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jbrukardt

Kohler Command CH20 - Loud knocking after hard sta

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jbrukardt

Pulled out my Simplicity Sunstar for the first time this season that has a Kohler Command CH20 in it, prior to winter storage the whole thing was seafoamed, the carb was cleaned, and the oil was changed along with a new oil filter.

I ran it for about 3 hours, cutting my fields and lawn, fired right up and worked perfectly, then i hit a snag. I bottomed out in a drainage ditch and got stuck. RPMs dropped super low and i started puffing white smoke. Immediately shut off the engine, got myself out of the situation and fired her back up. Hard hard start, 20 seconds of cranking before she fired up very slowly, but once going, ran smooth and I mowed for another 2 hours with no issue and good power.

Pulled her in front of the garage to do a post mow-cleaning, and upon turning over again to pull into the garage, no start, just slow crank. Engine voltages are good, fuel pump is working, etc.

It was getting dark at that point, so i figured maybe it was a heat issue, and let her sit overnight. Went out again this morning and cranked it over. Once again, super hard start, but did eventually turn over.

White smoke, running rough for maybe 5 seconds, then knocking, bad knocking....

what did i do to my engine Im not too familiar with the kohlers, but i cant imagine i threw a rod or something like that (oil level is fine, etc).

Suggestions on what i can check (push rods, valves, something stuck?)

tl;dr

bogged out my engine

white smoke, extremely hard starts

started up once after a hard start, ran a further 2 hours without issue

wouldnt start second time, when it finally did the next more, rough engine, white smoke, and knocking

I shut off immediately on hearing the knocking to prevent further damage. Help!

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jbrukardt

The white smoke didnt seem such a huge concern, but it was a new potential side effect so i thought it would be worth mentioning. The hard starts and consequent knocking scare me, them be engine destroying noises

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jlasater

Can you get a hold of the drive shaft and turn the engine over by hand, or at least rock it back and forth to see if the conrod bearings are toast?

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jbrukardt
quote:Originally posted by jlasater

Can you get a hold of the drive shaft and turn the engine over by hand, or at least rock it back and forth to see if the conrod bearings are toast?


id="quote">
id="quote">We'll see, it would be easy if i could just spin the drive shaft that goes to the deck, but with the engine off that clutch is going to be disengaged so that wont do the trick. I'll try once i get some daylight. I havent had a chance to do much at all, im going to pull the plugs and check for fouling in case oil got someplace it shouldnt along with trying to run each bank individually by pulling the plug off to see if i can isolate the knock.Im just really worried to run it for more than a couple seconds with the knock in case it is a rod. I dont feel like losing a 1000 dollar engine to a thrown rod :(

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Dan123

You might pull the oil filter off or the dip stick and see if it smells like gasoline. Also you will be able to tell if the oil looks thinner than it's suppose to be.

Can you turn the key on and switch the front pto clutch on and see if you turn the engine over. You might want to disconnect the mower shaft before you try this.

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BLT

Take the spark plugs out and lay some rags over the plug holes and then spin the engine over a see what the rags catch. If you puffing a lot of white exhaust smoke, that generally means unburnt lube oil.

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jbrukardt

Ok, update

1) Crank sound with spark plugs in, WRRRRR RRRRWWW RWWWWW slow, about one sound per every 1.5 seconds. I recorded a video but for some reason it got deleted

2) Crank sound with spark plugs out, RRRRRRRRRR, constant crank, fairly normal sounding

3) Inspection of spark plugs: long story short, theyre a complete mess

Right plug: EbjcuuN.jpg

Left plug: QDYHJAm.jpg

Put a cloth in each spark plug socket and tried to crank, no oil came out on the cloth.

4) Popped the air filter, some oil where it shouldnt be, but not soak through or that big of a mess

Filter: xcCa0Vu.jpg

Carb plate (larger puddle): syy7D7r.jpg

5) Popped off the OHV covers.... well, theres a very obvious problem

Right rockers and general area looked fine

BVd9k52.jpg

Left rocker set.... well, theres my knocking most likely

8FtcAjb.jpg

Ok, so in summary, I essentially have two problems:

A) oil somehow got everywhere it shouldnt, gummed up my plugs, probably contaminated the carb pretty decently. That explains the hard starting to a degree

B) Somehow a rocker popped off of the valve (push rod is still seated) and thats my chatter/knocking. This was the very last thing it did, i havent run the engine for more than 15 seconds total like this, its very noisy and clearly something was wrong, so maybe no permanent damage?

So I guess what im asking now, is whats my recovery from this?

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jbrukardt

Hmm, upon further reading, might i have a collapsed hydraulic lifter? Id rather not have to take the head off if i dont have to. This engine has NOT been through the service bulletin update that replaced the hollow push rods with solid ones for kohler engine to the best of my knowledge

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makeitfit

Maybe the rocker arm itself just came loose?

For it to shift over to the side like that the fulcrum had to be loose.

If the exhaust valve isn't opening, it can't vent compression and thus the slow crank. Since exhaust can't get out, it'll back up into the crankcase past the rings and push oil out with it.

If it were mine, I'd loosen that rocker, check the pushrod and make sure its not bent, then just reassemble it torquing the rockers all to factory spec, top off the oil and see how it runs.

I had one on a Cub Cadet do the same thing a few years ago, I put it all back together, re-torqued the rockers and it was fine from then on.

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maxtorman1234

Also looks like a lot of debris/chaff buildup under the shrouds, Would be a good idea to pull them off and clean that out so the head can cool. I second the above post, as long as your threads aren't damage for the rocker arm, you should be able to bolt it back in place and your troubles SHOULD be taken care of.

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jbrukardt
quote:Originally posted by makeitfit

Maybe the rocker arm itself just came loose? For it to shift over to the side like that the fulcrum had to be loose.If the exhaust valve isn't opening, it can't vent compression and thus the slow crank. Since exhaust can't get out, it'll back up into the crankcase past the rings and push oil out with it. If it were mine, I'd loosen that rocker, check the pushrod and make sure its not bent, then just reassemble it torquing the rockers all to factory spec, top off the oil and see how it runs. I had one on a Cub Cadet do the same thing a few years ago, I put it all back together, re-torqued the rockers and it was fine from then on.


id="quote">
id="quote">Thats the general plan i think. Loosen the stanchion, check the arm, realign, retorque to 100 inch pounds, put it back together, new plugs, see how she fires up.I think i have a larger problem which is going to bite me at some point though. There has always been a bit of oil out the feeder tube. I think i may have a decaying headgasket one one or both of the heads :/ Thats going to be a pain in the neck to replace later. Due to the sunstar layout, im pretty sure you have to pull the engine to do head gaskets

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jbrukardt
quote:Originally posted by Brettw

Have you checked the condition of the breather assembly? If there is one on the Commands?


id="quote">
id="quote">there is one yep, and I actually havent recently, the reed could be damaged/decayed and causing the problem. Ill have to take a look first.Back on the original topic, im still wondering what the heck caused my current issues, being stuck on a 20 degree slope for maybe a minute should not have put oil in all the places it did. Im thinking that as mentioned by makeitfit, maybe that rocker just popped off by chance and caused oil to get through the rings causing all these problems, and it had nothing to do with the slope, just pure coincidence.

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jbrukardt

Bad news :/

pulled the rocker, push rod, and rocker seat, inspected them, all look fine and in good and shiney condition

Reinstalled, torqued stansion to 100 in/lbs (rocker was still floppy until the hydraulic lifter reinflated when i cranked for 1 rev, then got rock solid)

Ft5eqny.jpg

Fired her up, ran for 4.5 seconds.... clack clack clack. rocker is off again, in the same position to the left. Closely inspect, notice a small crack in the block.... doesnt continue down the rod shaft, but still, not good.

96fOkDL.jpg

Closely inspect valve, its a little mishapen where the rocker arm meets (probably from the rocker arm clattering against it, even just for a few seconds)

LIAuNvU.jpg

Whats causing the rocker arm to continue slipping off? Theres no detent to keep it on the valve or to hold it in place like on the back end of the rocker with the push rod, its just smooth surface on smooth surface.

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CarlH

Some Commands have pushrod guideplates that keep the pushrods properly aligned and therefor the rocker arm properly oriented on the valve stem.

I don't know why some Commands have guideplates and others do not.

I'm inclined to suspect the lifter for that pushrod is not keeping pumped up or not leaking down enough. Maybe too much leakage or some crud in it. Too long or too short on lifter travel can cause problems.

That crack in the rocker stand may indicate some misalignment that could cause problems also.

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Kenh

Is there a remote chance the engine got hot enough to seize the valve stem???? It's a relatively rare occurrence but it could happen. That side of the head has some burnt oil on it indicating a much higher temp than the intake side. Just thinking out loud here.

Ken

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jbrukardt
quote:Originally posted by Kenh

Is there a remote chance the engine got hot enough to seize the valve stem???? It's a relatively rare occurrence but it could happen. That side of the head has some burnt oil on it indicating a much higher temp than the intake side. Just thinking out loud here.Ken


id="quote">
id="quote">its possible, i noticed all those heat related indicators as well... but when i crank it moves and works (I watched it when i did the manual crank without the OHV cover) just fine so its not frozen now.

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jbrukardt
quote:Originally posted by CarlH

Some Commands have pushrod guideplates that keep the pushrods properly aligned and therefor the rocker arm properly oriented on the valve stem.I don't know why some Commands have guideplates and others do not.I'm inclined to suspect the lifter for that pushrod is not keeping pumped up or not leaking down enough. Maybe too much leakage or some crud in it. Too long or too short on lifter travel can cause problems.That crack in the rocker stand may indicate some misalignment that could cause problems also.


id="quote">
id="quote">The closer i look at that "Crack" the more i think its a molding void or a manufact defect, its raised, not recessed. I think its still important to note, but im not sure its an issue anymore.I wish this did have rocker guides, even two little ridges would keep it right where it needs to be, that would be a much better design. I should probably at this point pull the head and take a look at the lifters (and heck, just replace them, theyre 12 bucks a piece) and do the head gaskets while im at it. On this tractor, that is a massive pain to do though to the best of my knowledge :( I may be getting in over my head here, no pun intended. I wish you could just just pull the lifters with a magnet like you can on some other engines

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Brettw

It appears as though the rocker seat is twisting? Nothing holds this in place? Would some locktight on the stanchion keep that from twisting? There must be some type of guide for the push rod, or the seat should keep the rocker from twisting, or a detent on the rocker itself? What would prevent this from happening otherwise? Something is obviously amiss or missing, or there would be no way to keep these things aligned. Seems they would do whatever they wanted.

I am referring to the rocker "seat" as the rectangular piece the cap screw goes through?

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jbrukardt
quote:Originally posted by Brettw

It appears as though the rocker seat is twisting? Nothing holds this in place? Would some locktight on the stanchion keep that from twisting? There must be some type of guide for the push rod, or the seat should keep the rocker from twisting, or a detent on the rocker itself? What would prevent this from happening otherwise? Something is obviously amiss or missing, or there would be no way to keep these things aligned. Seems they would do whatever they wanted.I am referring to the rocker "seat" as the rectangular piece the cap screw goes through?


id="quote">
id="quote">Confirm that the rectangular piece that the cap screw goes through just "sits" into the rocker. Here are a couple photos of how it goes together, and the individual components. I agree.. it seems odd. There are actually two revisions on this engine. I have this one, revision Bhttps://www.partstree.com/parts/?lc=kohler_engines&mn=CH20-64512+SIMPLICITY+%2820+HP+%2814.9+kW%29%29&dn=catalogs_2824

vqAtta9.png

This is rev A: its pretty significantly different https://www.partstree.com/parts/?lc=kohler_engines&mn=CH20-64512+SIMPLICITY+%2820+HP+%2814.9+kW%29%29&dn=catalogs_2823As for the parts themselves, heres what they look like:Rocker:

9hcvpo4.png

Rocker pivot:

JWiN1rU.jpg

kAdAL8h.jpg

The more i think about what you said, the more im perplexed..... what about that assembly keeps the rocker from rotating besides a measly 100 in/lb of torque?

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jbrukardt

couple guys on another forum think that that manufacturing void actually is a crack, and is causing the sleeve/stud to be looser than it should be, thus negating the 100 in/lb of torque and allowing it to vibrate free.

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maxtorman1234

Just my 2 cents, but I've seen this on many aluminum blocks, transmission cases ect, I personally don't believe it is a crack, However I don't have an explanation for why your rocker keeps twisting off the side. Since the rockers are the same, have you tried alternating the 2? I've never seen this issue, Out of the 7 i've owned and my 5 current commands are all the same as yours pictured, the 100 in/lbs is sufficient to hold the rocker in place.

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maxtorman1234

Also, you can pull the lifters out without taking the head off, I think kohler sells a tool for this, also I have been able to hook them and lift them out.

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jbrukardt

You know, thats something to try, just switch all the rocker hardware and see if the other one suddenly starts exhibiting symptoms...

Thats good advice sir, process of elimination. Ill do that tomorrow.

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