K-301 Backfiring

IHCubCadet147 · #1 06-21-2019, 10:22 PM

I’m trying to get one of my 129s running. I’m not sure how long it has been since it last ran. When I first tried to start it, it just turned over but didn’t try to start. I went to cut grass, and tried to start it again after I was done. Now it was backfiring through the carb at first. I let it sit a few minutes, tried again and not it was backfiring through the exhaust.

What would cause this? My dad thought maybe the timing was off.

There was a stuck valve, I was able to free it up. I also sanded the points, but did not adjust them. I’m pretty sure the carb is adjusted right, or at least close enough for it to run.

dale c. · #2 06-21-2019, 10:25 PM

set the gap to .020 and see if it will run.. carb could be gunked up too

Billy-O · #3 06-21-2019, 11:04 PM

Lean condition will do that, but you seem sure the carb is alright. Did ya check the condenser?

cooperino · #4 06-22-2019, 07:14 AM

If you can't recall the last time it ran there is a good chance the fuel system is pretty gunked up unless you prepped it for storage when you parked it. I would also think the points wold be dirty and maybe making poor contact as well. When you cleaned the points, with the cover off, did you crank the engine and see the points working ?

I would start by cleaning the fuel system entirely and cleaning/adjusting the points. As stated a lean condition could cause this. Not enough fuel.

Is it doing this with choke fully closed?

IHCubCadet147 · #5 06-22-2019, 08:51 AM

Quote:

Originally Posted by dale c.

set the gap to .020 and see if it will run.. carb could be gunked up too

The carb is clean, I will check the points gap.

Quote:

Originally Posted by Billy-O

Lean condition will do that, but you seem sure the carb is alright. Did ya check the condenser?

The carb should be close since I just took it off my running 129. The condenser was on my 149, it was only changed because I got a new when it was rebuilt.

Quote:

Originally Posted by cooperino

If you can't recall the last time it ran there is a good chance the fuel system is pretty gunked up unless you prepped it for storage when you parked it. I would also think the points wold be dirty and maybe making poor contact as well. When you cleaned the points, with the cover off, did you crank the engine and see the points working ?

I would start by cleaning the fuel system entirely and cleaning/adjusting the points. As stated a lean condition could cause this. Not enough fuel.

Is it doing this with choke fully closed?

I bought it non running, so I don’t know when it was last ran. I put a good, clean carb on it and a clean gas tank. I did not check if the points were working.

When I first tried starting it, with the choke closed, it did nothing. When I opened the choke it started backfiring. Then it was doing it both ways.

IHCubCadet147 · #6 06-24-2019, 06:35 PM

I checked the points, they were adjusted properly. Now I noticed it was blowing fuel and air out the carburetor. What would cause this?

ol'George · #7 06-24-2019, 07:05 PM

Stuck valve (s), check to see if it is moving, and it's adjusted properly
Check both valves.
let us know what you find.
usually it is the exhaust that sticks.

IHCubCadet147 · #8 06-24-2019, 09:48 PM

Thanks George, it was a stuck valve. I freed it up a couple days ago, but it stuck again. I freed it up and now it runs, much better than I expected.

ol'George · #9 06-24-2019, 09:55 PM

Quote:

Originally Posted by IHCubCadet147

Thanks George, it was a stuck valve. I freed it up a couple days ago, but it stuck again. I freed it up and now it runs, much better than I expected.

If it was an exhaust, it might give a problem down the road.
Sometimes they do, other times, no problem.
Glad you found it.

dodge trucker · #10 06-24-2019, 11:13 PM

I recently had to work on a friend's 1250. took the carb off to put Heli coils in the casting where the back of the air filter bolts to, had to Heli coil 2 of the 3 holes. Of course was out of Helicoils, so had to wait for Fastenal to get some in. so I temporarily put a #30 from a K341 onto his K301 so he could use it in the meantime. . It adjusted out ok, ran great, had good power but backfired on shutdown every time. whether from full throttle or from idle, if it had been allowed to run for more than 30 seconds. Only ever did this on shut down not while under load.
A week later I put the original #26 back on after I got the Helicoils, and no more backfire.
Now that said, I had an M12 on a Woods ZTR once that came with a #30 (IDK if it was original or a PO mod) and it ran great and never backfired on shutdown.... weird.