Author Topic: Chain gets derailed  (Read 293 times)

erdat

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Chain gets derailed
« on: July 20, 2020, 08:53:06 AM »
Althought the chain is tide within the specs, it gets occasionally derailed in rocky terrain from the rear spocket. What could be possible cures? Nothing seems to be bend. What should I look out for? I would appreciate any help. Thank you,
Erdat
'15 SE-R 250
Ankara, Turkey

motif

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Re: Chain gets derailed
« Reply #1 on: July 20, 2020, 12:47:36 PM »
is chain really up to specs? also what is the condition of rear and front sprockets and chain itself?

erdat

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Re: Chain gets derailed
« Reply #2 on: July 21, 2020, 12:23:06 AM »
Thank you motif. The sprockets are all good, but I will check again. I am considering to switch the chain guide. I was thinking more that the chain guide is flexing, but I am not sure. Perhaps I should şnvest n a new chain and then progress. By the way, the bike has 80hrs,

-Erdat
'15 SE-R 250
Ankara, Turkey

hamilton

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Re: Chain gets derailed
« Reply #3 on: July 21, 2020, 12:48:06 PM »
A TM Designworks or BRP chain guide would help with keeping the chain in place. The late model ktm/husky guide is the same.
Beware with the less flexible chain guide you run the risk of breaking the swingarm mounting tabs. I would suggest the bulletproof guide brace also if you upgrade.
If your chain has 80 hrs on it, might be time for a new quality o-ring replacement.
Also check the wheel bearings for play, and don't trust the chain adjustment marks on swing arm / axle blocks they may not give you the correct alignment.

https://www.tmdesignworks.com/p-74-bullet-proof-designs-swingarm-guard-pn-bpd-ktmcg11.aspx


« Last Edit: July 21, 2020, 02:09:53 PM by hamilton »

erdat

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Re: Chain gets derailed
« Reply #4 on: July 23, 2020, 09:25:41 AM »
Cool. That will be my plan of action
'15 SE-R 250
Ankara, Turkey

akoudlai

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Re: Chain gets derailed
« Reply #5 on: July 30, 2020, 04:56:36 AM »
Are you setting the chain with the bike off the ground on a stand and without the rear shock linkage resting on the stand?

Make sure the stand is only touching the bike at the skidplate/frame. then set chain play.

Double check there isn't too much play side to side which is an easy way to tell if your chain is due for replacement. it might feel right but under load stretch more than you'll see by pulling with your hand. When setting your chain, also make sure your rear wheel and axle is pushed towards the front of the bike firmly until it hits the stop blocks. After tightening the axle and riding the bike for a few minutes recheck the amount of play in the chain (its usually a bit more play after tightening the axle and putting some load on it.) here is a good video if you are unfamiliar with the process: https://www.youtube.com/watch?v=xQz2kIiJZ6k

Then with the chain fully on grab a link at the rear of the sprocket and pull that link away from the center of the wheel. If you see any light / gap between the chain and the sprocket, its time for a new rear sprocket. Always change both sprockets and chain as a set. Even a slightly worn sprocket will wear away a new chain quickly and vice versa.

It's really unlikely that you need a new chain guide. Most guides will function fine even with significant wear.eb make sure its fixed firmly to the swingarm without any play, and that the guide isn't totally worn out.

Finally if you've eliminated all of the above as possible problem, check all you swingarm and wheel bearings to make sure there isn't play in them and even your engine mounts and brackets. this way you make sure that there's no "looseness" is any other part of the drivetrain that is letting your chain slip under load.

If you end up getting a new chain / sprockets, I would go with an X-ring Chain. All the benefits of aan Oring, but better for dirt/offroad.

2017 SER 300 Six Days

erdat

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Re: Chain gets derailed
« Reply #6 on: July 30, 2020, 12:53:59 PM »
akoudlai thank you for all the detail d explantion. I will go over the process.
Erdat
'15 SE-R 250
Ankara, Turkey

Brian in Colorado

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Re: Chain gets derailed
« Reply #7 on: July 30, 2020, 07:00:06 PM »
Erdat, first question I have is, had you removed the wheel before this started to happen? If so it's probably the technique of how you reinstalled the wheel. First thing I would do is set the bike upright and measure center of swingarm bolt to center of axle bolt on both sides. This will establish alignment of wheel. A pointer in how to snug your axle against your axle alignment blocks is stuff a rag between your chain and rear sprocket and spin wheel so rag gets in between sprocket and chain, this will snug it up and force the axle up against the adjustment blocks now tighten axle nut. If chain tension is in question, raise bike off the ground and remove rear shock and lift wheel up and check does the chain tension have slack at the top if so chain is too loose. If it stops before wheel is at top of travel it's too tight. That's a good time to check for wheel bearings as well. When you find the right tension for full wheel travel mark your axle adjustment on where your marks are on the swingarm and use that as your reference marks until you do change chains and sprockets. I think between what others have suggested and this you will find a solution. Also if the chains has come off a few times it might be a good idea to replace chain and sprockets.
X-Ride
400 EXC
Evergreen, CO-USA