Results 1 to 2 of 2
  1. #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

  2. #2

    Join Date
    Jul 2013
    Kubota, Lawnboys (5), Toro/Suzuki's (2), Honda HR17

    Re: 8403 running weird


    No Nikasil.

    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.

Similar Threads

  1. Service Manual for 8403
    By 69HemiGTX in forum Lawn Boy Forum
    Replies: 1
    Last Post: 04-17-2019, 08:25 PM
  2. Weird Payments
    By lawn mower fanatic in forum Commercial & Residential Lawn Mowing
    Replies: 18
    Last Post: 08-25-2013, 07:18 PM
  3. Very Weird
    By Kodie's Lawn Service in forum Stihl Forum
    Replies: 0
    Last Post: 07-30-2013, 09:08 PM
  4. Weird steering
    By metz12 in forum Small Engine & Mower Repair
    Replies: 14
    Last Post: 12-29-2012, 01:24 AM
  5. Walk behind Is it weird?
    By chrisafisher502 in forum Mower & Equipment Operation
    Replies: 2
    Last Post: 09-14-2012, 09:23 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts