Carburetor problem

[reb]

This isn't on a tractor, but it does relate to agriculture on a small scale. Besides, I don't know of a better place to get some free skilled advice.

I have a shredder with a B&S engine. After rebuilding the carburetor I have had some difficulty getting it to run. It now will run for 3 or 4 minutes before it floods out and stops. It looks to me like the float valve will not seal properly. When the carb is apart, I can turn the top assembly over and the valve does not allow me to blow air through it, but when it is assembled and installed on the engine it gets liquid fuel into the throat (it is an updraft carb). There is also evidence of gas around the gasket between the bowl and the top assembly. There is no apparent leakage from the bowl, around the main jet. I checked that with the carb apart. The float looks ok. When I take the thing apart there is no sign of fuel inside it.

I'm thinking that maybe the seat for the float valve is faulty. It is not a separate piece as in some carburetors, it is a hole in the casting. My next idea is to somehow attempt to lightly dress that hole to remove any small imperfection.

Anyone here had the same problem or have any ideas?

 

[AndyL52]

You can put valve grinding compound on a q-tip and polish the needle seat. Did you put a new float needle also? If not, that could be it.

 

[sox3]

The seat of the carb should be replaceable. They are usually brass. when the bowl is overfilled it can leak from the vent. You should also check the top to bottom pieces with a feeler gauge. The top sections will warp sometimes. Blowing into the inlet is not a test, need to use a carb pressure tester to test needle and seat. We would just replace both. The new fuel eats up the needle and seats.

 

[reb]

Thanks for the ideas.

Some versions of this carburetor have replaceable seats. This one does not. The bowl is apparently overfilling and leaking from the vent. I will check for warpage, tho things look normal. Would a slightly warped top cause the float valve to fail to seat?

I tried a new float needle and the old one. Got the same results with each.

I will try the q-tip idea and check for warpage after I get the latest additions to the honeydew list out of the way.

 

[Willl]

Brass float ?, if so shake it to see if it's leaking.

 

[mrmikey]

Did you check for the correct height of the float? Sounds like the same symptoms my 17H Kohler had when the float tangs were bent from bouncing thru the woods.......Mike

 

[reb]

It is a brass float. I agree, the symptoms seem to fit a leaking float, but I can't find a sign of a leak. After I let it set for a day or so, it starts on the first pull, then dies after a few minutes. BTW, removing the fuel cap doesn't change the problem, so it isn't a plugged vent.

When I set the float level correctly, the engine ran worse than it does since I lowered it a bit. Maybe it should be a bit lower.

Such a simple carburetor shouldn't be so hard to fix.

 

[sox3]

Can you give us the model type and code of the engine?

 

[reb]

Can you give us the model type and code of the engine?

This is where it gets complicated. This engine is pretty obviously not the original engine on the shredder. The model # is 190402, type 3034 01, code 87 040609. I looked that up on the web and the parts breakdown shows a different carburetor and air cleaner. This carburetor looks externally the same as the one on my rototiller: model 171432, type 05029. Someone switched engines and apparently used the original carburetor and air cleaner. The original part numbers were lost in the swap.

This should be a simple repair. I keep learning there is no such thing as a simple, quick task.

 

[sox3]

That happens a lot. They also switch the blower housings too, which have the model #'s on them. If you have access to a local mower shop, buy a used carb or just the top that has the replaceable seat.

 

[KubotaSam]

Some small engine carburetors use a rubber donut in the bottom of the hole to act as the seat for the needle. I have no idea if yours should be like that, but I thought I would pass on the info.

 

[KubotaSam]

I googled your Model and type numbers. This site shows (if you scroll down to pict 18) a carburetor with the rubber seat like I was talking about.
Disassembly, Cleaning and Repair of Briggs and Stratton Medium Two-Piece Flo-jet Carburetor

 

[reb]

KubotaSam--good link. That carburetor is pretty close to mine. The rebuild kit I got included a rubber seat, but that area of the carburetor is different--the seat was too small. There was no seat in it when I took it apart, either. The tip of the original needle appears to be rubber. The kit included one like the original and a shorter one without the rubber tip. It also included a replacement for a carb with a removeable seat assembly. It looks like there are several versions of this animal.

I will take it apart one more time and try the suggestions here. After the wife's latest additions to the honeydew list are out of the way.

Thanks all for your ideas.