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09 YZ 250 false neutral

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This past weekend during the GNCC ironman race, out in the fields, my bike would hit false neutral sometimes when shifting 4th to 5th or when trying to shift again when in 5th. Also at time when in 4th or 5th not touching the clutch or shifter, it would drop out of gear into false neutral, down shifting would get it back into gear but I don't know where to start in trying to diagnose the cause of the problem. I seached false neutral but found nothing like my problem. Most where problems of falling into neutral when going 1st to 2nd or back because of the wrong type of oil. I never have that problem. any ideas?

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your 4th-5th fork is toast. When you pull it apart you will notice the fork is wore in the center becuse its bent. I have a new fork in my tool box because there real comin to go out. Check the dogs on the gears also they could start to round off because the fork is bent and not properly enguaging going into 5th. This is why you pop out of 5th when you carry a load in 5th. The 4th 5th fork is the bent looking one. The other two are streight but also inspect them for the same damage. Im 99.9% shure thats your problem. My 06 250 has close to 500 hours on it now ive been around the block and back. If you have access to a machiene shop the new 5th fork can be improved before you install it. I polished the shafts and debur the sharp anngle at the end of the shaft on the fork and it has led to better shifting and I havnt had that fork go out on me yet.

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Thanks for the info. This bike has about 10 woods races on it and only a few riding days...maby a total of 35-40 hours on it has been maintained well. Think it's possible for it to go out in that many hours???? The reason I ask is because in the type of racing I do, I am hardly ever in 4th or 5th gear. Also what causes the fork to get bent in the first place? Jamming the shifter too hard? Thanks again.

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It could turn out to be your shift fork, but I would check the shift mechanism to make sure it is working as designed. You didn't say it was jumping out of 5th gear, as would be typical of a bent shift fork. If you had a bent fork, it would usually jump in and out of gear. if the shift mechanism is not positioning the gear in the correct position, it wil tend to slip into what might be considered "neutral' (in between gears)......If you DO have to pull it apart and check componenets, be sure to inspect both gears that engage to make 5th, as well as for indentations in the shift drum where the fork is in position for 5th gear.

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Yes it did pop out of gear when under a load. It would hit false neutral when shifting and also "fell" out of gear when accelerating hard and not touching the shifter or clutch....looks like it's pointing towards shift fork...still don't know what could cause it to get bent in the first place...:thumbsup:

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It could be as simple as a chunk of crap in the groove of the drum. Dum design of that fork and I believe they have to sharp of a gnarl on the end of the shaft were they tapered it. The way there pined to the shaft and the fork design they bend easy compared to the other forks. I took all my fork and put them on a lathe and micropolished my shafts and rounded the ends the slid tons better into the case afterwords. If I had the time I would design a solid fork and these transmissions would be bullit proof.

If it were me id pull it apart quick and clean everything up and inspect. But I have all the tools to properly do so. You could keep riding it but it might wreck the gears if it keeps happening. Could be as simple as a piece of crud stuck somewere or it could be the fork.

Everything has it weakest link 5th fork just happens to be a yz250's.

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...still don't know what could cause it to get bent in the first place...:thumbsup:

I've taken out a couple of shift forks in my day racing YZ250's and most of the time it's due to shifting under load and the fork is not all the way in when engaged. Racing is racing and it will happen time to time but the YZ's are known to happen more often than bikes.

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I've taken out a couple of shift forks in my day racing YZ250's and most of the time it's due to shifting under load and the fork is not all the way in when engaged. Racing is racing and it will happen time to time but the YZ's are known to happen more often than bikes.
I've done the same on a different bike and my son's KX is apart currently awaiting new forks. All it takes is one blown shift under power. Keep riding it and the dogs/gears will be ruined by jumping out under a load.

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I've done the same on a different bike and my son's KX is apart currently awaiting new forks. All it takes is one blown shift under power. Keep riding it and the dogs/gears will be ruined by jumping out under a load.

Most shift forks are "bent" by falling on the shift lever, and, depending on what gear you're in, that is where the problem will occur, plain and simple. When you fall, the lever digs into the ground or whatever, and puts intense pressure on the fork. All of us have bent shift levers, the same force that bends your shift lever is also present trying to "bend" your shift fork. "Speed shifting" has nothing to do with "bending" the fork, although it may have a cumulative effect at some point. If you spend more time in, say, 3rd gear, that is the gear you will most likely be in when you fall, and most likey have a problem. I have a vintage YZ 360 that I have raced the crap out of for the past 20 years, speed shifting, jamming, no clutch you name it, never had a shift fork issue, but I like my shift lever real high, and have seldom fallen on the shifter. These things are tougher than a wood pecker's face, but, we do still manage, on occasion, to mess them up. Just my .02....:thumbsup:

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Most shift forks are "bent" by falling on the shift lever, and, depending on what gear you're in, that is where the problem will occur, plain and simple. When you fall, the lever digs into the ground or whatever, and puts intense pressure on the fork. All of us have bent shift levers, the same force that bends your shift lever is also present trying to "bend" your shift fork. "Speed shifting" has nothing to do with "bending" the fork, although it may have a cumulative effect at some point. If you spend more time in, say, 3rd gear, that is the gear you will most likely be in when you fall, and most likey have a problem. I have a vintage YZ 360 that I have raced the crap out of for the past 20 years, speed shifting, jamming, no clutch you name it, never had a shift fork issue, but I like my shift lever real high, and have seldom fallen on the shifter. These things are tougher than a wood pecker's face, but, we do still manage, on occasion, to mess them up. Just my .02....:thumbsup:

...have you ever had a tranny apart and see what is the shift shaft is connected too? The shift shaft is connect too the shift cam (drum) and not to the shift forks at all. You can crash all day and not bend a shift fork...but miss shift under extreme load of the motor and it will cost you $. Please read the link for a better understanding....

http://www.factorypro.com/tech/Transmission,%20second%20gear,%20missed%20shift.htm

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Most shift forks are "bent" by falling on the shift lever, and, depending on what gear you're in, that is where the problem will occur, plain and simple. When you fall, the lever digs into the ground or whatever, and puts intense pressure on the fork. All of us have bent shift levers, the same force that bends your shift lever is also present trying to "bend" your shift fork. "Speed shifting" has nothing to do with "bending" the fork, although it may have a cumulative effect at some point. If you spend more time in, say, 3rd gear, that is the gear you will most likely be in when you fall, and most likey have a problem. I have a vintage YZ 360 that I have raced the crap out of for the past 20 years, speed shifting, jamming, no clutch you name it, never had a shift fork issue, but I like my shift lever real high, and have seldom fallen on the shifter. These things are tougher than a wood pecker's face, but, we do still manage, on occasion, to mess them up. Just my .02....:thumbsup:

SO we must fall in 4th and 5th gear while riding. Id be hamberger If I fell at that speed. Its because 4/5 fork is total different design then 1/2/3

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:ride:Falling on the shift lever and transferring all of that energy to the shift drum, and then the fork, is by no means the only way to bend a fork. As newp500 mentioned, the shift linkage may not position the gear to engage its mating gear correctly, a weak spring somewhere in the linkage, etc. I know from 40 years of pulling trannys apart what I've seen. While definitely adding to the problem, If speed shifting were the primary reason for transmissions jumping out of gear, we'd all be doodling around in low gear, as that is the only one that we don't speed shift into.:thumbsup:

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Most shift forks are "bent" by falling on the shift lever, and, depending on what gear you're in, that is where the problem will occur, plain and simple. When you fall, the lever digs into the ground or whatever, and puts intense pressure on the fork. All of us have bent shift levers, the same force that bends your shift lever is also present trying to "bend" your shift fork. "Speed shifting" has nothing to do with "bending" the fork, although it may have a cumulative effect at some point. If you spend more time in, say, 3rd gear, that is the gear you will most likely be in when you fall, and most likey have a problem. I have a vintage YZ 360 that I have raced the crap out of for the past 20 years, speed shifting, jamming, no clutch you name it, never had a shift fork issue, but I like my shift lever real high, and have seldom fallen on the shifter. These things are tougher than a wood pecker's face, but, we do still manage, on occasion, to mess them up. Just my .02....:thumbsup:

I disagree.

I've done damage twice by hanging between gears at RPM. When the tranny drops back into the lower gear it chucks in with great force. I even caught one fast and pulled the clutch in but it hurt things any way. The first dinged the drum slightly but that was an easy fix. That bike shifts terrible when warm!

My sons KX was hurt the same way. He told me he missed a shift and aterwards it was hard to shift into 3rd. His description and my inspection shows a bent fork.

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Another thing that can happen to cause your symptoms is holding the shift lever up or down too long after the fork has already slid the gear together. This can cause the portion of the fork that touches the gear to literally "smoke" and the resulting wear gives the shift fork less side to side movement, making it hard to engage gears all the way.

Sounds rare, but sometimes when racing people want to be "sure" they hit the next gear so they'll shift under load and hold their foot under the shift lever, keeping it up to "force" the transmission into the next gear. Not only can this only do harm if the dogs on the gears don't line up smoothly, but if it does shift from gear to gear and you continue to hold it "to be sure" you're just smoking the shift fork.

Like a few people mentioned, definitely check the dogs for chips or rounding. Usually when the bike is clunking into gear or dropping out of it it's because the forks is bent, smoked or the dogs aren't hooking up correctly. Rarely does it seem to be a shift drum, shift star, or detent spring issue.

Don't ask me how I know... It involves multiple transmission a gsxr 750's...

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