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Discussion Starter · #1 ·
Hi yes I just bought a used 2018
cbr300 and I’m having trouble with the chain rubbing my back tire I have tightened up the chain but it still feels like the chain is still hitting the side of the tire I’m thinking it’s time to change the sprockets and chain can anyone help me on what sprocket kit or what sprockets are worth buying I don’t want to spend money on something that I’m going to have to replace cuz I bought a crappy sprockets so please I could really use some help thanks
 

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Is your tyre the standard width of 140/70 as it shouldnt be rubbing on the chain. You should easily be able to see clearance between the side of the tyre and the side of the chain.

JT make good sprockets, I've put a link below to their chain and sprocket kit where you get to chose your chain.
 

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Unless the previous owner changed the rear tire and put a much larger tire on the bike it's impossible for the chain to rub on the stock tire and a new chain is not going to fix that-have a look at the tire first check the size
 

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Discussion Starter · #5 ·
Unless the previous owner changed the rear tire and put a much larger tire on the bike it's impossible for the chain to rub on the stock tire and a new chain is not going to fix that-have a look at the tire first check the size
Is your tyre the standard width of 140/70 as it shouldnt be rubbing on the chain. You should easily be able to see clearance between the side of the tyre and the side of the chain.

JT make good sprockets, I've put a link below to their chain and sprocket kit where you get to chose your chain.
hi yes the tire was changed to a 160/70 like I said I just bought the bike and didn’t see the tire size until now can I use a 150/70 or do I have to use tge 140/70
 

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hi yes the tire was changed to a 160/70 like I said I just bought the bike and didn’t see the tire size until now can I use a 150/70 or do I have to use tge 140/70
Dunno I never fitted a 150 to a CBR but generally you can get away with going 1 oversize.
 

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Discussion Starter · #7 ·
Unless the previous owner changed the rear tire and put a much larger tire on the bike it's impossible for the chain to rub on the stock tire and a new chain is not going to fix that-have a look at the tire first check the size
Yes the person I got the bike from said he put a 160/70 mc 17 and a 120/ something on the front and my chain keep loosening up every other ride around the block so I know I need to change the tires back the guy who sold it to me said he didn’t like the slippery feeling the bike felt with the 140/70 on it and I don’t understand why it didn’t have and rubbing on the tire when he sold it to me but I get it home ride it a couple of times around my neighborhood and the tire on the chain side is chewed up pretty good but he drove it to show me it rain good and I rode it no problems I get it home ride it 3 times and chain won’t stay tight and the tire is chewed up I guess I will have to just buy some new tires and go ahead and change the chain and sprockets which I have read a chain will last up to 15000 miles well the bike is a 2018 and only has 3,480 miles on it it looks brand new but the chain won’t stay tightened and the tire issue thanks for the help y’all
 

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The chain should not be stuffed after only 3,400 miles so it sounds to me like maybe your rear axle nut is lose and its allowing the rear tyre to kick over and rub on the side of the swing arm and loosen the chain at the same time. Is it the right hand side of the tyre that's rubbed? (Work this out from the orientation that you are sitting on the bike.) If so then that theory could be correct.
Are your chain adjusters both reading the same position?
 

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Discussion Starter · #9 ·
The chain should not be stuffed after only 3,400 miles so it sounds to me like maybe your rear axle nut is lose and its allowing the rear tyre to kick over and rub on the side of the swing arm and loosen the chain at the same time. Is it the right hand side of the tyre that's rubbed? (Work this out from the orientation that you are sitting on the bike.) If so then that theory could be correct.
Are your chain adjusters both reading the same position?
So the rub is really not a rub I’m going to go take some pictures and post it give a min and I’ll post it
 

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Discussion Starter · #10 ·
So the rub is really not a rub I’m going to go take some pictures and post it give a min and I’ll post it
The chain should not be stuffed after only 3,400 miles so it sounds to me like maybe your rear axle nut is lose and its allowing the rear tyre to kick over and rub on the side of the swing arm and loosen the chain at the same time. Is it the right hand side of the tyre that's rubbed? (Work this out from the orientation that you are sitting on the bike.) If so then that theory could be correct.
Are your chain adjusters both reading the same position?
The chain should not be stuffed after only 3,400 miles so it sounds to me like maybe your rear axle nut is lose and its allowing the rear tyre to kick over and rub on the side of the swing arm and loosen the chain at the same time. Is it the right hand side of the tyre that's rubbed? (Work this out from the orientation that you are sitting on the bike.) If so then that theory could be correct.
Are your chain adjusters both reading the same position?
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Discussion Starter · #11 ·
The chain should not be stuffed after only 3,400 miles so it sounds to me like maybe your rear axle nut is lose and its allowing the rear tyre to kick over and rub on the side of the swing arm and loosen the chain at the same time. Is it the right hand side of the tyre that's rubbed? (Work this out from the orientation that you are sitting on the bike.) If so then that theory could be correct.
Are your chain adjusters both reading the same position?
Ok I posted some pictures and everything looks tight it when I get on it and ride the chain just start popping the curve part of the tire all the way around but there is about a quarter of a inch or so between the chain and where it is hitting the tire the other side of the tire that’s not on the chain side is perfectly fine look brand new so I really don’t think it is the tire really I think it’s the chain is slapping back and forth cuz the chain has tight spots in it right or am wrong cuz that’s really all I can come up with cuz this has ruined a perfectly good tire when the guy was just riding it to and from work and road it to my house and we drove it around my neighborhood and then the next day I ride it a few times and the chain got loose and I followed the YouTube video to the T and tightened it up and then road it to the store at the end of my road not even a mile there and back and the chain was loose but not crazy but loose so if anyone has any more information to help a guy out cuz the bike is like brand new and I just can’t see why the parts are not good and why now is it when the guy road it every day to work I used to work with him and seen it every day
 

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Ok so I can see straightaway from the photos that the tyre has been trimmed back with a knife, it’s not from rubbing on the chain or swing arm.
I would just give the chain a good dose of lubricant and keep riding it and only adjust it when it’s really lose. It’s possible the bike has been sitting for a long period at some stage and the chain has developed some tight links, esp if it wasn’t getting regular cleaning and lubrication. Your sprockets are probably fine.
 

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A CBR300R will ride better with the stock 140 tyre. You don't need to put on a bigger tyre. If the chain keeps going loose then you are not tightening the axle nut properly. It should be torqued to 88 Nm.
 

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You need to change that tire ASAP it's dangerous as it could chew through the tire and cause a blow out-and yes replace it with a stock 140 -the fist indication of a worn out chain are stiff links or a chain that will not stay in specs- and a chain that is not maintained properly will wear out very fast these stock chain are not high quantity-so you might want to talk to the previous owner he might have the OEM tires at 3,500 miles they should be only half worn and due to the short chain life both sprockets should be changed along with the chain
 
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