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  1. #1
    Join Date
    Apr 2007
    Location
    North Tonawanda NY
    Posts
    449

    Default To much advanced timing effects

    My old man has built and raced just about every type of 2 stroke and 4 stroke bike/atv/car. With 50 yrs of his experiance of tuneing them I asked him some questions.

    Q) why advance timing?
    A) By advancing the timing you are igniting the air/fuel mixture a little sooner.

    Q) How does this give more power?
    A) It takes time for fuel to burn so the spark always fires before the piston reaches TDC. In other words, the spark fires before the piston is finished with the compression stroke. What this does is gets the air/fuel mixture burning and close to maximum combustion pressure at just the right time.

    Q) What happens if its not advanced far enough?
    A) It fires too late and you lose power.

    Q) What happens if its advanced to far?
    A) It fires too soon and you get pre-ignition, and possible
    sparatic engine rpms.

    Q) I run my banshee +5 will it hurt it?
    A) Temp,fuel delivery,atmospheric pressure,elevation,compression,stroke,
    squash band will be very crucial.If everything is spot on it still may
    be very finicky. So modifying timing could cause harm.

    Q) You said finicky can you explain that?
    A) Remember your altering fuel/air burn time, so adjustments through out the
    mixture ranges will be more susceptible to slight changes in,mixture ratio,
    type of fuel,heat,elevation,atmospheric pressure,ect.

    Q) I have my banshee jetted perfect. I have done plug chop after plug chop
    at every rpm range and the plugs look perfect. But I do notice when I am
    between 1/16 and 1/8 throttle the engine seems to have a loppy sound,
    almost like its miss fireing but when I pull the plugs they look good, any
    suggestions to fix that.
    A) YUP thats the finicky word i mentioned. If your jetted correct and you
    cant get the engine to run smooth all the way through the rpm ranges
    drop your timing down 1 degree at a time untill you hit that sweet spot.


    I really didnt wanna drop my timing down so I loaded it up and took it to his house. He tor into it changing jets,needles,needle height,. What would get rid of my 1/16 to 1/8 issue would make the throttle responce horrible. So he put everything back to where i had it, and adjusted my timing from +5 to +2
    took it out to test it. BAM perfect everywhere.

    I now believe that yamaha set the stock timing on the banshee so its less
    susceptible to variables. I hope this information helps someone in the future.

    And although I might of lost 1/2 to 1 hp I am much happier how smooth it runs throughout the entire rpm range.

  2. #2
    Join Date
    Oct 2004
    Location
    pennsylvania
    Posts
    14,217

    Default

    advancing the timing by up to 4 degrees* on a banshee is always a gain and is confirmed on dynos ,you wont lose power on this model at this range .you must realize while yes there are many variables this igntion system was designed in 1969 off the lc350 yamaha road bike giving a weak poor performance curve especially after hopups are performed .once you start getting up over 5 degrees those variables mentioned come into play and there are more than what you listed .high timing aside from detonation on low octane rating fuel will idle poorly, lose a thousand peak rpms ,and kickback during startups.every application is different its best to consult your builder before going to high. on certain exotic builds with methanol ive run my cub on plus 12 degrees and some have even gone much higher in the teens.in my opinion that finniky dead spot you mentioned shouldnt be a result of your igntion timing (dont drop it down) its far more likely a needle adjustment that needs done because of an improper air fuel relationship at that rpm range, not an ignition issue
    Last edited by flotek; 07-02-2011 at 11:10 PM.
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  3. #3
    Join Date
    Apr 2007
    Location
    North Tonawanda NY
    Posts
    449

    Default

    I fully understand and agree what your saying, but in my situation soaked the carbs for 24 hours, rejetted and tried stock needles,alba needles, and vitos needles. I could get it to run what seemed to be perfect untill I tried to hold a constant low rpm in 2nd and 3rd gear. It just didnt wanna run smooth but if i was in 4th it is fine. I just could not get these stock mikuni's to my liking.
    But just dropping from +5 to +2 I can lug it,drive through the woods at just above an idle,go from idle to WOT,cruise down the old track bed at any throttle, and rev the crap out of it with not as much as a hic-up now.

    I am still working on why +5 is giving me the fits and +2 isnt.

  4. #4
    Join Date
    May 2007
    Location
    SOMD
    Posts
    7,770

    Default

    Thanks for the write up!
    "Paul,
    Thanks for sending the pictures - looks like a lot of fun! You did a great job."
    Regards,
    Bob Hannah

    My motor is from 79'....Where will your 450 be in 30 years???
    DC facebook / Paul Baugher
    For details click here

  5. #5

    Default

    You old man sure knows his stuff.

    It took me forever and a day to get my carbs just how i want them but i'm very picky. And i jetted mine a little rich so it's good all year around. I wanted a no hassle bike. I dont mind losing a little power here and there. I am at +6 timing but i run strait fuelmax 110.
    little serval cub 01 banshee and an 02 yz250

  6. #6
    Join Date
    Jan 2005
    Location
    Virginia
    Posts
    13,051

    Default

    there is some good info here.
    i did sticky this and moved it to "Tech Info" but it didnt show on the home page. so it's back in the banshee forums.

    thamx for posting this.

  7. #7
    Join Date
    Apr 2008
    Location
    Arizona
    Posts
    3,139

    Default

    Thanks for posting along with Flotek too, somewhat contradicting at certain points but both very good information.
    2004 Banshee
    421 cheetah cub HJR drag porting N1-5 override 35mm PWK's (alcohol converted) Shearer Small Bores Slingshot Clutch
    +2 +1 lonestar arms with elkas and +2 durablue axle custom extended Lonestar +10 swingarm


  8. #8
    Join Date
    Oct 2008
    Location
    Anderson, Indiana
    Posts
    2,840

    Default

    What Flotek is saying is true. The ignition mapping from 1969 is why +4* won't hurt on your machine now. Sounds like if the 1/8th - 1/4th throttle issue is bothering the curve your pilot/needle setup is off slightly. The reason your machine lags a little on +5* is you were slightly lean I am betting and reducing the timing soften the affect. Tuning a two stroke is a royal pain in the ass and is why people get tired of them and go to four strokes.

    Your Dad though is right about the effects of timing and the variables that dictate good performance.
    If it ain't broken yet, you ain't tryin' hard 'nuff.

  9. #9
    Join Date
    Jan 2008
    Location
    VA
    Posts
    601

    Default

    I must be lucky
    Mine with Clean carbs and a carb rebuild kit, (New)stock needles on the 2nd clip with a 27 pilot and +5 timing is flawless.I have flotek porting and 19cc coolheads and running on 100ll.I didnt have any problems jetting it.I also used the carb sync tool(must have).With that tool i set it to 4.5 to 5 for idle.I think that maybe some of the carb parts just wear over time.I would get new needles and a rebuild kit and see what happens.
    2003 Banshee- Flotek Aggressive Trail Port,Modified Shift Star,lightened flywheel,Pro shift arm,
    ,CPI sb pipes,Chariot coolhead,billet impeller,pods,

    lightened flywheel http://flotekperformance.com/home
    2001 CR250-pro circuit pipe
    2001 CR125-Erric Gorr 134 big bore-Fmf Fatty-38 carb swap-2007 air boot-k&n filter-100LL-New ufo plastics-Powder coating parts-

  10. #10
    Join Date
    Apr 2008
    Location
    Arizona
    Posts
    3,139

    Default

    what carb tool do you have and where did you get it? I need one sooo bad for my black banshee
    2004 Banshee
    421 cheetah cub HJR drag porting N1-5 override 35mm PWK's (alcohol converted) Shearer Small Bores Slingshot Clutch
    +2 +1 lonestar arms with elkas and +2 durablue axle custom extended Lonestar +10 swingarm