Lowest working RPM?

[California]

This is my first diesel and I'm trying to learn an 'ear' for proper operation. Warming up at 1800 rpm sounds smooth, but below 1600 cold the diesel knock seems excessive. Even warm, below 1200 rpm it sounds like if it were a gas engine it would immediately ping a hole in a piston. (A stethoscope shows this clatter focused at the injectors, not in the lower end!)

The owner's manual advises warmup at 1500 rpm then slow idle 800 rpm; working speed 1800 to 2400 rpm.

This doesn't sound good to my inexperienced ear. I know its a compression ignition engine but the 1500 rpm warmup and any operation below 1200 rpm, even just idling, has extreme diesel knock.

However the unit is 25 years old and still in great original condition so far as I can see, so it must be designed to withstand its recommended use ???

I would appreciate any advice you experienced operators can share. I've looked around and I see advice on injector pattern, premium 'designer' fuel to match Japanese fuel standards, and advice to simply ignore the racket - 'they all do that'.

Comments? Thanks!

 

[greg_g]

Keep in mind, this is a thumper - two cylinders have a distinctly more "diesel sound" than others. Short of that, perhaps the valves have never been adjusted. It's a 600 hour maintenance item, along with clean/inspect injector nozzles. It's pretty easy to understand what happens the sound of two cylinder engine, when one cylinder has a tendency to cut in and out.

I'm concerned about "warming up at 1800" though. My manual specifies a warm up idle at 1000, and and operating speed of 2200. Doesn't make sense to warm up a tractor at 80% throttle.

//greg//

 

[Trev]

Welcome to the board!

I can only tell you that on my 3-sylinder JD4300, I always start it with throttle at lowest setting, about 800 RPM, give it a minute or two to get the oil circulated a bit, and then bring it up to about 1200 RPM for warmup. I go back in the house, wait 15-20 minutes, and then go out and do my work.

Lately, for snow plowing, I've been just setting the hand throttle at 2000 RPM, and then varying my speed with the foot throttle if I need a little more oomph for pushing back a snowbank or something. (Note: manual tranny rather than Hydrostatic.)

Never noticed any of the kind of sounds you describe.. so don't know if I just don't know what you're hearing or if yours is doing something odd.

HTH,
Bob

 

[Soundguy]

My NH 1920 has a shibaru diesels . I start it up at 800-1000 rpm, and let it sit there for a minute, then may bump it up to 1200 , and then go.

My yanmar 1700.. a 2 cyl.. well lets just say that when I got it I thought it was gonna throw a rod.

These 2 cyl yanmars are what we call yammer-hammers.

Pretty soon you will be able to distinguish between a real 'problem' sound, and the yanmar 'trademark' sound.

1800 seems a tad high to warm up... just my opinion though.. seems like 1000 or 1200 again would be easier.

Soundguy

 

[jimstractors]

The 2 cylinder Yanmar's all run loud, especially at lower rpm's. They call it "yanmar hammer". The 3 cylinder models run much quieter and smoother. Most the older manuals I have suggest warm up for 5 min at 1500rpm. Then working rpm is 2200-2600 rpm. See attached pages.

 

[normde2001]

The best advice is to ignore the racket. Believe it or not those Japanese know what they are doing. All their #'s sound right.

"The owner's manual advises warmup at 1500 rpm then slow idle 800 rpm"

 

[California]

Ok, I'm convinced to accept the idle racket as normal for this two cylinder thumper. I really appreciate the advice all of you have offered. I'll warm it up by the book.

The valves were all .007 to .008 - I assume this is close enough to the .006 spec. At slow idle the tappets are apparent but not loud.

Low rpm full load operation: How about when full rated hp isn't needed? Is it reasonable to work this engine at lower rpm, say 1000-1300 with intermittent loads that make the governor occasionally lose ground for a moment? How slow is too slow for this type of use?

Again, your comments to get me started in the right direction are greatly appreciated. I have a lot to learn!

 

[normde2001]

If mowing, you need to stay at about 2200 rpm to keep the pto at 540 rpm, the rated speed for all mowers. Any other job, just pick an rpm/gear that feels comfy so the engine does not strain/lug, (not a good thing).

 

[jdmar]

I have a 2--hammer 1500 and the JD 4300....TOTALLY different sound/feel/run. I love both but the JD starts up and immediatly runs smoothly. The Yanmar has typical 2-banger "roughness" but I would not idle so high for warm-up. Make sure your oil pressure is OK and let it warm up slower...maybe 1000-1200 about. With work I agree..run it were it feels strong but not needless rpm and definately don't bogg it. For PTO work you do need to run at the right RPM (usually just under "max" by a couple hundred) to keep your implement at appropriate speed. Good luck...I like these little tractors...they work

 

[gbirky]

Diesels have a tendancy to overheat in continuous low speed high load operation. Basically, you aren't moving as much air through the engine, while burning almost as much fuel. The heat has to go somewhere - so it goes to the coolant. Just watch the coolant temperature under these conditions.