mowed, just a few mowings will pay me back.

I can only hope here.

Molerj · Mar 8, 2011

Good Luck! And I agree, a Murray mower isn't worth putting much money into.

handirifle · Mar 9, 2011

I don't care what BRAND it was, if I buy one for $500 I'll not put another $900 into an engine. I'll save my pennies and buy a new Husqy.

By the way, B&S told me that although mine is a 20hp, it has a much larger displacement than current 20hp models and they recommend a 24+. That might be why the discrepancy in model numbers.

handirifle · Mar 18, 2011

Well, I used the gray aluminized epoxy putty, took the dremmel and scored the area to be treated. I then filled in the gap areas with the putty and drove the valve seat back in. I then cleaned up the excess and let it dry.

After a few days of sitting, I lapped the valve to the seat, and put it back together. Crossing my fingers, I started it up. IT RUNS!!!!! I actually mowed with ot for about 30 min, before having to get ready for an appointment.

Not sure how long but time will tell that one.

Now, I did notice some other issue, that valve may not have been the only problem. This one is not as serious. At lower RPM's like below half throttle, it surges, unless the choke is pulled partially out.

Now I have zero experience with governors on engines. i understand what they do, but never seen one work so not sure if this is a gov problem or a carb issue. My gut says carb. What, in either the carb or governor would cause a surging? And it's only below half throttle. Above that it SEEMS fine.

2manyrocks · Mar 21, 2011

Could be the carb passages are partly dirtied up or if it is old enough to still have adjustable needles, that the settings are a hair off.

I'm shocked it is running--next question is how long it will stay running...

It's odd to me that there appear to be several horizontal shaft engines coming out of China, but I haven't noticed any vertical shaft units of any size above the small push mower types.

handirifle · Mar 22, 2011

2manyrocks said:
I'm shocked it is running--next question is how long it will stay running...

I hope it runs a long time, but we will see. I haven't started it again lately, since we've had almost 5" of rain since Friday, and I live in the bottom of a lot of hills = near marsh land. So I have some time before it can be used. If I take it out there now, it will be stuck for a couple weeks in the mud.

The only adjustment on this carb appears to be the idle. From what I have been reading in researching the surge issue, I will order a carb rebuild kit, and go from there. It's leaning towards the fuel pump, at least according to what I've read.