PeeWee86
Extreme
You are right about the 21/49 gears. I believe that all Vipers that came with 1 3/4” or taller lug tracks have this gear ratio. The MTX’s have the smaller 7 tooth drivers as well. When I converted my MTX to run at lower elevations I changed to 22/48 gears and switched to 8 tooth drivers. The 8 tooth drive sprockets are probably more efficient than the 7’s but the downside is the speedometer and odometer are off by 13%. There is no cost-effective way to change the calibration. The 22/48 gear combination allowed me to use the original 90p chain. On the Ulmer gearing chart this would give me a theoretical top speed of 104 mph. The fastest I saw this past winter was 92 mph gps. I only have 650 miles on the sled I believe it is still breaking in. I’m sure there’s a few more miles an hour in the set up but I am realistic in believing that with stock power and a 1 3/4” track I may never see 100 mph. I might be slightly under geared on the trail but I do enough off trail riding that I feel that I have a set up that’s optimized for my needs. If you plan on staying with the 7 tooth sprockets the 21/41 gears that I had previously suggested would give a similar theoretical top speed to my combo.
It’s hard to compare gearing with the guys with the RTX/LTX sleds. Shorter length tracks, shorter lug height, and different track pitch make for an apples to oranges comparison.
It’s hard to compare gearing with the guys with the RTX/LTX sleds. Shorter length tracks, shorter lug height, and different track pitch make for an apples to oranges comparison.
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PeeWee86
Extreme
I will preface this by saying I have never driven a sled with a 162 track.(I have trail ridden on a 154”.)
The difference in cornering feel between the 141 and the 162 may not be as drastic as you would think. Shorter tracks allow a person to hit the throttle and drift or slide through the back side of a corner. That characteristic is diminished substantially in a 137 versus the feeling one gets with a 121 or 129. I feel like my 141 inch track no longer slides through the corners. Once the ability to slide has gone away, I don’t feel like the handling differences due to track length are all that significant.
Viper!33
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I have not ridden the 141 unfortunately and I would bet your pretty spot on in saying that much track will still have a hard time sliding out of corners. I was leaning towards going with LTX gearing of 21/41 so I only have to change my lower gear and chain this should theatrically give me 101.9 mph with a 1.95 ratio - if I can hit 90 I'd be happy.
Viper!33
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Is there anyway to shorten the chain from 90 link to 86 or not a good a idea?
Viper!33
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Also looking at it, it may be cheaper to keep the 90 link chain and change the two gears...
PeeWee86
Extreme
I changed out my two gears for about $75 and the 8 tooth sprockets for about $80. I have a hydraulic press so swapping out the sprockets wasn’t that bad. The speedometer calibration has not bothered me at all but it is inconvenient when the odometer is off. Calculating fuel mileage and distance to the next gas stop gets a little more difficult. If you search other posts that I have put up here I have given the part numbers for the two gears that I used. The bottom gear was a Yamaha part and the top one was a Cat part number. It was cheaper that way. Unfortunately there aren’t a lot of gear combinations that work with the stock 90p chain.
Can the chain be shortened down? Absolutely. Is it a good idea? That’s a harder question. Twenty five years ago I used to do it all the time. I did a lot of racing on a very tight budget. I this point in my life I can afford to buy a new chain if I need one.
When the chains are manufactured all the pins are pressed in and peened on the ends. Sometimes you can look at every pin and find the last one that was installed when the chain was made into a circle. The peen will not be as big. That is the easiest one to remove. I used 2 x 6 with a channel mitered out of it to hold the chain. Often you need to use a small file to slightly reduce the diameter of the peen before attempting to drive it out with a hammer and punch. It’s a lot easier to reassemble the chain if you do not drive the pin all the way out. Leave it stuck in the last plate. I guess it’s hard to explain in writing.
Can the chain be shortened down? Absolutely. Is it a good idea? That’s a harder question. Twenty five years ago I used to do it all the time. I did a lot of racing on a very tight budget. I this point in my life I can afford to buy a new chain if I need one.
When the chains are manufactured all the pins are pressed in and peened on the ends. Sometimes you can look at every pin and find the last one that was installed when the chain was made into a circle. The peen will not be as big. That is the easiest one to remove. I used 2 x 6 with a channel mitered out of it to hold the chain. Often you need to use a small file to slightly reduce the diameter of the peen before attempting to drive it out with a hammer and punch. It’s a lot easier to reassemble the chain if you do not drive the pin all the way out. Leave it stuck in the last plate. I guess it’s hard to explain in writing.
Viper!33
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No that makes perfect sense actually on the chain, I think I will error on the side of caution and just replace it if I decide to go that gearing route. I have found the ulmer chart and am looking at possibly going with the 24/46 gearing which shows 103.8 mph at a 1.92 ratio and still be able to reuse my chain, does it matter what gears I'm using or the overall ratio as far as performance? After hearing about the speedo I think I would rather deal with the 7 tooth drivers.
PeeWee86
Extreme
It’s the overall ratio that matters. If the top sprocket gets too small it starts to lose efficiency but that doesn’t turn into a problem until you get under about 19 teeth. For the same reasons, in theory, the 8t drivers are more efficient than the 7t drivers. The 24/46 combination should should work if the gears are readily available at a reasonable price. I know you can get the 24 but I’m not sure about the 46.
I mentioned in an earlier post that I had an inexpensive clutch set up for the low elevation MTX’s. For the long version read my posts in this thread:
https://ty4stroke.com/threads/secondary-spring-wrap.152040/
This is the Cliff Notes version:
Stock bu10 clutch arms with 5.9g rivet in the tip and 4.3 g rivet in the center. Yamaha does not make either of these sizes. The 4.3 g rivet is a lightened 4.5 g factory rivet. I made my own 5.9 g rivet.(cost $15 for all 6)
Stock green/green/green primary spring or pink/green/pink if you need 100-150 more rpm in midrange and on top.(cost $0 or $25)
44/38 cam set at a 3/3 or a 6/1 wrap (cost $75 if you know where to shop.)
I am using the no longer manufactured Shockwave adjustable helix which I have set at approximately 46/38. I wish it had a little bit less of a progressive cut and that’s why I recommended that cam listed above. I have used the 8dn belt from day one and I have the Straightline/Ulmer exhaust can. On my sled this setup will pull 8650-8700 through the midrange and finish near 9000 RPM once I’m north of 70 mph. It seems to backshift well when I get off trail into deeper snow. I’m certainly not going to say this is the best set up out there but it is cost-effective.
Next year I’m going to experiment with the Bikman Goldstar weights that have the adjustable magnets. I have lots of contacts in the industry from a 30+ year racing career. Last January I was riding with the co-owner Bikeman and he said he could send me a set for evaluation. I really need to start a low elevation MTX clutching thread.
I mentioned in an earlier post that I had an inexpensive clutch set up for the low elevation MTX’s. For the long version read my posts in this thread:
https://ty4stroke.com/threads/secondary-spring-wrap.152040/
This is the Cliff Notes version:
Stock bu10 clutch arms with 5.9g rivet in the tip and 4.3 g rivet in the center. Yamaha does not make either of these sizes. The 4.3 g rivet is a lightened 4.5 g factory rivet. I made my own 5.9 g rivet.(cost $15 for all 6)
Stock green/green/green primary spring or pink/green/pink if you need 100-150 more rpm in midrange and on top.(cost $0 or $25)
44/38 cam set at a 3/3 or a 6/1 wrap (cost $75 if you know where to shop.)
I am using the no longer manufactured Shockwave adjustable helix which I have set at approximately 46/38. I wish it had a little bit less of a progressive cut and that’s why I recommended that cam listed above. I have used the 8dn belt from day one and I have the Straightline/Ulmer exhaust can. On my sled this setup will pull 8650-8700 through the midrange and finish near 9000 RPM once I’m north of 70 mph. It seems to backshift well when I get off trail into deeper snow. I’m certainly not going to say this is the best set up out there but it is cost-effective.
Next year I’m going to experiment with the Bikman Goldstar weights that have the adjustable magnets. I have lots of contacts in the industry from a 30+ year racing career. Last January I was riding with the co-owner Bikeman and he said he could send me a set for evaluation. I really need to start a low elevation MTX clutching thread.
Viper!33
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Thank you for the clutching info, I'm not to that point yet but it will be good for future reference. On that note I have never messed with clutching and have always had my clutches serviced professionally. I think I am to the point where I would like to try messing with them myslef. They do not seem that complicated, and I'm a fair mechanic, better parts changer, lol. What tools are involved to do them correctly besides a puller? A press? Special do dads?
