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Post by mopedman1234 on Feb 27, 2019 10:29:00 GMT -5
And also when I had the stock air box on it was not running very well. It was sputtering sometimes and since I got the aftermarket one it runs a lot better.
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Post by repherence2 on Mar 4, 2019 21:12:33 GMT -5
Hi, I have a 2002 Yamaha bws 50 with a 70 cc big bore, polini air filter, and Yasuni Z exhaust. When I take off I have a quick burst of acceleration but then all the way up to 40 kmh it doesn’t pull very well. Once I hit 40 it hits top gear and gets in the power band and pulls really hard until too speed. I was wondering what contra spring clutch springs and variator weights I should adjust to. Thanks. Your acceleration problem could be due to a dual angle torque drive (rear pulley). Some have linear slots, some have slots that transition from one angle to another. Regarding your jetting, I know you said with the air box on, it sputters, but it will run decently with the pod filter. If you are staying with the pod filter, I suggests you run a Cylinder Head Temp gage! Not fun when you seize or soft seize the motor.
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Post by repherence2 on Mar 4, 2019 23:24:57 GMT -5
I regards to clutch springs, contra spring, and roller weights, ...those are like an orchestra, it comes down to a balance of the transmission tune and your riding style or preference. the clutch springs will dictate when your clutch engages. I like to set mine high with the big bore. I have run NCY red clutch springs on a lightened NCY clutch but I still wanted more. so I switched to a Stage6 torque control clutch with the heaviest springs. I really don't care for the soft and quiet roll out from a dead stop. I tune my trans so that the engine has to rev up before the clutch engages, I like my clutch to engage toward the upper part of the power band, thus higher revs. My clutch does not bite super hard though. I have ridden an Elite (from a tuner from QuikFix Honolulu) that revved up high and the clutch bit super hard, so if you weren't ready for it, you could end up getting hurt. so it all depends on how you want the power to come on. however, if your clutch engages too early (when your bore is not high enough in its power band) you may end up running into tuning problems, thinking it is your carb tune but in essence your clutch engages low in the power band and your bore struggles because it is not making power.
Contra spring dictates upshift and downshift rate. stiffer contra down shifts faster and it stays in the lower gear longer, so if you have to climb hills or you like accelerating hard out of turns, the stiffest spring is what you will like. the down side is faster wear on your belt, your CVT runs hotter, and you tend to flat spot your rollers faster. The medium spring works well for me. the CVT stays cooler, I get less belt wear, and my rollers don't flat spot anymore. the downside is that my bike struggles on long inclines, as though it is not in a low enough gear to actually pull hard up the incline. don't get me wrong, the red NCY spring (stiffest) gave me much more acceleration up hills and long inclines, but I didn't think the maintenance and parts wear was worth it. I tried the soft spring and it really did not care for the way it shifted with the big bore, maybe I could have tried lighter weights and gotten it to work, but I was shitty at tuning during that time period.
Roller weights, the way I see it, they dictate the RPM at which your Variator starts to shift/transition. heavier weights makes the shifting action of the variator start at a lower rpm, while lighter weights will make the variator start shifting at a higher rpm. it's like you tune your variator, via roller weights, to the RPM region that your bore/pipe combo is making it's most power so that while your CVT is changing gears, your engine is putting out it's max power. too heavy, and you never get into the power band while it is shifting. too light, and you go right past the peak of your power band and your CVT starts changing gears on the high rpm downslope of the power band, no power. something that was recommended to me by a shop was to buy a set of Tuning weights. they came large sets,3g to 14g, in sets of 3 for each particular Gram increment. you install 3 at a time and go for a quick run, you keep trying different gram sets until you find the total Gram weight that suits your liking. from there, you know the Gram weight setting that you like, and you buy the appropriate roller weight set. Tuning weights are only for tuning, they are not meant to run for normal use, they are a tool to help you narrow down your weight setting faster/easier. I never did buy a Tuning weight set. I ended up buying an assortment of roller weight sets from a shop over time and amassed roller sets from 2.3g to 8g. I have found that to a certain extent, roller weights also plays a factor in your top speed.
in the end, you Orchestrate a balance with your CVT. you choose how you want your clutch to hit, via clutch springs, you want it to hit hard or do you want to roll out soft and quiet. you choose how you want your CVT to downshift, via contra spring, you have to climb hills or inclines or you like to come out of turns with power, or do you prefer the soft acceleration up inclines and not so much power accelerating out of turns. to each their own, it is what You prefer as the owner/rider, it's your horse. you also choose how hard you want your bike to "pull" on acceleration via roller weights. it is really up to you and what state of tune you want your bike to be in.
but ya, Tuning roller weight set, a main jet set, and Cylinder Head Temp gage, and some springs if you want to get into fiddling with that. when/if you get that Temp gage, stay below 350F. if you decide to get a Temp gage, you might as well invest in a Tach, it makes tuning CVTs a lot easier. as far as you air box versus your air filter, with the air box, the air inlet on the box is small so your bore/pipe combo was lacking enough air, hence the sputter (too much fuel). with the polini filter, it gets more air, therefore you don't encounter the sputter, you don't mention a "bog" with the polini filter, but that does not assure that you are not on the lean side. lean can result in overheating and soft seizing your bore. I say get a temp gage and jet set to get your carb in tune first. albeit, it may require you to get stiffer clutch springs to get the RPMs higher into the power band. if clutch engages too early, it loads your motor prematurely before it can even develop power, and then you end up thinking it's a carb tuning problem.
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