15.5 b&s backfire???


Old 11-17-06, 03:06 PM
dingodogathome's Avatar
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Location: austin tx.
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Question 15.5 b&s backfire???

hi all, iam new here, was on a autoforum for years..but got out of it.

Heres my problem i have a Sabre riding mower i went through it and replaced everything that i could find bad. While doing this i replaced the muffler with a new one from John Deere. And now the thing backfires when you try and start it sometimes and i mean a real good backfire to..hehehaha. It still run great when it starts and it starts right up,,its just sometimes it will back fire when you try and crank it .fast or slow idle.
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Old 11-17-06, 05:15 PM
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It might have a lot of carbon buildup in the combustion chamber.. Might want to check the intake valve for burning also..
Old 11-17-06, 06:02 PM
dingodogathome's Avatar
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Location: austin tx.
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Thought about that but it seems if it was a burnt valve it would have done it at least once when i redid the carb. on it , So ive cranked it about 100 times in the last week messing with it and it didnt do it before the carb started leaking.(for years)

It started right after i put on the new muffler. Its really strange and the muffler is the correct one. Fits perfect and everything. New gasket even. I dont think its the carb. becouse it runs really really good. got me baffled ive been building engines for the last 8 years so i know how to do this kinda thing. The small engines are worse than the big ones...hehehahaha
Old 11-19-06, 02:23 AM
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I've corrected the same problem before but I honestly don't remember exactly what did the trick for me but here are a couple things to try: Because you replaced the muffler the carburetor is no longer set properly. Re-adjust the low end and it will usually correct the problem. Just because it's there I'd remove the main jet at the bottom of the bowl and clean it vertically and horizontally as well. Some of the engines, as you know, are fitted with an anti-backfire solenoid. Sounds like your carb is not fitted with one but if it is: Pull it, clean it and spray it down good with old formula WD-40 or Liquid Wrench to insure it's not sticking? Hope this helps, Ron!

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