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B&S 3.5 Runs rich


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12-30-04, 05:38 PM   #1  
chomot
B&S 3.5 Runs rich

I recently put new rings in my B&S Model 92982 Type 3293 01 Code 89091304 on a Craftsmen 917372150 self propelled bag mower. It was smoking pretty badly so I finally broke down and fixed it. I have always liked this mower because it acts more like a vacuum cleaner in it will suck up just about anything into its bag.

All I did was replace the rings and gaskets as necessary; it was running fine before I started any work. There was a LOT of carbon in the head etc and I cleaned it all out and reassembled everything ok. During the tuning I was trying to get the carb to run leaner but on the diaphragm type carb I do not know to much about adjusting them. The only adjustment I could find is a needle screw on the throttle plate area. This did not give me the results I was looking for. It either ran ratty or rich no good middle ground and it would start only when I held the choke open no matter what I adjusted.

I took carb apart and the diaphragm was OK not dried out, cracked or anything as I had replaced it last year. I blew everything out with compressed air and cleaned it all up real good and still the same results.

This engine has a LOT of hours on it and I noticed the throttle shaft was loose in its bores and was wondering if it could be sucking gas from the little hole in the lower end shaft boss? That area does have access to the diaphragm area I noticed. I also noticed the gasket on the choke link cover was a bit old. If that cavity leaks air with that cause a problem?

Anyway this one has me stumped.

Thanks

Chomot

 
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01-01-05, 12:47 AM   #2  
Hello chomot!

When it cranks up, does the choke open? If not, either the pre-load on the choke rod is not set properly, or the diaphragm needs replacement. Are you running it with the air filter screw in place? It needs to be in place even without the filter (when testing/adjusting) for it to run right. The gasket on the choke rod cover is not critical. It wouldn't hurt to change it though.


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01-02-05, 09:25 AM   #3  
chomot
This is turning into a good thread.

I did not know that about the filter screw needing to be installed I will give that a try. Once it is running the choke does open up. It will not start unless I hold it open though.

What is the process for adjusting the choke rod? All I see is this rod attached to the diaphragm that sits in a socket on the choke plate. The choke plate has a little clock spring around it. Is the gasket on that cover plate important? Mine has a small hole in it.

I did some further reading and found a comment about truing the carb and figured out that all that is is insuring the bottom of the carb and the top of the tank is flat and if not make it flat with some 400 grit sand paper and a flat surface. My question is what is the trick to removing the plastic down tubes with out breaking them?

Thanks for the help Cheese

Chomot

 
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01-02-05, 03:48 PM   #4  
chomot
I just spent some time today working on the carb some more and noticed something interesting.

I took it all apart and checked the surfaces for flatness with a strait edge and that was ok, so I keep looking for plugged passages, dirt etc and worked to figure out the flow paths.

I pulled the nylon plug out that holds the metering screw to the main jet. I cleaned it all up and reassembled. During reassemble I noticed that not a whole lot holds the metering screw into place. I discovered the O ring at the base and the rubber flat washer have to be in place tightly for it to work ok and that it is easy to have this fall out on you. I figured that was my flooding problem.

I got it back together and running ok and the richness/flooding seams to have been resolved but now it likes to serge and not run reliable for long. It will be running ok and steady and then just die.

The throttle shaft is worn pretty loose, does that cause problems in these?

This it turning into a lot more work than I wanted it to.

Take care

Chomot

 
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01-03-05, 06:34 PM   #5  
chomot
Fixed it........

The final problem was that the fuel pump spring and spring cap was on the wrong side of the diaphram. It should be on the carb side, not the tank side where I found it.

How I found it that was I noticed the diaphram was deforming and causing a leak into another cavity. When I bought a new diaphrame there was a diagram in the box that showed me the correct placement of the sping.

Anyway it runs great now and I just wanted to complete this in case some day it helps someone else out.

Chomot

 
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01-03-05, 09:51 PM   #6  
Great! Thanks for keeping us posted on your progress. Sorry I didn't get back to you yesterday....I had business to tend to and was too tired to check the posts when I got in.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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