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Frustration on carb adjustments

25791 Views 74 Replies 10 Participants Last post by  Gravely16G, 
Canary Al
The last time I did any real work with my 8183-KMT was mowing up in VT. After that I used it once to jump-start my Ford 4000 and was not aware the starter remained engaged for an extended time. I brought it home and it took awhile to figure that out with alot of help on here. This is a M18S 1997 Kohler Magnum engine on my 1981 4-wheeler.

The last 2 times I did work with it I recall needing to keep the choke half on to keep it from bogging down. I decided it was time to dig into the issue of getting the carb working better - a big deal to me as I am still learning - everything.

I should start by saying I had the carb off and out to a small engine repair shop to totally clean the carb and install a rebuild kit last spring. I put it back on the tractor and after following the directions in the engine manuel to adjust the carb, it ran pretty strong all summer. I did ask alot of it over the summer, mowing some tall weeds and such to reclaim some of our yard.

In the last week I put a new air filter on it, changed the fuel filter to one of the Napa golds Richard says are best, carefully installed new spark plugs, and let it sit for a couple of days with a little MMO in both cylanders.

It's warm today so I set the 2 adjustment screws to the pre-start positions outlined in the manuel and started it up. A little choke and it caught well just as it always does. After letting it warm as is required I proceeded to carefully follow the procedure in the manuel. It has to warm for about 10 min in order to need no choke to run.

I did manage to get it running a lot better, particularly at idle. I do not have a tach so I am not certain at what speed i have it idling butt is is low an runs smooth there. When I accelerate, it hesitates a little but eventially comes up to full speed. At that point it "hunts" - is I believe the correct term from reading on the forum about this issue. It surges and then slows over and over again.

I have no way to put a load on it other than to drive it. The deck is up in VT I took it down to the end of my driveway and back up - a fairly steep grade, but not long. In 4th -1 it surges as it does without a load on it, but doesn't quit - that at about 2/3rds throttle. I no longer have to run the choke half on to keep it from stalling while under load.

Any suggestions on what to do next are appreciated.
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M
If it just bogged down under load I would be inclined to say the main jet needs to come out further. However, hunt and surge is more of a supply problem, at least based on what I've gone through so far. I know it took forever to get the air out of my NAPA fuel filter - you would just see it trickling in at first.

Mine also surged under applying load before I adjusted the governor and set the linkage spring back to the factory spots.

- N
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M
By the way, does feathering the choke stop the surging?

-N
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M
I guess my point is the surging implies that the jet is capable of passing enough fuel to rev the motor up, but the fuel is in short supply - or your throttle is going funky on ya.

- Nathan
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Canary Al
MountainDweller said:
By the way, does feathering the choke stop the surging?

-N
Click to expand...
feathering the choke does stop the surging, but then it seems to be running rich.

And yes there is air in the line fuel filter. The way it is parked in my shelter the tank is lower than the engins - a little lower and the gas has run back to the tank. All my adjustments and such were done while level.

I have not touched the govenor mechanism - guess I better study the manuel on that subject.
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M
Canary Al said:
feathering the choke does stop the surging, but then it seems to be running rich.
Click to expand...

I bet it's a fuel delivery issue. Like I said, there was all sorts of air in my filter for the first week - I wonder if the pump wasn't getting fully primed or something like that - maybe it was pretending to be gravity feed until it was primed. Putting the choke on helps to suck the fuel through to the carb, but also makes it run rich. I don't know if there is a bleeding procedure for the fuel system, but I bet that will help.

- Nathan
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M
Fuel systems are section 6 in the manual here:

http://www.oldgravelys.net/pdf/Kohler_M18_M20_Serv_Man.pdf

It speaks of various possible obstructions, including insufficient venting of the fuel tank. Maybe it's as simple as running the gas through the lines with the pump/carb end disconnected or loosening the cap to get it started? That's what I'd try at least.

-N
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Richard-tx
Hunting is almost always caused by too lean a mixture. Back the main jet out 1/4 turn and see what happens. If it still hunts after backing out the main jet 1/2 turn then the main jet is likely occluded. Take the main mixture screw out and give it a shot of compressed air and reinstall.

THe other thing that will cause hunting is the governor set too sensitive. Move the linkage per the manual.
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Jimmy in NC
Since it goes away with choke I'm also going to say fuel. If it is the governor, they normally doesn't level out with fuel.

This is a video of my Onan with a governor linkage just one hole off:
http://www.youtube.com/watch?v=LsGhWXpjmq4&context=C3c94f31ADOEgsToPDskL7_w_x_z_j82sljDayUlNS

Governors are pretty sensitive.
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Canary Al
Well I spent an un-productive afternoon trying to divest my M18S of this hunting problem. I tried everything suggested – thanks for the ideas – except Richards suggestion I blow out the main fuel adjustment screw. All to no avail.

The engine has to run for quite a time with the choke at about ½, to run at the upper RPM’s without some choke, or no choke on it. When it gets to that point is surges. It doesn’t surge as fast (often) as Jimmy in NC’s video does. As I said before, adding a little choke will stop the surging but not smoothly - I’m sure it is running rich that way.

I tried backing the main fuel adjustment screw out a ¼, a ½ etc. up to a full turn or better. None of these adjustments seem to change anything. I have made sure, I believe there is nothing blocking fuel or air – unless that is happening inside the carburetor.

I changed the setting – again I think – on the governor by moving the spring in picture below from the second to the end hole, to the end hole – in the picture, I am referring to the right side of the spring, closest to the spring coil. I must admit I find all this more daunting than the electric problems I eventually figured out. Reading the engine service manual pages about the governor leaves my head spinning

I did not “take the main mixture screw out and give a shot of compressed air..” as Richard said to do. I am not certain I understand that. Question: I am to back that screw out completely? Remove it and the spring? What is underneath it? Is there something more to remove under it? If I give a shot of compressed air in the hole where the screw was? Is that OK? Nothing bad can happen doing that? That’s about the only idea left out there to try.

Picture 1 is the spring I moved on the governor mechanism – (move described above)
Picture 2 is the other side of the carb – my choke cable is missing and the choke is in the half-on position. I’m expecting a new one from Richard’s any day.
Picture 3 is a view of my carb from directly above it
Picture 4 shows the engine end of the throttle cable – the casing doesn’t come far enough but it is what they sent me, and it does operate the throttle smoothly

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Canary Al
Well I spent an un-productive afternoon trying to divest my M18S of this hunting problem. Thanks for the ideas – I tried everything suggested –except Richards suggestion I blow out the main fuel adjustment screw - more on why below. All to no avail.

The engine has to run for quite a time with the choke at about ½, to run at the upper RPM’s without some choke, or no choke, on it. When it gets to that point it surges. It doesn’t surge as fast (often) as Jimmy in NC’s video does. As I said before, adding a little choke will stop the surging but not smoothly - I’m sure it is running rich that way.

I tried backing the main fuel adjustment screw out a ¼, a ½ etc. up to a full turn or better. None of these adjustments seem to change anything. I have made sure, I believe there is nothing blocking fuel or air – unless that is happening inside the carburetor.

I changed the setting – again I think, as directed in the manual– on the governor, by moving the spring in the picture below from the second to the end hole, to the end hole. In the picture I am referring to the right side of the spring, closest to the spring coil. I must admit I find all this more daunting than the electric problems I eventually figured out. Reading the engine service manual pages about the governor leaves my head spinning

I did not “take the main mixture screw out and give a shot of compressed air..” as Richard said to do. I am not certain I understand that. Question: I am to back that screw out completely? Remove it and the spring? What is underneath it? Is there something more to remove under it? If I give a shot of compressed air in the hole where the screw was? Is that OK? Nothing bad can happen doing that? That’s about the only idea left out there to try.

Picture 1 is the spring I moved on the governor mechanism – (move described above)
Picture 2 is the other side of the carb – my choke cable is missing and the choke is in the half-on position. I’m expecting a new one from Richard’s any day.
Picture 3 is a view of my carb from directly above it
Picture 4 shows the engine end of the throttle cable – the casing doesn’t come far enough but it is what they sent me, and it does operate the throttle smoothly

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Grand Sierra
As long as it ran good before playing with carb your problem of needing choke is that its starving for fuel. Most likely reason main jet clogged clean carb see if that corrects problem. Id take pics before taking anything apart unless you have done this it makes it easy to get it all back together.
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Richard-tx
You have *that* carb.

This should help.


If adjusting the idle mix screw seems ineffective, remove the screw and blow 120 psi of compressed air in the hole. Reinstall the mixture screw and set it to two turns out from lightly seated.

More than likely the idle speed will be too high so adjust it to a reasonable idle speed with the idle speed screw.
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Canary Al
This engine has a mechanical fuel pump. Question: Doesa fuel pump either work, or totally fail? Is it possible for it to work enough for the engine to run, but not well enough to run well?

I have tried the compressed air into the open hole where the "Main Fuel Needle" goes, with no decernably different result.

While the engine is running I can observe a mere trickle of gas going through the in line gas filter. Should not that filter appear full?
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Jimmy in NC
Some filters never fill all the way. I've had some run with just the filter looking damp. Pumps do not normally "half fail" but I'm also not saying it can not happen either. Normally they just die.
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Canary Al
Jimmy in NC said:
Some filters never fill all the way. I've had some run with just the filter looking damp. Pumps do not normally "half fail" but I'm also not saying it can not happen either. Normally they just die.
Click to expand...
Engine still exhibits all signs of gas supply problems - hunting at higher RPM - needing some choke even tho warm to run w/o hunting. Adding full choke when it is about to stall will keep it running, but poorly. Pull back choke to get it to level out at seemingly rich. Has to be very warmed up to idle. Once it is, idle speed adjustment does respond. Adjustment of main fuel needle seems to have little if any effect. Very frustrating.
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jepics
Keep at it Al - this is a valuable thread. I've had the same issues with my 18-G since I got it a year ago. Last March I thought I got it licked, but I haven't used it since then, and I need to pull the carb and clean it out again.

It also had a float valve that didn't seal - gas got into the oil, so I just let it sit since last Spring. I got as far as draining the oil and replacing the filter before I started it this fall. I've been procrastinating on attacking the carb issues you're having.

It is one of the problems of having too many tractors - there's always another one that can do the job, and reduce the criticality of a particular problem. "I'll get a round tuit."
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Canary Al
jepics said:
Keep at it Al - this is a valuable thread. I've had the same issues with my 18-G since I got it a year ago. Last March I thought I got it licked, but I haven't used it since then, and I need to pull the carb and clean it out again.

It also had a float valve that didn't seal - gas got into the oil, so I just let it sit since last Spring. I got as far as draining the oil and replacing the filter before I started it this fall. I've been procrastinating on attacking the carb issues you're having.

It is one of the problems of having too many tractors - there's always another one that can do the job, and reduce the criticality of a particular problem. "I'll get a round tuit."
Click to expand...
Thanks for the encouragement. You may understand - it actually helps.

To be honest with myself I had been adding a little choke to to keep it doing the job for probably 6 weeks before the season was over up in VT. I was putting off getting the carb working right - and then got sidelined with my electrical problems.

One thing that does not seem right to me is the gas line filter has almost no visable gas in it. Huh? I can never remember seeing that around small engines. I mean I have it at full throttle - it is consistently hunting - I add a little choke, the hunting abates, and all the time i am checking that gas filter and it is for all practicality of view, empty. I started wondering if it was full and the gas was clear and I did not realize it. No, I can see a little trickle of the gas coming into the filter. Obviously it is being consumed as fast as it goes through there. I can remember seing it half full or better at times?

I checked the gas tank cap. Leaving it on and tightly turned in - removing it completely. No change in performance. I actually did this - probably silly, but I had once observed a seasoned and accomplished guy do it. I covered the edges of the open gas tank and created pressure in the tank by blowing into it. No difference and I got a blow back of fumes once I had it pressurized! Not fun. Have brushed the teeth a couple of times since coming in, and still feel like spitting!

I put it away for the day. Tomorrow will be warm enough to try something else. I am wondering if there is some slight occlusion from the gas tank to the filter. Something that allows it to run but not get the full source of fuel it needs to run right. I put on a new gas hose from the tank to the engine last Spring, but have made no big effort to eamine the inside of the tank. I was thinking of removing the tank from the 8122 and setting it up in the 8183-KMT. I know that tank is like new, as i spent alot of time making it that way. It's all i can think of at this point and i am haunted by that emty gas filter.

Oh yes - and I can't use the 8122, It is most definately smoking badly. All seems to point to it has an issue with the rings. That was to be my over-the-Winter big deal. If indeed that is the problem I don't even want to start it. I put a couple of capfulls of MMO in it and it is parked. Sigh.
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R
I have the same carb. on my 16G. The main jet is exactly one turn open. It requires a brief warm up in cooler weather, none in the summer. I doubt you have a fuel supply problem, as if you did, the engine would run out of fuel and stall, even with full choke.
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jepics
Canary Al said:
.

One thing that does not seem right to me is the gas line filter has almost no visable gas in it. Huh? I can never remember seeing that around small engines.
Click to expand...
:ditto:
Canary Al said:
I add a little choke, the hunting abates, and all the time i am checking that gas filter and it is for all practicality of view, empty.
Click to expand...
:ditto:
I was able to observe when the float valve opened and closed, the level of fuel in the filter did change.



Canary Al said:
I checked the gas tank cap. Leaving it on and tightly turned in - removing it completely. No change in performance. I actually did this - probably silly, but I had once observed a seasoned and accomplished guy do it. I covered the edges of the open gas tank and created pressure in the tank by blowing into it. No difference and I got a blow back of fumes once I had it pressurized! Not fun.
Click to expand...
:ditto: And I had learned earlier not to do this with a compressor (split a small B&S gas tank!) This actually does help get fuel to a starved carburetor, and I do it with a low pressure air tank (no more than 10lbs) & rubber-tipped blow gun thru the venthole in the cap nowadays!


Canary Al said:
Sigh.
Click to expand...
:ditto:

My 16-G had similar problems - I gave it to my brother and he bought one of those gallon cans of carb cleaner with a basket - he soaked the whole carb in there before blowing it out. He's not had any problems since.

I will try that next and let you know what happens.
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