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Hi all,
I have a Cub Cadet rider with the above engine. I removed the rocker arms to address another issue. Now the engine will start but as soon as the lifters pressurize, I lose compression (holding the intake valve open). After the engine sits it'll start but same issue. Rocker stud adjusted to 100 in lbs. I can't adjust the clearance obviously. Do I need to remove the lifters and bleed them down? Can I do this without removing the head? Thanks in advance for the replies.

Depending on the model #, the head will have to come off to remove the lifters. If it will start after letting it sit, the lifter is probably bleeding down. I'd check the oil pressure before I didn't anything else. Again, depending on the model #, Kohler had a rare issue of too much oil pressure which sometimes would pump up lifters.

VegetiveSteam said:

Depending on the model #, the head will have to come off to remove the lifters. If it will start after letting it sit, the lifter is probably bleeding down. I'd check the oil pressure before I didn't anything else. Again, depending on the model #, Kohler had a rare issue of too much oil pressure which sometimes would pump up lifters.

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If I remember correctly there was also an issue if the oil viscosity was too high could also cause over pump of the lifters. I think that had to do something with 30W used in temps below 50 F if I remember correctly. Bringing it up since people tend to use whatever weight oil they love best.

ILENGINE said:

If I remember correctly there was also an issue if the oil viscosity was too high could also cause over pump of the lifters. I think that had to do something with 30W used in temps below 50 F if I remember correctly. Bringing it up since people tend to use whatever weight oil they love best.

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I am working on a similar engine. Kohler single CV15S on a John Deere. Has fuel and spark, and checked compression and only got 39 psi. Even with compression release on camshaft, that is really low. Mower ran for three weeks after customer bought it used and died while mowing. Unable to restart since. What are thoughts on compression reading? Would think 70-100 psi would be acceptable.

Tiger Small Engine said:

I am working on a similar engine. Kohler single CV15S on a John Deere. Has fuel and spark, and checked compression and only got 39 psi. Even with compression release on camshaft, that is really low. Mower ran for three weeks after customer bought it used and died while mowing. Unable to restart since. What are thoughts on compression reading? Would think 70-100 psi would be acceptable.

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I think your thought would be acceptable. For the most accuracy of engine health would probably need to do a leakdown test. Worked on a generator a few years back that had a 5% bypass on leakdown but only showed 5 psi on compression gauge. Engine had a clogged spark arrester screen.

VegetiveSteam, it's definitely bleeding down, because as soon as it starts, it pumps up and holds the intake valve open. Is there a way to properly adjust these? In doing research it seems all lifters bleed down as an engine sits. I was thinking about removing the lifters and bench bleeding them, reinstalling them and trying that.

smallengineguy said:

VegetiveSteam, so you're saying the lifters should not bleed down as it sits? It's only the intake side that is doing this. Thanks for the reply.

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The lifters will bleed off while sitting, even more if that is the valve that is open because the extra valve spring pressure tries to close the valve against oil pressure

So how do I get it to adjust in correctly? There is no lash spec at all. All I can do is tighten it to 100 in lbs. Is the lifter faulty? Should I tighten the rocker with the lifter pressurized or bled off?

Tiger Small Engine said:

I am working on a similar engine. Kohler single CV15S on a John Deere. Has fuel and spark, and checked compression and only got 39 psi. Even with compression release on camshaft, that is really low. Mower ran for three weeks after customer bought it used and died while mowing. Unable to restart since. What are thoughts on compression reading? Would think 70-100 psi would be acceptable.

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I just worked on a Briggs that showed just under 60 on compression gauge. The problem was sheared key, once I fixed that, starts on first pull. YMMV.

smallengineguy said:

So how do I get it to adjust in correctly? There is no lash spec at all. All I can do is tighten it to 100 in lbs. Is the lifter faulty? Should I tighten the rocker with the lifter pressurized or bled off?

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No sorry. I wasn't saying the lifter shouldn't bleed off. They will bleed especially like ILENGINE mentioned if that particular valve stops in the open position once the engine stops spinning and puts pressure on that lifter.

As far as how to adjust the rocker arms, there is no adjustment. You just torque them to the spec. Now, it's best to do that with the lifters bled down, if not as you know, the valve will be held open. At that point, I typically roll the engine over by hand until that particular valve is being pushed wide open and let it sit. Over time, that will normally bleed the lifter.

What I was getting at with my earlier statement was, if the lifter or lifters are bleeding down while it sits, enough to let the engine start, then taking them out and bleeding them will probably make no difference.

If you can, will you post the engine model and spec #?

And again, if you can, check the oil pressure. There was an issue where the pressure relief ball could stick and cause very high oil pressure. Anything under 30 lbs of pressure is fine and I've even seen them pushing 50 lbs with no issues. you start getting over 60 lbs and lifters could start pumping up. And it may not affect both. High oil pressure could possibly only affect one.

ILENGINE said:

I think your thought would be acceptable. For the most accuracy of engine health would probably need to do a leakdown test. Worked on a generator a few years back that had a 5% bypass on leakdown but only showed 5 psi on compression gauge. Engine had a clogged spark arrester screen.

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Yep, leak down test is the next step. Hydraulic lifters, no hour meter, 19 year old engine. Both my leak down tester gauges broke. Guess I have to buy another one.

VegetiveSteam said:

At that point, I typically roll the engine over by hand until that particular valve is being pushed wide open and let it sit. Over time, that will normally bleed the lifter.

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That worked! I left the intake wide open/compressed over night and came out today and it started and ran. Sometimes the basic things work! Thanks VegetiveSteam.

You’re welcome. Glad it worked. Hopefully it lasts.

The lifter was not allowing the oil to bleed when valve pressure was removed from the pushrod. The internals are supposed to move freely, and open the 'capture' chamber so oil can relieve the pressure. When the lobe starts to push on the lifter base, the insides move and close the relief valve and capture a slug of oil. That slug is what makes the insides solid with the lifter body, and thus able to push on the push rod. If the oil gets captured and is not allowed to escape when pressure is relieved, it may pump up and hold the valve open.
Essentially, the lifter was sticking so oil could not leak out(likely to go up the push rod). It broke free and started moving again.
If you look in the Kohler shop manual, it indicates some valves are adjustable, and the clearance must be measured with the lifter bled down completely, The retainer is then tightened to the point a specificed clearance is reached. I do think the procedure is for older models. But, what is an 'older' model? The newer models use the tighen to x.xinch/lb adjustment.
tom

Either intermittent valve sticking in the guide, or hydraulic lifter pumping up and not letting the intake valve seat could cause back puffs.
Have you checked the cooling fins for any sort of blockage such as clippings or nests? Has the oil been changed regularly enough that it likely is not causing gummed valve stems/guides, or lifters that may have sticking check valves?
Have not heard much of the rocker studs moving in the cylinder heads on Kohlers, but comparing the height of all would verify they are in place(or all have moved...).
If it is down on power, you might check fuel availability - pump if equipped, filter, fuel line condition and outflow from the tank. Fuel line can decay internally but look perfect on the outside.
When started and warmed up, will the engine increase rpms without hesitation when you move the control from low to higher rpms?
tom

ADDED: You may get more information/response by posting on a twin cylinder post, or posting with that label. This is labeled for singles.