KT17 surging
 

Picked up a 782last year that ran--barely. Made a dedicated sprayer machine out of it. Works great but we can't get it to run perfect. Darn thing surges, sometimes a lot, sometimes at all throttle speeds. Here is what has been done.
New plugs, all fuel line new, removed and washed tank (great flow to pump). By the manual, we adjusted the governor (the pc that clamps to the shaft).

Opened the carb up 3x's at least. Removed the 2 large welch plugs (that's all was in the kit). Last time I drilled out one of the small brass plugs so I could visually see I could poke a wire thru the small brass vertical tube (air supply?) that feeds into the main jet area. I blew so much air (non-osha approved air gun) that I blew one of the welch plugs out. This is a Walbro carb, only adjustment is the low idle. Start by the book, sometimes run it in 1/2, sometimes open it 3 turns----sometimes it help, sometimes it doesn't. After I put the carb back on yesterday it ran great, tweaked jet 1/4, backed outside and let run for 10 flawless minutes. Decided to drive it around over some rough/hilly ground. Sure enough after a couple minutes the surge was back. We tweaked the carb, shortened the fuel line so it would barely touch the block (thinking heat/boiling fuel), problem still inconsistent. It actually started surging on one test run and the second we raised the hood, it quit.:bash2:
I did notice 3or 4 tiny black specs in the fuel bowl at one point yesterday--thinking something is coming loose from the pump (lines are new) Filled the tank fairly full, bypassed the pump, and added an inline filter. Her is how it behaves now, the first few minutes, it runs rough, now once it is hot it runs well enough that I logged about 2 hours running yesterday. Honestly, the only thing I know to do is pick up one of those aftermarket carbs and a fuel pump. Our theory is trash is coming from somewhere and intermittently obstructing something. We have yet to find a bunch of trash or varnish anywhere in the fuel system, and the fuel pump was swaped out for a used one I replaced on a M18 that got lots of new parts.

Are we missing the obvious somewhere?

Is the linkage tight? If there is wear it will "hunt".

kt engines have points, might be worn and sometimes ignition issues look like fuel system issues.

I think you are on the right track.
Those walboro's with the main jet on the side are lean, and all the jet screw does is basically allow you to lean it more.
It is normal to get little flecks of fuel line in the bowl, especially when you replaced it all.
I can only suggest you keep cleaning them out till you get them all.
Were you able go get the emulsion tube out to clean it?
( it is the one in the center above the bolt that holds the fuel bowl on)
Cant remember for sure, but thinking it was covered on the top by an expansion plug.
With all the time you have spent, might be better to get one of those epay china adjustable ones as you mentioned, and be done with it.
Just make sure if you do, it has the correct choke pull linkage for your application as there are front and rear pull linkages.
Make sure their pix is the style you want.
Do take care removing/replacing the fuel hoses as just a slight fleck can cause an obstruction.

You talking about the rod with those 2 special back plastic clips/bushings?:bigthink:

Havent' bothered ignition yet. Seems like we are chasing a moving target, that's why we went after fuel.

How do you remove that tube? looks to be pressed in place. Yes there is a brass plug above it, and one to the side--I drilled out the one on the side.

FWIW, I even removed the adjustment screw at one point with the engine running and plugged the hole with my finger and it went to running better.

Yes....:beer2:

I feel your pain, I've tried my hardest to get a single adjust Walbro clean.
At least 3/4 of them now. I know Jonathan thinks less of me, but I just replace a walbro.

John, I had a M20 that I repaired and sold awhile back that had a sticky throttle valve. See this post.
http://www.onlycubcadets.net/forum/s...ad.php?t=44023
I never figured out why it did that. I just ran it on to bench, but maybe in a tractor it would have surged. It was like when it was running the shaft had a bind, when stopped it was free as a breeze. Good luck.