4 mill banshee tuning

Discussion in 'Yamaha' started by fullthrottle, Jan 20, 2016.

  1. fullthrottle

    fullthrottle Member

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    Oh ok that makes sense. Just trying to rule out all possibilities. Thanks alot
     
  2. Larry's Shee

    Larry's Shee Active Member

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    That's what us damn Yankees would consider summer temps, lol. Forgot to add I'm 1000 asl. Forgot to ask about filter set up. Blaster and shee levels are different, tho same carb. Never figured that one out. Next time I go out I'll get the spec.
    With clean carbs and float set, 330 should be close.
     
  3. fullthrottle

    fullthrottle Member

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    Right now i have some really rough looking k&n pods i plan to do something else but not sure what. i like the way the blaster air box is set up without a lid but ive read alot of bad stuff about the stock air box on a shee. i know the float level on the shee should be 21-22. Ive heard from a couple of people that 330 should be close but then what is causing it to lose power on the top end. Once it gets close to the power band it just starts spitting and sputtering like its missing. Im going to throw some bigger jets in when they come in and see if it helps because im really not sure what kind of porting it has.
     
  4. Larry's Shee

    Larry's Shee Active Member

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    Start with cleaning, oiling the pods. Check the fuel cap vent is clear/works , clean petcock and screen, check flow before installing line. Double check carb clean and float level and flow into bowl. New plugs. If you have adjustable timing plate, no more than +4*

    Things that could be wrong :
    Pods could be to small/short.
    Carbs could be to small to work with radical porting.
    Pipes not work with porting.
    Porting will not work period !!
    Domes smaller than 22cc need race gas. You may be experiencing detonation !!

    As to jetting, jump to a 350, if worse then drop to 310. If neither clear it, then it's something else.
    Do a leakdown and squish test.
    Get a degree wheel and check port timing.
     
  5. fullthrottle

    fullthrottle Member

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    I had read that as long as the compression is under 160psi race gas was not necessary. If that is what is comes down to then i will have to tear it back down and put different domes (would this require head modification?) or just sell this engine and get a stock one. I will look into a squish test and degree wheel (never fooled with either of those before) hopefully i will get the right hose to cap off the exhaust side tomorrow and do a leak test
     
  6. fullthrottle

    fullthrottle Member

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    Would the 4 mil setup run good if i would to put some stock ported jugs on? Im wondering if this thing has some crazy drag porting and if it does then its really not even going to run good for what i do. If i could just order some stock jugs and different domes (can someone please explain exactly how the domes work because i dont think i fully understand) then i think i would have a more practical setup because right now I really dont want to got to bigger pipes or carbs but would like to leave the bottom end like it is and once again thanks for all the help guys i think i might have jumped the gun on getting this one and not knowing what i was dealing with but i will figure it out :)
     
  7. Larry's Shee

    Larry's Shee Active Member

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    If you have a stock bumper the rubber caps are right size to cap off exhaust port !! I use Fernco rubber plumbing caps.
    There's more to it than just cranking pressure, tho that's a good rule of thumb.
    Most of what I threw out were worst case scenario.

    Obviously trying tuning is easiest and cheapest rout to start with.
    Will it rev out in neutral? Not that I like doing that much, no more than running without filters.

    By off chance , it doesn't have a spacer plate under the jugs or head does it?
    It does have a cool head, correct?

    A Banshee isn't some mythical monster, think of it as two water cooler blasters working together.
    You bought a project of sorts, don't give up yet. More often than not, it's usually the simplest of things. Such as it could have a junk aftermarket Stator that will ohm out in spec, but won't fire under load.
    Speaking of ign, check that the timing nubs on outside of flywheel are clean and pickup gap is .018''
     
  8. fullthrottle

    fullthrottle Member

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    I dont have the stock bumper on the shee and they have both fallen off on my blaster. No it wont rev out in neutral either. And it really isnt a very high rpm where it cuts out. Its right about where the powerband feels like it should be. No spacer plates that i can see and yes it does have cool head. I will try and take a look at the flywheel sometime today. Im not real familiar with the flywheel/stator side of things because the only other 2 stroke ive actually worked on has been my blaster. Im actually more familiar with diesels and work at a diesel shop so it is a learning curve
     
  9. Larry's Shee

    Larry's Shee Active Member

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    Get a Clymers Repair Manual too.
    Also check that both carbs open fully at full throttle.
     
  10. fullthrottle

    fullthrottle Member

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    Just got my jets in the mail! i threw in the 27.5 pilots but come to find out it had 30 pilots in it. I went ahead and tried the 27.5 pilots with 350 mains it seemed to do somewhat better with higher rpms but bogged really bad and kept dying when i was just trying to keep it running in neutral. Im going to throw the 30 pilots back in and maybe try 370 mains and see what happens. I feel like im heading in the right direction but 370 just seems huge. still working on the leak test:(
     
  11. Larry's Shee

    Larry's Shee Active Member

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    Don't recall seeing much mention of 350m let alone 370m in any setup no matter porting or pipe styles. At this point I would highly suggest a leakdown test over trying bigger jets at this point.

    By off chance this doesn't have a boost bottle does it?
     
  12. Larry's Shee

    Larry's Shee Active Member

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    Also, it hasn't backed the spark plugs out has it ?
     
  13. fullthrottle

    fullthrottle Member

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    It did have a boost bottle i pulled it off today to see if it made a difference and it didnt? What difference would it make? And no it hasnt backed out any spark plugs. At this point i just want to figure out the starting problem. Neither the 30 or the 27.5 pilots made any difference with starting what is the next thing i should check besides a leak test as far as starting?
     
  14. Larry's Shee

    Larry's Shee Active Member

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    As to the boost bottle, it causes cracks to the intake boots. If they are, even though they may not leak now, they will at some point. Ask me how I know this, lol. How did you plug the holes?

    Àt this point I think a leak test should be done before any further tuning attempte. One thing you can do is clean the timing nubs on flywheel and set pickup gap to .018".
    What does spark look like?
    You can see through pilot jet ?
    Fresh fuel ?
     
  15. Larry's Shee

    Larry's Shee Active Member

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    Clymers calls for 20-22 mm for the floats.
     
  16. fullthrottle

    fullthrottle Member

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    I put the stock crossover tube back in. I did clean the timing nubs with some light sandpaper. The spark plugs keep coming out wet and i can see through the pilot jet and i do have fresh fuel. I need to find some hose the cap off the exhaust for a leak test. At this point im trying to get it somewhat running so i can sell it. I have no desire to fool with it anymore and im just trying to make my money back. Thanks alot for all the help
     
  17. Larry's Shee

    Larry's Shee Active Member

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    Couple things I didn't catch first time around.

    V4 reeds, they like bigger pilots, go back to 30p, may even need to try 32.5p.
    Saw no mention of adjusting air screw after changing pilot.
    You changed two things at one time. When tuning always best to only change one thing at a time.

    No2 on to starting problem.
    Several things you need to check/double check.
    When carbs were cleaned, did you blow air through ALL pasages including choke passage s? Choke plunger inspected?
    Was choke crossover tube installed? 3" hose opposite choke knob.
    Float bowls on correct carb? Bowl with little "BB" on front side goes on left (choke) carb.
    Slide cutaway facicng air filter?
     
  18. fullthrottle

    fullthrottle Member

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    Yes to all that with the carbs except the part about having the correct floats i will have to check on that. I checked the reeds a couple days ago and they are defiantly bad so i will be ordering the replacement petals. Ive been watching some videos and forums and im pretty sure the problem is the cdi but i cant find any way to test if the cdi is bad. Im thinking about just ordering one and sending it back if it doesn't fix the problem
     
  19. Larry's Shee

    Larry's Shee Active Member

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    The cdi is pretty much a go/no go unit , which would probably need an electrical engineer with oscilloscope to test. I believe I mentioned aftermarket stators are a more likely culprit.

    Worn reeds are a known hard start issue.
    Highly suggest replace them, do a leakdown test, then proceed with tuning .

    The BB on the bowl is from manufacturing process, cross drilled hole plug. Blaster carb has same item. It's to draw fuel for the enrichener.
    Also check choke plunger.
     

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