leaky Walbro carb, post-cleaning

Austin Healey

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Took apart my Walbro carb on a 15-year-old OHV Briggs engine, 17 hp, in my Craftsman tractor, cleaned it out (but didn't change any parts), put it back together, and it's leaking. Candidates: the float valve or the seal on the electrical fuel shutoff? Any thoughts (especially if it's the fuel shutoff?)

Also, for this model carb, there seems to be only a $14 minor rebuild kit available (on eBay), which only has a few parts (search for: LMT-WALBRO-REPAIR-KIT-BRIGGS). But there are plenty of new carbs available for around $20 (not OEM, of course -- finest Chinese replicas). Any experience with those? My carb has the following numbers: 4993, LMT, 67

The engine is running, but only w/ at least half choke, and lots of backfiring. However, I think most of my (original) problem (backfiring on shutdown and constant surging) was caused by never-adjusted valves and/or a never-decarbonized head. Both of those will be my next step.

All comments appreciated
 
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Austin HOW is your carb leaking ??? When you shut the engine off gas pours out of the venturi / throat ???

Or is it leaking back into your crankcase filling it with gas ???

Or is it leaking from the bowl where it meets the body of the carb ??

Let us know Mon Ami ~!~!
 

Austin Healey

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The carb is leaking into the fuel throat after it's turned off. Could it be the float valve?

Thanks,

Graham
 

Boobala

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Sure sounds as though the Float is your problem, did you watch the link I sent awhile back ..??

http://outdoorpowerinfo.com/repairs/briggs_28b702_carb.asp

you can adjust the valves BEFORE you work on the carb, shouldn't need a new carb unless yours is damaged in some way, avoid a cheap rebuild kit, you get what you pay fo in these kits, BUT don't buy the most expensive either... keep us updated, Boudreaux will most likely chime in again, he's PDG with Briggs carbs. .. :thumbsup:
 

Austin Healey

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Re: leaky Walbro carb, post-cleaning, FIXED

Well, to wrap up this thread:

Like a total idiot, after cleaning the carb the first time, while hooking up the fuel hoses I installed the old inline fuel filter (that I had added) backward. So all the junk that the filter had trapped was flushed into the carburetor. So, I got to clean it again.

I also discovered the carb was leaking gas into the engine because the hole in the brass seat for the float needle had become enlarged, so the needle's rubber tip wouldn't seal. Ordered a repair kit for 20-something dollars, replaced the seat, put everything back together ... and the engine wouldn't even turn over.

Removed the spark plug, cranked the starter, the engine turned over and the gasoline that had leaked from the carb into the cylinder was forcefully expelled thru the spark plug hole (a good thing).

Replaced spark plug, hit the starter, and while the engine happily turned over, it still wouldn't start.

Sprayed a shot of starting fluid into the carb intake and the engine fired right up, for about two seconds until the fluid burned off, so I knew I had compression and spark. Therefore ... no fuel.

Took apart the carb again and discovered that the main jet, which is mounted on the side of the fuel riser in my carb, was clogged. I hadn't even known it was the jet until I found some more documentation online -- I thought it was just a little bolt.

Cleaned it out, reassembled the carb, reinstalled it ... and the engine still wouldn't start.

Then realized I'd forgotten to plug in the electrical connector for the fuel shutoff at the base of the carb. Plugged it in, cranked for a while, and the engine finally started ... for the first time in months.

I still need to adjust the valves, but at least I now have the damn thing running.

Thanks for the helpful suggestions from others. I'm sure I'll be back again. :)
 

shiftsuper175607

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Re: leaky Walbro carb, post-cleaning, FIXED

Well, to wrap up this thread:

Like a total idiot, after cleaning the carb the first time, while hooking up the fuel hoses I installed the old inline fuel filter (that I had added) backward. So all the junk that the filter had trapped was flushed into the carburetor. So, I got to clean it again.

I also discovered the carb was leaking gas into the engine because the hole in the brass seat for the float needle had become enlarged, so the needle's rubber tip wouldn't seal. Ordered a repair kit for 20-something dollars, replaced the seat, put everything back together ... and the engine wouldn't even turn over.

Removed the spark plug, cranked the starter, the engine turned over and the gasoline that had leaked from the carb into the cylinder was forcefully expelled thru the spark plug hole (a good thing).

Replaced spark plug, hit the starter, and while the engine happily turned over, it still wouldn't start.

Sprayed a shot of starting fluid into the carb intake and the engine fired right up, for about two seconds until the fluid burned off, so I knew I had compression and spark. Therefore ... no fuel.

Took apart the carb again and discovered that the main jet, which is mounted on the side of the fuel riser in my carb, was clogged. I hadn't even known it was the jet until I found some more documentation online -- I thought it was just a little bolt.

Cleaned it out, reassembled the carb, reinstalled it ... and the engine still wouldn't start.

Then realized I'd forgotten to plug in the electrical connector for the fuel shutoff at the base of the carb. Plugged it in, cranked for a while, and the engine finally started ... for the first time in months.

I still need to adjust the valves, but at least I now have the damn thing running.

Thanks for the helpful suggestions from others. I'm sure I'll be back again. :)


Experience is the best teacher...you are learning the same way most of us do.
You will never forget.
 

Austin Healey

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Well, the fun continues. The day after I got the tractor to run, I went out to actually mow the lawn with it ... and it wouldn't start. Same symptoms as before: no fuel.

Took apart the carb again for the 3 millionth time and discovered the jet was clogged, again, and there were a fair amount of loose particles floating around in the bowl. Cleaned out everything and reassembled. Was doing the final assembly of the air cleaner when I noticed a stream of fuel pouring out of the carburetor.

Took apart the carb again for the 3 million and 1th time. Checked the float, needle valve (new) and the fuel shutoff solenoid. All seemed OK, but I cleaned 'em again anyway. Removed the spark plug and cranked the engine to blow out the gasoline. Reassembled everything, and the engine ACTUALLY STARTED AND RAN and I mowed the entire back lawn. So far, no sign of flooding or leaks.

When I blew the gasoline out of the cylinder, a gratifying quantity of carbon deposits came out with it. I don't know if that was due to another soaking of the valves in gas, or the extra-enthusiastic combustion when I was using starter fluid in an effort to make the engine run. But, whatever the reason, the engine runs much better than before I started this project. Previously, it would often die under load and would frequently "hunt" while running. Today was very smooth, with no hunting at all, and no backfire after I shut off the engine.

Stay tuned for further developments, if any.
 
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