[case680rob]

Recently I bought a "new" (to me) carb for my 190. The old one was long past repair, the aluminum body was literally crumbling inside the fuel bow.

Prior to replacing the carb, my engine ran really good... Had decent power, was smooth, what would be expected from an old K301. I gave it a new spark plug, air filter, plug wire, and adjusted the points for proper timing per the service manual. No change in power, just general maint.

The "new" carb is a Walbro, adjustable high and low, both screws are on the side. Looks to be mid 80's or newer, just a guess. The throttle shaft was severely worn, so it was properly bushed on the top of the carb and the inner end of the throttle shaft was "football" shaped so it was cut down and built back up with "Quick Steel" putty and finished with a file to proper size.

The rest of the carb appered to be in perfect shape, spotless, and ready to run.

After installation, I have a new problem. The engine surges terribly. Great idle and mid throttle, but at full throttle it's always hunting. Not as much when under load at full throttle, but unloaded it's pretty bad.

On a hunch, I adjusted the governor. No change.

Any ideas here? Float too high? Air leak at the engine?

It's never done this before, so I know it's the carb, that's the only thing that changed when this began.

HELP!

Rob

 

[ljones]

I had the same problem on mine and it was air leaking in. It could be too lean also. Walbro carbs are not the greatest, you would have been better finding a carter #26 for it.

 

[hobbyman]

Stinking Walbro. Definitely sounds lean. I would double check there are no restrictions and open up the main if you can. I was at the impression Walbros are generally leaner and a lot have a fixed main jet. If it has an adjustable one it is just above the bowl.

I guess it is also possible to have the wrong size carb. Brian Miller's site does have recommendations for some mods on these like drilling out the jets. http://gardentractorpullingtips.com/carbfuel.htm I have had luck doing this with motorcycle carbs when I was in a pinch. Small handheld micro drills can be found at a lot of hardware stores. But once you go up you can't go back.

Sometimes you've got to pop out all the welch plugs and really boil her out...

Heading your way in a week. Will wave from the gorge.

 

[Snotrocket]

Did you clean it really well? Sounds like a plugged up jet to me, but it could be a number of things.

When I clean the tiny passages in the jets I take a bread tie and strip off all the paper leaving only a thin piece of wire
to snake out any gunk stuck in the jets. Even a tiny piece of dirt will screw it up.

 

[case680rob]

The "high" jet is adjustable, similar to the factory carb but in a different location. On the side just above the float bowl, instead of a long screw-needle coming from the top.

I didn't do any cleanup prior to installation, it was nearly spotless when it arrived. I'm not gonna say that the high jet or something related isn't plugged, but I don't think it is. Maybe it sucked something up when I started it the first time.

I'll check that out, along with re-sealing at the intake port, next time it doesn't rain here...They didn't name this state Washington for notning ya know...

Rob

 

[Rob_P]

They didn't name this state Washington for notning ya know...

I thought it was "Warshington" :lol: I'm gonna guess a lean mix due to air leakage, also. Let us know what you find.

 

[Rockdog]

So, is there info around here for repairing worn throttle shafts? I think I'm gonna need to do this...

 

[Stewart]

On my K321 the throttle shaft was loose where it was connected to the plate that is hooked up to the governor so that the butterfly would wobble and cause surging even if I held the governor rod. I recrimped the plate and the problem disappeared. :trink:

I had new bushings installed and she ran smooth. try the propane trick to see if you have an air leak :thumbsup:

:drinkbuddies: :canada:

 

[case680rob]

I got my bushing from ebay. Go on there and type in "kohler throttle shaft bushing" and it should come up. The top bushing was about five bucks after shipping. Check the other end fo your throttle shaft too, sometimes they wear, mine was shaped like a football from wear. I ground it down almost to a pencil point where it was shaped like this and then built it back up with putty, "quick steel" was what I used but there are lots of brands of it. Any grey and black putty that you have to mix before you use it should work. My throttle shaft wobbled all over the place before, now it's alot better. Just make sure to put enough putty on that you can use a fine file to take it down to match the original size of the shaft.

Rob

 

[hobbyman]

Brian Miller gives the size of the bushing you can use and also sells entire new shafts/kits. If your choke shaft is loose it can be bored and bushed too.

 

[case680rob]

Pulled the carb off and sealed with Permatex Avaiation Form-A-Gasket (the brown stuff) and still no improvement. So I got it dialed in best I could and ran it for a bit, no change. Then I sprayed the entire outside of the carb and gasket joint with carb cleaner, with the engine running, I found the leak. Seems the throttle shaft is still leaking. If I put the straw right at the throttle shaft and give it a squirt the engine speed changes.

When I bushed the shaft, the bushing was made to go in place of a seal that was originally on the carb. Should there be something there now? Maybe a felt washer or something? I'm pretty sure that's where my problem is, just not sure what to do about it besides replacing the entire throttle shaft so I can use the original seal type of that went there.

Rob

 

[hobbyman]

Rob, are you sure it's the right size? What is the diameter at the butterfly? That "seal" you mention is usually just a felt ring meant to keep dust out... I wouldn't expect it to prevent a vacuum leak. With a small amount of play it should still run ok . My old 321 easily had 2mm of play and would run and idle fine. I still wonder about adjustment and blocked passages. The idle circuit could give you troubles too. How far out are your low and high speed screws? Do you get any response from them?

 

[case680rob]

The bushing is the right one, I'm fairly sure of that. There isn't really much play there, way less than 1mm if I were to measure it with calipers or something. It did have a felt ring that was split too bad to use, but before installing the bushing there was a rubber seal, sorta like a tiny version of a wheel bearing seal on the back of a hub, in place around the throttle shaft sitting in the hole where the bushing now is.

Idle mix adjustment is fine, I get proper response from that screw. High adjustment screw does have an affect on how it runs at high throttle, just not what it should. If I set the screw in the standard two or so turns out from bottom, and run the engine to adjust high screw, it runs OK. Then I put load on the engine by pushing the blade against a hillside and go to adjust the high screw. I turn the screw in until the engine falters, and start backing out. I never get the engine to falter by backing the screw out. I have a feeling that if I were to take the screw out of the carb with the engine running it wouldn't change a thing except create a vacuum leak.

Rob

 

[hobbyman]

What I was wondering was what is the size of the throat on the carb? If it is <1" diameter its too small. 13/16" was for 7 hp engines I think. Not sure if that could be the issue.

Or drill out that main...

Maybe the old carb can be salvaged if it was running better with it?

 

[case680rob]

The inside diameter is at least an inch, I think it might be a 30mm. It was listed as being from a K301, but then who knows if it was original to that engine. If anything the carb is bigger than it needs to be. And if it had any sort of jetting other than the adjustable low and high I don't see it.

If I were to pull off the float bowl you would see the center threaded part of the casting with a little hole inside. The high adjustment screw comes down at about a 45 degree angle into that hole, metering the flow of fuel into the center casting area. Above that point there is a very thin brass rod that comes all the way from the top of the carb and down into the center area just above the adjustment screw. The passage which this rod is run through has a diameter that is probably three times the diameter of the rod. If the rod is 1/16, the hole it runs through is 3/16 or so, maybe a little smaller.

There is no removable jet in this carb, like that of the main in the original. Could it be that it is meant to have one? Or do I need to double check that the high adjustment passage is clear?

Rob

 

[case680rob]

I thought it was "Warshington"

We had a break in the rain/snow/hail mix for a few hours, so...
New info. Did a full throttle spark plug test, came out PURE WHITE. Not blistered, just super bright white. That confirms a lean condition. Even if I back the high adjustment screw out until it almost falls out and test again there is no change in insulator color.

I'm thinking either there is blockage in the high adjustment passage or the float level is so low that the engine can't pull fuel through the opening.

Going to pull the carb apart next time I get a break in precipitation again. :mechanic:

Thoughts anyone?

Rob

 

[1031d]

My 195 had a Carter N on it and someone stripped the air cleaner bolts out and cracked one hole back into the choke shaft so at the CCI show last summer a guy had a "running" K321 in pieces and we made a deal on the Wabro carb. Was so full of junk and corrosion it's beyond me how it ran. I rebuilt it, replaced the bent idle screw, bushed the throttle, put it on and it runs good. I did put a thin felt washer under the throttle arm that came with my kit. Did you put the windage gasket under the carb? It should go on top of the bowl o-ring. It's like a flat rubber gasket with a "D" shaped hole in the middle. My wheel horse ran bad without it.

 

[case680rob]

Hmmm, don't have one of those. I know what you mean though, I have seen them on carbs and in rebuild kits before. Think I can get away with making one out of inner-tube rubber?

 

[hobbyman]

Hey Rob, does your carb look at all like this? http://outdoorpowerinfo.com/repairs/koh ... k_carb.asp If I saw some pics of yours I might have some more ideas. I think that inner tube you were describing is the emulsion tube. From the link above, you see the jet on some is small and pressed in from the side, should be under the fuel level in the bowl. If you put an 1/8" drill bit between the float and the bottom of the carb, fuel should shut off right when it hits the bit. That's what our shop used to use.

I would like to retract any comments I made about drilling out jets until you are totally sure all passages are not restricted and you can get a spare jet just in case modifying it could make things worse. Whenever changing a jet size you should verify the stock size you should have, then research if others have found a better fit.

You should probably track down a carb kit with all the welch plugs. As you can see from the link above, there is usually something hiding behind those little plugs. There are several passages you can access and run a small wire through. To remove them, you drill in with a small bit, very shallow so you only go through the plug. Then thread in a sheet metal screw and pull out. Occasionally this is the only way to really see and clean all passages.

Did the person you got the carb from pull it off a running engine? Or is the previous status totally unknown? There is a paint can size pail of berryman? carb cleaner that is the best I have seen to boil out carbs. My old man used to use it with some heat on the kitchen stove. Good way to piss of the wife and inhale some bad fumes.

 

[hobbyman]

Or maybe its this one? http://outdoorpowerinfo.com/repairs/koh ... e_carb.asp

Run your fine wire through all of those holes. The main "jet" on this is just an open hole.