Export thread

Last fall I semi rebuilt the Walbro carb with a new float and needle valve (the one with the rubber tip). I adjusted the valves to B&S specs (intake: .003-.005, exhaust: .005-.007), put it all back together, and put it in my shed for the winter.

Today I started it up after 4 months of sitting. It started right up, but there seemed to be a lot of smoke coming out of the exhaust. Some of the smoke was from when oil leaked out of the valve cover and on to the exhaust. I let it run for awhile, some smoke diminished, but could smell (I think) a rich mixture, and a small amount of smoke.

I added fuel stabilizer last fall. I changed the oil, today, 30 weight, and restarted it, and rode it around my yard, with blades static. There was barely any smoke now, but I could smell the richness of the fuel mixture. The motor starts right up and ran smoothly as it did last year.

Is there a simple method to set the carb? The manual doesn't give much info on setting it up.

Thanks

Need to clear some things up first. Rebuilt carb with rubber tipped needle? Did you check inside the needle seat area to see if you had a viton seat or brass seat? Did you make sure that the float was set level? What are the Model and Type numbers for you engine? The spec you listed seem a little tight to me. Does your carb have 1,2, or 3 adjusting screws? Did the oil you drained out smell like gas?
The reason I'm asking all these questions is that it sounds like your new needle did not seat properly and allowed fuel to go from your tank to the crankcase, via the carb. Most B&S engines in 99 had valve clearances of .005-.007 intake and .007-.009 exhaust. Finally I need to know the number of screws to tell you how to set the carb.

Rivets said:

Need to clear some things up first. Rebuilt carb with rubber tipped needle? Did you check inside the needle seat area to see if you had a viton seat or brass seat? Did you make sure that the float was set level? What are the Model and Type numbers for you engine? The spec you listed seem a little tight to me. Does your carb have 1,2, or 3 adjusting screws? Did the oil you drained out smell like gas?
The reason I'm asking all these questions is that it sounds like your new needle did not seat properly and allowed fuel to go from your tank to the crankcase, via the carb. Most B&S engines in 99 had valve clearances of .005-.007 intake and .007-.009 exhaust. Finally I need to know the number of screws to tell you how to set the carb.

Click to expand...

Hi Rivits

The 'needle valve' I said I replaced is the rubber tipped square valve (attached to float) that drops into the seat you need to replace with special tools in the bowl. I hope that clears that up. I'm not versed in engine repair terminology. Sorry.

I did not replace the brass seat. It "was" leaking fuel into the cylinder last year and that is fixed. The carb has 2 screws for adjustment. I never touched them when I redid the carb last year. The specs for the valve setting are right out of the B&S manual. See pic.

Model: 917.256524

Type: ???

S/N: 100996B 012199

I have a new post up. Here is the URL.

http://www.lawnmowerforum.com/craft...ng-mower-15-5-hp-turbo-cool-917-256524-a.html

I hope this helps.

Thanks

Ok on the valves, I just wanted to make sure. Let's talk about the needle and seat.
B & S uses two different needle and seat combinations. One uses a Viton tipped needle and a brass seat. The other is a solid aluminum needle with a Viton seat insert. Viton is the material which you call rubber. I have had people interchange these to bad results. When interchanges they will not close properly allowing fuel to go posses it should not, like the crankcase, and YES even the muffler. That's why I asked about the oil. Two screws on this model are a little confusing. Where are they located?

Rivets said:

Ok on the valves, I just wanted to make sure. Let's talk about the needle and seat.
B & S uses two different needle and seat combinations. One uses a Viton tipped needle and a brass seat. The other is a solid aluminum needle with a Viton seat insert. Viton is the material which you call rubber. I have had people interchange these to bad results. When interchanges they will not close properly allowing fuel to go posses it should not, like the crankcase, and YES even the muffler. That's why I asked about the oil. Two screws on this model are a little confusing. Where are they located?

Click to expand...

The old needle was exactly like the new one I put in. The mower sat for 4 months (this winter) with no gas leakage into the cylinder. Last year within 7 days the piston would lock up because of the gas that would accumulate in the cylinder. That issue is solved.

See pics of my carb. I see only 2 adjusting screws.

You can see the oil sitting on the bottom- open end of the carb.

Thanks

Ok, this should be easy. The only adjustment you have is the idle mixture. Your high speed mixture is preset by the main nozzle. To adjust the idle mixture warm the engine and then bring it down to idle. If it won't idle, turn in the idle speed screw until you get to the lowest point at which the engine will run. Now you have to adjust the idle mixture screw out slowly and the idle speed screw. You will continue to do this until you have the engine running at the idle speed you want. At this point turn the idle mixture screw in until the engine starts lugging and then out 1/4 turn. You should now be done. If this doesnot work then you will have to look to see if the main jet in the carb is clogged.

Thanks again...Will try today.