Quad is having problems at full throttle

Discussion in 'General Support' started by Oh4Blaster, Apr 13, 2018.

  1. Oh4Blaster

    Oh4Blaster Member

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    Hey guys, I’ve been trying to track his damn problem down for weeks and it only seems to want to stick around.

    My quad is having problems getting to full throttle. As soon as you mash it to take off it bogs out at the top of every gear. Other than that the quad will kick 1-2 kicks, idle fine, but as soon as you go from 1/4 throttle to maximum fun it bogs out. It will hesitate in some spots too but when you go full throttle it bogs out and dies. Sometimes after it dies it won’t start again till you let it sit for a minute.

    Mods for the blaster:
    Full FMF fatty to turbinecore2
    KN filter
    Bore .20
    VForce4 reeds
    Needle is one up from the middle
    I run amsoil dominator 32:1

    My stepbrother and I swapped the coil and it ran a little stronger but still had the same problem and the only guess I have could be a bad stator not transmitting spark when it needs to spin faster or not a big enough main jet. Any input you guys have would help out.

    The problem started to happen after we were doing laps at my buddies field.
     
  2. Awk08

    Awk08 Moderator Staff Member Technician Forum Supporter

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    engine compression ?
    I see no mention of main jet for the FMF pipe ? (270-310 range)
    put the needle clip back in the middle slot
    when's the last time the carb was disassembled and jets cleaned ?
    air filter clean and reoiled ?

    amsoil dominator suggests what mix ratio for that oil ? 50:1 ?
    I had nothing but troubles with that oil at 32:1 on a perfectly jetted blaster.
    ditch that shiz and get some Maxima Super M or Yamalube and mix 32:1

    reeds good ? no cracks or chips and closing completely ?
    no spacer behind VF-reeds ? that's a no-no !
    plug boot not burnt up inside ? and connection to wire good ? unscrew the boot, cut off 1/2" and re-screw boot back on
     
  3. Brenden Duso

    Brenden Duso Member

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    I had a similar problem with my blaster last season , as soon as I got above 3/4 throttle it bogged , couldn’t give you an exact solution but after fresh top end ,new reeds air filter and it solved the issue
     
  4. Oh4Blaster

    Oh4Blaster Member

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    Alright guys I narrowed it down to a jet problem after blowing through a brand new box of plugs +2 more. The diodes are black as night. I took the carb off and like the manual said check the main jet and it’s stamped 260 and everything else is set to the fmf specs but I’ve added VForce4s and they claim 10-15% more air so my question is would I add in a 240 main jet then? I don’t think I’d have to add a 280 because that would make it more rich than it already is I assume and 300 is huge. Quad is only .20 over so I think a 240 would be ok. Any input from you guys would help. My quad is sitting there sad and chained up. Help me terrorize the woods again
     
  5. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Reeds seldom call for any changes in jet size.

    The recommended main jet for a FMF pipe is a 260, but with an aftermarket air filter and a pre mix ratio it would pay to go to a 270-280 main.

    The needle should be in the middle clip position and a32.5 pilot jet.

    If the airbox lid has been taken off you will need to increase the main jet further.

    Plug chop to confirm the needle and main jet.
     
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  6. Blaaster

    Blaaster Moderator Staff Member Technician Forum Supporter

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    Idle adjusting.
    Set float level, make sure that all jets are clean and fuel flows freely from the float bowl drain
    when the screw is cracked open.
    Start with air screw 1.5 turns out.
    Set idle screw so that it has some sort of idle. With TORS it is the big screw under seat on top of
    unit. With no TORS is is the brass screw midway down carb body.
    Warm up motor and then set idle screw for a faster idle, 2000rpm+
    Adjust air screw either way to get the fastest idle.
    Adjust air screw a little at a time leaving 10 secs or until the motor responds.
    Re adjust idle screw for desired idle .
    if the air screw ends up being more than 2 1/2 turns out the pi;]lot is too big.
    if the air screw is less than 1/2 a turn out the pilot is too small.


    Then plug chop..

    This is the process of confirming that you are using the correct carb settings for a efficient and
    healthy engine…
    the process can be done at wide open throttle to confirm the main jet or at 1/2 to 3/4 to
    confirm the needle position.
    Contrary to public belief one cannot effectively alter the tune of a carb above 1/4 throttle by changing the
    air screw setting. The pilot jet and air screw setting has little to no affect on the AFR above 1/4
    throttle.
    Before you make the plug chop run it is important that the float level is correct, the idle is set
    correctly and there are no air leaks in the system, otherwise the smoke ring may lie about the
    AFR.
    WHEN ALL OF THE ABOVE ARE CORRECT PROCEED WITH THE FOLLOWING.
    Warm up motor to operating temp.
    Fit new maker specified plug, ride WOT ( or 1/2 to 3/4 throttle for the needle ) through the
    gears and hold that throttle opening in 5th or 6th gear for 10 seconds, or as long as you can
    safely.
    Switch off the ignition and pull in the clutch, apply brakes to come to a stop quickly.
    Take the plug out and replace the old one for the ride home.
    Carefully cut the threaded end off the plug to expose the insulator.
    There should be a smoke ring of a cardboard or biscuit colour around the insulator.
    If it is non existant or a very light colour, you are lean and require a larger main jet.
    If it is a lot darker you are rich and may go down a size in main.
    I prefer to run a little on the darker side, I may loose a little power but it is worth it for the
    peace of mind that I won't need a rebuild so soon.
    You have to get up a reasonable speed so that you can get the engine to pull strongly.
    Then hold it Wide Open Throttle (WOT) for 10 secs or as long as you can.
    The idea is not to get speed but to make it pull strong at full throttle to get onto the main jet
    circuit.
    I find I can safely do it on a short run by applying the brakes some.
    If you have not enough room you can use 4th or 5th gear with good results.
     
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  7. Oh4Blaster

    Oh4Blaster Member

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    Blaaster thanks for that info. I actually called vforce and spoke to a tech to see what they would recommend and I was told 280 would be fine with my setup. I’m going to mess around with it tomorrow but want PA to warm up already so all this work isn’t done for no reason lol
     
  8. Oh4Blaster

    Oh4Blaster Member

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    Hey guys the problem is fixed. It turned out to be some with the jetting and that brass piece the needle sits in. I had a shop look at it and they found that the main jet was hard going in and wouldn’t seat all the way. The threads were also messed up where the jet screws into which was letting fuel sneak by and flood the quad in the top end. Swapped my 260 for a 280, they fine tuned it for the vforce4s and now we are back in action.
     

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