Kawasaki FB460V..stumbles midrange and up-valve specs off..

Discussion in 'Mechanic and Repair' started by mowisme, Oct 17, 2012.

  1. mowisme

    mowisme LawnSite Senior Member
    Posts: 887

    I've cleaned/tanked the carb several times (was like new inside before this)- It idles perfect..But as I accellerate it stumbles out. no real higher rpm without stumbling bad. I've checked the coil gap, igniter seems to be working..So since it is a mid 80's mower I thought I better look under head. Cylinder/piston look good. minimal carbon on piston surface. Both valve faces and inside of head covered with thin/dry carbon. can almost wipe off with finger. It must have been running rich. I know misture screw was at 2 1/4 out..but tried it at 1 1/8 but no differance in running. Now..At TDC on compression I get a valve clearence of .04 to a very tight .05 on the intake? I get a .05 on the exhaust. Would the tight clearance on the intake cause it to stumble out and miss forsay as I get (or try to) into full throttle? would that be the reason so fouled by valves?could it or is it maybe floating out at higher rpms. Thanks for any help here..I need this mower for muching in a week. (I.E..rob/slapper?)
     
  2. mowisme

    mowisme LawnSite Senior Member
    Posts: 887

    I looked at manual wrong- looks like clearances are within specs? not sure what it coulkd be now except carbon maybe on seat..but runs really smooth at low rpms. Their is black soot even on tapered seat side of valves..but shiny ring where they seat (I'll have to get better look.
     
  3. kawakx125

    kawakx125 LawnSite Bronze Member
    Posts: 1,120

    checked your timing at all? a little carbon is normal, your burning something so it's gonna happen. what does the plug look like? it sounds like a fuel delivery or ignition issue to me
     
  4. lotsagrass

    lotsagrass LawnSite Senior Member
    Posts: 610

    I have a 2006 Kawasaki V-twin 28HP that had a somewhat similar problem. Ran great even at high RPM but would sputter when under a heavier load. Eventually it got to the point where it sputtered and backfired a little even with no load at higher RPM. It turns out the coils were bad. This engine only had about 150 hours on it too. So, I wonder if you may have a coil problem.
     
  5. kawakx125

    kawakx125 LawnSite Bronze Member
    Posts: 1,120

    just because you have spark doesn't mean its a good or consistent spark, i'd definitely be looking closer at ignition components first
     
  6. mowisme

    mowisme LawnSite Senior Member
    Posts: 887

    I cleaned up the valves and put them back in..outside of light carbon (not hard) they weren't bad. Once I get a new head gasket I'll get it back together and look at ignition things. I will see if anybody can 'test' the coil. I'll look at all wiring,ect. Maybe the igniter is workinbg somewhat but not so good at higher rpm? Doesn't it have something to do with advancing timing? Anyway- Ill focus on ignition after I get head and stuff back on. Thanks again- Gene
     
  7. juspayme

    juspayme LawnSite Senior Member
    Posts: 299

    u have to turn the blades on under load pull on spark plug wire at a time off if the mower shuts off its the coil
     
  8. lotsagrass

    lotsagrass LawnSite Senior Member
    Posts: 610

    I think he's talking about a single cylinder engine, so if he pulls the plug wire off, it's going to die no matter what :) I know what you mean though....using this process to test a 2 cylinder engine. But I think he has a 1 cylinder engine.
     
  9. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Mowisme...you got to get a digital camera...so that we can see what you are seeing..
    Is the sparkplug fouled ? Have black soot on it ?
    Soaking a carb is not cleaning anything more than the parts you can see..
    You have to remove the mixture tube and the jet and clean them..then before reinstalling them..spray cleaner thru everything that looks like a hole...
    Posted via Mobile Device
     
  10. mowisme

    mowisme LawnSite Senior Member
    Posts: 887

    Piston Slapper..I did as you mentioned. I soaked the parts individually for 8hours..took jets out first..cleaneded every hole with carb cleaner couple times as well as the wire thing after soaking. I took out the tube in center and idle jet on top, these all cleaned too. finished with air blowing. I really think maybe something else at it runs like brand new until throttling up past mid-range. I'm quite sure I got carb real good. I haven't tried yet since cleaning up valves but working on getting it back together- rained all day yesterday and it is on trailer yet. The entire area around valve surfaces and out to gasket edge..including plug was covered in soft-powder like soot. not wet but more like black powder. not thick but thin layer. wiped most off with rag. I know carb adjust was way out from the 1 1/8 turns in manual..I think it was between 2.5 to 3 turns out- been that way long time..maybe that was the rich burning? I'll see how it runs once back together. for previous poster- It is a single cylinder. I'm leaning towards faulty igniter..works but not working right, as higher rpm's it seems to be maybe failing.
     

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