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Any one running a 25/45 combo?
Scott Taylor is recommending this for my 280 hp tune
 

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Same ratio as 21/38 (1.80).
You can do this ratio w Cat parts for about $250-$260. To do same ratio w SC parts costs $550. Yes, I know a 25 top gear is better than 21 gear but for a trail sled it would not be measurable unless on a very sensitive chassis dyno. There are many other things on a trail sled that would matter way more than the difference between these 2 top gears.
 

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21 tooth top gear w oil holes (for 15 wide chain) = 1702-490
38 tooth bottom gear (all Cat/Yamaha gears are 13 wide on bottom) = 2602-491
15 wide 84 pitch chain = 2602-838
 

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21 tooth top gear w oil holes (for 15 wide chain) = 1702-490
38 tooth bottom gear (all Cat/Yamaha gears are 13 wide on bottom) = 2602-491
15 wide 84 pitch chain = 2602-838

I just changed my top 21 gear in my 16 and there were no oil holes and, Id have to double check but I think it was all 13 wide stuff? Maybe I'm wrong but I'll find out when I tear back into it however if it is 13 wide I'm assuming I can update to this 13/15 setup?
 

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You must have gotten old stock or a different part number for 21 gear. 1702-490 current stock has 3 oil holes.
Obviously, you can't run 13-wide chain on 15-wide gear. If you update top gear to 15 wide, you'll have to get that 84 pitch 15-wide chain.
 

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I just changed my top 21 gear in my 16 and there were no oil holes and, Id have to double check but I think it was all 13 wide stuff? Maybe I'm wrong but I'll find out when I tear back into it however if it is 13 wide I'm assuming I can update to this 13/15 setup?

Everything else in the chain case is the same right?
 

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The OP from fatblack I assumed was relative to '17 & newer TCat. I guess I should have asked.
I don't know the '16 chain case. My answers were with regards to 2017 & newer TCat and Sidewinders.
I don't think the 2016 case is same as 2017 but that doesn't necessarily mean the gears are different.
 

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The OP from fatblack I assumed was relative to '17 & newer TCat. I guess I should have asked.
I don't know the '16 chain case. My answers were with regards to 2017 & newer TCat and Sidewinders.
I don't think the 2016 case is same as 2017 but that doesn't necessarily mean the gears are different.
I think the two stroke chaincase internals are all 13 wide, so maybe he got on the wrong forum?
 

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Go with the Taylor gears, the stock gears are made from sintered material, as it wears the material gets into top bushing causing wear, Taylor’s won’t do that, plus the 25/45 has less rolling resistance
 

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I believe the newer (17 and up) gears are made from a better material. I have never heard of a gear or chain failure on these sleds due to part failure.
I think the bigger top gear will get the chain away from the post inside the case. As soon as your chain loosens a bit it slaps that post putting aluminum material in the oil.
I am also looking for a gear change on my tuned 998 and have yet to decide on what to run. All out top speed is not my priority.
 

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All I can do is state my personal experience. I have had ZERO issues with stock gears as far as wear. And, I've never had chain ever hitting the center post. If your chain is hitting post, it's TOO LOOSE!
I've run 21/38 almost from day one with a 280HP PEFI tune with lots of long carbide studs on my 2017 ZR9000 Ltd. I've looked at my chain case every year and it looks great inside. Very little if any wear on gear teeth, top gear still tight on jackshaft. Top gear bushing still gray in color so teflon coating is still good. Throughout the riding season, I check my chain tension essentially after every ride. You have to check it often as the chain does stretch. If you keep it tensioned as you should (1-1/2 turns out from finger tight) it will not hit the post and it will work just fine.
For the last season, I went up to Stage 4 PEFI (320HP) with same 21/38 gearing. No problems at all and no change in wear inside chain case. I run Amsoil Synthetic Chain Case oil
As I previously stated, it would take a sensitive chassis dyno to measure the difference between 21/38 and 25/45. On a trail sled, there are many more things that matter allot more than the difference between these two gear sets.
1.80 ratio with Cat parts is about $260. 1.80 ratio with Scott Taylor is about $575.
Bottom line for me is if you run 21/38 setup, with properly adjusted chain and good lube, it will last with no problems at all.
 

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you may not be hitting the post because of your chain length with the 21-38 ratio. You can run a shorter 84 pin chain. Stock 21-41 gearing the longer 86 pin chain comes very close and does not take much stretch for that chain to start hitting the post. that stock 21-41 puts a bigger "dog leg" in the chain even when tensioned properly. This is the reason i want a bigger top gear, not so much performance but to take some of the " dog leg " out of the chain.
I agree the stock parts are mostly indestructible now.
 

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21/41 = 1.95? This sounds like stock Sidewinder gear? Stock Cats come with 24/50 = 2.08.
The bigger diameter 41 gear (compared to the 38) on the bottom should actually provide more clearance except the longer chain does cause more dog-leg. But if you're gearing up to 1.80, you can do for allot less $ with stock Cat gearing and not sacrifice durability. You might even be able to keep your 21 top and just get the bottom and a chain.
You could go to a 22/41 with same chain. No matter what, you have to keep checking the chain throughout the winter, especially if you have big time HP and lots of traction as both add huge load to the chain.
 

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21/41 = 1.95? This sounds like stock Sidewinder gear? Stock Cats come with 24/50 = 2.08.
The bigger diameter 41 gear (compared to the 38) on the bottom should actually provide more clearance except the longer chain does cause more dog-leg. But if you're gearing up to 1.80, you can do for allot less $ with stock Cat gearing and not sacrifice durability. You might even be able to keep your 21 top and just get the bottom and a chain.
You could go to a 22/41 with same chain. No matter what, you have to keep checking the chain throughout the winter, especially if you have big time HP and lots of traction as both add huge load to the chain.
Hey flash as far as checking chain tension, are the gaskets on exhaust re-usable? Or do you use a copper one or just use hi temp rtv and don’t use a gasket at all?
 

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First, thankfully I don't have to remove my muffler to adjust chain. Just remove side panel. So I check it often. I have a 2.5" stainless steel performance muffler I bought from D&D. It's physically smaller than stock muffler so I can reach in with the right wrenches and check it. From the pic I post it's hard to tell but I have enough space behind muffler to get at chain adjusting bolt.
Secondly, I've used the stock metal gasket over and over and over. Never had a problem with leaks. I doubt even the hi-temp red RTV would hold up. It's only good to 650 degF. Under power and high boost, I bet it's close to 900-1000 degF, maybe more. At night, I've seen the top of my muffler almost glowing dark red!
 

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First, thankfully I don't have to remove my muffler to adjust chain. Just remove side panel. So I check it often. I have a 2.5" stainless steel performance muffler I bought from D&D. It's physically smaller than stock muffler so I can reach in with the right wrenches and check it. From the pic I post it's hard to tell but I have enough space behind muffler to get at chain adjusting bolt.
Secondly, I've used the stock metal gasket over and over and over. Never had a problem with leaks. I doubt even the hi-temp red RTV would hold up. It's only good to 650 degF. Under power and high boost, I bet it's close to 900-1000 degF, maybe more. At night, I've seen the top of my muffler almost glowing dark red!
Looks like a tight fit , thanks for the info
 
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