Hawk Rear Sprocket Failures - reason why.
 

Ok, so I am finishing up with my bike, going over the rear end right now and I do believe I have discovered why a few folks have had the kush drive bolts shear or the C-clip come out. I did not find this until I had the rear wheel off. With the chain putting tension on the sprocket, it did not move.

https://www.youtube.com/watch?v=OK3XgXEN1cY

After installing my JT Sprocket....

https://www.youtube.com/watch?v=4_0LYF-irMQ

For your own safety please check your bike, please please please!

After working with the stock Snap Ring, I do not believe these to be a weak point. Snap Rings are NOT intended to take lateral thrust loads, and if the sprocket has play like mine did, under power, it could be enough to eventually cause a failure.

Also, something I wish I would have noted in the video, make sure those kush drive stud flats - the ovalish shaped part that sits on the back side of the sprocket - are seated inside the channel on the back of the sprocket. If those are aligned wrong, one side will actually ride up on the outside of the channel and put a lateral load on the stud and it will not seat right to the hub.

So, out of curiosity, and since I dug out my calipers, I went ahead and measured the stock 50 tooth rear sprocket and the JT sprocket. Same thickness. The only thing I can assume is that either one or more studs were not seated in the channel when tightened, causing a gap to allow the play. The nuts were plenty tight when I went to remove it, so they were not loose and the Snap ring was fully seated as well. It is a mystery to be sure.

I think you stumbled on to something. One more thing to check when assembling. I checked mine today after watching your videos. Good catch.:tup:

I can't imagine yours would be loose considering you did a sprocket swap already. If it was, then maybe an occasional sprocket check might be in order as part of a routine. It would make sense why some people have had such catastrophic failures with so few miles and others have put thousands of miles on theirs with nary a problem. I spent 10 hours going over every nut and bolt on my bike. I had it down to frame and engine at one point.

One of the last things I want to do is pull the head stock/triple apart to grease those bearings, but for now it will be fine. I got tired of melting to death in the 90 degree heat wave that hit us out of nowhere.

yeah i went through my bike pretty well during assembly... ill be going through periodically as well when im doing upgrades and such... but helluva catch there buddy. i havent found any slop in my rear wheel yet but im probably going to pull it apart and go through it just to be sure.
:tup::tup::tup:

It was just the sprocket itself that was sloppy. I never would have found this had I not removed the wheel, because with the chain on it had the tension holding it in place. I think anybody that gets a new Hawk should take the extra few minutes to check this.

Good Job Megadan!
 

Great video! I checked all the bolts when I got my Hawk, but I didn't take the rear wheel off. Did you, by any chance, measure the C-Clip?

Have a great weekend!

No, I kind of forgot to do that. I was kinda tired by this point. I pulled my bike apart on a 90 degree day. Suffice it to say I was worn out and forgetful

Ya know what? Come to think of it, mine was like that, too, until I swapped the sprocket. It has to either be the studs installed wrong from the factory, or the center hole in the rear sprocket is machined too big (allowing it to slop around on the hub).

The center may be a bit bigger, because as I noted in the second video, with the nuts on finger tight the JT sprocket only had a very tiny bit of play to it. It may be a combination of multiple things at work.

Do you have a link to the JT sprocket?

JT Sprockets JTR269. That is rear one the front is JT Sprockets JTF259. You have to add the number of teeth to the model number.

Essentially, what Hertz just said, but because I can...

You can select any of the available tooth counts in the list, but I started with the popular 17 front 45 rear, because it allows for doing 60-65mph without the motor screaming for its life at redline, and uses the same number of links as the stock chain (even though I upgraded to an O-ring chain).

Rear = https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Front =
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I am probably going to play around with sprocket teeth counts more in the future once the bike gets broken in to try the best combination for me, my weight, local terrain, and type of riding I mainly do. I may step the rear down to a 43 tooth with the 17 front for street riding, and then if I decide to do more off-road stuff, switch back to a 15 or 16 tooth front for a bit shorter gearing - a 16/43 combo (and 15/40) is more or less the same ratio as a 17/45, but would require removing a few links from the chain. Front sprocket changes are pretty easy, and usually going +/-1 or 2 up front doesn't generally require removing or adding links to the chain.

did you happen to look at the studs and see if there was any play in them?

I replaced mine because I had one that was stripped when i got the bike, it looked like it was cross threaded and cranked on with an air gun.
I got 4 new ones from a local Honda dealer, the new ones were much tighter fitting in the hub, I had to grease them up and tap them in with a mallet.

Im not sure what the tolerance is for them but the ones that came with the bike would go in and out without any resistance at all.

I got a slight wiggle with the chain on so I'm sure it is worse with the chain off. I'm not riding until it is fixed. If only there were more time in a day.

The cush drive studs had a bit of play in them on their own. When I seated the studs on the sprocket and then put it on the hub they were nice and tight, oddly.

I am all for upgrading them. What model Honda did the studs you bought come from? Or what Part Number?

I got lucky with the cross threading as far as the wheel goes, but 2 of the bolts that hold down the rear tray to the bike were both cross threaded, and a couple of others were partially stripped. I spent a lot of time with my tap set chasing threads. I have a couple of holes I am going to try Loctite's new Form A Thread on.
Probably a good idea, and yea, there never does seem to be enough time in the day. Always pesky "responsibilities" that seem to eat it up lol.

the bag they gave them to me in dosent have a model # just has a hand written number on it 90128-312-000

i brought one out of the Hawk with me and had them match it up.

That is a Honda part number. Thank you!

OK I think I need a reset and education. I have worked on plenty of cars and replaced many wheel studs. What the heck is a cush drive and why wouldn't this just have studs like a car. I think I need a "Hawk Talk" Lesson.

I googled it and I see a rubber thingy that absorbs the shock of the acceleration and deceleration??????

Someone please educate my sorry butt.

Cush drives are found on most bikes as a means of reducing not only driveline shock, but smooths the transition of power to the rear wheel to aid control and driveability. In a big way it aids with traction by giving a slightly more progressive feed of power to the rear tire. It has the same effect on deceleration as well. That is the laymans way to explain it at least.

so why is my sprocket loose when the nuts are tight?

Because those studs arent really meant to hold the sprocket on fully. They are there primarily for power transfer from the sprocket to the rear wheel. That said, they should serve a small function to retention, but the primary retainer is that snap ring. The end of the stud that goes into the bushings on the wheel should not have much play in them. Mine do, but I managed to get it to seat correctly. I finger tightened the studs to the sprocket to ensure the studs flats were fully in the channel on the back of the sprocket. Then I installed the sprocket on the wheel, put the snap ring back on, removed the nuts one at a time to loctite them and reinstalled each one before doing the next, and then tightened them down. This method took all of the play out of the sprocket. I plan to go back and check it after a couple of rides to see if it loosened up again, and probably install the honda studs as a matter of course aince they are likely much higher quality anyway.

OK I think I'm slowly getting this.

So I got thinking last night and took a look at mine last night, with it fully assembled and chain tight, I could still move my rear sprocket side to side about 1-2mm.
I looked at ordering the same JT sprockets that you did to gear up (17/45). But at check out I realized amazon said "typically ships out within 1 or 2 MONTHS!"
Anyway they also had no chains in stock like MotoCheez recommends.


Can the stock sprocket be tightened down in anyway without the use of new sprockets like you recommend? I read that you said the center bore may be the culprit, so I guess not.

[QUOTE=RustyShackleford15;258572]
I looked at ordering the same JT sprockets that you did to gear up (17/45). But at check out I realized amazon said "typically ships out within 1 or 2 MONTHS!"QUOTE]
I went with the 15/40 combo because the 45's where out of stock. very close to the 17/45 gear ratio. I later got the 17 for the front which I like more for the highway.

The center bore is just a speculation. I never measured it. Try my method I used on the JT Sprocket to see if your stock sprocket can be installed without any play.

Method. 1. Remove Snap Ring (with a proper pair of snap ring pliers), remove sprocket and studs from wheel.
2. Install studs on the sprocket finger tight - ensure the flats sit in the groove on the back of the channel.
3. Install sprocket and stud assembly to wheel, and reinstall snap ring - ensuring the snap ring is FULLY seated in the channel on the hub.
4. Removing and reinstalling one at a time, take off the nuts on the sprocket, add loctite to the stud threads, and spin the nuts back on finger tight.
5. Once all studs/nuts have loctite, tighten down in a cross pattern.

If that doesn't take the slop out of the sprocket, then it is most likely the sprocket that is the problem. Definitely report back if that is the case and add to the cause. I think with enough evidence gathered, we may be able to petition RPS of a known safety hazard due to a production/manufacturing flaw. I can sure promise you they will start honoring warranties if they get threatened with legal action backed by evidence of multiple failures.

As far as the 17 and 45 being out of stock, that happens a lot (Thousands of Hawks have been sold recently). As Jerry stated, you can simply get a 40 tooth rear, or you can go with a 16 front/43 rear. Those two combinations have more or less the same gear ratio as a 17/45. The 16/43 may require removing a link or two from a 130 link chain, the 15/40 combo will definitely require removing some links from a 130 link chain. Personally, I like the 16/43 combination, and kind of wish I went that route. It starts with around a 2.70 (2.69 exactly) ratio just like the 17/45, and with a simple +1 or -1 on the front sprocket, you can choose between slightly better highway with a 17 (2.53 ratio), or slightly better off-road with a 15 (2.87 ratio). Not a huge difference, but it definitely gives some flexibility.

Whatever you choose, realize that it is just a starting point, and you will want to adjust the ratio to your preference and how the bike is used a majority of the time. Since I plan on mainly riding around on the road, but still occasionally want to run a mild trail from time to time, I tried to find a good compromise. Either way, the stock 15/50 gearing is just way too short for this bike and transmission gearing.

Sprockets
 

The factory sprockets from the factory are junk.
I have a 16 front and notice a big difference.
I have a new 44 rear(45 was out of stock) that I am going to try and hopefully I won't have to remove any links.

On a side note I learned the hard way that you can't go by the adjustment marks when tightening the chain.I just line up the center of the tire with the center of the frame when replacing or removing wheel.

Yeah, those 45's sell out quick! A 16/43 combination would give you more or less the same ratio as the 17/45, so a 16/44 is going to fall right between them. Most likely you will need to remove at least 1 link, possibly 2.

Also, yes, the alignment marks are garbage. I lined mine up the same way you did, and then used a tape measure to fine tune my alignment.

I went ahead and ordered 4 of the 90128-312-000 Honda sprocket studs. These come up under a 1971 Honda SL350. Being so old, these are a discontinued part from Honda, so they may take a little bit of work to track down, and supplies are going to be limited. Paying $30 for 4 studs... Oh well, better than crashing.

Ok, just to revise this, any Honda SL stud is a no go. The pin side that goes into the hub bushing is way too big. I can only assume the part number on the bag, 90128-312-000, just happened to be a handy bag to throw other studs into. That said, I do have 90128-361-000 on order and they hould be here Monday or Tuesday next week. These are visually and dimensionally very similar to the OE Hawk studs, but the pin side is a tiny bit larger. These are for an MT125 and XL175

On the note of the stock sprocket, as mentioned in my build/project/bike thread, even my initial fix to tighten down the studs that did firm up the sprocket did not prevent it from getting a little loose again. It was still worlds tighter than the OE Sprocket was, but loose none the less. That narrows this problem down to the studs just being too small on the pin side. They allow up and down as well as angular movement within their respective holes, which allow the sprocket to rock. Once proper fitting studs are in place, this problem should disappear. Once I get these new ones in, and assuming they are all I need to solve this, I will make a video on this subject to bring it to an end.

Ok, so as an update now that my new, different, studs arrived.

Honda Part Number 90128-361-000 for the MT125 and XL175.
These are a viable alternative to the factory sprocket studs, in my case they are still a teeny bit loose in the bushings on the hub, but way better than the factory ones.

I whipped out my digital calipers to do a little measurin'.

OE Hawk Stud. Threads - M10. Pin side - 8.8-8.9mm diameter. Flange thickness 2.7-2.8mm. Each stud had .1mm of variance from part to part.

Honda 90128-361-000 Stud. Threads - M8 (uses the smaller set of holes on a JT sprocket). Pin diameter 9.2mm. Flange thickness 2.8mm. Consistent across the board within a few thousandths of a mm.

Wheel hub bushing sleeve the pins go into had a lot of variance to them. but overall they averaged out to 9.3mm. From the research I have done on these bushings, they should be 9.2mm, so this would explain why my factory studs were a hotdog in a hallway. .4 to .6mm of gap. Now I have about a tenth of a mm of gap with the new studs.

With the sprocket installed over the new pins and just the snap ring the sprocket with no nuts on the studs has less play than the OE studs had with the nuts torqued down and loctited. This makes me confident enough in this setup to ride the bike once they are tightened down. I think the variance in flange thickness and pin side diameter combined with the large difference in I.D. of the bushing sleeves just created a perfect scenario for play. I have total confidence in the M8 stud size to hold the torque/power of a CG250 engine, although I would prefer to retain the larger M10 sized threads. Given the quality of the metal the Hawk OE Studs are made out of, I am far more confident in the strength of the Honda studs, even if they are a bit smaller. For my own peace of mind I do plan on using Loctite retaining compound on the studs, which is the main reason I haven't fully installed them yet. I just need to figure out which one is best for the application. Either 638 or 680 are the front runners, because of their ability to fill larger gaps (up to .25mm and .38mm respectively), but this will come at the cost of high tensile strength which can make potential stud removal later a pain...

To put it lightly. Tadaaaaaaaaaaaa!

Managed to get my 43 tooth installed on the back with zero play!

How you might ask? Well, as mentioned in my previous post, even with the Honda studs, there was still a teeny bit of wiggle to the sprocket, and even after tightening the nuts down on it it was still there, so I decided to eliminate one little variable, which was the miniscule gap between the sprocket and the snap ring. After pondering a few different ideas, I settled on the simplest solution. I managed to locate some M8 wave washers that were just about the right thickness to take up the space between the sprocket and the snap ring ( roughly .5mm, or .002". I put the washers on the studs, then the sprocket, then tightened them down, installed it all, and just barely managed to get the snap ring in place.

Zero wiggle, anywhere, even with the nuts just finger tight. I have a feeling the wave washers apply just enough outward force to keep it all equalized, and when tightened down the sprocket sits dead flush with the snap ring.

I did also apply a couple drops of Loctite 620 retaining compound to the pins as well, but seeing as it takes at least 12 hours to cure with the primer, at this point it is just extra security.

Figured I would update this after my recent fixes. After 300 miles the sprocket is rock solid still. It took less than that after my first attempt at just tightening them up to come loose again. I think I got it.

I just ordered the 45 tooth sprocket from amazon the earliest ship date is august 16th it looks like all the hawk owners have scarfed them all up lol.
I am going to run down to my local bearing distributor and pick up a blank 45 tooth 428 chain sprocket and chuck it up in the lathe and bore it out and drill out the bolt holes till the one from amazon gets here .

Thanks so much Megadan! This was bothering me for the last few weeks. I've had this problem and I also recently noticed that my rear swingarm was crushed after torquing to "specs" and I've read tons of wheel bearing issues also so I took everything off for inspection today.

The wave washers totally eliminated ALL wiggle in the sprocket. I feel much safer now. I also found that none of my inner races (Front or rear) would spin freely. I apparently crushed the bearings inner races too tightly on the internal spacer tube. I'm replacing all my wheel bearings now and only putting the axles back on until my judgement says they're tight. I'm not using anything north of 30ft lbs for sure and probably less. I just don't think the China steel can handle it.

Glad it worked out for you. I have a feeling the snap ring groove was machined juat a bit too far out. I would recommend getting the honda studs as well. The factory studs just have too much play, at least mine did.

The wheel bearing issues are seemingly another common issue with the 2017 bikes. My rears were also locked up. Same with the swing arms. I tightened mine until the wheel spacers seated gave gave them a snug up after that. I also used loctite 242 on the axle nut just for assurance.

Long-ish term update. Since doing the last fix I have logged over 700 miles on the bike, and I am happy to report that my sprocket is still rock solid. I am confident enough at this point to give my own seal of approval on the wave washer/shim method to take up the gap between the sprocket and snap ring. I still highly recommend getting NOS Honda studs to replace the factory ones, but it may not always be necessary.

Did you trim the wave washers to match the stud with a rounded section cut off or just tighten down till it squashed flat?

Do you have links the hardware you are using?

Since I used a smaller stud size, they fit within the groove without needing any trim work, save a tiny little lip, which I just left on and they deflected around. The wave washers are so thin they don't take much force and bend relatively easy. You could trim them up if needed though.

The studs were the Honda part number listed at the top of this page in my post. The rest of the hardware came from the local hardware store.