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Discussion Starter #1
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.
 

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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



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Discussion Starter #3
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.
 

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4stokesLazy2strokesCrazy!
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Thanks for the write up!
 

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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.
 

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PLAYTIME'S OVER BITCHES!!
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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.
 

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Thanks for posting along with Flotek too, somewhat contradicting at certain points but both very good information.
 

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Old School but still Cool
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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.
 

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I must be lucky :Clap:
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.
 

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what carb tool do you have and where did you get it? I need one sooo bad for my black banshee
 

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I have always wanted to know about the carb sync tool. I do mine by sight and feel and it runs fine as far as I'm concerned. Has anyone ever thought sight and feel were good enough only to be amazed by the carb sync tool? I've been trying to find a local with one to borrow so I can see if its worth adding to the tool box.
 

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Old School but still Cool
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After I bought the carb synch tool I wondered how I went so long without one.
 

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ive heard a few people say that they thought they were close by sight and feel and were amazed at how far they were off. i need a sync tool.

to the OP, what octane fuel do you run? always heard that +4 was as far as you can go on 93 octane.
 
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