Hawk 250 - Bigger Front Sprocket, Possible Case Damage??

[HawkTwoFifty]

I am hearing that the most recommended sprocket combination for the Hawk is a bigger 17-tooth front sprocket, and a smaller 45-tooth rear sprocket. So I was just reading elsewhere online today that going bigger on the Hawk 250 front sprocket is actually not a good idea. I heard this claim from a Hawk 250 owner who consulted with a motorcycle mechanic on such an upgrade and am now wondering if this is a valid concern. So I just wanted to run this claim through the fine members here who most likely know whether it is true or not.

Apparently, the mechanic informed this Hawk 250 owner that in the event of a chain breakage, having a bigger front sprocket decreases the amount of space between the front sprocket and case. And in the event of a chain breakage, this lack of space would allow the chain to violently wedge itself between the sprocket and case and cause significant damage to the transmission case.

Does anyone know if this is a valid concern? My new Hawk 250 will be delivered to me on Monday so I am unable to see if this may be a valid concern by looking at it yet. I am trying to buy upgrades for the bike before it arrives and a sprocket change seems to be most recommended for street use.

So if this is an actual valid concern, I was wondering if the same results in gearing can be achieved by just changing out the rear sprocket only. If so, can someone please tell me what size to go down on the rear sprocket to get similar 17/45 results? And if I am able to achieve desirable results on just a rear sprocket change, does anyone know of the proper chain size (number of links) that I would need to go so that I dont have to remove links in the new upgraded chain that I also plan to buy?

THANKS!!!!!!

[JerryHawk250]

15 front and 40 rear will be very close to the same ratio as the 17/45.

[Lit Hawk]

I'm at 17/45 and had heard about case breaking. I've ridden it almost daily to work and have had no problem for about 2 weeks straight. I am also worried about it busting case, speedo sensor and chain. Ive been muddin and riding deep ruts popped a couple wheelies(small) and have had no problems. When I changed sprockets I didn't remove the master clip correctly and must have opened it some. The damn chain bust off and locked up my rear wheel I slid all over the road. Luckily I was only doing like 20 and had just left my house didn't fall but had to bring my car lift it on the hitch it was locked up bad. It still didn't bust the case and yeah the 17 is a big sprocket. I like the gearing it's a lot better than the 15/50 stock(a lot better). When I can I want to switch to 16/? Maybe 40. My top speed on my hawks 64gps.

[Megadan]

Jerry pretty much hit it dead on. If you are that worried about the front sprocket being too big and potentially causing damage in the event of a chain failure, then stick with a 15 tooth front and use a 40 or 39 tooth rear sprocket. You will definitely need to take a couple of links out of the chain if you do go this route. I currently run a 128 link chain with a 17 front and 43 rear - and others with a 17 and 45 - and it works perfectly. This would mean you would possibly need to run 126 links.

Now with that out of the way, let's cover the "why I don't worry about it" portion.
For starters, there are other bikes with this engine that come from the factory with a 17 tooth front sprocket such as the TT250 and the Bashan bikes.

I also wouldn't worry about it, because if you compare the 15 and 17 tooth sprockets next to each other, then you will see that they really aren't THAT different in terms of diameter. Honestly, there is a risk of the chain bunching up and cracking the case with a 15 tooth too. The tiny bit less room of the 17 tooth just increases the chance, but that doesn't mean it cannot happen with a 15 tooth front either.

So, if it bothers you that much, then run a 15 front with a 39 or 40 rear. The only real thing you lose is the ability to swap front sprockets to get a quick gear ratio change to gear down the bike - I.E. with my 17/43 setup for road use I can swap to a 15 front in the span of a few minutes and have a 15/43 setup that is a great for more serious off-roading, and then switch back to the 17 for road duty.

IMHO - the 17 is more than fine for a bike that sees mostly road use. Plus, proper chain maintenance with a good quality chain and performing proper inspections will go a long way to prevent such issues in the first place.

[HawkTwoFifty]

15 front and 40 rear will be very close to the same ratio as the 17/45.

Thank you for your reply JerryHawk250! Much appreciated!

[HawkTwoFifty]

I'm at 17/45 and had heard about case breaking. I've ridden it almost daily to work and have had no problem for about 2 weeks straight. I am also worried about it busting case, speedo sensor and chain. Ive been muddin and riding deep ruts popped a couple wheelies(small) and have had no problems. When I changed sprockets I didn't remove the master clip correctly and must have opened it some. The damn chain bust off and locked up my rear wheel I slid all over the road. Luckily I was only doing like 20 and had just left my house didn't fall but had to bring my car lift it on the hitch it was locked up bad. It still didn't bust the case and yeah the 17 is a big sprocket. I like the gearing it's a lot better than the 15/50 stock(a lot better). When I can I want to switch to 16/? Maybe 40. My top speed on my hawks 64gps.

Thank you for your reply Lit Hawk! When you say that you "didn't remove the master clip correctly and must have opened it some" can you please go into more details about this situation? Do you think that this caused the chain failure? If I remember correctly, there was just a nut to loosen on my old Japanese bikes, so I am unaware of any such clip on the sprocket.

Thanks!!

[HawkTwoFifty]

Jerry pretty much hit it dead on. If you are that worried about the front sprocket being too big and potentially causing damage in the event of a chain failure, then stick with a 15 tooth front and use a 40 or 39 tooth rear sprocket. You will definitely need to take a couple of links out of the chain if you do go this route. I currently run a 128 link chain with a 17 front and 43 rear - and others with a 17 and 45 - and it works perfectly. This would mean you would possibly need to run 126 links.

Now with that out of the way, let's cover the "why I don't worry about it" portion.
For starters, there are other bikes with this engine that come from the factory with a 17 tooth front sprocket such as the TT250 and the Bashan bikes.

I also wouldn't worry about it, because if you compare the 15 and 17 tooth sprockets next to each other, then you will see that they really aren't THAT different in terms of diameter. Honestly, there is a risk of the chain bunching up and cracking the case with a 15 tooth too. The tiny bit less room of the 17 tooth just increases the chance, but that doesn't mean it cannot happen with a 15 tooth front either.

So, if it bothers you that much, then run a 15 front with a 39 or 40 rear. The only real thing you lose is the ability to swap front sprockets to get a quick gear ratio change to gear down the bike - I.E. with my 17/43 setup for road use I can swap to a 15 front in the span of a few minutes and have a 15/43 setup that is a great for more serious off-roading, and then switch back to the 17 for road duty.

IMHO - the 17 is more than fine for a bike that sees mostly road use. Plus, proper chain maintenance with a good quality chain and performing proper inspections will go a long way to prevent such issues in the first place.

Thanks again Megadan! If a 17-tooth front sprocket is just slightly bigger than a 15-tooth sprocket, and other similar bikes use a 17-tooth, then I guess that I am worrying for nothing. Do you know if anyone offer a "case-guard for these bikes? Regardless, I am probably worrying for nothing if the diameter is only a very slight difference.

I do plan to buy a higher quality chain for this bike as I hear that this is recommended. So if I go 17/45 on the sprockets, would a 128-tooth chain be what I need to buy? And would you have any recommendations/links on a great quality chain to buy?

Thanks!!!!!!!

[Ariel Red Hunter]

Thanks again Megadan! If a 17-tooth front sprocket is just slightly bigger than a 15-tooth sprocket, and other similar bikes use a 17-tooth, then I guess that I am worrying for nothing. Do you know if anyone offer a "case-guard for these bikes? Regardless, I am probably worrying for nothing if the diameter is only a very slight difference.

I do plan to buy a higher quality chain for this bike as I hear that this is recommended. So if I go 17/45 on the sprockets, would a 128-tooth chain be what I need to buy? And would you have any recommendations/links on a great quality chain to buy?

Thanks!!!!!!!I'm not Megadan, but I recommend a Unibear HD chain. A lot of guys on here run it, and I've yet to hear a complaint....ARH

[JerryHawk250]

17/45 Is good if you plan on mostly off road or city driving. Not good for high speeds as you will be turning higher rpms.If you plan on doing highway drive you may want to go with a smaller rear like a 43,40 or 39. You can run the 15 front for off road and a 16 or 17 front for highway. This will give you more flexibility. The front sprocket is a quick and easy swap.

[Megadan]

Unibear, D.I.D., EK, anf RK all make good chains. I have a preference for O ring chains but there is nothing wrong with standard chains. Definitely opt for a 428H if you go standard. Most all O rings are built to HD standards already. If you get a standard chain just make sure to give it a good bath in your preferred lubricant to ensure the rollers are internally lubricated properly.

[Torgo]

I left my chain too loose on an adjustment a while back and it jumped. Chewed up the rear axle area a bit, but didn't break. I run a 17T and when it let go, it just cracked the sprocket cover. Found the room it needed. The cover itself is just a casting.

If your chain goes, which is already a low probability, adding that scenario and causing damage as described, just seems like a real outlier to me. I'd have to look again, since I haven't had the cover off in ages, but it hasn't crossed my mind. I'd think you could come up with an angle on one or more of the links when a chain breaks that could wedge in there regardless of front socket used.

The cover is a tight fit with a 17T, that's true, and some go back on easier than others it seems. I think the main consideration ends up being the ratio you want with the available rear sizes and where you ride. I still have the 50T stock on the rear. It'll get into the low 60s when I need to jump on a highway, but I don't go out of my way to run sustained like that. Personally I really like the 17/50 combination when I'm off road, it stretched out 1st and 2nd, and 2nd has a nice range for the trail conditions I see most often.