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buckdan

M20

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buckdan

I am not a mechanic, but I like to do a lot of my own work on garden tractors. Reason why I have become a member on this site is to make sure I am doing it right.

I am at a loss trying to figure out why my M20 will not respond quickly to full throttle. It hesitates, then speeds up. Also at high idle, seems like I need to choke a little to smooth out the idle to correct the surging. Low, medium throttle runs fine. My tractor is a Deutz Allis 1920/ 1691020. 20 HP Kohler/ 49506 with a Walbro carburetor.

I have sprayed carb cleaner down the throat of carb, has new plugs, new ignition module. Tractor has 595 hours on it.

Appreciate any input from members that experienced similar problem, thanks.

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midnightpumpkin

Your symptom sounds a lot like the way the KT17 in my 17GTH_L was acting.

Give it full throttle, it would almost die, speed up, almost die, and repeat that cycle.

Here is a post on how I corrected the problem. Worth a try in your case.

http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=123279&SearchTerms=17GTH-L

Again, thanks to Al Eden may he rest in peace.

John U

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fishnwiz

I would remove the High speed adjustment screw and spray with carb cleaner and replace and adjust.

Before you remove the screw ...take note of how many turns it takes to get the screw turned all of the way in until it will go no further. DO NOT OVER TIGHTEN!. Now you can back the screw all of the way out and clean it....this way , when you screw the adjustment screw all of the way back in until it stops after cleaning, , you will know how many turns out you will need to get the HS screw back in to where it was set before you removed it and you can then make any adjustments from there. Best of luck.

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fishnwiz

SEAFOAM IS a gas additive that you use on all combustion engines. A lot of guys, including me swear by the stuff...others, not so much. It comes In a white cone top can and is purchased for between 6-9 dollars from any auto supply or tractor supply store.

I have had excellent success with the stuff from cleaning carbs to removing carbon in engines.

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acfarmer

Seafoam is the best suff to soak a carb in thses days as regular carb cleaner has almost no effect on the hard green goo that will build up.Seafoam has also cleaned out diesel and gasoline injectors for me plus it takes water out of the fuel system.

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MikeES

Does your M20 even have a high speed fuel mixture screw? Many M20s with the Walboro carb have a fixed main jet which was set lean for emissions. If this is the case you can richen the low speed or idle mixture screw out to get a little more fuel which will help with throttle response.

You should go through the governor set up also, which may be causing the surging.

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buckdan

I have two adjustment screws. I am guessing one is the high speed adjustment screw, the other idle speed? I have adjusted the high speed to 2 1/2 turns out giving me the smoothest idle. I have yet to purchase the sea foam to see if i can get better results. I still get the surging at high speed but correcting it with a little choke. I am thinking I need the governor set up properly.

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HubbardRA

Some of those carbs were set entirely too lean from the factory. I have opened up the jet .001 and eliminated the problems all together on quite a few engines. My generator required that it be run on half choke to run smoothly. I had cleaned the carb, and that jet a couple times with no success. I finally opened the jet up .001 and now it runs without any choke after it is warmed up. I am actually just doing the same thing that we would do with the screw on an adjustable jet, but there is only one way to open up a fixed jet and that is by drilling it larger.

I know that I am probably the only person on this site who would drill a jet larger, but it has worked for me several times and I have not ruined a carb yet. I have a special drill index with very small drills in .001 steps that I use for cleaning and opening up jets.

Almost any engine will run good with the main jet .001 larger unless it was running very rich before opening up the jet. Most fixed jet carbs come from the factory with a very lean main jet. That is part of EPA's pollution controls on small engines.

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MikeES

I assume that you know this..., but just to review.

The main fuel jet screw (high speed) is in the top of the carb (initial setting 2-1/2 turns out).

The idle fuel jet screw (some call it the low speed) is the one that comes out at an angle (initial setting of 1 turn out).

The is also the idle speed screw that is the smallest and horizontal that controls the throttle plate stop.

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buckdan

With my limited knowledge on walbro carbs, I have finally identified the two adjustment screws. The high idle is 2 1/2 turns out. The idle stop, or low speed, is also 2 1/2 turns out. I'll correct this to 1 turn out.

I have increased more tension on the spring and have corrected the high speed governor hunting.

Many thanks to all with your valuable knowledge.

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