1976 YM240 engine question

furndog · May 29, 2011

Hello Fellow Tractor Friends,

I have a 1976 Yanmar YM240 tractor that I have really enjoyed using. I bought it last September. My uncle has helped me resolve a couple issues, the current being that the back wheels are aftermarket Kubota wheels - the center hole on the rims is larger than the stock wheels, so 6 bolts take all the load on the back wheels instead of the wheel hub. He is making some type of metal attachment to weld onto the inside of the rims so they fit snugly on the hubs and that takes the load instead of bolts.

Anyway, every time I run the tractor, he tells me it sounds bad - it has too much knocking. He had me order a service manual and we are going to take the bottom pan off the engine (sorry I am not overly mechanical) to do some inspecting. I am wondering if anyone can offer any insight as to how the Yanmar diesel engine sounds compared to other diesel engines? Is it known to sound louder with more knocking and pinging?

The engine runs strong (to me), I plowed with the FEL all winter and I have been mowing with my finish mower (my uncle just rebuilt the gear box, it is now a peach) and it runs fine, does not smoke and does not leak any fluids.

Thanks for any help anyone can offer!

Matt in Michigan

California · May 29, 2011

YM240 is famous for that harsh clank. I describe the sound of mine as like a bunch of idiots with sledge hammers pounding on a manhole cover. It really is that harsh. No change since I bought it in 2003. Other posters here say theirs are similar but not as loud as mine.

Click on my sig below, scroll to the bottom, and listen to the two soundfiles. I think you will conclude that your fuel knock is normal.

Power Service Diesel Fuel Additive or similar labelled to increase the Cetane rating will help a little in making the clank less harsh.

clemsonfor · May 30, 2011

California said:
YM240 is famous for that harsh clank. I describe the sound of mine as like a bunch of idiots with sledge hammers pounding on a manhole cover. It really is that harsh. No change since I bought it in 2003. Other posters here say theirs are similar but not as loud as mine.

Click on my sig below, scroll to the bottom, and listen to the two soundfiles. I think you will conclude that your fuel knock is normal.

Power Service Diesel Fuel Additive or similar labelled to increase the Cetane rating will help a little in making the clank less harsh.

I see you have changed over to the politically correct version of the description of your engine knowking sound! I remember what you have said before, much funnier before i must say.

furndog · May 30, 2011

Thanks for the info California - I swear mine sounds exactly like that!

My uncle did help me figure out the proper way to start my Yanmar, he seems to think the lever on the left side (as you sit on the tractor) is a compression lever - you lock it to the left (horizontal) to start so the starter spins freely and then it automatically moves back to the vertical position and starts much easier. Can you confirm this is true? He said you can shut it off my engaging the same lever, but I think the manual says to just to lower the throttle all the way down.

Thanks so much for you help!

Matt

clemsonfor · May 30, 2011

He is part right and part wrong.

You should start your engine with the compression release lever. It will help spin the motor up fast and build oil pressure untill the engine fires off. I start everytime from a cold start like this. After its warm i dont do it that way but just with the key. You do not want to shut it off that way cause supposely your not suppose to. Just lower the fuel to off, if it dont stop pull the rod on the injector pump to close the fuel off.

Some warn that the pistons could contact the pistons using the compression release to stop it. Personally i dont see how the valves dont contact the pistons if they were going to when you spin it up with it open when starting? BUt i follow the manual casue its not hard to shut it off the right way and it wont hurt the tractor that way.

California · May 30, 2011

Furndog your uncle's instincts are right but the details are a little different. Clemsonfor pretty well covered it. That is the compression release in front of your left knee. Twist and hold, crank 8~10 seconds to circulate some oil before attempting to start. There isn't any automatic return, aside from just jarring it back to closed.

Then I twist the key left for another 6~8 seconds to run the ThermoStart (manifold heater).

Then finally twist the compression release to Open, spin the starter, and after an instant as the starter reaches full speed then turn the compression release back to Closed. The reason for this is so the starter doesn't have to push against the diesel's high compression.

It should fire on the first or second compression stroke.

After the first start of the day just start it like a car, twist the key only.

Some diesels have a 'pull to kill engine' lever but these don't. The manual says never use the compression release to stop it [except for an emergency], just pull the throttle to zero. If the throttle won't kill it you need to adjust the linkage.

Aren't these great toys!

Neat 1500 · May 31, 2011

yep mine clanks and bangs too! add some 2 stroke oil to its diesel and that will quieten it down a bit, i do this at 300:1 as this is what i also do to my landcruiser.

shawnjvl · May 31, 2011

Neat 1500 said:
yep mine clanks and bangs too! add some 2 stroke oil to its diesel and that will quieten it down a bit, i do this at 300:1 as this is what i also do to my landcruiser.

We don't have diesel Toyota Landcruisers in USA, I wish we did I would own one.

furndog · May 31, 2011

Thanks for all the help guys, I really appreciate it! I figured out the thermostart by playing around with it with the air filter top off. You can look down and see it glowing after holding it on for a few seconds. I have to turn my key on (to start) and hold the thermostart buttton (without clutch pressed) - I use that in the winter and it really seems to help. I now know to start with the compression lever engaged until it is full speed and then release so I have compressiona and she fires up. I will also be sure to continue to shut it off using the throttle and not the compression release.

Thanks Guys!!