Need Chain Advice

jonlasaga

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Hello everyone I have still been working on my predator 212 swapped yl2. Unfortunately the chain keeps coming off just about every time I ride it. I cant figure out why this is so I was hoping maybe someone here could give me some ideas. I started by checking to make sure it had nothing to do with the chain tension or chain and sprocket wear. I have replaced the chain recently and checked for any issues like loose links or seized links and it is all good. i have not replaced the sprocket but it seems to be in working condition still. This didnt stop the chain from coming off though. I also checked alignment between front and rear sprockets and it was very straight.
IMG_20200910_170926858.jpg

My next idea was to create this tensioner but it actually caused the chain to derail more so I scrapped this very quickly
IMG_20200915_173658242.jpg
Next thing i tried was two tensioners right above each other so that there wasnt any uneven force on the chain this was alot better but only about as good as it was with no tensioners it also caused the top end of the chain to wobble where it used to only be the bottom end. this seems to only happen on clutch engage and disengage but its still causing chain derailing somehow.
IMG_20200915_173709336.jpg
This final one is the best i could get of my chain alignment just to show its straight. With the tensioners I was able to run it alot looser as you can see in the photo but the looseness also caused that chain wobble which seems to either happen on clutch engage or just from the engine vibrating. I also noticed that the engine shakes pretty violently under full throttle but it is secured well so Im not sure whats causing it or if it is the cause of my chain issue.

So what i would like to know is does anyone have any suggestions to help the chain stay on more consistently? Also do your guys predators shake like crazy at full throttle? I wish I could get a video but the only time it happens is when I cant be holding a camera.


Quick edit forgot to mention that the overall length of the chain is 67 inches and the slack measurement I calculated was .2 inches of slack this is far too tight and I run it at 1 inch about instead.
 

anderkart

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First thing I'd try is taking it off the jackstands and try sitting on the seat while checking your chain tension. You might discover your chain tension drastically varies with the swingarm traveling up and down while riding. You could try this while sitting in your normal riding position and then also try again by sitting as far back on the seat (or rear fender) as possible to fully compress/bottom-out the shocks to duplicate chain tension while hitting big bumps.
 

Crazznewt

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Also check for warpage of the big sprocket. Make sure bearings are adjusted correctly and the axle isnt bent. Check the chain for stiff links or damage. A worn clutch can shake hard. And no, my Predator doesn't shake. Good luck man.
 
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jonlasaga

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First thing I'd try is taking it off the jackstands and try sitting on the seat while checking your chain tension. You might discover your chain tension drastically varies with the swingarm traveling up and down while riding. You could try this while sitting in your normal riding position and then also try again by sitting as far back on the seat (or rear fender) as possible to fully compress/bottom-out the shocks to duplicate chain tension while hitting big bumps.
I have tried checking chain tension with the bike sitting multiple different ways already but it doesnt seem to make much of a difference. I can compress the springs for a moment if I kinda jump on the bike but I cant really keep them compressed. The chain slack measurement also seems to be about the same no matter how hard you compress the springs but there really isnt a whole lot of travel either. When I check it off the jackstands normally it is also about an inch of slack and if I jump on the springs it will compress and measure at about .9 of an inch.

Also check for warpage of the big sprocket. Make sure bearings are adjusted correctly and the axle isnt bent. Check the chain for stiff links or damage. A worn clutch can shake hard. And no, my Predator doesn't shake. Good luck man.
I can verify that the sprocket isnt warped as well as the axle just because I had it apart recently to free the rear brake lever and repack the cush drive. The chain links have also been checked nothing loose or seized but im not sure what you mean by having the bearing adjusted correctly. How would you do that?
 

Crazznewt

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To check your bearing adjustment or for bearing damage: raise your bike up on the center stand or find another way to get the weight off of the wheel you are checking, grab your wheel at opposite ends and see if you can move the wheel from side to side to see if there is play.
 
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jonlasaga

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To check your bearing adjustment, you grab your back wheel at the tire and see if you can move the wheel from side to side.
Oh I see what you mean. I did inspect both rear wheel bearings when I took it apart and they had no play in them the wheel also has no play in it when its secured so I think the bearings are good. I can also spin the wheel up to full speed without having any kind of imbalance or shaking from bad bearings. The sprocket did have some play inside the cush drive when I took it apart but after replacing that it all fits nicely without side to side play it just didn't end up helping my chain situation at all.
 

Dingocat

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You could try unbolting your shocks. Then you can manually move the swingarm without needing to compress the shocks.
 

mckutzy

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Its slack when is it under recoil... because the drive point is way ahead of the pivot point.... mostlikely need a jackshaft to position the drive point at the pivot or just behind....
 

jonlasaga

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You could try unbolting your shocks. Then you can manually move the swingarm without needing to compress the shocks.
That is a good idea Ill give that a try and see if the chain becomes misaligned or too tight then. Thanks
 

jonlasaga

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I unbolted the shocks and compressed the swing arm as far as it would go today. There is only a little more than 2 inches of throw in the suspension so it was still at a slack measurement of .89 at the top. Im not sure that it is caused by recoil because of that it seems to take it just fine.

Are you running a #40 pitch chain with a #420 rear sprocket by any chance?

View attachment 123019
I am running 40 chain and a 40 chain clutch that I can confirm. I was told by a friend who knows more about chain that my rear was a 40 chain sprocket but I didnt check myself. I will do some measurements on the sprocket today as well to see if this is the case. Im not sure if i have this connfused though. Isnt 40 and 41 chain compatible with 420 or is that just 41 and 420 or 40 and 420? Also if I were to need to change over my sprockets and chain would I be better off looking for just the 40 chain rear sprocket or should I switch my whole drive system over to a 420 chain setup? Thanks for the measurement chart by the way.

Ok Ive checked the sprocket and Im not entirely sure if its 40 or 420 but the link moves left and right a little bit on the sprocket so I think it might be a 420 sprocket.
 

anderkart

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You could accurately measure the width of your rear sprocket teeth with a Caliper tool.
Maybe your rear sprocket teeth started out 5/16" wide but are simply wore down to a 1/4" or less now.
A new #428 rear sprocket might solve your problem. Or instating a #41 chain instead, if the teeth on your clutch are only 1/4" wide; not 5/16".
 

jonlasaga

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You could accurately measure the width of your rear sprocket teeth with a Caliper tool.
Maybe your rear sprocket teeth started out 5/16" wide but are simply wore down to a 1/4" or less now.
A new #428 rear sprocket might solve your problem. Or instating a #41 chain instead, if the teeth on your clutch are only 1/4" wide; not 5/16".
I measured my clutch sprocket and rear sprocket against the chart above and the numbers dont match at all. My clutch is advertised as working with 40 41 and 420 but the sprocket measures out to 5.35 mm and the rear measures out to 7.35 mm between plates. The oem sprocket that comes on the bike which is what I believe I have is a 420 chain sprocket after some research but that doesn't match what Im measuring here at all. Do you think that running 420 chain or 41 on these sprockets would help? Or are these sprockets just too out of spec to work? I dont know why my measurements are so far off. The front especially is an entirely new clutch.
 

itsid

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428 won't play nice with the #41/420 clutch
since it uses bigger rollers, (8.5mm instead of 7.77)
and thus either the 428 chain will be binding on the clutch sprocket,
or the 420 chain (really.. #41 chain is useless .. 420 has all identical dimensions and is twice as strong roughly)
will be rattling on the 428 rear sprocket, both is not actually worth it.

My guess. you actuall already have a 428 rear sprocket and you'd need to replace it with a #41/420 instead (NOT #40!!)
Also keep in mind that sprocket plate width is NOT identical with inner plate width of the chain.
the sprocket must provide a bit of clearance (hence it'll be a hair smaller in all possible dimensions apart from pitch ;))

don't forget to measure the roller diameter as well (chain and sprocket cutouts)

Here's a few hints:
#40 chain is wider than #41 and uses slightly larger rollers
#41 is perfectly identical with 420 chain
#40 is almost identical with 425 chain (not noteworthy smaller rollers than 425)
428 chain has bigger rollers than #40 and 425 even (same inner width though)

Also triple digit (motorcycle) chain (420, 428, 525, 530 etc) never carry a number sign (#)
ANSI chain (#35, #40, #41, #50) ALWAYS does ;)

it's "chain number thirtyfive" or "chain number fourty" when talking about ANSI chain
but "fourtwenty chain" or "fivethirty chain" when talking about motorcycle chain

'sid
 

jonlasaga

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428 won't play nice with the #41/420 clutch
since it uses bigger rollers, (8.5mm instead of 7.77)
and thus either the 428 chain will be binding on the clutch sprocket,
or the 420 chain (really.. #41 chain is useless .. 420 has all identical dimensions and is twice as strong roughly)
will be rattling on the 428 rear sprocket, both is not actually worth it.

My guess. you actuall already have a 428 rear sprocket and you'd need to replace it with a #41/420 instead (NOT #40!!)
Also keep in mind that sprocket plate width is NOT identical with inner plate width of the chain.
the sprocket must provide a bit of clearance (hence it'll be a hair smaller in all possible dimensions apart from pitch ;))

don't forget to measure the roller diameter as well (chain and sprocket cutouts)

Here's a few hints:
#40 chain is wider than #41 and uses slightly larger rollers
#41 is perfectly identical with 420 chain
#40 is almost identical with 425 chain (not noteworthy smaller rollers than 425)
428 chain has bigger rollers than #40 and 425 even (same inner width though)

Also triple digit (motorcycle) chain (420, 428, 525, 530 etc) never carry a number sign (#)
ANSI chain (#35, #40, #41, #50) ALWAYS does ;)

it's "chain number thirtyfive" or "chain number fourty" when talking about ANSI chain
but "fourtwenty chain" or "fivethirty chain" when talking about motorcycle chain

'sid
Thanks for the info it helps alot since this is my first project ever with a chain drive. I just don't have the experience with them to know what i'm doing yet. I decided to order a 420 chain to see how that fits since I cant immediately get a sprocket for the bike. I've done some looking over the past couple days but its very difficult to find one that is 60 tooth just like the one on there that also has the same bolt pattern and inner diameter. Do you have any suggestions on places to look where I can search sprockets based on bolt pattern and inner diameter? I guess another option would be to do a jackshaft to get my gear ratio down to 6:1 while running a smaller than 60 sprocket but I dont see many advantages to doing this unless I have a TC running on that jackshaft. Especially since that would mean that I would have to have 2 chains with separate tensioning for each and I would have to juggle that to keep the bike reliable.


I received my length of 420 chain today and it did not fit on the sprocket so you are likely correct that it is a 428 sprocket that I have here. Still no luck finding a sprocket that will fit though that is also 60 tooth.
 
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jonlasaga

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I purchased this sprocket a couple days ago because the blank spots on the sprocket lined up just about right to cut my own holes that would fit the sprocket carrier. https://www.amazon.com/gp/product/B...n_title_o00_s00?ie=UTF8&psc=1&tag=coa_us_g-20. I put it on and balanced it after cutting the holes to make sure there was no sprocket wobble. unfortunately when I took it for a ride after about 5 minutes it came off the sprocket again. The only thing I can think of now that would be causing the issue would be the fact that Im running 40 chain on a 420 sprocket but it doesnt sound like the chain is binding like it did with the 428 sprocket. Do you guys think its worth running a 420 chain on it or do you have any other suggestions?
 
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