Murry lawn tractor Model 40604B

[Rivets]

Please just buy the gaskets you need. Yes, I know it will cost a bit more, but if the problem would not bet solved we will know that it is not from trying to save a buck or two. Those who say cardboard will work just fine can start hating me now, but you have to go to the back of a very long line.

 

[Harold2689]

Ok, I'll look more at the carburetor. What you say makes sense, and does provide an answer as to why the oil is diluted with gas. I'll start by taking the bowl off of the carb and check the float to see if it cuts off the fuel flow. There is a manual fuel shutoff valve and an in-line fuel filter between the fuel tank and the carb, but I never use it to shut off the fuel flow.

This problem seems a lot simpler than the head gasket, etc., and if it is the problem, I'll leave well enough alone, and won't take the head off at all. I will need to buy or make a few gaskets to replace those for the intake, exhaust, and the one for the breather cover over the valve springs. It will be a few days until I can get back there to work on it, but I will definitely keep this thread updated.

Thanks so much for all of your help and advise.

Ok, I removed the carburetor last week, and finally got to it today. When I removed the bowl, everything looked ok. I blew in the fuel line and manually raised & lowered the float, and it did cut off my air flow. I put it all back together, and cleaned everything as best I could. I made new gaskets (I picked up a small amount of material from the local garage who does all our auto work) and put everything back together. I think you were dead on the money with the float shutoff sticking open. When I opened the drain plug to drain the oil out of the crankcase, BLACK GASOLINE poured out! It had the viscosity of gas, it smelled like gas, but it was black from having diluted all the oil in the crankcase. It is supposed to hold a quart of oil, but I drained almost 2 quarts of gas out of the crankcase. THAT'S why it wouldn't run! I'm guessing that every time the piston want down to the bottom of its stroke, gas-diluted oil was blowing by the rings, and the valve guides, and flooding the cylinder. With the spark plug loose, much of it was blowing out the spark plug hole and the exhaust. Thus all the smoke, and not being able to run.

After I had everything put back together, I refilled the crankcase with 10W-30 synthetic oil, put in a new spark plug, opened the manual fuel shutoff valve, and hit the starter. I'll bet it didn't make two revolutions, and it fired off! I didn't have the top blower shroud on yet because I just wanted to see if it would run. It ran fine, and started to burn residual oil off the muffler, but NO smoke was coming out the exhaust!

I shut it down and completed the reassembly of all the cooling shrouds, and fired it up again. I let it run for several minutes at high speed, with no load, and it ran quite well, with one misfire about every ten seconds or so. After it warmed up, I drove it out of the garage, engaged the blade, and actually cut a little grass. Under load of the blades and moving forward, it never missed a single time. It appears to be running as good as ever now. When I brought it back into the garage, I shut off the manual fuel shut off, and let it run out of gas.


All back together...


Now, the only thing left is to reinstall the front grill and hood.

I want to thank you so much for your help. It really made this repair a lot easier, and it is greatly appreciated.

Harold

.

 

[Harold2689]

Today I put the rest of the "pretty stuff" back together. Reinstalled the front grill & the hood. It fired right up and I actually cut the grass with it. It ran great! Before all this happened, I usually ran the throttle about half way to get a comfortable engine rpm and forward speed in 4[SUP]th[/SUP] gear. Today, I barely had the throttle at one-quarter. It is running strong and smooth...

This thing was made in 0272, so it's 44 years old!

It's actually running here, no smoke, and it's purring... 44 years old! Imagine what it'd look like if I washed and "polished" it!


Thanks again for your help!


Harold

 

[NorthBama]

good work Harold nice looking 32 year machine

 

[BlazNT]

Today I put the rest of the "pretty stuff" back together. Reinstalled the front grill & the hood. It fired right up and I actually cut the grass with it. It ran great! Before all this happened, I usually ran the throttle about half way to get a comfortable engine rpm and forward speed in 4[SUP]th[/SUP] gear. Today, I barely had the throttle at one-quarter. It is running strong and smooth...

This thing was made in 0272, so it's 44 years old!

It's actually running here, no smoke, and it's purring... 44 years old! Imagine what it'd look like if I washed and "polished" it!


Thanks again for your help!


Harold

Your mower is a 1990 with that date code. I would need to see the sticker to know for sure. This is a 32 year old murray. Born in 1984.

 

[bertsmobile1]

Nice to hear you have it up and running.
However your method of use concerns me.
Mowers should always be used at full revs ( ~ 3600 rpm)
Working at lower speeds can and does damage the engine and is not helpful to the rest of the mower either.
You have a speed controller to vary your ground speed.

 

[Harold2689]

Your mower is a 1990 with that date code. I would need to see the sticker to know for sure. This is a 32 year old murray. Born in 1984.
View attachment 30034

I assumed it was manufactured in February of 1972. In any event, It's still in pretty good shape for being 32 years old... :thumbsup:

 

[Harold2689]

Nice to hear you have it up and running.
However your method of use concerns me.
Mowers should always be used at full revs ( ~ 3600 rpm)
Working at lower speeds can and does damage the engine and is not helpful to the rest of the mower either.
You have a speed controller to vary your ground speed.

All my life (and I'm now 70) my dad always chastised me for running any lawn mower or small engine, "wide open." I guess as I grew older, I outgrew the desire to always have an engine running so fast, and now, "slow and easy" still gets the job done. Apparently it hasn't hurt this 32 year old engine and tractor running it that way, as the only problem I had here, after 32 years use, was a one-time, stuck open float valve in the carburetor.

I currently drive a 2000 Ford Ranger truck with 192, almost 193,000 miles on it, still with the original clutch and original disc brake pads. My last vehicle was a 1986 Ford Taurus MT-5 (manual transmission 5-speed). When I got rid of it, it had 211,000 miles on it, also with the original clutch. I did, however, change brake pads on it a few times though...

At my age, I've slowed down, and I believe I'll keep running my mowers and vehicles "slow and easy" too. It's been getting the job done for 32 years so far, and as long as I can keep it running, I'll continue down that same road...

 

[bertsmobile1]

A govened engine runs at the speed that the govenor is set for.
A direct throttle engine is a different matter as you can over rev it.
It is not just the engine, the blades are designed to work at a specific speed, bearings are designed to run at specific speeds to get the desired up draft and clean cut.
If you are happy then it is your mower and you are entitled to do with it as you wish.
OTOH this is a public forum so it is important that correct information is presented.
I currently run a 1981 L300 that had done 1,360,000 km and is still on std bore although it has been reringed twice and had 2 sets of big ends.
Neither of the bearing changes were necessary but they come as a kit complete with pistons .

However it is warter cooled and mower engines are mostly air cooled.
Older engines were over cooled , you could run them forever with 2" of mud packed around the cylinder & head but newer ones will cook at the drop of a hat and the slower the engine runs, the worse it cools.
Also the slower the engine runs the less the alternator output is and in some of my customers case, they had been replacing batteries every year or two for this reason.

 

[BlazNT]

View attachment 30035
I assumed it was manufactured in February of 1972. In any event, It's still in pretty good shape for being 32 years old... :thumbsup:

Murray used the code differently. 2 is the year in this case 1992 and 27 is the day of the year. So it was born on January 27, 1992
The date code for the 90"s and newer is DDDY
Model number explained for this and newer years is first 2 numbers is deck size. Next 4 is model number. Anything after that and it is a code for who it was manufactured for.