Other surging culprits?

[turfboy1997]

Let me get this right, the "IDLE CIRCUIT" is the external jet on the side of the carb, the one that was once under the sticker when new? I need to make sure I'm looking at the right part. With a name like "idle circuit," it makes one think of electrical components, even though "circuit can apply to anything closed.

Happy Saturday.

That is correct. i have heard it called idle circuit, idle jet, metering circuit. Whatever its called it usually gets clogged easy and causes surging. If you replace that part and it still surges you need to get a #67 micro drill bit and drill the main jet. After you drill and When you start the machine you will see what the EPA did to the duraforce engine by making them design them that way to pass emission standards. They basically killed the brand.

 

[Two-Stroke]

Thanks, turfboy1997. I'm glad you found this thread.

 

[Rumrunner]

Thanks for the tip. So, which one's the Main Jet?

Also, just a couple replies up you stated a #67, but on your surging thread you mentioned a number 76, or a size ranging from #75-77. Is 76 what you meant?

 

[Rivets]

Just my opinion, but in your case I would not punch (drill out) the main jet with a micro drill. If you don't know what you are doing, you will cause more harm than good, and you will end up buying a new jet or all new carb. I have punched over a hundred jets and there are times that I have had to replace parts because I made a mistake and went too fast. It sounds easy for a mechanic, with the right tools, but not worth the time, money and effort for the average person. Would be cheaper for them to purchase a new jet and replace.

 

[Rumrunner]

OKAY I got my Briggs idle jets in today. Didn't make one bit of difference. So, I decided to pull the carb apart and check everything. Ready for the funny stuff? I remember reading something about the governor side throttle plate having incorrect hole sizes. BE ADVISED: Some of the new carb rebuild kits come with the wrong plate, even today. I swapped it out with my old one and seems to do better until it just died on me. Something told me to look at the plug and I couldn't believe what I saw, black and dripping with oil. What gives? As I said before, I'm using the gen II oil at 8oz per two gallons. I changed the plug and all was better, but when finished I looked at it and I found it pretty ugly too with oil drippings.

Now, my questions from before remain unchanged, plus new ones now:

Why did it run flawlessly after rebuild with the wrong throttle plate?

Why was all perfect until the machine killer wife hit a stick, but with an intact flywheel key?

Why could the machine be smadging plugs now?

What can other causes be for the surging? It still is doing it some.


Thanks again all.

 

[Fireman 123]

Here's my opinion. You don't have near the machine as the one you used back in the day. I can't offer any more advise than what you already have about fixing it. I've had a few DF and liked none of them. Push 'er to the curb. Find you an older F series, and you won't go wrong! Good luck.

 

[Rumrunner]

Well, now that you mention it, I got my hands on a model 8253 yesterday. It was free, and for a good reason- it looks worse than bad. I think there's only a slight chance of it ever running again. It's just a plaything to make me a better 2-cycle guy. I have stuff to do, but I'll tear into it in the next couple weeks.

 

[maca3731]

Let me get this right, the "IDLE CIRCUIT" is the external jet on the side of the carb, the one that was once under the sticker when new? I need to make sure I'm looking at the right part. With a name like "idle circuit," it makes one think of electrical components, even though "circuit can apply to anything closed.

Happy Saturday.

I have a Duraforce engine that would surge. The carburetor has a small piece of black tape on the side. If the tape is pulled off, there is a brass jet that can be screwed out of the carburetor. The jet can be reamed slightly larger with a very small drill bit or a torch cleaning tip. The Lawn Boy engine that had this jet gave problems because the jet was too small in order to meet emission standards. I did two of these and the mowers ran like a new engine afterward. Be very careful and don't ream the hole too much. Do it with caution.

 

[WhyZed]

It is possible the float has been adjusted out of spec do to the violent hit, or the float valve (needle valve) has been damaged. Not enough fuel in the bowl will create a lean condition.

If it was running fine without surging before, I wouldn't go drilling nuttin. That isn't the problem and you could really mess it up..

I can make mine surge easily by leaning out the main jet/high speed nozzle. You have one of those that's adjustable on yours?

 

[Rivets]

Surging 99% of the time is caused by either too much or not enough fuel getting to the cylinder. Float level would not caused by a hit. Clean and rebuild the carb first.