ATV Florida Forum

yeah i know , this has been talked about before but i have always used a twist throttle on my quad . been thinking about putting the stock thumb throttle back on but hate the stiffness . any suggestions . i have read on yfzcentral.com that some guys were cutting the spring in the carb , but then the more recent posts were advising against that assuming that by shortening the spring it would only make the action stiffer .

I put a thumb throttle off of a 400 ex on mine and it helped with the angle
of the lever.The most improvement was when i took the carb apart and took the spring where it attaches to the throttle shaft and moved it to the other tab. You have to grind or cut a notch in the other tab.
do a search on yfz central and it will show you how to disassemble.
After doing this I could ride all day and never feel it.
 ;D

I just ordered a different carb spring for mine. When it get here and I put it in I'll let you know how much it helps.

I see you live in Greenacres! You're Lawnmans friend correct? I think we've gone to the track together before, my name is Jack. I can modify your carb to make the throttle MUCH easier to push, PM me, and I'll shoot you over my phone number if you'd like some more info and would like come over and have me modify the carb.

cut the springs in the carbs...

Cutting the spring will make your throttle even stiffer! Cutting the springs adds even more tension to it.

Some guys sells the spring on ebay all you do is change it out and its a litter spring and much easier to push.

Just do a search on ebay and type in yfz450 carb spring and it should come up. It cost like 25.00 for it but its worth it.

The way I do it does not require a stock spring, and can be done for free!

really?  cutting the spring reduces the amount of resitance to return the needle back to stock position which in return would reduce the amount of force to press the throttle....done it before on banshees....not sure what your talking about, but cutting the springs in the carbs is an easy way to do it.

I bought one of the spring kits from Ebay, I have not installed it yet though

Cutting the spring increases the tension on it. Would you like to put down some money on this? It's been proven time and time again on the YFZ's.

yes i would been there done that  buy cutting the spring you reposition  the spring hook there for you  chang the levrage on the spring   or if its the other kind of spring you are shorting the spring so there is less spring   this has been done and proven :o ;D

i have to agree with cut and smoke,
I have cut the springs on stock banshee carbs and 34PJ's several, several times to make them easier to pull.. my thumb was tired no more!

I put the ebay spring on and took the spring off the throttle and no I can ride for ever

Hey Banshee guys get out of the YFZ tread !!!!!!!!!!!!!!!!!!     >:( >:(




The spring off of ebay really works. I did it to mine !!!!!!!!!!!!!

The spring on pj and pwk are completly different than the FCR.

If you cut the spring and repositioned where is sits on the wheel, then the effects you're feeling are from repositioning the spring on the wheel. The way I have mine set is reset on the wheel, no cutting and it's VERY soft, probaly a little too soft for most, so to make it stiffer you can cut the spring until it's to your liking.

florida, you keep telling them guys over on yfzcentral how they should modify their springs and PUT THEIR CARBS back together.  Now I am not jacka$$ when it comes to quads and carbs.  I will have documentation from a physics book to demonstrate to you my theory.  there is a linear equation between the force and the distance of compression of a spring.  you tell me how much money you want to lose and we will make the bet.  Oh by the way, did you get your yfz running yet?  from the looks of this thread you were having trouble. 

http://www.yfzcentral.com/invision/index.php?showtopic=27553&hl=carb+spring

you obviously don't realize who your debating with do you?  will have you some documentation soon, so i can spend your money instead of mine.  $1, $10, $100, etc?  you name it.

You didn't have to get any bro. There are two locations to hookup the spring on the throttle wheel. You grind a groove into the tab that isnt used, hook the spring up into there and wala, much softer throttle. No, I don't know anything about a spring or how it works, but anytime somebody cuts their spring they always say it made the throttle stiffer. I don't know what you're talking about on yfzcentral, I did a writeup on how to dissasemble, modify where the spring sits, and reassemble it. What's wrong with that? I just came on here to help out a friend, not start an arguement like which ussualy happens. Also with that carb, it was on a friends bike. Turns out after I did the mod he took it to the dealer and they completely screwed up his jetting, they put a 148 main jet on a piped YFZ.

I am not trying to start an arguement, but when someone comes on a public forum and offers a bet to me about something that I KNOW I AM CORRECT ON, it offends me.  I don't mind being called stupid when I am wrong, but I have had 4 years of engineering college and I am no idiot, and don't like to be wrote to on a public forum like I am an idiot.  I have no problem debating about what is right or wrong, but don't talk to me like I am an idiot.

Okay, here is the proof that cutting a spring in a carb will take less force and work to compress.  It is somewhat hard to understand, but bare with me.  Okay we have a few constants that won’t change. 
·   the distance the spring is compressed is constant
·   the spring constant is constant (imagine that)

Force = spring constant * distance
Through a few integration steps we come up with the formula that:

Work = ½ kx₁² * ½ kx₂², where x₁ is the original position of the spring and x₂ is the finished position of the spring.

Original spring
Spring constant = k = 20N/m
Spring length = 5 in = 0.127 m

*With carbeurator closed spring length is 2 inches, which means spring is compressed 3 inches, which = 0.0762 m compressed is the original position x₁.
*With carbuerator open spring length is 1 inch, which means spring is compressed 4 inches, which = 0.1016 m compressed is the final position x₂.
With the above formula;

W = (.5)*(20N/m)*(0.1016m)² – (.5)*(20N/m)*(0.0762m)²
W = (0.1032 Joules – 0.0581 Joules)
W = 0.0452 Joules
W = 0.0333 ft*lb

Cut Spring
Spring constant = k = 20N/m, same as before
Spring length = 4 in = 0.1016 m, which means 1 inch was cut off of the spring

*With carbeurator closed spring length is 2 inches, which means spring is compressed 2 inches, which = 0.0508 m compressed is the original position x₁.
*With carbuerator open spring length is 1 inch, which means spring is compressed 3 inches, which = 0.0762 m compressed is the final position x₂.
With the above formula;
W = (.5)*(20N/m)*(0.0762m)² – (.5)*(20N/m)*(0.0508m)²
W = (0.0581 Joules – 0.0258 Joules)
W = 0.0323 Joules
W = 0.0238 ft*lb

So the difference is substaintial.  Now I rest my case.  If you cut the spring in a carb it will decrease the force/work it requires to compress the spring.  The graph for force to distance is directly proportional. 

TEACHERS PET!!!!!!!!!!! ;)

chillin..... a spring is a spring...... if you cut it....stretch it... its softer.... doesnt really matter what bike its on...

LOOK AT THE BIG BRAIN ON SMOKE!!!  YOU TELL THEM!

(CLEARS THROAT)...     PISS OFF!  8) :o   WE THOUGHT YOU WANTED HELP FROM GUYS WHO HAVE "REAL" BIKES NOT LAWN MOVERS... ;D ;)

You guys dont get it. Picture this.... the carb spring in your banshees looks like a coil spring on a car. The carb spring in a yfz works more like a spring in a recoil starter. Apples and oranges. The relocation mod that he is talking about works because it puts less preload on the spring. At the same time cutting THAT type of spring COULD stiffen the action.

Oh your talking about the wound up one not the coil spring one right...?
I have cut on on a 4 banger that was the "coil" spring not the wound up one..

You got it Ware, there are no "coil" springs in a Yfz carb.

OK ill take my stupid a$$ and go stand in the corner now....

OK Ware 5 min. in the corner for you and you can come back out and play. I want Smoke to spend the whole day there though and think about what a bad boy he has been.

so i was right in what i said  it can be done the  spring is like the  mukini on my ds  cut and relocate  thank you have a nice day i am not just a banshee guy been there done that   that from 20 year of building bike motors  no school needed

 :'( :'(my thumb hurts :'( :'(my thumb hurts :'( :'(
 Just do what I did, I fabbed up some floor boards for my bike and put a gas pedal on it. It worked so good that I also put a clutch pedal on it and relocated my shifter to the right of my gas tank :drive.gif now no more sore thumb.

your waked  chillin :)

svtbolt is sellin a twist grip i think