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View Full Version : 60 lbs compression on kohler with 150 hrs!


amarino
04-09-2007, 11:46 PM
I bought a scag 48" walk behind last spring. Mower is approx 10 yrs old, but had new engine with 10 hrs on it when I bought it. Kohler command pro 15. Now, with approx 100 hrs on it, it takes forever to start (pull start) and has low compression of 60 lbs. Stated smoking a little while running also. Could it be a valve problem, or more likely a piston ring? Dont yell at me, but I didn't change the oil until 80 hrs, and being a new engine I probably should have changed it much sooner. I have read about other kohlers with low hrs having similar problems.

-Thanks, AL

khouse
04-10-2007, 12:54 AM
Is the choke fully closed when applied? After you get it running does the engine pull OK?

Envy Lawn Service
04-10-2007, 02:39 AM
Considering the engine had 10 hours on it when you bought the mower, I would assume that more than likely it was due it's break-in oil change at that time.

So the break-in oil was probably ran in it a full 80 hours.
VERY BAD NEWS THERE!

All the break-in metals mixed into whatever the break-in oil was spells disaster when ran to 80 hours. I'm surprised it lived to this point. It's likely all chewed up inside from cirulating all those metal shavings in it that long.

On a new engine, I always change my oil and filter at 5-10 hours, then again at 25, then again at 50, then again at 75, then again at 100. Sometimes at a tighter interval in the early hours if I see a need. After 100 I resume whatever I deem a normal interval for that engine.

Richard Martin
04-10-2007, 05:20 AM
Do you have a Kohler service manual for this engine? Kohler single cylinder engines have a compression release that lowers cylinder pressure by roughly 50% under 700 RPM. That would put your effective pressure up around 120 psi.

From the Kohler Manual:

These engines are equipped with an automatic compression release (ACR) mechanism. Because of the ACR mechanism, it is difficult to obtain an accurate compression reading.

To check the condition of the combustion chamber and related mechanisms, physical inspection and a crankcase vacuum test are recommended.

Before I would tear into the engine I would drain all of the gas and put fresh gas in it. Then I would pull the bowl off of the carburator and make sure there isn't any water or trash in it. I would also put a new spark plug in it.

amarino
04-10-2007, 09:52 AM
Thanks for the replies. When it starts, the engine seems to have plenty of power, and runs good except for a little smoke at high rpm. I checked the choke and it looks like its closing fully, but I will check again. Anyone know where I can get the service manual? Its a CV15T engine. Worst case, where can I get a new motor? I cant afford much, so the cheeper the better :)
Also, when I first got it, it had plenty of compression when starting.

khouse
04-10-2007, 10:45 AM
I don't think you have anything more than a hard start problem. You said it runs good after you get it started so compression is not the issue. Why buy a new engine? How much oil do you add per day/hour?

Richard Martin
04-10-2007, 01:33 PM
I agree with khouse. Before you start looking for a new engine try to find out what is worng, if anything, with your old engine. Those single cylinder Kohlers are tough engines and they last a long time even when abused. What kind and weight oil are you putting in it?

The service manual can be downloaded from www.kohlerengines.com.

amarino
04-10-2007, 02:12 PM
Usses about 1 quart per week (15-20 hrs).

Envy Lawn Service
04-10-2007, 03:45 PM
Usses about 1 quart per week (15-20 hrs).

That's a good bit of oil.
It's getting by somewhere.

More than likely eat-up internal parts.

But there is one more simple possiblity.
The block breather valve

I don't know if that's an issue with the Kohler 15 or not.
But I do know a lot of oil can go through just that.
While the engine is running, it sucks right out and into the airbox/carb.

Check the airbox/carb for signs of engine oil pulling through.

amarino
04-11-2007, 11:37 PM
Cleaned the bowl...lots of dirt there! Starts good now but still confussed on the 60lbs of compression.

Restrorob
04-11-2007, 11:59 PM
still confussed on the 60lbs of compression.

How many times are you pulling the rope to check ?

Richard Martin
04-12-2007, 06:18 AM
How many times are you pulling the rope to check ?

He can pull the rope until he's blue in the face but the ACR is still going to bleed off compression until the engine starts.

Restrorob
04-12-2007, 08:05 AM
He can pull the rope until he's blue in the face but the ACR is still going to bleed off compression until the engine starts.

Believe me, You are not telling me nothing new Richard.

When a leak-down tester is not available and a compression tester is used weather a engine has ACR or not it takes three or more pulls to get the gauge/compression to pump up to get the maximum compression reading. Weather it's 40 lbs or 120 lbs.

thecrankshaft
04-12-2007, 08:12 PM
From my experience, 90 psi compression is a minimum - yours is lower than that.

With 60 psi compression and dirt in the carburetor bowl, I bet you your engine is dusted out. Have you checked the air filter? Maybe not if you're not changing your oil. If you see any dirt on the inside tract of the air filter/base, I bet if you pull the head off of your engine, you're not going to find crosshatch in the cylinder bore.

While 80 hours is a little long for a break-in oil change, the filter should catch all of the particles.

ed2hess
04-12-2007, 08:34 PM
I got a relative new 15hp Kohler that is also hard to start.....3 -4 pulls and sometimes many more. If you choke it at all cold or hot it simply won't start until you take it off choke. I just was about ready to open a thread on it. I wonder if the hydraulic valves are not functioning properly? Two reason to question it...hard start and it sound a little like I got a potato in muffler when it is running. I am going to put some sea foam in the 2 -3 ounces to see how that affects lifter...good or bad idea? The engine seems to have ok power and doesn't backfire or use any oil. Next I will pull the carb bowl to check for water/debris and change the gas filter and put in new plug. Then it will be off to shop I guess:confused:

Restrorob
04-13-2007, 01:29 PM
ed,

You can try the sea-foam but I just don't believe in additives, If the lifters are noisy and you are running the recommended 10w30 oil I believe I would check the oil pressure. If good then replace the lifters. You should go ahead and perform the other task as you mentioned and that may help with the starting issue.

ed2hess
04-13-2007, 07:55 PM
ed,

You can try the sea-foam but I just don't believe in additives, If the lifters are noisy and you are running the recommended 10w30 oil I believe I would check the oil pressure. If good then replace the lifters. You should go ahead and perform the other task as you mentioned and that may help with the starting issue.

I didn't really expect to see any long term effect from sea foam but wanted to see if it had any effect. No noisy lifters......did Kohler have some problem with soft cams in the last year or so?

Restrorob
04-13-2007, 08:04 PM
No cam issues I have seen, I have only replaced one due to a faulty compression release. I thought potato in the muffler with speaking about valves meant noisy. But, If there is no noise from the lifters you may have a baffle broke loose inside the muffler restricting exhaust flow, That I have seen quite a few times.

amarino
04-14-2007, 02:02 AM
Since cleaning the bowl and air filter it starts on 1st or second pull hot or cold. Cold requires full choke. When checking compression I pulled at least 5 times. Went up to 60 after 2 pulls then stayed there. Interestingly, I left the compression gauge in and came back the next morning and it still read 40 lbs!

Thanks for the suggestion to clean the bowl...that seemed to do it!

Envy Lawn Service
04-14-2007, 03:15 AM
No cam issues I have seen, I have only replaced one due to a faulty compression release. I thought potato in the muffler with speaking about valves meant noisy. But, If there is no noise from the lifters you may have a baffle broke loose inside the muffler restricting exhaust flow, That I have seen quite a few times.

I'm going to second that one also Ed.

I haven't ever had to work on a kolher 15, but I always like to consider the simple stuff first.

Since you said it was relatively new, you could take it in and let your shop figure it out.

Richard Martin
04-14-2007, 07:23 AM
Since cleaning the bowl and air filter it starts on 1st or second pull hot or cold. Cold requires full choke. When checking compression I pulled at least 5 times. Went up to 60 after 2 pulls then stayed there. Interestingly, I left the compression gauge in and came back the next morning and it still read 40 lbs!

Thanks for the suggestion to clean the bowl...that seemed to do it!

No problem. Just make sure those gas cans are clean before you put gas in them. Also since you did find trash in the bowl you may want to look at a better fuel filter or putting a fuel filter on it if it doesn't have one. Dixie Chopper has a real nice water/fuel seperator fuel filter that does an excellant job. They're a little pricey at around $15 to $20 a piece but when you don't have to worry about the gas it's worth every penny. A friend of mine uses them on his Exmark ZTRs and has never had a problem with anything in his carbs or gas. I've had them on both of my Dixies with zero fuel issues.

mcambrose
04-24-2007, 12:01 PM
Did you check the breather tube for cracks. It is usually a small black rubber hose which connects from crankcase to the intake plate which bolts to carburetor. I have lost a couple of engines because of these little tubes. They crack and let dirt into the air entering the carburetor. I have replaced all of mine with an upgraded breather tube. If this is your problem, you will probably need a new set of rings to stop the oil use.