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Briggs 17 hp engine blowing white smoke


hoosierdaddy58's Avatar
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05-22-12, 05:42 PM   #1  
Briggs 17 hp engine blowing white smoke

Hi,

Picked up a Craftsman Lt1000 this week. Wouldn't start for the previous owner. Pulled the dipstick and saw it was overfull and reeked of gas. Figured it was just a bad carb needle. Got it home and drained the oily gas out of the crankcase. Put in new oil. Checked valve lash and noticed and broken pushrod no doubt from it hydro locking. Replaced the pushrod and it started right up. Alot of smoke at first as I figured it would. Mowed with it after the smoke cleared. Started it over the next couple of days and whenever I started it for the first time, it bellows white smoke for about a minute then clears up. I already put on a new head gasket when I replaced the pushrod. I checked the oil again figuring it was still contaminated and sure enough it looked like it hadn't been changed in a year. Tipped the mower over as I drained the oil again to hopefully get the old oil out better. The oil is good now. Still when I start it, the engine bellows white smoke for about a minute then clears up. So then I removed the flywheel and checked the crankcase breather. It is the reed type. It looked ok, just cleaned it and re-installed. Is there anything I could be over looking besides it being the rings?

Thank you

31C707
0230 E1
020907ZA

 
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05-22-12, 06:25 PM   #2  
Hello hoosierdaddy58,


White smoke in most cases is a result of moisture/condensation build-up inside the crankcase. Since you had a crankcase full of fuel the ethanol surely pulled condensation in even though you've changed the oil twice.

I'd let it sit and run about 1/4 throttle for 45 minutes or so to make sure all condensation is burnt out, Let it cool completely then try starting again.


Good Luck

 
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05-26-12, 06:14 AM   #3  
I let it run for 45 minutes yesterday. Started it today and still have smoke at startup. Any other ideas on what it might be.

Thank you

 
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05-26-12, 09:24 PM   #4  
Is the oil level a bit too high?


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05-27-12, 02:11 AM   #5  
Oil is just under the full mark. One thing I have noticed is that it doesn't start the first time I turn it over. Just went through the carb yesterday. It runs smooth at low and high speeds. Thinking maybe the continued cranking to get it started is contributng to the smoking problem. Going to check the valve clearances again. Any other ideas would be appreciated.

 
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05-27-12, 10:26 AM   #6  
Is the choke closing fully?


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05-28-12, 09:05 AM   #7  
Choke is closing fully. At least as far as the linkage will let it close. Not 100%, but i would say it is 80%. When the choke is open, it is all the way open.

Went to check the valve clearances once again. Brought the piston up to tdc and gas just ran out of the spark plug hole. Great! Still leaking past the carb. Took the carb apart and put in a new needle. By the way, the carb that is on the mower is not the one it came with that had the original bad needle. I put one on it that I thought was good to use. Anyway, no leaks past the carb now. Changed the oil again. Tipped the mower over a little to get all the gas/oil mix out of the crankcase.

I have been keeping an eye on the oil. No gas smell or discloring. Do I need to run it for an extended period of time again because of the gas getting in the crankcase again? Ready to pull my hair out. Runs great other than it smokes you out when it starts up. Starts better too.

Thank you

 
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05-28-12, 10:53 AM   #8  
"Choke is closing fully. At least as far as the linkage will let it close. Not 100%, but i would say it is 80%"
Then it's not closing fully. 80% is not enough for a quick start. You may need to adjust the throttle cable.

The gas getting into the cylinder would also be a cause of the smoke and hard starting. I don't see any need to run it for an extended amount of time.


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05-28-12, 05:25 PM   #9  
Adjusted the linkage and the choke closes good now. Started up pretty good. I noticed that there was some gas sitting in the carb. So after I shut the engine off, I turned the fuel shut off valve off. Let it cool down and the next time I started it, started right up and just a little smoke. Will try again tomorrow and see if the carb is being the cause of the smoking at startup.

 
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05-29-12, 05:37 PM   #10  
Left the fuel shut off I the off position after running it yesterday. Got home from work today, turned the key and everything was perfect. Started right up smooth and no smoking. Shut it off and left the fuel valve open. Just checked it and with the flywheel cover off I can see gas sitting in the carburetor and the intake elbow. So I started it and of course it didn't start easy and smoked. I put a new needle in the carb the other day and I haven't found any gas in the spark plug hole or in the oil. It is like the float level is too high and is just filling up the carb body back into the intake elbow that hooks to the flywheel cover. I don't see any float adjustments on my carb. As long as I turn of the fuel shut off, everything is good now. Just need that final little fix on the carb and all should be good.

Thank you

 
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05-29-12, 06:09 PM   #11  
Just need that final little fix on the carb and all should be good.

hoosierdaddy58,


There are two carbs listed for your engine, If you have the Nikki carb, The white plastic fuel transfer tubes are known for warpage. Replace this tube with part# 698780 kit which includes new seals and see if that doesn't solve the leakage/flooding issue.....

 
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05-29-12, 07:37 PM   #12  
That'll do it... if this info helps, usually I can replace the just the small o-ring with a regular o-ring and stop the leakage rather than putting the kinda-expensive kit on.


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05-30-12, 01:41 AM   #13  
Should have included that it is a Walbro carb.

 
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06-01-12, 09:27 AM   #14  
Take a q-tip with some rubbing compound on the end of it and put it in the seat area and twist it around several times to clean and polish the seat. Wash it out and put it back together and see if that stops your leak.


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06-02-12, 07:36 PM   #15  
I did the q tip with compound trick. Same results. After sitting for about an hour, intake elbow was full of gas. Decided that I had spent too much time on this carburetor. Got another identical one out of the drawer. Soaked it, cleaned it, new needle, cleaned the seat, float good, etc.. Put it on the engine. It started right up and ran good. Went back a couple of hours later only to discover the intake elbow was full of gas again! What did I do to deserve this? LOL. Could vent holes cause this to happen. After two carbs having the same problem, I am wondering if it something else causing this. Any possible solutions would be appreciated.

 
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06-02-12, 08:48 PM   #16  
Leave the gas cap a little loose and try again. If pressure is developing in the tank, it could be forcing fuel out the needle.


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06-03-12, 07:09 AM   #17  
Started it up and ran it for a few. Turned it off and left the gas cap loose. Went back an hour later and had gas in the elbow once again. Pulling my hair out.

 
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06-03-12, 10:47 AM   #18  
Something is still wrong with the needle/seat area. Try polishing the seat on this one. Is this the same needle from the other carb?


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