K301 - RPM while mowing

[Bar Nuthin 336]

Searched the forums but didn't find anything.

 

I'm curious to peoples' thoughts on what RPM they operate their Kohlers (K301) for extended mowing. My engine seems pretty decent, no smoking or out of the ordinary knocking. It just seems that operating for a couple hours at a time at full throttle/RPM would be abusing the engine. Of course, RPM will directly affect blade speed.

 

What do you experienced guys run yours at when mowing?  FYI - 1976 C-120 Automatic with a newer 42" SD deck. I haven't mowed with it yet, other than a few test strips.

 

[Racinbob 11,120]

As long as your max speed is properly adjusted you do want to mow at WOT. It won't hurt the engine. Same for most any of the PTO driven attachments. One exception is a sickle bar mower. I run that tops at 1/2 throttle, sometimes less. 

[pfrederi 17,788]

Keeping RPM up is important for quality cut and in your case keeping the hydro fan moving enough air to keep it cool.

[Bar Nuthin 336]

13 minutes ago, pfrederi said:

Keeping RPM up is important for quality cut and in your case keeping the hydro fan moving enough air to keep it cool.

 

That's what I love about this site. You get answers, supported by logic and experience.

[kpinnc 12,299]

The upper limiting factor on a K-series or Magnum engine so far as operating RPM is the cast flywheel. For a stock engine, that limit is 3600 RPM. When pullers modify an engine to go faster, the flywheel is the first thing they change. Point being, the internal components can tolerate much higher speeds. 
 

The lower end should be half throttle, or 1800 RPM. That is because the engine is both splash lubed and air cooled. Running less  for extended periods result in both poor lubrication as well as excessive heat. 
 

Point being- these engines were designed to run literally thousands of hours at 3600 RPM. Your engine is actually happier at full throttle! 
 

So make sure the cooling fins are clear and the sump full of oil, and work that Kohler! 

[Bar Nuthin 336]

2 hours ago, kpinnc said:

The upper limiting factor on a K-series or Magnum engine so far as operating RPM is the cast flywheel. For a stock engine, that limit is 3600 RPM. When pullers modify an engine to go faster, the flywheel is the first thing they change. Point being, the internal components can tolerate much higher speeds. 
 

The lower end should be half throttle, or 1800 RPM. That is because the engine is both splash lubed and air cooled. Running less  for extended periods result in both poor lubrication as well as excessive heat. 
 

Point being- these engines were designed to run literally thousands of hours at 3600 RPM. Your engine is actually happier at full throttle! 
 

So make sure the cooling fins are clear and the sump full of oil, and work that Kohler! 

 

Mine seems to be happiest around the 2500-2800 rpm range.  At least that's what my cheap induction tachometer is telling me. 

 

I'm not sure I've hit the sweet spot with tuning it yet.  I plan on taking a second look at my valve clearances and points gap. Feels like I have early detonation at higher rpm's.

[kpinnc 12,299]

On 11/7/2024 at 8:01 PM, Bar Nuthin said:

I'm not sure I've hit the sweet spot with tuning it yet.  I plan on taking a second look at my valve clearances and points gap. Feels like I have early detonation at higher rpm's.

Probably a good idea to check your points adjustment as well. 
 

There should be a peep hole at the front of the flywheel cover. If you slowly turn the flywheel, you should find a mark on the flywheel visible in that hole. Just set an old analog ohmmeter across your points, and they should break as the flywheel mark becomes visible in the hole. 
 

 

[Bar Nuthin 336]

1 minute ago, kpinnc said:

Probably a good idea to check your points adjustment as well. 
 

There should be a peep hole at the front of the flywheel cover. If you slowly turn the flywheel, you should find a mark on the flywheel visible in that hole. Just set an old analog ohmmeter across your points, and they should break as the flywheel mark becomes visible in the hole. 
 

 

 

I was just looking at that today, I found the timing mark (marked "S") but need to borrow or buy a meter. Probably ought to own a multimeter anyways. Any recommendations for a hobbyist entry level meter?

[kpinnc 12,299]

5 minutes ago, Bar Nuthin said:

I was just looking at that today, I found the timing mark (marked "S") but need to borrow or buy a meter. Probably ought to own a multimeter anyways. Any recommendations for a hobbyist entry level meter?

Analog meters are becoming few and far between. Even more so with a decent quality. 
 

I was always impressed with the old school Simpson meters, but never got to keep one of the old ones issued back in the day from the phone company. I settled for a clone, but it’s been good for about a decade. 
 

I guess Craigslist and other auction sites might occasionally have these. 
 

 

Edited November 9 by kpinnc

[Bar Nuthin 336]

@kpinnc Going through my toolbox and found this El Cheapo meter. Has to be at least 30 years old. Couple of fresh batteries and it seemed to work fine.

My tractor ran noticeably smoother after adjusting the points gap to .018. Who'd have thought such a small change would produce such results?

Bad news is the bottom contact on these points is almost fried already - so I'll repeat the process with a new set when I get them. I also ordered the little push rod that rides the camshaft.

 

Edited November 10 by Bar Nuthin

[kpinnc 12,299]

3 hours ago, Bar Nuthin said:

Going through my toolbox and found this El Cheapo meter.

Plenty good enough for testing your points break! 

[lynnmor 7,338]

13 hours ago, Bar Nuthin said:

@kpinnc

Bad news is the bottom contact on these points is almost fried already - so I'll repeat the process with a new set when I get them. I also ordered the little push rod that rides the camshaft.

 

If the points have a significant uneven wear (buildup on one side and pitting on the other), replace the condenser.

[Bar Nuthin 336]

On 11/10/2024 at 9:40 AM, lynnmor said:

If the points have a significant uneven wear (buildup on one side and pitting on the other), replace the condenser.

 

Turns out the tractor did not have the correct coil (no internal resistor). Most likely the reason for smoking the points so quickly.  New coil, points (+ rod) and condenser installed!

With the new cam push rod, the static timing set the points gap back to .020

 

Edited November 19 by Bar Nuthin

[Fordiesel69 263]

3600 rpm is needed for proper airflow.  When you run the engine at a low RPM, which was previously mentioned at 1800 RPM the engine produces much less HP.  RV generators that used onan or kohler engines often ran 1800 gensets (for sound) and these were normally big K301 / K321 engines rated at like 7 or 8 HP, with a fairly low wattage generator end.  Conversely the standby generators would often use a small K161 / K181 at 3600 rpm and these would produce the same wattage as the RV's but with tiny engines running faster.

 

 

[clueless 3,008]

On 11/7/2024 at 10:44 AM, Bar Nuthin said:

 

That's what I love about this site. You get answers, supported by logic and experience.

Don't know about logic and experience but I do know Kohler, the folks who designed and built these engine says run it wide open. That's how I roll for the past 38 years, hasn't been a problem yet.