KT17 Weirdness

[BrianX128 109]

So I'm not sure what I have going on, engine is a KT17 series II. Doesn't use any oil, good even compression in both cylinders. I can't remember the numbers from when I tested it in the fall, but it was "good" when I looked it up. I had an issue with a dead plug running the engine on 1 cylinder and thought it was the coil but it ended up being a intermittently bad plug, cleared up once I got two new plugs and ran great.

 

I noticed this spring the first time I started it up a few weeks ago it ran rough and seemed like the exhaust looked hotter than normal coming out of the stack, I was doing a lot of around the yard work and it cleared up after the third or fourth start and shut down running sticks to the woods. Seemed happier choked 1/4 of the way but once it cleared it was fine fully open.

 

Yesterday I get it out again for the wife to drive around as we're going to mow saturday and the yard is wet so I can't get the big zero turn out and she wants to help (this mower is hers) and it's doing it again.

 

I'm thinking I have an exhaust valve that is sticking partially open and clears up with time and it doesn't do it when it's ran more frequently but after sitting for over a month it creates issues but I'm wondering if that is correct from the symptoms it's having. It basically coughs ever 5 seconds like it's trying to backfire, choke affects it but doesn't fix it no matter how you play with it or the main screw on the carb, and the slower it runs the more you can "feel" something doesn't seem right.

 

Then magically it's fine. can idle down to 1400 (I have an rpm gauge on it) or rev up to 3400 and no coughing or anything. If you pull the plugs when it acts weird, one is black and fouled up. If you clean them and toss them back in once it is running normally and pull them after 45 minutes of use, they are both clean still. Once it's running right too, it stays fine. I ran it a lot yesterday at least 3 hours doing random yard chores and it was fine. Fine this morning as well. 

Edited April 3, 2020 by BrianX128

[Ed Kennell 42,008]

I'd run a tank full of concentrated  Seafoam thru it before I went any deeper.    

[ebinmaine 72,699]

8 minutes ago, Ed Kennell said:

I'd run a tank full of concentrated  Seafoam thru it before I went any deeper.    

That's not a bad idea at all.

 

 

I was thinking maybe you had a dirty fuel system issue or sticking parts in the carburetor but then I read where you only had one cylinder doing this.

 

 

Have you tried switching the plug and or the wire from one cylinder to another and see if the problem changes?

 

 

[pfrederi 18,681]

If it has a lot of hours on it may be time to pull the heads (at least the one that fouls the plugs and do a de-carbon....

 

[SPINJIM 1,986]

Similar problem with my KT17 was solved with an electric fuel pump (for what it's worth).

   Jim

[Bill D 2,250]

When was the last time it got new points, condenser and plug wires?  If a plug wire is "leaking" it could cause problems.  Bad condenser or points would make it act weird as well due to weak spark.  Check all electrical connections cleanliness and tightness.  Bill

[BrianX128 109]

2 hours ago, ebinmaine said:

That's not a bad idea at all.

 

 

I was thinking maybe you had a dirty fuel system issue or sticking parts in the carburetor but then I read where you only had one cylinder doing this.

 

 

Have you tried switching the plug and or the wire from one cylinder to another and see if the problem changes?

 

 

 

Yeah, it doesn't seem to effect anything. The "front" piston is the one that fouls the plug. Last year, the rear piston is the one that had the plug die and I verified it was the plug and not the coil / coil wire when that happened. 

 

I do wonder if it is something fuel related though, as it never seems to clear up while running it always clears up after you shut it off and go get a screwdriver and some stuff to mess with it and you start it back up and it's gone almost like there is an air bubble in the fuel or it's not able to pull constantly.

[ebinmaine 72,699]

18 minutes ago, BrianX128 said:

 

Yeah, it doesn't seem to effect anything. The "front" piston is the one that fouls the plug. Last year, the rear piston is the one that had the plug die and I verified it was the plug and not the coil / coil wire when that happened. 

 

I do wonder if it is something fuel related though, as it never seems to clear up while running it always clears up after you shut it off and go get a screwdriver and some stuff to mess with it and you start it back up and it's gone almost like there is an air bubble in the fuel or it's not able to pull constantly.

We had a saying in the Auto parts industry.

 

You must do the maintenance before you do diagnostics.

 

I consider a carb rebuild on a small engine to be maintenance, especially with the use of garbage fuel mixed with ethanol.

 

 

 

I do like the above idea of running Seafoam to clean the engine but the external fuel system needs to be in tip top shape.

 

[Ed Kennell 42,008]

Is the fuel cap vent open?        You probably guessed....I'm cheap.     I do all the simple inexpensive things before I throw expensive parts at a problem.

Edited April 3, 2020 by Ed Kennell

[953 nut 60,027]

3 hours ago, Ed Kennell said:

I do all the simple inexpensive things before I throw expensive parts at a problem.

    Any fool can throw money at a problem until they finally hit on the actual problem by process of elimination. However, if you haven't replaced the fuel line and filter in the past couple of years it should be done as a part of preventative maintenance. Also, if you are using ethanol enhanced gas PLEASE STOP!  That junk will mess up your fuel system. https://www.pure-gas.org/

6 hours ago, Bill D said:

When was the last time it got new points, condenser and plug wires?  If a plug wire is "leaking" it could cause problems.  Bad condenser or points would make it act weird as well due to weak spark.  Check all electrical connections cleanliness and tightness.  Bill

Again, if you haven't done an ignition tune-up in the past couple of years it is deferred maintenance that should be done.

7 hours ago, SPINJIM said:

Similar problem with my KT17 was solved with an electric fuel pump (for what it's worth).

   Jim

If your engine is hard to start after setting for a couple of days the fuel pump could be a problem. It is located on top of your engine and the tank is under the seat so if the pump is marginal it will have problems problems lifting the fuel up there.  You can test it by installing a temporary tank higher than the pump to see if the problem clears up.

11 hours ago, BrianX128 said:

 

I noticed this spring the first time I started it up a few weeks ago it ran rough and seemed like the exhaust looked hotter than normal

Did you pull some of the engine tins to check for accumulated mouse/bug nesting materials. Could be one cylinder isn't being cooled well.

6 hours ago, ebinmaine said:

We had a saying in the Auto parts industry.

 

You must do the maintenance before you do diagnostics.

 

I consider a carb rebuild on a small engine to be maintenance, especially with the use of garbage fuel mixed with ethanol.

 

 

 

I do like the above idea of running Seafoam to clean the engine but the external fuel system needs to be in tip top shape.

 

          deferred maintenance will get you at the most inconvenient times. You need to take charge of the situation.       

[richmondred01 2,307]

23 hours ago, Ed Kennell said:

I'd run a tank full of concentrated  Seafoam thru it before I went any deeper.    

yep mechanic in a can. 

[SPINJIM 1,986]

Sounds like you're sucking too much fuel to the front cylinder, and causing it to foul, and not enough to the rear cylinder.  Any chance you have a leak in the intake manifold near the rear cylinder that's causing it to suck air instead of fuel, but that closes up after the engine gets hot and the metal expands to close the leak?   Just a thought, before you tear into the heads.  Next guess would be a stuck valve.  Let us know what you find, for our own education.   

  Good luck,  Jim

[BrianX128 109]

Well it mowed for 2 hours today with no issues. I've only ran non ethanol gas in it but I've only had it for 10 of it's 650 hours of life according to the hour meter.

 

I do think its fuel related the more I mess with it. I tried a new fuel filter and it seemed happy today but the old one flowed fine. The hose had plenty of length to cut in case it was leaking where the clamps were.  I think the carburetor is likely gross but I don't want to mess with it while it's seemingly happy. I'd say intake is second culprit and my initial valve guess is third now just because it seems odd its able to be fine cold ever if it was the intake.

 

I'll just have to keep an eye on it at this point. 

[ebinmaine 72,699]

8 hours ago, BrianX128 said:

just have to keep an eye on it at this point

Keep us posted too please, for the sake of future learning.

 

[BrianX128 109]

Yesterday I fired it up to do some yard work and haul a cart of dirt around digging a drain and it was falling flat on it's face unless I had it 3/4 choked like it wasn't getting any fuel at all. Left the choke there and after 15 minutes it was still running good there, I tried pushing it in the whole way and then it ran fine there too.. Makes no sense. 

 

I wonder if the fuel pump is broke. When it starts to die it coughs inconsistently like my old ford IDI diesels do when they are sucking air into the injection pump after working on the fuel system and getting a little air in a line or something.

[lynnmor 7,822]

Do you intend to pull the carburetor and remove the dirt?

[BrianX128 109]

Yeah, I just wonder if SpinJim's guess of the intake leak is more likely now because it closes off whatever the issue is pretty quick. I started it and came back one minute later after getting my phone from in the garage to take this video and it was already running normal. I'll try to get a video of it running messed up tonight if it will do it.

 

 

 

[BrianX128 109]

Here's a video of it acting up after it's first started up. After this video I let it idle for a minute and shut it off for a minute. Then when I fired it back up, it was 100% fine. Would idle with the choke pushed in fully, wouldn't gain rpms or run any better if the choke was out part ways and was if it never happened. Just hoping for some suggestions of where to look first when I try and look into it, hopefully this weekend if time allows.

 

 

[c-series don 10,033]

I’d take the carburetor off and thoroughly clean it out for starters, install new fuel lines and a filter. Flush the gas tank. This way you can eliminate that aspect of the problem. 

[8ntruck 7,835]

Neat little tachometer.  Got a brand and/or model number?

[BrianX128 109]

They are on e-bay from a user named apexmeter221. 40$, you wire it into the leads from the stator and there is a little pinout on the back that you pick pulses per revolution. It only works for stators that do 8, 12, or 16 pulses per revolution. If I remember right the KT17's are 9 pulses from 18 pole changes from the 6 magnets so it's not 100% accurate but it's very close.