K321 Running at 40 deg. BTDC

[Jarrapedo 6]

Hi all, been following the threads for years and really appreciate what everyone has to offer here.  This is my first post, mostly due to being at my wits end with my C145.  So let me do my best to summarize:

 

I have owned this C145 for 9 years, roughly 4-5 years into ownership I decided to change points, condenser, adjust valves, etc. as preventative maintenance.  When I completed all this the tractor would run fine for about an hour but towards the end of mowing (about 1hour 15 minutes) the motor was really hot and began to labor to the point that the governor was doing everything it could to keep her running....did some research on red square and learned that the 0.020" points setting is more of a starting point and the best way to get the timing right was with a timing light.  With the use of the timing light I never could get the "S" mark to be aligned with the mark on the housing.  0.010" and the motor would run rough/sporadically and anything more than 0.016" and the motor wanted to labor well during mowing.  I set the points at 0.013" as a middle ground to have the motor seem to run right and to not experience laboring of the motor. The motor ran well at 0.013", started right up, never back fired when throttling up or down or shutting it of, it ran pretty good and made pretty good power too so I let it be.

 

About two years ago I had a cracked head right at the spark plug threads, it wasn't bad but before i noticed the crack the plug would continue to come loose every few times I would cut grass, I also noticed that the head bolts would become loose as well, so I was needing to check these occasionally too and bring them back up to 30-35 ft-lb.  But again, motor ran well so I chalked up the cracked head to the plug coming loose and vibrating until the head was fatigued enough to initiate a crack.

 

This brings me to about two weeks ago, I was mowing and nearing the 1hour 15 minute mark and started to hear what I though was a pinging; there were a lot of leaves so I had been running the motor at about 3400rpm, I generally cut at 3200 but with the leaves mixed in with the grass cutting I was running at about 3400 for 15-20 minutes.  I was nearly finished mowing (just 2-3 more passes) and I heard another ping, then another when i was going up a hill so I throttled back down to ~3200 thinking it was junk gas in an effort to finish the job.  Well, she never finished, made a bad hissing sound and died in the yard.  I pushed her back to the barn, took the head off expecting to find a hole in the piston because I was still able to spin it by hand and could feel the compression stroke some but instead found a pretty sever crack in the head. valves looked good, still seated good, combustion chamber was pretty clean, spark plug (gaped to 0.025") was a nice golden brown, there is some wear on the cylinder walls, but I think this is to be expected when I have ~800-1000 hours on the motor.

 

So now that I've had the same problem twice I am coming to terms with the need to time to motor where the "S" mark is visible but I am still having trouble doing this, I can take the points all the way down to 0.003" and it runs (not very well) and with the use of a timing light that is adjustable I am seeing that at 0.003" the S mark is centered when the timing light is set to about 10 degrees, when I change the points to 0.015" the timing light setting is around 30 deg with the "S" mark centered, at 0.020 its at ~ 40 deg and at 0.025" the timing light is showing about 50 degrees BTDC to have the "S" mark centered.

 

I'm really not sure what to do, could something in the engine be way off?  I've never torn the motor completely down, it came to me in good running order but I don't know the history.  Any help you all can offer is very much appreciated.

 

Thanks for taking the time to ready this 'summary', and I look forward to hearing suggestions.  Thanks!!

[roadapples 6,983]

@953 nut can you help this man.

 

  And welcome to Red Square

[Achto 29,394]

@Jarrapedo 

The "S" mark on the flywheel is the advance mark, the "T" is the TDC mark. I suggest trying to static time your engine instead of using a timing light. For this you will need a muti-meter. Using this method has been spot on for me every time.  Here are the instructions to walk you through it.

Kohler static_timing.pdf

 

Also I think that it may be time to replace that head.

Edited November 3, 2020 by Achto

[The Tuul Crib 7,339]

T😎

[953 nut 59,940]

Sounds like you are using an Adjustable Timing Light.  The ATL is used to determine timing that is beyond the degree markings on a harmonic balancer on an automotive engine. You should have it set at "0" when checking your points on these engines. Presuming the internal microprocessor that is used to delay the strobe to the selected degree is working properly it will give an accurate reading at "0". If you can borrow an inductive timing light to check yours against that could be a good idea.

Once the cylinder head issue is resolved you can check it against the setting achieved with Static Timing.

8 hours ago, Jarrapedo said:

tractor would run fine for about an hour but towards the end of mowing (about 1hour 15 minutes) the motor was really hot and began to labor

There are several things that could contribute to overheating. Remove the engine tins and clean the cooling fins, they do tend to plug up with grass clippings and dirt. If the carburetor is set too lean this can result in overheating too.

[Jarrapedo 6]

I will try the static timing method soon and feed back.  Attached are photos, and for further clarifications

 

1. the head has been replaced both times a crack has been found

2. the timing light is lower quality but my K341 which is having a points gap of 0.018" is showing the "S" with the timing light set at 0 deg.

3. Flywheel shroud is free/clear of clippings/debris

 

It occurred to me late last night that possibly when the motor was rebuilt (piston stamped 0.010) that maybe the flywheel wasn't returned to the right position relative to the cam positioning.  Maybe I need to pull the head, bring the motor to TDC on compression stroke and check for the "T".  If no "T" present I think i could simply scribe a new mark through the window and mark it with a silver sharpie.

 

Basically I want some confidence that I wont again destroy the head or anything else, I've been a WH guys for 3 generations and doing my part to keep them running for my lifetime and my kids (still have my grandfathers C-100 which he bought new).  

[Jarrapedo 6]

Hi All,

just an update, I've static timed the motor and using this method my points gap is 0.014".  Thanks for the static timing suggestion, so much easier to do this without the motor running.  I also checked my K341 with this method and its timed correctly with 0.018" gap, so I have good confidence in this method.  So a couple more questions:

1. What would be the cause of the points gap being so far away from the 0.018" recommendation?  The motor is due for a rebuild this winter and I'd like to address anything that would be causing this, maybe something is worn out that is not generally part of a rebuild like the post on the points or the cam shaft bearings, or even the cam shaft it self.

2. What could have been causing the heads to damage if the motor wasn't as advanced as my timing light was suggesting?  Is 3400rpm too much intermittently?  The spark plug would loosen and occasionally the head bolts needed tightened, the motor is not running hot with the correct points setting, the spark plug is burning clean, the carb is set where motor idles very well and runs w/o misses at 3200 - 3400rpm.  Replacing heads gets costly and would like to avoid this.

 

Thanks all

[Achto 29,394]

2 hours ago, Jarrapedo said:

1. What would be the cause of the points gap being so far away from the 0.018" recommendation?  The motor is due for a rebuild this winter and I'd like to address anything that would be causing this, maybe something is worn out that is not generally part of a rebuild like the post on the points or the cam shaft bearings, or even the cam shaft it self.

2. What could have been causing the heads to damage if the motor wasn't as advanced as my timing light was suggesting?  Is 3400rpm too much intermittently?  The spark plug would loosen and occasionally the head bolts needed tightened, the motor is not running hot with the correct points setting, the spark plug is burning clean, the carb is set where motor idles very well and runs w/o misses at 3200 - 3400rpm.  Replacing heads gets costly and would like to avoid this.

 

1. Wear on the push rod for the points or wear on the cam would be the cause for the difference in my opinion. It could also just be a tolerance issue from the factory. 

 

2. The crack in the head could be from over tightening the spark plug. It could also be from a lean fuel condition causing excess heat. May be run your main jet out another 1/4 to 1/2 turn. Your engine is designed to run at 3600RPMs continuously. Lower RPMs can cause a lugging condition while under load. This can cause excess heat and oil starvation. Lugging an engine is probably the worst thing that you can do to it, specially during the break in period. Lugging an engine during break in, almost always scores the cylinder & wrecks the rings. 3200-3400 is not what I would consider lugging though.  

Edited November 4, 2020 by Achto

[953 nut 59,940]

21 hours ago, Jarrapedo said:

when the motor was rebuilt (piston stamped 0.010) that maybe the flywheel wasn't returned to the right position relative to the cam positioning.

The flywheel is keyed to the crankshaft and is not likely to be the problem. However, if the camshaft was put in one tooth off when the rebuild was done that could explain the apparent timing issue and the overheat/poor running issues.

1 hour ago, Achto said:

crack in the head could be from over tightening the spark plug. It could also be from a lean fuel condition causing excess heat. May be run your main jet out another 1/4 to 1/2 turn.

 

[oilwell1415 563]

Lots of good info above, but one thing not mentioned was the effect of heat on the head and the things it touches.  Have you actually checked the head temp?  You can get an infrared thermometer cheap and know for sure if it's running hot or not.  This is really important on aluminum components because aluminum expands more than ferrous metal and it loses half of its strength at 400 degrees F.

 

As the engine warms up everything expands.  With an all iron/steel engine everything expands at the same rate.  With an aluminum head, the head expands more than twice as much as everything else.  Engines are designed to account for this, but if the head gets hotter than it is designed to run it overcompresses the head gasket to the point that the gasket can't recover.  Same with spark plugs and spark plug gaskets.  This is probably why you had to periodically retighten them.  It also has the added effect of slightly increasing the compression ratio every time you tighten the bolts, which would make the problem worse.  While all of this is happening, you could also have a head that is so hot that it is structurally compromised while at the same time being put in a bind and not allowed to expand due to the head bolts.  This places a compressive stress in the material that has to go somewhere.  Then when the material cools that stress turns into a tensile stress that is trying to pull the material apart.

[Tuneup 1,452]

I haven't seen the flywheel key in all of this. It only take a partial shear of that key to set the flywheel way-off. Certainly requires a check and maybe a replacement while in there.

[Jarrapedo 6]

Haven't forgotten about you all yet, just have been a bit nervous to run the tractor much to get a temperature...I'll report out soon.  Also, I've seen gov. speed should be set to 3600 but in other places I have seen 3400rpm, is running at 3200-3400rpm causing a problem?  My thinking was if I am running 12% less speed, would I be extending the life of the motor by that same %?

[953 nut 59,940]

In my opinion the 3600 is a ballpark number and 3200 shouldn't be a problem. The worst thing would be to run it at low RPMs because the cooling air flow and splash lubrication would suffer.

[Jarrapedo 6]

when running at 3000rpm, mulching leaves for an hour the head temp was 340F near the exhaust valve, is this a normal temp? Spark plug area of the head was 325F.  I'm, still a bit nervous to run it at 3400 because we haven't yet identified what could be causing the problem.  The top end is due for a rebuild and I really hate to put the effort into this with not fully knowing what caused both head failures, I do work my WH's pretty hard but I maintain them, still looking for the smoking gun I guess; only thing I should do before the rebuild is run it at 3400 for an hour and keep an eye on the head temp.  The carb is set pretty good, basically the main is set to prevent misses, I do keep the setting closer to the rich side, maybe just a 1/8th turn out more from where it runs clean.  Thanks for all the suggestions and things to check.

[oilwell1415 563]

340 is probably a reasonable temp for unleaded fuel, but it doesn't leave much room to go up.  If it's running 340 just mulching I'm curious to know what it would get to under a heavier load in hotter weather.