Low compression?

[chipwitch 73]

Spring is here and I'm new to having 4 seasons having just moved from the deep south.  I have an old C-165.  Back toward the end of fall, it started hard and took a lot of coaxing to cut grass.  I'm just now getting around to putting the battery back in and wanted to check compression before trying to start it.  I just have one of those cheap gauges that you press and hold in the spark plug hole.  I believe it to be accurate.  Anyway, dry I got between 55 and 60 psi.  Same result with successive attempts.  I poured a tablespoon of oil into the cylinder and tried it again.  This time I got consistent 80 psi results.  I'm guessing that's low?  If so, I would appreciate some guidance from here.  I'm not unfamiliar with engines but I'm not a pro either.  Locating parts has been a challenge in the past.  I'm hoping y'all will be able to help me find the parts I need and what needs to be done to breathe some life back into this engine.  I don't see a model number, per se, but I have attached a photo of the engine tag.

[squonk 42,628]

Your engine has an automatic compression release so you will get a low reading. Does your engine use oil, smoke. Do you know ow many hours are on the engine? Worn out ignition points could effect ignition timing. Dirty carb could not be supplying for full power. Lots of variables. I'm thinking your engine is tired and ready for an overhaul.

Edited April 22, 2021 by squonk

[pfrederi 18,360]

Engine is from 1987. It is a K301 12 hp.  If you can borrow or buy a leak down tester that will give you info as to bad valves or rings  or both.  If not The pull the head decarbon her and check the valves

[gwest_ca-(File Mod) 11,261]

Is there a chance this is a CH16 engine? Can find one 455xx spec number.

https://www.partstree.com/models/ch16-45509-kohler-command-pro-single-engine-made-for-cub-cadet-16hp-11-9kw

 

Garry

[chipwitch 73]

5 minutes ago, pfrederi said:

Engine is from 1987. It is a K301 12 hp.  If you can borrow or buy a leak down tester that will give you info as to bad valves or rings  or both.  If not The pull the head decarbon her and check the valves

It's a 12 hp?  I thought it was a 16!  Can you share your resource for identifying it?  Just knowing it's a K301 is a huge help.  I couldn't find anything.  Great, so I bought a 12 hp when I thought I was getting a 16.  I bet the seller knew it.  I'm surprised it could swing a 48" mower deck as well as it does while climbing pretty steep slopes with only a 12 hp.

 

I've never removed a head before.  What will I need for a minimum parts-wise?  Just a gasket?  Can you reuse the head bolts?

 

Ugh... just looked up the tractor id... it's a c-175.... with a c-165 black hood and a 12hp motor.

 

 

 

[chipwitch 73]

12 minutes ago, gwest_ca said:

Is there a chance this is a CH16 engine? Can find one 455xx spec number.

https://www.partstree.com/models/ch16-45509-kohler-command-pro-single-engine-made-for-cub-cadet-16hp-11-9kw

 

Garry

I can't be sure, but I think it's the 12 hp.  I also have a C-125 and they (the engines) look identical to my untrained eye.

  Maybe I'll try putting the mower deck on that one to try it (if the linkage is all intact).

 

Edited April 22, 2021 by chipwitch

[gwest_ca-(File Mod) 11,261]

Write the number a different way and the 45 522 18 is was the part number for a K341 short block from Kohler.

 

Garry

[rmaynard 15,936]

Count the number of head bolts. K341 16HP has 10 bolts. Others have 9.

[squonk 42,628]

Yes count the bolts. Someone might have changed the shroud and those numbers will mean nothing.

[chipwitch 73]

54 minutes ago, rmaynard said:

Count the number of head bolts. K341 16HP has 10 bolts. Others have 9.

Good call.  The engine in the OP has 10 head bolts.  The engine in my c125 only has 9.  Seems that what you're saying contradicts what pfrederi suggested, that it was a 12 hp?  I only checked one of the many Horse k341 exploded diagram and it did indeed only have 9 head bolts.

 

[chipwitch 73]

17 hours ago, squonk said:

Your engine has an automatic compression release so you will get a low reading. Does your engine use oil, smoke. Do you know ow many hours are on the engine? Worn out ignition points could effect ignition timing. Dirty carb could not be supplying for full power. Lots of variables. I'm thinking your engine is tired and ready for an overhaul.

squonk,  I wasn't aware of the "ACR".  No idea how that works.  So how does one do a compression test or even a leak down test if as I assume the ACR is allowing the pressure to release?  I'm not afraid to get my hands dirty or to search and read, but I'm really struggling here.  First off, just from this thread, there's a discrepancy as to what HP my engine is.  My assumption is that the engine tag is on a heat shield that may not be the original and that I have the 16 hp based on what you and rmaynard wrote.  Is there a way to get a more positive identification so I can order parts?  I really can't understand not stamping the serial number into the crankcase... it's like they don't expect the engines they manufacture to outlast a decal!!  <SMDH> Second, and this one really confuses me, if I try to locate parts for my engine, assuming it is the k341, there are a dozen k341's with additional 4 or 5 numbers after it, listed on the parts sites just for WH alone!  Then Toro has some as well?  And of course the dozens of other engine variations for other mower manufacturers!!  I would greatly appreciate some insight on how to navigate these numbers.  What are the 4 or 5 numbers after the k341?  Are the parts for all k341's interchangeable?  And last, assuming I have the k341, I have only just now discovered the free service manual on Isavetractors.com.  Are there any other such resources that are better or I should be aware of??  Really appreciate y'all.

 

<ETA>  Reading about the ACR in the manual now. 

 

 

Edited April 23, 2021 by chipwitch

[squonk 42,628]

If you were to order internal parts. It's best to have a machine shop check everything first. They would know what piston or rod to get. External parts and gaskets should be the same no matter what.

 

Harbor Freight sells a cheap leak down tester. When using it the trick is to keep the cylinder on Top Dead Center when applying air to the cylinder. What I do is get it on it's compression stroke move the piston to TDC and mark the crank pulley. When you apply air to the cylinder the pressure will want to move the piston. I turn the engine back to the pulley mark so I know it's at TDC. Then listen for any air leaking.

 

Around the head = Head gasket

Carb = Intake vavle leak

Exhaust pipe + Exhaust valve

Oil fil tube and or breather = Worn cylinder and rings

Edited April 23, 2021 by squonk

[chipwitch 73]

32 minutes ago, squonk said:

If you were to order internal parts. It's best to have a machine shop check everything first. They would know what piston or rod to get. External parts and gaskets should be the same no matter what.

 

Harbor Freight sells a cheap leak down tester. When using it the trick is to keep the cylinder on Top Dead Center when applying air to the cylinder. What I do is get it on it's compression stroke move the piston to TDC and mark the crank pulley. When you apply air to the cylinder the pressure will want to move the piston. I turn the engine back to the pulley mark so I know it's at TDC. Then listen for any air leaking.

 

Around the head = Head gasket

Carb = Intake vavle leak

Exhaust pipe + Exhaust valve

Oil fil tube and or breather = Worn cylinder and rings

How would a machine shop determine the correct parts?  I have my own small machine shop and am quite capable of using mics but I don't really work on engines.  If it's just a matter of measuring cylinder diameters/checking for roundness, crankshaft wear etc, I'm capable of that.  I've just never had occasion to do it.  So my question about knowing what parts to buy was regarding all the 5 digit codes that follow the engine (k341-#####) on the parts store websites.  If parts are categorized by that number and the numbers on the engine are in the form of a decal which may or may not be the right one, it seems impossible to be assured the parts you're ordering are correct.  Is there a cross reference somewhere where you can order pistons, rods and rings by diameter and stroke?

 

I looked at the leak down testers at HF.  They have 2.  One is like $25 and the other is $80.  I think I'm going to get the $80 or maybe just put one together (I have most of the components already in my shop).  I just moved from the city to a rural farm.  I was lucky to get a 67 acre pasture/woods before the prices really took off.  My machine shop isn't back up and running yet but should be in a few months.  So, I'm acquiring more and more small engine things and seems like I'll need to be better acquainted with them.  I've got a 25hp Kohler engine in a Terramite that started making a lot of noice... something internal has let loose.  Haven't tore into that one yet.  Seems like a smaller single cylinder engine tear-down and rebuild is a smart way to start.  Needless to say, the leak down tester sounds like a good tool to have if I'm going to be doing my own work.   I can understand how it works if both valves are closed on compression stroke, but exactly how will a leak down tester tell me anything if the exhaust valve is cracked open by the ACR?

[rmaynard 15,936]

To test compression on an engine with ACR, you must be able to rotate the engine at over 600 RPM's. That's the speed where the ACR kicks out and the exhaust valve fully closes. I've seen it done by hooking a motor via v-belt to the PTO pulley.  

[pfrederi 18,360]

The ACR only bumps the exhaust valve open for a fraction of the compression stroke at TDC valve is fully closed.

[squonk 42,628]

https://isavetractors.com/engine-rebuild-kits/

[oliver2-44 10,380]

Regarding those numbers after the K341

1st are you going to buy OEM Kohler parts or one of the aftermarket overhaul kits?  The aftermarket kits are generic and you just have to measure if you need to bore cylinder or grind crank to get correct size. 
The Kohler individual parts are all mostly the same. They did use 2 different style pistons, but you can match the picture to what you have.  

Remember, IF it needs an overhaul (you need to do the leak down test -Or- you could pull the head and measure the bore. 
 

we all have ways about how we go about things. So I will say—-

If it were me, I would do the leak down test. Remember it’s an older engine expect at least a little leakage. If you have a lot of air coming out crankcase oil fill tube your headed for a overhaul

 

If everything seems to have only a little leakage I would try this (partly for the experience since you’ve not been in small engine)

 

1 . Pull the head, measure the bore 1/2” down from top, middle and bottom, in line with the crank and 90 degrees. Compare to the manual and post readings here

 (If bore isn’t terrible) 

2. Pull the carb and clean it. Be sure to clean the tiny holes in the long main needle top middle and bottom. 

3. Pull the breather and clean (pay attention to how parts go in order and up/down

4 Pull the valves clean them on a wire wheel. Mic the valve stem in the valve guide wear area and compare to manual   Then lap them iin the seat with lapping compound (this is good experience if you still end up overhauling)

5 Clean the carbon off head and piston, I like to use a plastic scraper so as not to gouge it. Then sand head flat with wet or dry sandpaper on a piece of glass or other very flat surface 

     Put it back together torquing the head bolts per manual. See how it runs  You may get a few more years out of it. 

 

PS. The Manuel’s section on RedSquare has the Kohler Manuel and other good info

[chipwitch 73]

oliver-244, that sounds like a good approach.  I started cobbling together a leak down tester yesterday.  I just have to make one more part to test the engine.  I'm kinda hoping the leak down will come back "acceptable" and I can get another season out of the mower before I tear it down.  It would make for a good winter project.  Maybe it's just the carb needs cleaning or points (I didn't realize these weren't magneto) need to be cleaned/set/replaced.  Also thought a valve adjustment might be in order.  If I can avoid removing the head until winter, I'd prefer it.  I have so many small engines that need work.  I've got an old 316 I bought for $50.  Not sure the engine condition.  I also have a D160.  I've had it running but not in about 5 years.  A polaris 700 that started acting up last summer... All that and I don't have a house built yet and probably won't happen until next year.  I'll post back my leak down results, probably tomorrow.

 

[chipwitch 73]

Update.  It looks like I'm down 30% on the leak down test.  Looks like it's the intake.  I was expecting the air coming out the breather, but even with the filter and cover off there was a noticeable air stream coming from somewhere under the carb.  Intake gasket in addition to the intake valve?  Maybe sucked in enough crud to damage the intake valve?

 

[squonk 42,628]

You probably got an intake valve all goobered up with black carbunkles. Taking the head off is so easy. Scrape out the crap, soak it with carb cleaner a new gasket (cheap) and see if there is any improvement.

[chipwitch 73]

1 hour ago, squonk said:

You probably got an intake valve all goobered up with black carbunkles. Taking the head off is so easy. Scrape out the crap, soak it with carb cleaner a new gasket (cheap) and see if there is any improvement.

Thanks!  I'll take the head off tomorrow and see what it's like.  That won't consume too much of my time, if you're right.  Definitely worth the shot.

 

[squonk 42,628]

You might want to pull the carb too. air shouldn't be leaking out UNDER the carb unless it's the gasket is shot or it's actually coming out the breather. A leaky gasket will make it run lean and make it start hard and be down on power.

[chipwitch 73]

After cleaning the engine I can see the leak is coming from the breather, not the intake.  Looks like a tear down unless my homemade leak down tester is inaccurate, which it could be.  I made it with only one gauge figuring that my compressor regulator would serve as the primary one.  I noticed a 10 psi difference between the two gauges and compensated by increasing pressure at the regulator 10 psi.  Plus, I would think the length of the orifice could also be a factor in addition to the diameter.  In any case, it required a good deal of force to hold tdc while pressurized, ballpark estimate of 50+ ft lbs at the flywheel.  I'm going to try firing it up again.  Maybe I can learn something new.

[pfrederi 18,360]

Air coming out the dipstick???

[chipwitch 73]

1 hour ago, pfrederi said:

Air coming out the dipstick???

 

I realized last night I had forgotten to pull the dipstick so this morning I pulled it and retested it.  Yes, it's coming from the dipstick.  Close the dipstick and naturally the path of least resistance would be the breather.