This is first time I've heard about it on a Monkey, but it's becoming a thing on the new gen Groms. Apparently it's a bushing that's too tight on the 2nd gear shaft. They're all spinning all the time, regardless of gear, so it just sits there and heats up until it makes noise, then doesn't go away until you put a load on the shaft shifting down into 2nd. There's a guy that makes a kit to fix it, or you can do what most people have been doing which is either 1) go to the dealer, complain, and then they won't do anything or 2) ignore it until it self-clearances and goes away.. You can google grom 5th gear whine and find a lot of threads on it.

 

Apparently it's a bushing that's too tight on the 2nd gear shaft. They're all spinning all the time, regardless of gear, so it just sits there and heats up until it makes noise, then doesn't go away until you put a load on the shaft shifting down into 2nd.

I suspect the factory overtightened chain is what causes this. It seems the driven 2nd gear is right next to the countershaft bearing so when the chain is too tight, there's enough flex to cause those gears to not run parallel. I bet the worn bushing/gear would show evidence of that being the case with a very slight taper worn into them from one end to the other. I think when 2nd gear is selected, the dogs get engaged with it and add support so it stops rattling around on it bushing. I would expect the end bearing to have enough wear to need replacing also but maybe not. I would probably replace it anyway while I was already in there.

 

Neither of those parts are superseded. The gear rides on the bushing, not next to it. First, second and third gears are locked onto the mainshaft and in constant mesh with their countershaft gears so any time the clutch is out, all those gears will be spinning. Likewise, forth and fifth are locked onto the countershaft and in constant mesh with their mainshaft gears so they're all spinning whenever the bike is moving. Third, forth and fifth are used to engage the gear you select and disengage the rest by sliding sideways. Anyways, a tight chain will cause the countershaft bearing, shaft, bushing, oil and second gear to run hot and wear out.

 

Then why does my grom do it, chain has been in spec since I bought it with 0 miles. Honda's chain spec wrong?

 

Yea, this isn't a chain or chain tension issue unless the factory spec is trash. I double checked the tension when i first brought it home knowing this was a potential issue. I'm pretty religious about chain tension and keeping it clean/lubed.

Bottom line, im going to do my best to get it fixed under warranty, or I'll tear into it myself if I have to. I love this bike too much to give up on it, but the whole "Honda reliability" thing makes me laugh now. I've had better reliability out of harleys.

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Well I guess I'm wrong and a severly overtightened, misaligned chain like I had wouldn't have cause that particular gear problem. This is the first I've heard of it but still haven't found any actual proof of it being the cause of the noise. Any pics or documented discussions you can link me to? All I found was the "kit" that claims to fix it. In the past, Ive seen the output bearing overheating and wearing out due to an excessively tight chain and assumed a gear butted up against it would suffer also.

Anyone that gets it fixed under warranty won't get to keep the old parts so please try to get pictures of them.

 

There's something called brinelling that happens to installed ball bearings that are under a stationary high load and receive minute vibrations. Most of these damaging vibrations occur during transport over land. I've personally witnessed the effects with PW50 steering head bearings when I was doing setups full time many years ago but didn't know what it was called. All were overtightened and developed notches in their races between the time they left the factory and when they arrived at the dealership. Being a slow moving bearing, there was no problem with just loosening them until the notches were undetectable and sending them off.

With the high-speed bearings in our Groms and Monkeys, even after readjusting before being ridden for the first time, the deep notches can be expected to cause noise, accelerated wear and excessive heat under the same conditions being reported . I doubt many of our minis will be immune to this problem until the bearing is replaced. I'll be switching to synthetic soon now that my Monkey is fully broken in and continue to avoid long high speeds runs.

 

At least its only happening to a "very" small number of the 22 and up groms and now a monkey. Most likely hondas not even concerned about it. Dont get me wrong it sucks for the folks dealing with it but in the numbers game 10 bushing/bearing issues out of more than 10,000 bikes sold without issues (guessing) its considered a non-issue.

 

I read a post by Yellow22 stating his problem was diagnosed as a countershaft bearing failure and was covered under warranty. He mentioned he lives in Arkansas which is pretty far inland so his bearing would've had quite a brinelling by the time it got to the dealership. I live close to DC with sea ports somewhat near by so I wouldn't expect my bike to have as much damage done to the bearing. I'm curious how far inland others with the noise live or bought their bike from.

 

You're going to need to elaborate here.. what effect does a seaport have on if the transmission whines because of tight tolerances? 🥴 Do you think they ride the bikes from the port to the dealership? 😂

 

Magilla-
Our 22 groms were shipped out of a southern California port to massachusetts (waited 5months and every few weeks checked w/dealer on there location) no bearing issues here.
Also changed out shipping oil (break in oil) very early (under 100 miles) one of the groms only had half a quart of oil when new.
A lesson for Everyone Never Trust the Dealers do your own maintenance check before every ride especially when bought brand new.
Also i dont think bikes rock back and forth in the crate enough to cause brinelling?

 

Magilla-
Our 22 groms were shipped out of a southern California port to massachusetts....
Also i dont think bikes rock back and forth in the crate enough to cause brinelling?

I'll have to check the labeling at the dealership. You might be right about my '23 Monkey also being shipped across country.
No they don't rock. They receive minute vibrations transmitted thru contact with the transport vehicle. Mainly trains and trucks. Look it up.

 

Like I said, I've see the effects of brinelling on PW50s first hand. It can happen with anything that has loaded bearings. It's a well-known effect as I described and if you don't believe me, do your own research and argue with the engineers who know more about it.

 

Just looking into all the possible causes. I don't buy the notion that it's a 2nd gear problem. I can't really see brinelling as a the cause either because of the rubber swingarm joint.

I did a bunch of reading about rolling element bearing and now think the cause is simply improper break-in. It's said they take 500 miles to break-in and the people that are having issues are saying they're at full throttle all time after a short (piston ring) break-in. The 600 mile break-in procedure suggested in motorcycle manuals matches the bearing manufacturer's. Slow, gentle, low load riding until the hardened steel surfaces of the races become polished. According to the them, the same symptoms being reported are what could be expected if prolonged rpms are too high too soon. Excessive heat and accelerated wear are also symptoms.

Unless somebody with the whine says they weren't balls to the wall for an extended period of time before the bearing surfaces had time to become polished I'm going with that as the cause.

 

Good news. It appears Honda has discontinued the countershaft bearing installed in 2022-2024 models and now offers two other choices. You can use the updated part or the one used on the older models. One costs more than the other.

2022 - 2024 :
91015-KZV-J01
BEARING, RADIAL BALL (6203)
(NA USE ALT:96100-62030-00)

2022 - 2024 (updated) :
91015-KSS-901 $5.60

- 2021 :
96100-62030-00 $8.38

 

Magilla- I'm not going to argue with you. We bought ours and recieved june or july of 2021 me and my son were just a handfull of owners that got them this early. Remember Covid when shipping containers were shipped and waited endlessly in ports and sent to different ports across the US? Yes that was us but being patient paid off- The salesman is a good acquaintance of ours and gave us updates as soon as he got them.
Unless of course we were lied too.
These are groms not monkeys so posting in the monkey section is probably pissin' the monkey guys off, have a great day

 

Just a quick update after my appointment with the dealer today. First off, I had to ride the bike almost 15 miles to get the noise to show up this morning. I finished that ride at the dealer to get them to test ride it hot and noisy. They came back and told me my clutch was out of adjustment and the noise was the chain being too loose. I paid them to tighten it up despite checking the adjustment the day before and finding it within spec. Went for a test ride before loading it back up to see if the noise was truly gone. 7 miles later the noise is there and just as loud. Back to the dealer. This time the service manager and another employee took it for rides. They came back, asked to see my video of the noise then told me it was the oem tires making a whine noise. I asked them how shifting could change the noise the tires made. They had no real response. I asked what the next steps were because it was still broken. I was informed that the next steps were to break the engine unit open and look for damaged parts. If they find damage, warranty should cover repairs, if not I'm on the hook for ~$1000 in labor. So I decided to roll the dice. An appointment is set for end of next month ("first available opening"). I said I'd spend the next month trying to get this thing to destroy itself and hope it didn't lock up while I was riding. I was met with nervous laughter.

I'm stoked on my first legendary Honda experience. I've had better luck with harleys, even 20 year old harleys.

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Well, that's brave and potentially expensive, so I wish you well. I think your destruction option would be the best option for a new engine. It's odd that they could have potentially made a design error on the new engine, as we all know they've been around forever in different formats and have been previously considered indestructable.

 

It's a gamble for sure, but I want to see this through. I've found others in various corners of the internet with the same problem. I've only read of one person that got the dealer to open up the engine and find damage. Most everyone else stops updating the thread, or just gets mad and sells the bike. I really like this little bike and I'm willing to take one for the team, so to speak.

As for riding it into the ground before the next appointment, I think it's already working. I put on almost 100 miles today in ~100 degree heat. It's making the noise more, louder, and it's even made the noise in first a few times. It's going to be my ride to work for the next month, about 25 miles each way.

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As for riding it into the ground before the next appointment, I think it's already working. I put on almost 100 miles today in ~100 degree heat. It's making the noise more, louder, and it's even made the noise in first a few times. It's going to be my ride to work for the next month, about 25 miles each way.

Any updates? Mine has been quiet since keeping it under 65 mph.

 

I hit 70 mph today and I got the noise . Had to slow down quite a bit for it to go away but stayed in 5th gear. It was over 90*F out and I'm running a good 10w40 full-synthetic at 2300 miles. Once cooled down, no noise up to 60 mph. I don't plan to do much over 60 mph in the future. Previous highest speed was about 65+ with no noise.

I won't be looking for warranty work unless it happens again. In the mean time, I'll try to keep it under 65 mph like I normally do. Bike still runs strong .

 

Nothing yet. I just dropped mine off at the dealer for tear down and inspection. My last ride was pushing 100 degrees out and I put 75 or so hard miles on it. It made the noise once or twice in first gear, so its getting worse. I didn't want to break 500 miles before it went in as I didn't want to do the first oil change and have them blame it on my service work. At 475 miles when I dropped it off, the oil was very dark, almost black and water thin. Something is going on in there. As soon as I hear from the dealer and inspect the guts in person, I'll share the news and pictures.

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Following I just got the whine this morning in 3rd to 5th stops when I shift into 2nd.

 

I just had this issue with my 23 monkey. It happened at 560 miles after going about 50 mph for about 5 miles. I've seen other posts on this an know it happens on the Grom also.It has been fairly well documented that the issue is the bushing/gear second gear. This post has some pictures Engine noise 2023
Ive also seen other pictures showing the shaft being discolored where that bushing sits. As far as I can tell, none of those parts have been changed by Honda, as the part number is still the same. Mine stopped making the noise shortly after I slowed down and shifted into second. When I got home I did my 600 mile oil change. Hopefully the issue doesn't come back.

 

I got word from the dealer today and it sounds like the second gear bushing. I'm going in on Tuesday to take pictures of the carnage and hear what honda has to say. I'll keep yall posted.

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I'm looking forward to hearing what they have to say. Let us know if there is something specific the rest of us can say to our dealers or Honda to get this fixed under warranty.
Here is another explanation of the issue

 

That makes more sense than a bushing that's too tight which I would expect more serious problems to occur shortly after squealing. If I was replacing mine, I'd buy two or more bushings and use the thickest one. There might not be any measurable difference but they're cheap enough to check. Even the new one in the video looks looser than necessary.

 

 

So mine started making the noise at just under 200 miles. I wanted to make sure it did it again when I went to work. Low and behold it did. I changed the oil with 10w-40 Mobil 1 race oil, and changed the filter. The oil when I drained it was almost the consistency of water. I took it out for a similar route to work which is at or above 45. I couldn’t get it to make the noise again and on the 2nd half of the trip I was taking to higher rpms to see if that would effect it too. Still no noise I’ll update after a few days of riding. I think it may the oil Honda is using can’t handle the temperature.

 

Just got home from the dealer. It looks like I had a second gear bushing failure. The gear is blued from the center out. The thrust washers on either side of it and it's bushing are all purple/blue and it looks like the shaft it rides on got hot too. Nothing is galled or scared up at all, just obviously very hot. The gear and bushing do rock on the shaft quite a bit. I was told the oil didn't show metal when they drained it and they find no other damage inside the cases. The dealer is waiting on final word from Honda as they asked for pictures of the damage.

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