A Kohler engine question .

[Quebecnewf]

I have a Kohler 18 hp on my mill . This engine has been a very good engine and has given no problem over 25 years of sawing . 

I am noticing now that the engine seems to be running a little off. It's sounds as if the choke is half on . Checked that and it's not . Checked air filter and found that it was not seated properly so some ( more than I wanted ) was getting into the carb. Corrected that problem but engine still seems to be running too rich, too my ear. Tried running it with the air filter removed and no difference .

Changed plugs and they looked a little too black as well.

My question is given the above info is it possible or probable that my carb needs a complete tear down and a clean out. I am thinking that 25 years is a long time and there may be blockagesand buildup  over the years. My mill sets idle as well for at least 3 months each year.

What are your thoughts and what experience have you had with this over the years?

Quebecnewf

[marcnaz]

Carb kits are fairly inexpensive if that's the case. You can try running a little Seafoam through it first to see if that makes a difference. If it's blowing black smoke or there is black carbon on the plugs that's usually a getting too much fuel issue or not enough air.  If the air cleaner is ok, then too much fuel can be a stuck choke, or stuck or badly adjusted float or float valve, leaking needle valve, or its not burning all the fuel because of low coil output or bad spark plug wire with high resistance. Suppose bad spark plug (weak spark) could also be the issue but less likely.

Luckily carb kits and coils and such are only $15 or so depending on your model, but check the price of a complete new carb. It may be the same price as a rebuild kit or only $5-10 more and a lot less time and hassle unless you just like to tinker. Surprisingly Amazon has many small engine parts for pretty cheap.

[doc henderson]

might check you fuel for water after such a long winter as well.  look for a bi-layer.  i recently had this problem from a gas jug that sat with out a cap and then placed fuel in mill.  all the above sound good to check as well

[dgdrls]

Does it start well??
try some aerosol carb cleaner or Sea Foam through the fuel system and see if that helps.
then work your way up from there.  I like the thought of a new Carb if the easier remedies don't help


D

[hamish]

Pull and decarbon the heads and give it a simple valve lapping.  After 25 years.......well geesh........

[Quebecnewf]

Pull and decarbon the heads and give it a simple valve lapping.  After 25 years.......well geesh........

Thanks for all the info guys . Going to start trying different things . Carb cleaner etc etc first.
With regard to pulling and de carbon the heads is this something that is easily done . I've never done it so what are the steps. Can it be done without removing the engine from the mill . Do I need replacement gaskets if I remove the heads?
What steps are involved in valve lapping? .

One thing that I am kind of puzzled about. If as I think the engine is running rich would not dust and sawdust in the carb cause it to run lean instead of rich?

I have some tinkering experience most likely just enough to get me in trouble
Quebecnewf

[John Bartley]

My thoughts :

Before taking anything apart, check that mice haven't blocked your exhaust or your intake ... even partially.  That will cause choking and plug fouling.  I've seen this ....

Spray carb cleaner and Sea-Foam are "feel good" ways to spend your money ... if  you suspect a fuel system issue, do it right.  Pull the tank and clean it, replace fuel lines, kit the carb if you have a competent mechanic to do it, otherwise replace the carb.  (fuel is my personal guess for your issue)

A Kohler 18hp motor is likely a Magnum 18? It would help to see a photo of the model number plate.  You'd have to have a lot of hours on it for the valves to need work .... I've seen them run 2000, 3000 or more hard hours and never have a head off.  Before you do any rebuilding ... do a cylinder leak-down test.  The kits are cheap and will tell you volumes about your engine condition.

Amazon.ca: leak-down tester

cheers

[doc henderson]

If it ran fine when put away last year, it is most like from sitting.  bad fuel or water in the fuel, or a bit of varnish in a passageway.  mine started revving up and down and my small engine guy said it its something in the idle circuit cause it still supplies part of the fuel on the high side.  he fixed it without removing the carb from the motor, cause he knew the screw to remove and put a wire through it.  smell the gas (if you are over 18 ) and if it smell like varnish you have bad fuel.  pump the gas into a clear container and let it sit, if you get a layer on the bottom that is water, and the fuel can be poured off the top and reused.  Best to drain tank, change fuel filters, replace with fresh fuel.  If seafoam does not work, take it to a small engine guy if you need it up and running quickly.  You learn to lap valves on you tube or small engine books.  I replaced a carb on my pressure washer.  13 hp  Kohler kit was 16,new carb 26 dollars.  They had one on the shelf and now I have some spare parts.  please let us know what you find.  sometimes running the adjustment screws all the way in counting the turns and back out can clear some junk.  sawdust on the airfilter would decrease air and make it run rich.  start by pulling the bowl and cleaning it all out and spraying stuff in all the holes.  wear glasses, good carb cleaner is nasty,

[luap]

You are right to do the simple things first, plugs ,air cleaner check exhaust. My experience with this is fuel related blockage. With the carb removed, remove the bowl being careful to not deform the bowl gasket. Set the gasket aside to keep it from being contaminated with cleaner. Some cleaners will distort the gasket making it difficult to reuse. The brass tube that goes from the bottom of the bowl to the carb throat can now be removed. you will see a screwdriver slot in the end. This tube will have a series of holes that must be open. The threaded end will have one very small hole that is usually the one that gets blocked.  You aren't going to get any common tip cleaner in this hole. Maybe a wire from a wire brush. I have a wire set down to .007 not readily available that I acquired after doing enough of these to relieve frustration of not having the right tool. Spray the rest of the carb liberally. your low and high speed mixture screws may need minor adjustment after engine warmed up. As has been suggested you can buy a carburetor for less or same as a rebuild kit. I have had good success using the amazon clones as I call them.  After running and warmed up I would certainly do a valve clearance check. 

[Southside]

smell the gas (if you are over 18 ) and if it smell like varnish you have bad fuel

Doc - if you are under 18, or act as such, and the gas smells like varnish then what does that mean?  :D

[Quebecnewf]

An update...

Went in and had my mechanic buddy spray everything down with carb cleaner. Ran a whole bunch down the throat of carb as well . Did not make any difference so we ( he) decided to pull the carb. Brought it to his shop . Lots of gunk in the float bowl . Did a big spray and cleanup . Blew out every hole and tube . Put it back on and she runs like a new engine .

Guess in another 24 years I will have to do it again.

So pleased it was just that . 2060 hours on engine and first time with any trouble. 

Thanks for all your responses . 

Quebecnewf

[luap]

  Now there's your dinner.  ( a Taryl Dactal fixes all you tube reference).  Nothing like that "It's working"! feeling.

[doc henderson]

i see the smiley but I think it is funny that my 17 y/o son cannot buy spray paint, in an effort to stop kids from"huffing".  As a pediatrician that just popped into my head.  Sad.  any way bad gas does have a smell that most old timers know.  In medicine we can diagnose a few problems by smell... i will spare you all.  As for you, if they card you at wal-mart, then you know you must be acting like a teen, and they may not sell you spray paint.  8)  @Southside logger

[doc henderson]

Q thanks for the follow up.  I had an uncle who was in motor pool in the military, and later a Pontiac mechanic.  he could fairly well diagnose most gas engine problems over the phone.  He taught me if it wont start, but hits on ether (again no huffing)  then it is a fuel issue, if not prob. spark and so on.  We all really like to hear the end solution.  Your mechanic buddy could eventually lap the valves and adjust them down the road.  Many small engine guys really advocate draining fuel from tank and carb for longer term storage.  This is why.  glad you are up and running, your victory is felt across the country.

[Southside]

Yea - I agree Doc the spray paint thing is foolish.  The local Tractor Supply will ask me for my DOB when I buy some, let me think - you have my name, address, phone number, and e-mail for the rewards program and now you want to include my DOB into your insecure system - not going to happen, so I make something up every time, sometimes it's dates like "December 7, 1941", once I said "July 4, 1776" - the girl, while typing in 1776 actually said "Oh wow, you were born on the 4th of July" - yup that level of attention to detail is why they don't get the real one....but I digress.  

[donbj]

One thing I learned long ago was to NEVER use regular gas with ethanol in small engines. They hate the stuff! Unless the engine is used regularly and has fuel running through it often the carb passages will gum up if the engine sits too long with this junk in it.

Premium non ethanol goes in all my small engines.

[sawguy21]

Glad you are up and running again. 8)

[Quebecnewf]

No ethanol in our neck of the woods yet. Hope to never see it by what most guys have to say about it. 

No sawing today were of on one of our last trips in the woods today to cut three long 24' spruce logs for a customer. 

Snowmobile conditions are very good here yet but could change fast now

Quebecnewf

[luap]

Since you just cleaned the carb, now would be a good time to replace the fuel filter.  Assuming this engine has a fuel pump, make sure you get one with a paper element, not the one with a bronze screen.

[marcnaz]

Glad to hear you got the issue fixed. Best things about most of these engines that they are pretty bullet proof and parts are cheap!