Failing 4th Gear..


20 replies to this topic
  • Kawabuggy

Posted June 10, 2007 - 06:30 PM

#1

Today while riding I noticed what I thought was a bad chain, or bad chain & sprocket combo. The bike was bucking, kicking, & hesitating-almost like the engine was misfiring. As the day pressed on, I realized that this was only happening in 4th gear.

In 4th under light acceleration, the bike will jerk and buck and you can hear the chain go from tension to slack, back to tension repeatedly. Shift into 3rd or 5th, and the problem immediately goes away. Under heavy acceleration in 4th, it feels like the bike tries to pull but then just starts slipping like you have pulled in the clutch. Let off the gas and it will start pulling again, but still bucking the entire time.

Now the questions, has anyone experienced this before? And if so, what parts did you need to fix the problem? I know I will have to split the cases, not worried about that. But would like to order parts in advance before I tear into it so that the bike is down the least amount of time. I have access to parts from a donor bike, but would like to hear about any "surprises" waiting for me when I get in there.

Hope everyone elses weekend went better than mine..:thumbsup:

  • Husqvarnasm450r

Posted June 10, 2007 - 06:48 PM

#2

I have experienced that be4 and right now that 4th gear is a trip man. I think its my chain stretched out. I took it back to the dealer and they fixed it for me.

  • Kawabuggy

Posted June 11, 2007 - 06:46 AM

#3

????? They must grow it good in your area...

Anyone else have any ideas or suggestions, or am I on my own on this one???

  • martinfan30

Posted June 11, 2007 - 07:20 AM

#4

on my last trip, my buddy and switched bikes(his 07 xrl) and i noticed that same thing on his. did it 1 time for about a quarter mile then nothing after that! been fine since.:thumbsup:

  • cleonard

Posted June 11, 2007 - 08:54 AM

#5

That doesn't sound like a trans issue.

I just can't think of a mechanism where gear selection would make the engine feel like it is missing. In my limited experience trans issues are usually oise/vibration from worn parts, gears that you can't select, pops out of gear, or a kaboom when something breaks.

One thing to be on the look for is metal in the oil and the screens. A small amount can be normal, a sudden increase means possible trans issues.

If it is the clutch, you will know soon nas it will slip more and more.

  • Kawabuggy

Posted June 11, 2007 - 09:44 AM

#6

No, it is definitely related to 4th, and only 4th gear. All other gears work perfectly fine and there is no hesitation or vibration. Only in 4th will it do these things. I am very confident that it is a 4th gear problem. The clutch is holding in all gears. I only get the slipping sensation under full throttle in 4th.

I am taking the motor down today.

  • XR650L_Dave

Posted June 11, 2007 - 09:58 AM

#7

a SMOOTH FEELING TRANNY PROBLEM CAN OCCUR WHEN A (crap sorry)
when a gears dogs start to wear, the gear pops out of the one next to it and spins free for a few moments, then the dogs re-engage.

This can be a cause of, or a symptom of, bent shift forks, so eyeball the dogs, the holes the dogs slide into, and the forks, and the shift drum as well.

Was happening to my buddies FJ1100, he got lucky, I replaced the one gear (dogs were worn) and it was fine.

Dave

  • cleonard

Posted June 11, 2007 - 10:07 AM

#8

a SMOOTH FEELING TRANNY PROBLEM CAN OCCUR WHEN A (crap sorry)
when a gears dogs start to wear, the gear pops out of the one next to it and spins free for a few moments, then the dogs re-engage.

This can be a cause of, or a symptom of, bent shift forks, so eyeball the dogs, the holes the dogs slide into, and the forks, and the shift drum as well.

Was happening to my buddies FJ1100, he got lucky, I replaced the one gear (dogs were worn) and it was fine.

Dave


How much wear is too much when it comes to gear dogs and the holes that they engage with?

  • XR650L_Dave

Posted June 11, 2007 - 01:49 PM

#9

How much wear is too much when it comes to gear dogs and the holes that they engage with?


Its probably a loss of the 'undercut' more than it is actual loss-of-material.

The dogs are cut back a little so each one has a little ramp so when driving force is applied the gear is 'sucked into' the adjacent gear (via the dogs) .

Too much ramp- hard to shift
Too little ramp- slips out easy.
Negative ramp gets forced apart as opposed to being drawn together.

Dave

  • Kawabuggy

Posted June 12, 2007 - 05:26 AM

#10

When I get the main/counter-shafts out I assume I will have to figure out which gear locks 4th in. Then how do I confirm exactly what the damage is?

Once I get it down, I will post pictures here and ask for input.

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  • XR650L_Dave

Posted June 12, 2007 - 08:04 AM

#11

I think the manual shows the power path through the gears for each gear.

Someone posted a pic of it here, or on 4strokes.

Damage will be a bent fork, a nasty looking groove in the shift drum, and/or severe wear on the gear dogs (or bent dogs) and where they insert into the gear next to the dogs.

Dave

Dave

  • motox-quadracer42

Posted June 22, 2007 - 09:42 PM

#12

have you torn it all down yet you left a comment in my thread about my second gear not working but when i just started to get into the engine the clutch was shot so im going to replace that and see what i get from that and if its still bad im going to pull the engine split the case and prolly replace the whole tranny

  • Kawabuggy

Posted June 23, 2007 - 06:14 AM

#13

Not torn it down yet.. Been very busy at work. Luckily I am not missing much riding time because it has been raining every weekend. I will get to it at some point in the near future..

  • Kawabuggy

Posted July 02, 2007 - 05:57 PM

#14

Finally got my motor out and torn down today.. Took me about an hour to get it out of the frame, and about 3 hours to tear it down.. I was moving slowly on the tear-down trying to memorize how it all goes back together.. I have a service manual, but I would hate to find that my manual does not have a picture of some part that is left over..

Regardless, I got the cases split, and got into the transmission... And the cause of failure is.......... I don't know! There is nothing obviously wrong that my untrained eye can see. I looked at 3rd gear carefully and can see that it has minimal wear on it. I can see that it has taken the most abuse, but it is still serviceable. Nothing that will catch your fingernail, and no obvious deep grooves, or pitting-just a little more wear than the other gears.

I don't know if this is normal, but my 5th gear is a dark brown, almost black color whereas all the others are silver in appearance.. The 5th on the main, and also on the counter-shaft are both like this. I will take pictures tomorrow and post links to them here so that maybe someone can help me make sense of this. I went over the shift forks, and measured each and every one of them and they are all well within spec (the ends that contact the sliders) by a safe margin. I checked the round "ears" on the shift forks and no abnormal wear there. Checked/confirmed that the shift drum is also in great shape and showing no signs of wear. I am beginning to second guess my 4th gear as the cause of my problems.

I did check the clutch. The discs are basically brand new showing ZERO signs of wear. The PO must have replaced it just before I got it.. Perhaps he was experiencing this problem and replaced the clutch thinking that was it.. Anyway, the steels (discs between the clutch plates) look to be brand new with no signs of hot-spots, grooves, scratches-NADA! I would think that with the riding I have been doing that something would be evident.. but no signs of damage to any of the clutch plates or steels. I measure the free length of the clutch springs and they are outside of spec so I am going to replace them. The clutch was not slipping though as I am sure I would have seen evidence of that on the plates/discs.

Anybody have any ideas where I can get: clutch springs (just the springs), case half gasket, all seals for bottom end of engine, & head gasket--IN A TIMELY MANNER! I would like to have this thing back together within the next week or so. Oh, forgot to mention-since I am in the motor, I need a 10.25:1 piston & rings as well. Might as well add more power! Since I can't see what the problem is now, perhaps the added compression will shatter the parts causing my issues so that I can then do a proper repair.. Ha ha!

Anything anybody else can think of that I might be over-looking?

Will post those pictures in the AM. Thanks for reading this l.......o......n......g... post.

  • wheelnut46

Posted July 02, 2007 - 07:05 PM

#15

...Might as well add more power! Since I can't see what the problem is now, perhaps the added compression will shatter the parts causing my issues so that I can then do a proper repair.. Ha ha!


You have a great attitude. I would still be throwing hammers and such after going to all that trouble and finding nothing.

:busted: :thumbsup: :thumbsup:

I hope you find the cause.

  • Kawabuggy

Posted July 03, 2007 - 08:00 AM

#16

I still have not had a chance to post pictures. I used my cell phone for the pictures but the quality is so poor that you can't really make anything out in the pictures.

I did some research on the numbers on the top of my piston "H56H8" and then centered on the piston is 4366P4 XH, and 1.00MM. I searched that number using Google and came up with a Wiseco piston that is 11.1:1. I did not know that this bike already had a high compression piston in it. Looks like I have a "603"-and not a 600! Ha! One less head-ache to worry about.

  • martinfan30

Posted July 03, 2007 - 08:06 AM

#17

usually when a gear is that color(especially if the others are not) means it got very hot somehow.

  • Kawabuggy

Posted July 03, 2007 - 12:56 PM

#18

The odd thing is that I just looked at a used tranny on E-bay, and you can clearly see that 5th gear is dark in color on that tranny as well-both on the main and counter shaft. 5th was working fine before I pulled it apart. Plus where the teeth make contact looks perfect-no signs of any type of scarring, pitting, scoring, or bluing.

One thing I figured out is that the 4th gear shift fork is bolted to the selector pin. The pin physically has to move back and forth between the case halves to make 4th engage. With my hands I can select all gears by turning the shift drum.. All except 4th. When I try to get it into 4th it is almost like it is binding up. It takes a lot of force to move the drum into the 4th gear position. The selector shaft does not feel like it is binding up as it moves freely in both case halves.. The slider for 4th looks good as well. Waiting on case half gaskets & clutch springs to put it all back together. I am hoping that it was just a fluke and something else is wrong with it... Will keep posting once I get it back together. The one thing I might try doing is intentionally bending the shift fork so that 4th has better engagement when the fork pushes the slider. Right now I can tell that the little "buttons" on the back of the gears that engage the next gear are only engaging 4th gear about half way when you select 4th on the drum. They don't appear damaged, but they are not seated all the way into the gear by the fork.. Almost like the fork is not pushing the 2 close enough together. Regardless, I am going back together with it, and will see what I have when I am done. I will bring my good digi camera to work tomorrow to see if I can get better pictures of everything.

  • j5hunter

Posted July 03, 2007 - 08:08 PM

#19

Please keep the thread alive as I have the same problem with 3rd gear. The description you gave was identical to what I have. Mine is an 87 XR600r. Good luck.

  • machman

Posted April 27, 2008 - 07:42 PM

#20

I just waited a year for a new transmission, and time and money to get my bike back together and I've got this issue with 3rd gear.

Frustrating to say the least.

Anyway, anyone got a solution?





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