B&S Twin Engine labors and smokes

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  #1  
Old 07-18-09, 12:45 PM
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B&S Twin Engine labors and smokes

Hello everyone,
Long time, no post. Was mowing the lawn this morning with my Murray tractor that has a {B&S} 17.5 Twin cylinder engine. Everything was fine until I shut it down and a few minutes later tried to restart it. It just cranked and would not turn over. I finally got it to turn over and barely run but only by removing the air filters and exposing the carb. Even then it ran very labored with white smoke coming from the exhaust. With the air filter and cover replace the engine barely idles and then ends up shutting down. I am completely lost on this one. It was running like a champ before I shut it down. One thing I did notice is that there was no backfire. Everytime I shut the machine down there is a 5-10 seconds of quiet and then a backfire. Sorry if my post is a little off kilter or lacking important info, but this season this machine has got my goat....
 
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  #2  
Old 07-18-09, 01:21 PM
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Check for spark first on a grounded plug. If you have a bright blue spark, then.....

With the engine cool, spin it over about five times with the spark plug out and the fuel shut off. Hand feed it through the plug hole with a teaspoon of gas.

Then see if it'll try to start with half throttle and the choke off. If it takes right off and tries to rev up, you probably have a fuel problem in the delivery to the carburetor or the carb itself.

That could be at the fuel solenoid, the filter, a plugged fuel cap (try loosening the cap), a collapsed fuel line, or a plugged outlet at the tank.

If the fuel and the spark check out, pull the valve covers and make sure the valves are moving.
 

Last edited by marbobj; 07-18-09 at 01:42 PM.
  #3  
Old 07-18-09, 10:50 PM
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Sounds to me like the carb inlet needle is not seating and is flooding the engine.
 
  #4  
Old 07-19-09, 04:02 AM
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Thanks for the input. I tried most of marbobj's suggestions, but ran out of day. Will have someone a little more in the know look at the carb. This is a great forum. Will update soon.
 
  #5  
Old 07-29-09, 10:32 AM
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Still waiting on a friend to look at the carb to complete evryones suggestions. While checking out the tractor the other day, I spun the motor by hand and it seemed fairly easy to do, very little resistance. I don't remember where I saw this over the weekend, but I read that with a spark plug removed you can do a "compression check" with your finger, being that you will feel your finger sucked towrds the hole and then pushed away while spinning the motor. If this a somewhat reliable test, I'm afraid my carb is the least of my problems.
 
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Old 07-29-09, 10:20 PM
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You're not generally going to just lose compression when you shut the engine off. If you feel air pushing your finger off the spark plug hole while cranking the engine, you have *some* compression. The fact that it cranked up tells me you have some compression as well. Pull the dipstick. Is the oil level overfull and does the oil smell like gas?
 
  #7  
Old 07-30-09, 05:56 AM
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Oil level is between Full and Add, slight to moderate gas smell on dipstick, oil seems a little thin. Engine still cranks but no longer "runs".
 

Last edited by legionlsd; 07-30-09 at 06:17 AM.
  #8  
Old 07-31-09, 12:04 AM
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Are the spark plugs wet? Also, have you checked for spark yet?
 
  #9  
Old 08-01-09, 10:16 AM
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Plugs are wet, there is a spark white in color.
 
  #10  
Old 08-01-09, 08:49 PM
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I still say carb problem.
 
  #11  
Old 08-04-09, 11:47 AM
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I agree. I'm afraid she's gonna end up at the shop after all. Thanks for everyones effort, I appreciate it.
 
  #12  
Old 08-10-09, 12:33 PM
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I decided to try and work on the carb afterall. I have included 2 photos and a video link. The needle valve seemed to be operating fine, to the untrained eye anyway. I cleaned up the carb some, then reassembled. Same result, does nothing but crank, gas shoots out of the carb {in mist form}. In the video I turn the motor by hand clock and counterclockwise to show what I think is very low compression.







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  #13  
Old 08-10-09, 10:28 PM
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You are right, you have no compression. You have either stuck valves or broken connecting rods. Pull the heads off and have a look.
 
  #14  
Old 08-11-09, 10:37 AM
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Yes Cheese,
I have a valve issue for sure. Thank you for the advice. I have posted 4 photos, 2 of each side. I'm assuming this repair is to much for a small engine newbie? Probably expensive at the shop {Just paid $400.00 for base gasket/lower oil seal repairs in the spring, no more big money for this old timer}. It's hard to see in the photos but the metal of the engine block is also gouged, so I don't think it could be repaired correctly anyway. I'm open to any advice, even if there is a way to "back woods" fix it, even if it runs like crap. I mow an 1- 1/2 sometimes twice a week and pushing it is murder. Can't swing a new machine until spring, and I mow well into October.






 
  #15  
Old 08-11-09, 11:37 AM
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Below is a link that shows how to replace the valve seat, the seat is the ring that came loose under the valve. Valves are pretty tough and hopefully the face is not damaged. You will need to remove the valve which requires a special tool. You may be able to improvise. I would not even replace the gasket. Just get the seat back in and hope for the best.

PER Notebook - Repairing Loose Valve Seats


This online manual I think will match your engine for valve removal.

How to Repair Briggs and Stratton ... - Google Books
 
  #16  
Old 08-12-09, 06:38 AM
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Thanks for the links, very helpful. I see JB Weld makes an epoxy that lists valve seats as one of the uses. I'm thinking about using the JB Weld AND peening, mainly as "insurance" against my feeble metal working skills.......I've read good and bad about the JB Weld....
 
  #17  
Old 08-13-09, 12:58 AM
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I don't know about the JBweld, but peening does work. I have done this with success without the JBweld. Something else to consider is why this happened to begin with. Generally valve seats come out with engine overheating. I'm thinking there is a bunch of stuff clogging up the cooling fins. I suggest cleaning out the cooling fins and remove the tin at the bottom of the cylinders and clean out that tin and the fins down there as well, since this is a common place for debris to collect and restrict airflow.
 
  #18  
Old 08-13-09, 04:55 AM
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I would almost bet the farm overheating caused it. The fins were full of debris from mice. I'm kicking myself in the butt because I ASSumed it was all cleaned out at the shop, my bad. It's all cleaned out now. I'll be going for it this weekend. Thanks to everyone so far.
 
  #19  
Old 08-14-09, 02:56 PM
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Well,
I reset the seats and peened them into place. Turned the engine over by hand and all looked well. Put everything back together crossed my fingers and turned the key. She slowly cranked for about 3 seconds {heavy laborish crank} and then it stopped, followed by a majestic cloud of white smoke from the starter. I think she's done. I am open to advice on new units..........I should start a new thread for that. Thanks to eveyone.
 
  #20  
Old 08-14-09, 09:55 PM
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The starter may have been done for from all the previous cranking. If it's a good mower and the engine did good before all this started, then it should be worth putting a starter on it. You can buy a good used starter for 50 bucks or so. Check with a local starter repair shop, they usually have plenty of parts for these and sometimes rebuilt units for sale.
 
  #21  
Old 08-21-09, 10:46 AM
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Cheese, Airman and Marbobj,
Thanks for the help guys, I got the old girl running. Now It's time to get the old snowblower fixed....................
 
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