Engine TB30 R Back fires every few minutes.

[whanner]

I have a 2 year old TB30 R Riding mower that has run fine for 2 years but this year has started back firing every minute or so. I have put a new plug in it and added Sea Foam to the gas but it didn't help much....any suggestions on what could be causing the problem? I noticed a spark from a factory hole in the carburetor behind the bolt that hold the carb in place...that seems odd to me. Here's the bolt where I notice the spark...notice the carbon

 

[Boobala]

Looking at your pic it appears the carb to intake manifold GASKET is leaking, try installing a new gasket, and be sure you snug it up real good, it may solve that issue....... DO NOT overtighten it's a plastic manifold.

I THINK the p/n for the gasket is 692137, (that's the NON-restrictor gasket) yuo haven't supplied your engine info so I'm shootin in the dark. When asking for help on the forums, ALWAYS, include your machine's info. ( see example ) .....

 

[EngineMan]

Check the HT lead and see the the coil is clean around it, maybe the spark going to ground...! you could remove the bolt and see what the hole is for.

 

[Boobala]

After re-reading your post and checking the pic AGAIN, you mentioned a HOLE in the carb, there should be a welch-plug in there, or are you just seeing the indentation where the plug is installed, you would get a better look by removing that bolt,see enclosed pic .........

 

[whanner]

Thanks for all the input guys... I'm not familiar with a welch-plug, to me it looks like the intake should'nt have that opening like maybe the plug is missing? going to look at it this week end.
thanks again!

After re-reading your post and checking the pic AGAIN, you mentioned a HOLE in the carb, there should be a welch-plug in there, or are you just seeing the indentation where the plug is installed, you would get a better look by removing that bolt,see enclosed pic .........

View attachment 36515

 

[whanner]

The motor is a Briggs and Straton 21r7 0039. Something else... the governor keeps trying to regulate the rpm. I i hold it in place it does ok.

 

[dfbroxy]

Try checking the valve gap. The intake valve may be staying open just enough to backfire into the carb. This could also be causing the problem with the gov. also

 

[Boobala]

The motor is a Briggs and Straton 21r7 0039. Something else... the governor keeps trying to regulate the rpm. I i hold it in place it does ok.

THAT model # DOES NOT JIVE with anything I've checked, you must be reading the wrong numbers, I suspect you have a single cylinder OHV engine with THAT model of carb, look through the enclosed manual, ( in link) and see if it's familiar......

https://docs.google.com/file/d/0B6NaqjIxWV1ybEN0LWo3azl6OUU/edit

The engine info will either be on the engine "shroud" or the valve cover

 

[ILENGINE]

THAT model # DOES NOT JIVE with anything I've checked, you must be reading the wrong numbers, I suspect you have a single cylinder OHV engine with THAT model of carb, look through the enclosed manual, ( in link) and see if it's familiar......

https://docs.google.com/file/d/0B6NaqjIxWV1ybEN0LWo3azl6OUU/edit

The engine info will either be on the engine "shroud" or the valve cover

Boo 21R707-0039. He is missing the welch plug that covers the transfer port hole for the idle circuit of the carb. Which could be causing the governor surge since it would be trying to run on the high speed jet only. the welch plug isn't available as an individual part from briggs but is a standard welch plug available from Walbro or other aftermarket suppliers such as Stens or Oregon.

the backfire could be due to a valve issue, but could also be a side effect of running lean due to the missing plug.

 

[Boobala]

Boo 21R707-0039. He is missing the welch plug that covers the transfer port hole for the idle circuit of the carb. Which could be causing the governor surge since it would be trying to run on the high speed jet only. the welch plug isn't available as an individual part from briggs but is a standard welch plug available from Walbro or other aftermarket suppliers such as Stens or Oregon.

the backfire could be due to a valve issue, but could also be a side effect of running lean due to the missing plug.

I too thought about a valve adjustment, but looking at his pic, and him NOT mentioning a hard-start condition, I ventured to the carb first, yes it certainly can be from valves causing the back-fire and I think he should adjust them regardless. I am in total agreement with you.