Slipping Out of Gear After 3-4K rpms

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Slipping Out of Gear After 3-4K rpms

Postby Fishrider » 25 Mar 2018, 20:22

New to this board, thanks for having me. This is my second Zephyr. I used to own one way back in the late 90s. I finally found one in my area(Denver, CO USA). Its a 92 750cc that had been garaged for 9 years with only 3500 miles on it. It has a little cosmetic damage from a drop, but other than that seemed fine. It took a lot to get it back into running shape, but I got it there. I went for a couple rides and the bike ran great. After sitting a few days, I took it out, and I have run into a problem. When I go over about 3-4k rpms, it slips out of gear making a loud quick clacking noise. It does this from stop in first gear, and any other gear once I am up to speed. Is this a clutch adjustment issue, or am I looking at a gear box problem? TIA

Mike
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Re: Slipping Out of Gear After 3-4K rpms

Postby Freddy » 26 Mar 2018, 00:19

What side was it dropped on? Like was it the left hand side and the gear change mechanism could have been damaged.

If its a genuine 3500 miles, and jumping out of every gear one would be inclined to think its not gearbox wear related.

I'be be looking closely at the gear lever. Is it fitted to the correct spline and adjusted correctly.

Front chain cover. Is it damaged where the gear lever comes through it.

Transmission cover ..... if nothing insightful is the change mechanism and drum behind the transmission cover ok.

All the above can be done quite easily with the engine in the bike.

However before doing anything, put it on the center stand, and sitting on the ground on the left hand side of the bike, rotate the rear wheel with your right hand and at the same time work the gears up and down through the full range with your left hand. Check that it appropriately 'clunks' into each gear, positive and solid. This may point you in the right direction.

Below is a parts schematic of the bits I'd first check out. Just for your information at this stage, see part number 92043, that spring loaded plunger sits it grooves on a star shaped cam on the change drum. It's the principal mechanism that locks each gear in place when shifted. It however is on the inside of the engine.

Image
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Re: Slipping Out of Gear After 3-4K rpms

Postby Fishrider » 26 Mar 2018, 03:06

Thanks Freddy! I think it was a slow moving drop. I can't see any damage near or around the gear lever. I can cycle through the gears just fine on the stand. I did mess with the clutch cable a bit, and now I can't get any power at all. I let the clutch out, roll on power and it just dies. It seems like it attempts to engage slightly, and then gives up. Is the clutch shaft supposed to be able to pull out when turned left? I am not sure if I messed something up there. I hope I don't have to crack the case to fix something. It was a long haul just getting it running again.

Thanks,

Mike
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Re: Slipping Out of Gear After 3-4K rpms

Postby Freddy » 26 Mar 2018, 06:34

Fishrider wrote:Thanks Freddy! I think it was a slow moving drop. I can't see any damage near or around the gear lever. I can cycle through the gears just fine on the stand. I did mess with the clutch cable a bit, and now I can't get any power at all. I let the clutch out, roll on power and it just dies. It seems like it attempts to engage slightly, and then gives up. Is the clutch shaft supposed to be able to pull out when turned left? I am not sure if I messed something up there. I hope I don't have to crack the case to fix something. It was a long haul just getting it running again.

Thanks,

Mike


By the look of the left hand side crash bar I'm thinking it was perhaps just a little more than a 'slow' drop.

Taking perhaps the easiest one first. Are you saying the engine just dies when you slowly let the clutch out, just about the point where the bikes wants to start to move? If so, by that description I say the side stand switch or clutch switch is problematic. If this is the case, first thing to check is if the metal tab on the side stand is correctly positioned and getting the side stand switch to operate correctly when the stand is put down and retracted. Next, the bike clearly went for a decent slide on the left (clutch lever) side. The bars and controls on that side would surely have got a bit mangled.

If you disconnected the clutch cable completely at the clutch cover end, and turned the arm to which it attaches counter clockwise, yes it will lift up. No problem, just lower it again and turn it clockwise to again engage the clutch push rod.
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Re: Slipping Out of Gear After 3-4K rpms

Postby Fishrider » 26 Mar 2018, 16:45

Well you were right about the switch, and maybe the drop as well. The switch needed some thorough glaring at. I have power again, but back to the original issue. There seems to be a correlation between when I move the clutch out, and the disengagement of the gear. If I am very careful, I can get the gear to engage. I am not certain of these observations, but I think that if I pop the clutch quicker it engages better than if I let it out slowly. I can get it to engage at higher rpms as well, but the problem still makes the bike un-drivable. The noise makes me think I am grinding something bad every time it happens. I am going to do a bit more testing when I back from work this afternoon.
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Re: Slipping Out of Gear After 3-4K rpms

Postby Fishrider » 26 Mar 2018, 22:18

Upon further testing it seems to be slipping in any gear when give it power over about 3000 rpms. I can get into each gear, but I have to spool up very slowly. If I don't I get that loud noise with no extra power. I swear the sound is coming from the left side of the bike.
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Re: Slipping Out of Gear After 3-4K rpms

Postby DaftRusty » 26 Mar 2018, 22:42

From the pictures you posted, it may be possible that your shift lever is indexed to high up. Having the lever to high means your foot can't pivot the linkage up enough to fully engage the gears. Unbolting the splined shift lever and rotating it counter clockwise will lower the shift lever.
If that dosen't help (not really convinced it will) you will need to remove the transmission shift linkage cover and look for bent/damaged parts. (have a new cover gasket ready as it is impossible to save the old one) If the fingers on the shift lever are damaged it won't turn the shift drum properly and none of the gear dogs will fully seat and it will slip out of all the gears.
I have also read of someone who dropped the bike and broke the pivot point off the engine case where the shift shaft pivots on. He could kinda shift gears, but the broken pivot point caused so much slop that it never shifted properly after that. You need a very very good welder to repair a broken pivot point or otherwise replace both halves of the engine case.
Unfortunately, looking for bent shift forks is a split the engine cases type of ordeal, and if you go through that much work then you could consider doing a 6-speed swap while you are in there.
650/750 6-speed Transmission Swap
1991 zr550
Factory Pro stage 1 jet kit
zx550 pistons and cams
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Re: Slipping Out of Gear After 3-4K rpms

Postby Freddy » 26 Mar 2018, 23:34

Fishrider wrote:Upon further testing it seems to be slipping in any gear when give it power over about 3000 rpms. I can get into each gear, but I have to spool up very slowly. If I don't I get that loud noise with no extra power. I swear the sound is coming from the left side of the bike.


Can we clarify some terminology. In your first post you said the bike 'slips out of gear', in the above post your say the bike is 'slipping in any gear'. Might seem like I'm be pedantic but they are very different things.

1. The term slips out of gear is generally taken to mean the gearbox won't stay in a gear, apply some power and it jumps into a false neutral with no drive. The engine losses drive completely, and the only way to regain drive is to put it back into gear again with the gear change lever. It is highly unusual for a gearbox to jump out of all gears, it is usually just one.

2. Slipping in any gear generally means the bike stays in gear but looses drive, because the clutch is slipping. The engine revs go up, but the bike speed doesn't. You just roll back on the throttle and the bike again regains drive. You don't have to touch the gear change lever to regain drive.

From your last post above, it sounds to me your problem is description 2. Is that correct?
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Re: Slipping Out of Gear After 3-4K rpms

Postby Fishrider » 27 Mar 2018, 00:05

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Re: Slipping Out of Gear After 3-4K rpms

Postby Freddy » 27 Mar 2018, 00:37

Based upon what I see from the video, that it happens in every gear, I'm wondering if the front sprocket is the problem. That would align with your belief the noise is coming from the left hand side.

I'd pull the front sprocket cover off and inspect. It's about a 10 minute job.

1. You undo the small bolt securing the gear change arm to the shaft running through the cover and slide the arm of the splines. The bolt has to be completely removed, not just loosened. Before you remove the arm take note of a small dot on the shaft that aligns with a mark on the arm. When refitting align these two marks again.

2. There are 4 small bolts holding the sprocket cover on. A couple are easy to see the others are hidden back a bit up 'tunnels'.

3. With the 4 bolts removed wiggle it free from the 2 dowels that locate it in position, and remove.

I'd actually completely remove the front sprocket. Inspect the internal splines, external teeth, and that its tensioned correctly. Removing the sprocket can be a bit problematic but lets cross that bridge when we come to it.

But post a picture of the front sprocket after you've removed the cover. I wouldn't be surprised if for some reason its all chewed up. If it is this is good news, because its easily fixed.
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