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Discussion Starter · #1 ·
2015 HCR 800 153
New to the forum, looking for some
Opinions!
So I broke my auto tensioner last year and had to ride out 10-15 miles to get back to the truck, the pad broke off and chain was riding on the metal arm of tensioner. So I replaced the new arm and bought BDX HYVO chain and gear replacement to get rid of the aluminum gear.

Everything installed good up until the tensioner, with this setup the chain is so tight I had to pry very hard on the tensioner to get it into the first notch of the auto tension block. There was barely ANY slack in the chain and everything was so tight it was unrideable.

The gears I bought was 21/49 so I swapped out top gear to a 20 just for some more slack and now the tensioner is roughly half way down the tensioning block.

I know that the chain will stretch slightly once ridden, and would like the 21 top gear in there but is this just too tight to run? Need some opinions other than the parts desk who didn’t offer much help!
The first two pictures are the 21/49 gear ratio with new chain and the tensioner being so tight.
Second pic is the 20/49 with new chain.
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21 is way too tight. It won’t stretch much when you ride. IMO, it will break the new pad, or something anyway. The 20 looks perfect. I don’t have my chart here, but was 21/49 ever a AC factory ratio? There are also two different length tensioners, however, I don’t remember what year they changed. ‘17 or 18 I believe. I also don’t remember if they were Longer, or Shorter. But that could be what you have going on. I am certain that your 21/49 combo is Too tight though.
 

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Discussion Starter · #3 ·
21 is way too tight. It won’t stretch much when you ride. IMO, it will break the new pad, or something anyway. The 20 looks perfect. I don’t have my chart here, but was 21/49 ever a AC factory ratio? There are also two different length tensioners, however, I don’t remember what year they changed. ‘17 or 18 I believe. I also don’t remember if they were Longer, or Shorter. But that could be what you have going on. I am certain that your 21/49 combo is Too tight though.
Yes I agree, the dealer and BDX said that gearing will fit. Once I showed the guys at the desk at dealer they said it’s way to tight, then I showed the BDX guys and said it’s fine. Just looking for other opinions but I think I’m going to stick with the 20/49. Appreciate your response.
 

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You are welcome. I have installed the roller style tensioners and the manual threaded adjusters before, I can’t say for sure if one of them would fit into that space and give you any more slack in the chain or not, but I would feel better about running a combo that tight with that set up opposed to what you have now. I just wouldn’t do it. Going to a 48 on the bottom would gear you “up” ever so slightly as opposed to going down like you did with the 20. If you were interested in that mph option. I’d guestimate less than 3 mph difference on paper either way
 

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What year did the chain tensioner change? Are you saying he has the proper one?
I never much use recommended ratios anyway, but I have modified tensioners and prefer the manual style for such application
 

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Discussion Starter · #7 ·
The 21-49 gear ratio is a recommended combination proper chain tensioner. The 20-49 is not . You should have a 90 link chain. Count your teeth. View attachment 2138096
The chain is 90 link, but on the 2015s isn’t the drive only 7tooth? I will get the part number off the tensioner I bought and see if they gave me the longer one that is causing that chain to be to tight while using the 21/49 combo.
 

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I don’t know which one is longer or shorter. I believe the later ones are shorter, ‘18 and up. Maybe 17. I have my parts gearcase parts all in a basket…not too organized. I just put ones together that fit.
 

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I think the issue is the adjuster. If you look with a track pitch of 3 stock was 19-50 with a 90 link chain. So with nothing changing besides gears a 21-49 will work. If you feel more comfortable with the 20 tooth then go with it. But the other should work. I’m almost positive that should be a roller type adjuster not a shoe but could be wrong. Stronger what do you think?
 

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Discussion Starter · #12 ·
So would you guys say that the 20/49 is looking fine to run this season? Next season I’ll try the 21 tooth sprocket, while I’m in there might try a manual tensioner just to get rid of this auto tensioner.
 

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Yes the 20 tooth top gear looks just right. Never know after a year if you get ambitious maybe the chain will stretch just enough to get the 21 tooth on there. It’s not that bad as it is but just a little too tight.
 
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