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A few questions about my new YZF 426

21 posts in this topic

Okay, I just bought an 01 YZF 426. The guy didnt have the manual for it so im kinda lost about a few things. I figured out how to start it with no problem and it has plenty of power but It seemed a little wierd when I hit top speed in 5th gear. It all of the sudden feels like its going to stall or something. All i know is that it didnt seem normal keeping it full throttle in 5th. And i was also wondering about the throttle response. When I twist it quickly from low rpm's there is sometimes a split second sputter before it revs, nothing major but just enough to make me wonder about it.

----THANKS

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Is it leaning out on top end? Or is that the rev-limiter? Also the bogging right off idle can be solved by a fuel screw adjustment, or you can buy a Boyesen Quick Shot for ultimate throttle response.

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Thanks for the help! I couldnt find a manual online before. Im gonna have to post again about the top speed, im having trouble remembering exactly what it was doing.

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You may be hitting the rev limiter in fifth gear. If that's the case it wouldn't really feel like it wants to kill. It would just feel more like it lost power and it will wine and sound like it's bouncing between higher and lower pitches. For the throttle response problem...that is normal. I have an '05 YZ250F and it does that sometimes and has since it was new. Try adjusting the fuel screw on the bottom of the carb. That can help. If you are not sure which one is the fuel screw (since you don't have a manual) try looking online for a picture that will show you which one is the fuel screw so you know you are turning the right screw. Also, if the bike has after market parts like a pipe and silencer you may want to call the manufacturer of the parts, let them know what bike you have and all the aftermarket parts you have and they can give you the correct jetting settings for the carb. You may have to re-jet the carb. Hope this helps.

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It could be that his fifth gear teeth are worn rounded or the shifter fork is bent. I've read something that grayracer posted about it before. Maybe he'll chime in on this.

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The rev limiter cuts off the ignition at 11,500 and keeps it off until the revs fall below about 10,900. When you hit that, it feels like a rhythmically regular misfire, and it will happen at the same RPM in any gear, not just 5th.

The jetting question, or a jet that's partly blocked, or low float level, or a dirty petcock screen, will make it feel as if it's running out of gas at high speed, and will be worse in 5th than in lower gears, but should still happen at least from 3rd on up at the same engine speed and load.

If it only happens in 5th (or only in any one other gear), you may have a trans problem. I know you were dying to hear that. The gears are locked in by the lugs, or dogs, on their sides. These are made with a slight undercut to them so that they hold in under a load. They can become rounded and worn so that the undercut is gone, or even reversed, and will then pop out and back in to mesh repeatedly under a load. The feel is like a chain jumping teeth, or a very harsh misfire, and 5th seems to be one of the gears this happens to most often. The fix for this problem is to replace the two gears that lock together for the gear that slips, and the shift fork that controls it. That, of course, means splitting the cases.

On the question of a quick twist causing the engine to stumble, you can reduce that in some cases, but you can't totally get rid of it. It will be there no matter what to some extent if the throttle is snapped hard enough from an idle. You need to learn to "roll" the throttle a bit more smoothly, which involves opening the throttle progressively faster as it opens and the engine responds. After you learn this, you'll do it without thinking, and the engine will respond very near instantly.

But a completely stock 426 accel pump can be improved on (the BK Mod...search for it ), and they can also get dirt in the accelerator pump linkage and around the shaft to the extent that they don't work right, so it does bear looking into.

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allright, im hoping nothing is wrong with the transmission, im going to get it out and ride again today, so i will post a detailed update this afternoon.

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Okay, i guess it just seems like the thing should have a faster top speed. It seems like it tops out in the upper 70's. But it goes from 0 to top speed unbelievably fast. Theres no speedometer so im not sure how fast im going but im just comparing to my old dirt bike. (TTR-225, my 426 is still heaven compared to that) I was thinking that maybe the sprocket is just different from stock. It was never raced so i dont think it has transmission problems... can anyone else with a 426 tell me how theres runs 1'st thru 5th gear? One more thing i noticed, it looks like a mixture of water and oil drips out of the bottom when i park it... not much, maybe a teaspoon full over 12 hours. Thanks for any info!

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...can anyone else with a 426 tell me how theres runs 1'st thru 5th gear?

Mine runs like a bat outta hell...I have no idea how fast I'm ever going on the thing but its scary fast. Hopefully Sandy Claws will be bringing me a Trailtech speedo for Christmas.

One more thing i noticed, it looks like a mixture of water and oil drips out of the bottom when i park it... not much, maybe a teaspoon full over 12 hours.

I think that's normal....oil coming from the breather hose. Mine does it more when I've been riding it really fast. Shouldn't be any water though.

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I really dont need to be going all out in 5th gear, at least when im riding where im supposed to be riding... the reason i brought up the whole top speed thing is because I was actually getting chased by someone because i went on their private road or something but it was hilarious for them to even try to keep up. top speed doesnt matter too much when you get get there almost instantly. heheh. Love this bike.

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Okay, i guess it just seems like the thing should have a faster top speed. It seems like it tops out in the upper 70's. But it goes from 0 to top speed unbelievably fast. Theres no speedometer so im not sure how fast im going but im just comparing to my old dirt bike. (TTR-225, my 426 is still heaven compared to that) I was thinking that maybe the sprocket is just different from stock. It was never raced so i dont think it has transmission problems... can anyone else with a 426 tell me how theres runs 1'st thru 5th gear? One more thing i noticed, it looks like a mixture of water and oil drips out of the bottom when i park it... not much, maybe a teaspoon full over 12 hours. Thanks for any info!

1st thru 5th? I'm trying to think of the last time I did that. Oh ya I remember, the front wheel never touched the ground until I was well into fouth gear. :applause:

When you run the snot out of it, it will be normal for it to leave an oil drip from the breather tube. Its a 426 tear, :bonk: its crying because you keep dogging it in high gear down the road. :cry:

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hahah, yeah, im not used to having so much power, my ttr-225, 3rd gear i could yank like hell and get it to come off the ground standing, 4th gear... had to get my knees on the seat and pull it up... 5th gear, that was just insane but i could do it now and then, 6th... never got it up. NOW the 426... i have trouble keeping it on the ground until 5th gear, just sitting normally. I really havent tried to pull it up in 5th but i know i could. I just cant wait until i can take this thing to some trails... or somewhere i can ride without having 10 people call the cops on me. Can't really sneak around on it either, because my itchy hand just keeps gunning the throttle just so i can see the dirt fly up behind me.

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I really dont need to be going all out in 5th gear, at least when im riding where im supposed to be riding... the reason i brought up the whole top speed thing is because I was actually getting chased by someone because i went on their private road or something but it was hilarious for them to even try to keep up. top speed doesnt matter too much when you get get there almost instantly. heheh. Love this bike.

Awesome! Welcome to TT! I keep waiting for someone to try and chase me! :applause:

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What front and rear sprockets are you running? A 14/49 combo is stock as I recall. The previous owner may have hung something lower on it.

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no matter wat u do the bike will always bog if u give it full throttle off idle but thats no problem cuz it wont do it wile ur riding the top speed thing is probly a jetting problem also i always hit top speed then ease the throttle back a tiny bit to keep from frying the valves good luck with ur 426

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