782 Running Rough

[IHRedRyan]

I’ve intermittently put a trickle charger on the 782 this winter. Fired it up yesterday for the first time in several months. 

It always likes some choke until it warms up , and it ran fine in the fall. But yesterday it was surging badly, ran for a few seconds and then would just about die and then rev up again. I let it do that for a few minutes , no change. 

The fuel in it is several months old , stabilized 91 octane, the fact that it ran at all makes me think it’s not likely bad gas.

It has an inline fuel filter, it looks clean. When we bought it I went through the carb but that’s already been 4 years ago. So I suppose maybe I should give it a good cleaning again and see if that fixes things. 

It has the original KT-17 series 1 , I’ve never been into one , are the fuel pumps known to go out or do they have any quirks I should be aware of?

Thanks in advance. 

 

 

[snoshoe]

Plugged idle circuit or binding throttle shaft or linkage.

[Mr. Plow]

Was it running on both cylinders?  A bad plug will make a twin run rough too.

[Mr. Plow]

Fuel pumps will go out, but usually present as gas dumped into the crank case.  Easy test of fuel pump is just to fill the tank above carb level, if it fixes it, then replace the pump (most, including myself, use an electric replacement).

Always a good practice to check a KT or Mag's oil before every use, a crank case full of raw fuel (failed pump or needle) can make a big mess quick.

[IHRedRyan]

Thanks for replies guys. I will confirm running on both cylinders and if so then pull carb for a good cleaning.

I always check the oil, it burns a little over the course of the mowing season. It was normal the other day. 

Knock on wood it’s been a great machine. 

[Legolord]

16 hours ago, Mr. Plow said:

 

Always a good practice to check a KT or Mag's oil before every use, a crank case full of raw fuel (failed pump or needle) can make a big mess quick.

It's also a good practice to check the oil on any piece of equipment before you run it. I blew up my 782 engine when I had to mow on a hill. I would've known the oil was a little low if I had taken 8 seconds to check it beforehand. Now I check the oil on my 149 even if I'm only going to move it a few feet lol

[iowaboy1965]

23 hours ago, Legolord said:

It's also a good practice to check the oil on any piece of equipment before you run it. I blew up my 782 engine when I had to mow on a hill. I would've known the oil was a little low if I had taken 8 seconds to check it beforehand. Now I check the oil on my 149 even if I'm only going to move it a few feet lol

Let's see some pics of that 782!

[Legolord]

2 hours ago, iowaboy1965 said:

Let's see some pics of that 782!

[IHRedRyan]

Confirmed getting good spark on both cylinders. Pulled carb and spark plugs , have some cleanup to do. 
 

 

[IHRedRyan]

I had the carb all apart and cleaned it thoroughly, back together with new gaskets and put on yesterday.

Fired it up and it still coughs almost/dies. Figured maybe it was the gas (maybe I forgot to stabilize and it’s from the fall). Took the carb back off , drained the bowl, made sure the main jet was still clean. Drained the tank, and put in some fresh stabilized 91 octane and a new inline filter for good measure.

Helped a little but, idled okay but stumbles when throttling up and even the occasional back fire. New fuel filter stays full , and there’s no sign of fuel in the oil. Makes me think it’s not the fuel pump. There is good flow coming out of the tank too.

Decided to leave fuel alone and move on to a potential ignition problem. Took the little rectangular cover off and cleaned the points and confirmed good gap. That helped quite a bit, wasn’t surging/almost dying anymore , just missing a bit and still theres some backfire when throttling up. Next I put some new champion plugs in and it ran great. Drove it up and down the lane and let it run for a good 20 minutes. No problems.

It had some NGKs in it that didn’t look bad , but i was content to have things fixed. 

Well today I took grandpa out with me, we cleaned the deck, sharpened the blades , greased the spindles. Fired up the tractor to warm it up to change the oil , and it was missing and backfiring a bit when throttling up again. 

But it idles great. Proceeded to change the oil and grease the steering box and front spindles.  I think next step will be a new condenser, unless anybody else thinks there’s a better course of action for me??  

Always something! Otherwise she’s ready for grass cutting season , but that won’t be anytime soon as it’s still very wet here from snow melt. Hopefully I can get this figured out before then. 

[Mr. Plow]

Make sure you have the correct gasket between the carb body and aircleaner elbow.  Some carbs have a slot in gasket face, some have a hole.....if you block the hole it can't breathe correctly and won't idle up correctly or at all.

May not be your issue since it was running better.

Is fuel screen clean in tank valve?  There is a screen on the stand pipe inside the tank above the shut off.  Just because there is fuel in filter doesn't mean its flowing correctly. 

BTW,  for some reason Mags and KTs like Champion plugs.

[Powered by IH]

Have you tried adjusting the carb?

What color is the spark at the spark plug?

[IHRedRyan]

I just copied the gasket that was there , I believe it to be correct.

Screen in tank looks clean , when I drained fuel it had good flow coming out.
 

And ya I forgot to mention I did adjust the carb settings , same behaviour. 
 

Will have to take a closer look at the spark. Thanks to both of you. 

[Mr. Plow]

Gasket is correct.   That hole at 10:00 will get you sometimes if you aren't paying attention. 

[IHRedRyan]

Fired the 782 up yesterday afternoon, still running rough. I swapped a known good ignition condenser onto it and that fixed things , it was night and day. It ran as good as it ever has and I cut the grass without issue!
 
I’d forgotten how much of a pain taking that little points cover on and off is. Hard to get the machine screw closest to the front started. 
 

I have a buddy who has a bench tester for condensers , I’ll get him to check the old one before I throw it away. It could just be that it wasn’t grounded well enough.