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I replaced my primary drive gear to a lightweight primary and it makes an almost clicking sound at idle, very subtle but noticeable. Also really noticeable when engine braking at deceleration. Is this normal? It is a TBparts lightened primary, both clutch basket and primary were re tightened with the impact drill.
 

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That's crazy I did the same install like 300 miles ago and I do not have any issues. If i could suggest something I would take the bike apart and look inside to see if maybe some parts were install incorrectly or the bolt was not fully torqued?
 

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Take the cover back off and check you haven't chipped a tooth off the white plastic gear.
Use a torque wrench when reassembling.
 

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I noticed the teeth are sharp on my TB parts primary gear, I think this one is a bad cut causing the noise.
When I installed mine, there was an extremely loud whine. It eventually went away and is no longer there. I think that was due to what you were saying.


But it never made it while at idle as it wasn't turning....

He may have had one too many ugga uggas with the impact.
 

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Mine is the same, fine at idle but once I engage the clutch I get the noise & harder to get into gear. I think the gears are to tight due to the bad cut on the primary gear. Btw is it worth getting the clutch upgrade with stiffer springs?
 

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I replaced my primary drive gear to a lightweight primary and it makes an almost clicking sound at idle, very subtle but noticeable. Also really noticeable when engine braking at deceleration. Is this normal? It is a TBparts lightened primary, both clutch basket and primary were re tightened with the impact drill.
Are you absolutely sure the noise is coming from the primary gear? Reason I ask is that I did this same mod a couple of months ago and had a very interesting experience. I also noticed a strange new noise at idle, when revving the engine, and most pronounced, while under engine breaking. I was pretty concerned, and was about to take the cover off to inspect, when I did one more check. I had my helmet off and kneeled down by the engine and blipped the throttle. To make a long story short, the noise was actually coming from the back of the bike, under the seat. Turned out to be my license plate, unsupported on the bottom of my fender eliminator plate mount, vibrating strongly, metal to metal on one side! A small strip of rubber along the bottom of the plate solved it for me. My theory here is that the lightened primary has different vibration modes back thru the tail of the bike than the heavier one had. It was easy to see the plate vibrate once I knew where to look. So keep an open mind while you troubleshoot yours...

JW
 

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Smart thing to check. Cheap bike or not, Kawasaki did NVH engineering. Removing a giant chunk of rotating mass means the thumper can thump more. Perfect Occam's razor explanation.

I'll watch out for this when I do mine, thanks. Plate already makes a bit of noise.
 

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The stock ones are cut pretty sharp too. The new part will need to break in and mesh with the bigger gear back there, just like when the bike was new. People here have reported whining coming from meshing gears... some had them replaced, some went away as they "broke in". I would be concerned with a new ticking sound though, almost like a piece of something is tumbling around in there? If it were my bike I would pull the clutch cover again and make absolutely sure you put everything back together properly and there is nothing broken in there. I'd imagine it could cause some serious damage.

Instead of using an impact you could put a 2x4 or something through the rear wheel so the swing arm stops it from turning as you wrench (put the bike in gear). Clutch basket has been known to break when hitting it with an impact. Hope you figure it out.
 

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Thanks guys, I actually called TB bolt & they explained that it's a common issue with the lighten primary gear whining. They basically said that the gears have a sharp cut & will eventually mesh after a few miles & the whining noise will go away. Thanks again for your help!
 

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Un-even break-in wear?

The stock ones are cut pretty sharp too. The new part will need to break in and mesh with the bigger gear back there, just like when the bike was new.
For sake of clarification, isn't this non-ideal? When brand new both gears are sharp and breaking in at the same rate. X hundreds of miles later the clutch gears are nicely rounded and we replace the primary gear with a fancy new sharp toothed gear. Now the rounded teeth need to break in the sharp teeth, potentially causing issues.

Same basic idea as replacing your sprockets at the same time as your chain no?

Probably fine for a glorified pit-bike, just wanting a better understanding of gear wear.
 

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Here is my totally novice take on this (which may or may not be correct):

When they say the gears will mesh yes it is true... but we are not talking about the sharp teeth rounding over like they do on your sprockets. Or the other gear (I'll call it the clutch gear I'm not sure its real name). By design the primary gear is cut pretty sharp and it will stay "pretty sharp". We're talking like thousandths of an inch change as they wear in. They will still look sharp after breaking in. I think this process is called "corrective pitting". It progresses quickly at start of gear life then tapers off during the break in period. They are hardened gears. The alignment is the most critical thing. A contact pattern will develop during break in. It should be a general circular pattern centered on the teeth to indicate correctly aligned gears with no lateral stress. More wear at the center of sprocket teeth, less as you get to the edges. In my post "first oil screen inspection" the first post has a picture there that shows the gear wear during break in:

https://www.z125owners.com/forum/engines-discussions/15559-first-oil-screen-inspection.html

That inspection was early on in break in process. There has been no significant change since. That patterns have just become a bit more even. Note the primary gear teeth are still a lot sharper than the gear they mate with.

You are looking for a nice even pattern on the mating surface of the gears. A little discoloration as the outer coating "wears in".

This "pattern" is actually a bunch of micro - pits. They are very good as they hold oil and help lubricate the gears as they mesh.

Some of gears are surface hardened, some are through hardened. Our sprockets are surface hardened, but the primary gear and the larger gear it mates with I think are through hardened but that may not be correct it has been a while since I checked this out. It makes sense to me though that they would be. This information here is the best summary I found when freaking out about my own gear wear during the oil screen inspection:

http://www.cscos.com/wp-content/upl...How-Their-World-is-Changing-Neville-Sachs.pdf

CTRL-F corrective pitting.

Perfect world yes I think you would replace both gears. But they should mate together fine assuming you don't have like 20k miles on the larger gear.

Important to note you are "breaking in" these gears all over again. The advantage of a "hard break in" here is lost because piston rings are already sealed. I would take it easy first 50-100 miles to give the new gears a chance to begin to mate. You will have metal in your gear box again, just like at first break in, admittedly much less.

Note: some corrective pitting to the clutch gear may have occurred with first primary gear, and maybe when the lightened primary is installed there will be a couple spots that were "corrected" earlier that didn't need as much of a correction with the new gear. This will result in not 100% contact as the teeth mate, theoretically increasing pressure on the rest of the teeth (smaller contact patch) which is why it is best to replace both, but the reality is we are talking about a 125cc mini bike here and you are probably fine.

So TLDR: Probably best to replace both, but in real world, with relatively low mileage, you will have some more corrective pitting and they will mesh together almost as well as if both were replaced. On a bike with, say less that 2500 miles I wouldn't worry about it at all.
 

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Killer explanation, I tried to "like" it 3 times but it just toggled on and off. Weird.

Maybe I'll open up both bikes at the same time and compare the pitting, just for giggles. Good news is, the lightened primary is going on the 2017 with very few miles.
 

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Primary whine too loud?

Hey Z-fam,

Finally got my lightened primary gear and HD clutch installed this weekend. (Wanted to do it @200 miles because I needed to drop the oil anyway)

I recalled from this thread that nearly every primary gear swap causes some additional noise. Part of this is from imperfect meshing as discussed, which may or may not fade. I figure a good amount of noise is also damped out of the system by the massive chunk of steel on the OE primary gear.

Anywho... my bike's primary/secondary was silent before the change, and now it sounds like an odd combination of a Dolphin in heat, RC car, and supercharger. Pretty much the exact sound as this thread, but at least 3x the volume. Off the line it sounds like a strained electric motor, and I get a nice supercharger whine running through the gears. It's legitimately the loudest thing about my Z until 45mph or so. I put a quick 50 miles on the bike, optimistically hoping for the noise to fade. I'm already starting to get used to it and part of me says "eff-it, funny noises for a funny bike" but OTOH it has ruined the stealth neighborhood cruiser appeal of the stock Z.

I've officially harassed MNNTHBX and TBoltUSA about this and while my impression from this thread was that the whining would subside over the first 50 miles or so, both these vendors claimed that the whine is around to stay.

From the thread linked above it sounds like the OEM primary and secondary/clutch-basket gears make this noise on a small amount of bikes, at a lower volume. So there is some variance in the tooth profile as manufactured for Kawi and the TBolt part, I just lost the lottery on combining them. It also sounds like learning to live with the whine won't harm the bike.

So, I'm conflicted... I love the better throttle response and reduced engine braking that the lightened primary provides, but I'm not yet sure it's worth the obscene sound effects. =/
 

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Chuck the new gear in a drill, and run the teeth against a belt sander to take off a few thousandths of an inch? Alternate would be to mount both gears in a fixture that allows them to spin and mesh like they were installed. Then take valve grinding compound and let them wear together a bit.

You may actually need to do both, noise like that is most often caused by too tight of a mesh, and this is stealing power and causing heat.
 

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...noise like that is most often caused by too tight of a mesh, and this is stealing power and causing heat.
This definitely occurred to me. Any noise is wasted energy technically, so loud noise, while amusing sounding, is power lost.

My co-worker seemed concerned with the amount of heat on the cover after a 15 mile ride, so that may be something to watch out for as well.

I think there's an out of cal thermocouple at work that I can grab, go for a 5-10 min ride, check the oil temp, repeat the same route on the stock bike.

Your suggestions are very good, I'm just a bit frustrated that I even need to consider them. Owell, like my buddy always says "if you don't want problems, stay stock."

At the very least it's probably time to open it back up and assess any damage. =/ Hopefully the quart of oil is the only wasted money going on here.
 
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