YFZ 450 revving

[FriesenYFZ]

I own a 2004 yfz450 and for the last little while it has been revving way too high. When I have the throttle 1/4 the way in it is revving the same amount as when i normally would have the throttle all the way in. I dont know if i need new sprockets or if it is a more serious problem. if someone could give me some tips that would be great.

[red4ever]

the first thing id check is the jetting/idle and the throttle cable. if that doesnt work then you could maybe try having the valves adjusted

[FriesenYFZ]

Thanks alot! I hope that that is the solution.

[GPracer2500]

I'm guessing your clutch is bad. A better description of the problem would help nail it down.

[NY06400EX]

+1 to what GP said - clutch is first assumption but we need a more detailed description to help diagnose.

[FriesenYFZ]

Well my quad runs good, and has never had any problems so i dont really know how to describe it. It just revs extremely high and if i put the throttle in pas half i feel that mt motor is going to blow, and i have to shift really fast. Im running 98 octane fuel with NOS octane point booster so I dont know if that has something to do with anything. I'm sorry if it doesnt make enough sense but that is the best i can describe it.

[cals400ex]

with lower gearing you will be at high rpms faster and you will have to shift faster. does it feel like you going faster when it revs high or is the engine revving high but it doesn't feel like you are picking up speed?

Check the cdi connection and make sure its tight.

If the clutch lever is adjusted to tight it will do that.

The clutch may not be engaging fully making it rev high and go slow.

If your clutch springs some how got week from heat that could possably be it.

Did it just start doing that or did you do something to the motor or sprockets and then it was like that?

[FriesenYFZ]

I have not done anything to change the quad around, the problem just started up about a week ago. I called the dealership and they said that it was my throttle cable and i checked it and loosened it a bit but there was still no change. The quad is picking up speed as normal, but it revs so bloody high so faast that i dont know what the hell the problem is. The other dealership said it was my carburetor and that i might have to buy a new one and that would put a big hole in my pocket and i dont want to spend $100 for them to look at my quad so im sorta stuck here. I've tried quite a few things but none have seemed to work so i guess taking my quad in is the best bet. If any one has anything else i could do that would be great.

[250r4life]

still sounds like a clutch... if youre engine is revving faster than normal, if youre clutch was good you would be accelerating faster than normal... unless of course you have less traction...

however, if youre engine is revving faster than normal and youre accelerating at the same as normal, probably because of clutch slippage...

Originally posted by 250r4life


however, if youre engine is revving faster than normal and youre accelerating at the same as normal, probably because of clutch slippage...

That gots to be the only thing it could be.

I would check the clutch arm (part on motor that cable hooks to) and see if its moving ok when you pull the clutch lever in. If its not going back far enoug when you let off the clutch lever then your clutch lever is adjusted to tight or something else. I would take the clutch cover out and take a look.

A thing with my quad was once i was driving and it all seemd normal. Then 1 day i start it up take it down the road and it seemd like i was going really slow but had to keep shifting and the rpm's made it sound like i was going fast but i wasnt. The float on the carb was leaking alot of gas. Turned out it only needed a rejet.

[GPracer2500]

Originally posted by Dhumpalo
...Then 1 day i start it up take it down the road and it seemd like i was going really slow but had to keep shifting and the rpm's made it sound like i was going fast but i wasnt. The float on the carb was leaking alot of gas. Turned out it only needed a rejet.

:confused: I can't make any sense of that.

Originally posted by GPracer2500
:confused: I can't make any sense of that.

My quad was running good. Then one day i start it up and take it down the road. Im shifting through the gears and the rpm is climing making it sound like im going fast but i had to keep shifting. I toped out at like 30mph in 4th gear and i found out it was only my carb and not the clutch.

[gump]

i had the same problem when i went up 1 jet size, i wound up turning the air srew out giving it more air and it ran better, before it was back firing from built up fuel. try giving it some more air

[GPracer2500]

Originally posted by gump
i had the same problem when i went up 1 jet size, i wound up turning the air srew out giving it more air and it ran better, before it was back firing from built up fuel. try giving it some more air

YFZ carbs (and basically all four stroke carbs) have fuel screws, not air screws. Backing out a fuel screw adds fuel to the pilot circuit, not air.