08 response prob

[stlyamadude]

ok so my problem is throtle response...i cant and wont say that the bike runs bad but i have rode other 08-09 and the response is better than mine...so i will start with my set up.......stock piston motor,cams ect....brand new air filter and oiled...no-toil..<ya i no,going to switch back to bel ray asap >...pro circut full system..t-4....45 pilot...168 main...55 leak jet...brand new diaphram for accel pump...boysen quick 2 cover....tied spring accel pump....fuel screw about 1 1/2....cleaned intire carb about 2 weeks ago....new spark plug about 3 weeks ago... st louis,mo...elev..about 500....little to no decel pop above 70 degrees...runs little lean 60 and below...stock needle..... i just have a slight hesitation/stumble on quick throtle opening...others ive rode are so responsive and i just cannot seem to make mine run like that..what am i missing??? i have been down on pilot,up...down on main,up on main..moved needle clip up and down...still have not seemed to get the results im looking for...and yes i have also looked at the user jetting several times over the last 9 months....possibly a diff needle??? anyone have any suggestion?? any would be greatly honored!!! thanks in advance

[grayracer513]

Try this:

If you're using wire on your AP linkage, cut it loose. Use a Merge Racing AP linkage spring instead, or at the least, use an O-ring instead of wire. Wiring the AP is for cavemen (apologies to any that are reading this).

Switch the leak jet to a 50.

Change the needle to an NFPP, start with it in 4.

[Yamiryder]

For the AP mod, i found a small zip tie works better than an o-ring as it will not stretch like the o-ring.

[stlyamadude]

I actually had the o ring in it for months but it broke..that's why I used saftey wire and tied it...and yes the o ring would stretch also..hints again why i used wire..I looked into getting a diff spring but what is the diff from having it tied and useing a stiffer spring??? Going to a 50 leak jet is actually richer correct..?? Smaller the number is richer on the leak jet and visa versa...???? And the nfpp needle is also richer I believe...sorry havnt looked in my book to refrence it yet..thanks guys for the response....both buddies bikes ive ridden are like fuel injected responsive and I just can't seem to get mine yhe same ..

[grayracer513]

The NFPP has a smaller major diameter with the same taper at the same height as the stock needle. This makes it richer between 1/8 and 1/4 throttle, but otherwise the same as stock. Changing the needle position on the stock needle will not make the bike richer or leaner within that throttle range.

Yes, a #50 will increase the amount of fuel delivered with the pump shot by decreasing the amount leaked off. It also reduces the minimum speed at which the throttle must be opened to produce a discharge at the nozzle.

The difference between wire and a spring or O-ring is that the accelerator pump diaphragm has a button on the bottom to limit its travel, and stops moving before the throttle is completely opened up. The length of the button is a part of the method by which the pump is intended to be tuned, whereas the leak jet, even though used as a means of richening the pump output, is not intended for that purpose. ( Read THIS ). When you use wire, the accelerator pump will stop the throttle linkage before it's completely opened unless you do one of two things: shorten the button on the diaphragm ( a bad move because this massively increases the fuel delivery to the point of having negative results in many cases), or leave enough slack in the wire to allow the throttle to open fully. The purpose of the linkage spring in the first place is to allow the AP linkage to come to a stop without impeding the throttle from moving through the remainder of its travel. It can and sometimes also is used to limit the force with which fuel is discharged from the AP nozzle by being made light enough to yield under a certain amount of pressure.

One of the things I usually always recommend for this sort of complaint (that people don't always like hearing) is that you can't have a carbureted thumper that's set up to run clean and sharply while also setting it up to be able to take a sudden snap of the throttle from idle, or from a very low RPM in gear. It just doesn't work that way, and although you can come to a very workable point close to that, the real cure for the problem is to be in the right gear more often and learn to "roll" the throttle, opening it more slowly and smoothly at first, and faster as the engine catches up. Learn this, and it becomes second nature. The bike will rev every bit as instantly as if it actually did have the throttle snapped open.

As with anything else, there's a point beyond which the throttle response is reasonable, and one below which it's not. If its performance isn't up to that point, you should go ahead and try to tune it better. But if it is, you should retrain yourself instead.

[stlyamadude]

i just wanted to say once again thank you gray...i always enjoy reading your replies you post to myself or anyone for that matter..i have read your post several times now and everything makes since to me...kind of...well not kind of, it does but just trying to sort through it..if that makes since..mainly the "read this" topic..very detailed and informative...unlike alot of people i will take your word for it along with i also understand and def agree with te thought process...yes when i wired the "leg' togther i did notice that it somewhat stopped full throttle opening but i was victom to well everybodies doin it so why shouldnt i...ya not always a good idea...i willlook ino using a heavier o ring but i am leaning more towards diffspring and rite jet oppesed to hey lets just wire it together then that will make it better..lol...i also agrre with user error..i if anybody could learn much and will work on rolling..i am still pondering the whole ap physics and what not...no not hard to understand but with the leak jet/diaphram/button/spring intire action at once including main and pilot all within the time frame of what maybe a second...still trying to sort out each action in relation to each other in sequence to fully understand it in MY head...almost there..ha ha not all of us are extrodinarly inteligent as you my friend...thanks again..i intend to change some settings tomorrow as long as i can get some seat time on sat..i have a hare scramble on sun and dont want any surprises on race day if you know what i mean...i will continue to read up in the mean time...

[vic2340]

Can anyone tell me what the zip tie or oring mod actually does. If it works so well why dont the bikes come stock like that.

[grayracer513]

The O-ring mod (and the much more caveman-like safety wire mod) work on the idea that the bike bogs because the accelerator pump linkage spring is too weak and compresses as the throttle is opened suddenly. The spring exists to allow the AP diaphragm to "bottom out" before the throttle opens all the way, then compress to allow the throttle to travel the rest of the way to fully opened. The wiring mod wires the linkage together in a solid piece, which then means that the diaphragm stop button has to be ground off, giving you a much longer pump shot than you ought to have. The O-ring mod does the same thing, but since the O-ring stretches, the spring functionality remains, but the sping is stronger by the O-ring teaming up with it.

The Zip-Ty mod modifies the main air circuit and the emulsion tube in the main nozzle, and is said to improve throttle response at lower speeds.

FWIW, I get along just fine without either one.