Hawk Rear Sprocket Failures - reason why.

[Megadan]

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.



After installing my JT Sprocket....



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.

[Megadan]

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.

[JerryHawk250]

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

[Megadan]

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.

[lmg1974]

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.

[Megadan]

Originally Posted by lmg1974

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.

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.

[kirbo7106]

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!

[Megadan]

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

[JeremyC]

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).

[Megadan]

Originally Posted by JeremyC

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.

[pistolclass]

Do you have a link to the JT sprocket?

[hertz9753]

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.

[Megadan]

Originally Posted by pistolclass

Do you have a link to the JT sprocket?

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.

[old kid]

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.

[pistolclass]

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.