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Thread: 8403 running weird
07-13-2019, 10:21 PM #1
- Join Date
- Apr 2019
- Hayes, VA
- Lawn Boy 8403 and John Deere 14SB
8403 running weird
My 8403 has been running weird lately. When I start it, it runs good, but slowly loses RPM, then slowly regains its speed. I know the carb is good because I just cleaned it, including the jets and passages. I thought it might be a plugged muffler and clogged exhaust port, but I just replaced the muffler with an NOS cast one, and I cleaned the exhaust port while I had it off. I'm wondering if it needs a new ring and piston. It's a 1984 model, so it''s possible that 35 years of use has taken its toll. Did the F Series engine cylinders have nikasil? On that note, has anyone ever used a ring and piston kit from Ebay, or is there a better one out there?Lawn Boy 8403
John Deere 14SB
John Deere 116
Stihl KM 90 R Kombi System
Stihl HS 81 R Hedge Trimmer
Stihl MS 260 Pro
Still MS 261C
07-14-2019, 06:03 AM #2
- Join Date
- Jul 2013
- Kubota, Lawnboys (5), Toro/Suzuki's (2), Honda HR17
Re: 8403 running weird
Have you done a compression test? Cleaning the exhaust port should be done with a wooden dowel as anything else may damage the cylinder wall, piston or rings. The loose particles of carbon can cause cylinder damage too.
AS far as I know the cylinder jug and piston are not available anymore (although eBay may have NOS parts).
I think one guy on this forum, put a new piston in a F engine and the compression wasn't raised substantially.
Last edited by jp1961; 07-14-2019 at 11:07 AM.
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