3.5 BNS Engine won't start

Discussion in 'Mechanic and Repair' started by sullidog, Jun 20, 2002.

  1. sullidog

    sullidog LawnSite Member
    Messages: 5

    Hi. I have a Rally push mower with a 3.5 BNS classic engine. It started fine until I made it's minor repairs wich were:
    Fixed leaky primer
    Replace diaphram
    I started the engine, after a second I heard the engine make a sound like it hit something and then it died. Just like I was mowing with it and hit a stump, but I wasn't. The engine is not locked up, nor does it force my arm back when I pull the cord. It turns over like it's suppose to, but it won't start. I have new full oil in it, and new plug. It also has good compression. Did a rod break or something? Please help because I want to sell it soon.
  2. Are the piston and valves moving?
    Check to make sure piston did not hit plug-is gap OK?
    Are you getting spark?
    Check you armature/point gap
  3. grasmo

    grasmo LawnSite Member
    from fl
    Messages: 34

    it takes three things to run an internal combustion engine. compression, ignition, and fuel.
  4. sullidog

    sullidog LawnSite Member
    Messages: 5

    Hi Bob. Sorry I'm a learner and I have a few questions. I pulled the plug out and it had a little oil and dirt on it. But didn't mess up gap. So your right a ring did hit it. How did this happen? Do I need to replace the ring? Next, where is the armeture? I know where the points are.
  5. Armature is under the blower housing.
    Doesn't really sound like the plug got hit so you need a spark tester to check that out.
    Also for $15 you can get a B & S repair maunual that will give you schematics and proceedures for pretty much every thing you need to know about their engines. Part #CE-8020
    Go to
    you can order manuals and tools, order yourself a tool catalog for 1.50- it will give you a way to order tools you need to work on their engines.
  6. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    does it have a safety handle on it - the one you have to hold down before it will run? if so then maybe it got screwed up? if it turns over with compression then the rod did not snap - nor did the piston hit the plug. if you spray starter fluid it the carb will that make it fire a few strokes? is you oil level grossely over filled? answer these questions and we all can help you some more...
  7. sullidog

    sullidog LawnSite Member
    Messages: 5

    Hi guys. Safety seems to be fine. However, When I took the plug out to recheck it, A small gasket like cap thing came out with the plug. What is this thing? I've never seen this peace befor.
  8. most plugs came with a metal collapsable gasket that was to be replaced each time plug was removed. Havent seen one come with a plug in ???? long. Shouldnt be a problem, just leave it on.
  9. hosejockey2002

    hosejockey2002 LawnSite Bronze Member
    Messages: 1,195

    Troy- I'm trying to say this in a nice way but if you're in the business of fixing small engines it sounds like you have a bit to learn. If I were you I would either try to get a job working for a small engine shop for a while or better yet, hook up with a community college or technical school that has a small engine technician program. In the long run, your business will be much more successful and profitable! :D
  10. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Messages: 956

    The fact you mention it made a loud noise makes me wonder if the flywheel key might have sheared. This would throw the spark timing off enough so that it wouldn't run.

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