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B&S 17.5 timing issues


lcowan3's Avatar
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09-19-04, 09:03 AM   #1  
lcowan3
B&S 17.5 top dead center query

This 17.5 B&S (Murray Riding Mower) has backfired since new. Now its about four years old. It backfired, stalled and flooded. I rebuilt the carb, bought a new one, still
it floods the plug and shoves gas in the oil. I have replaced the keyway on the flywheel. It does not smoke except when flooded. When it would start it sounds way off on timing. Now I have the head off and the piston is almost at the bottom of the cylinder when the magnet comes around for fire. When the piston is at T.D.C. the magnet is about seven inches back on the flywheel. Any ideas are greatly appreciated.


Last edited by lcowan3; 09-19-04 at 02:10 PM.
 
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09-20-04, 10:43 AM   #2  
Azis
Couple things, Is it possible that you are viewing this while the piston (the one you are viewing, this is a 2 cylinder engine right?) is at the top of the exhaust stroke? When one piston is at the top of its stroke the other shoud be at or near the bottom.
It is also possible that the flywheel key has sheared. If it was not torqued down properly this is a good possibility.
Also check for spark on "Both" spark plug leads.

Letus know how these checks go and we can go from there.

 
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09-21-04, 12:40 PM   #3  
lcowan3
17.5 B&S

Thanks for the reply. This is a one cylinder motor. We replaced the original key after trying the carb rebuild and replace. It appeared to be fine. The new one sheared this time and explains the timing issue, I think. We now have the motor apart and the timing marks are correct, the cam is fine. The reason for all of this is after it backfired and stalled we could not get it to start again. It would backfire through the carb and immediately fill the cylinder with gas. I have had the carb apart and blown B12 through every hole. We did not replace the needle. Then we put the other type of carb for this motor on it. The original has a solenoid at the bottom. This one does not. We were told the solenoid is to stop flooding and Backfiring. My father informed me this Motor is only one year old. My uncle has one of these Murray Lawn Mowers and its been in the shop often. It's only two years old. What is the deal.
Maybe it's time to rebuild the Craftsman.

 
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09-21-04, 02:11 PM   #4  
What are the engine ID #'s? If you in fact have a Briggs and it's a 17.5 horse and it's in a Murray, it will be a twin cylinder. You could have a Tecumseh and not realize it. The engine #'s will greatly help us to help you. However, lets go with some basics based on your posts. Fuel in the oil definitely indicates a carburetor issue. I strongly suggest (not just here, but with any carb recon) to remove the carb, use a bath type cleaner (NAPA #6401 works miracles), and service the carb with a genuine OEM kit (and in your case, I'd also replace the float). Lets worry about the timing issue when we know exactly what you have for an engine...post back with numbers!!!

 
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09-23-04, 07:41 AM   #5  
lcowan3
Briggs and Stratton on Murray

The numbers you requested are model #313707, type 0126-e1,
code #001211ze
I now have it running. When we tried the first carb after the rebuild it backfired and flooded. I sheared the pin and we did not know that. We had just put a new one in.
Just for your info this is a Briggs and Stratton and it only has one piston.
But thank you for your time.

 
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09-24-04, 09:06 AM   #6  
Azis
Glad ya got it

 
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09-24-04, 03:01 PM   #7  
Good job and good luck.

 
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