gearing question for the group of guru's

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maxco

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I have a 2000 mm ported and piped. I ride mountains all the time. Hill climbing is what I want to do. and do better. Top speed is kind of irrelevant, unless it can help climbing. I have geared down to 19-42. I am running 8 tooth drivers on a 151 track. Unfortunately I had to go to the 70 link chain. The 68 was on the cusp, but I could not, not make it fit. I installed the 70 link chain, but it now has to bend, alot. I know I am loosing efficiency having the chain bend so much. It may be so much that I am loosing what I was trying to gain by gearing down. So the question is do I go a different route because the chain has the maximum bend in it? I read that going to a smaller 18 top gear (to make the 68 work) is not the best way to go. They make a 43 tooth that could tighten up the chain. Or do I go to a 41 and go back to the 68 t? Or go back to a 20 tooth upper? I feel I may be jumping over a dollar to save a dime as far as efficiency is concerned. Thoughts?
Thanks
 
I've been running a 19 upper with the stock chain for the past 2000 miles or so, I don't think it makes that much difference as far as efficiency is concerned. Gearing down made a big difference off the bottom.
With that said, next time I feel like dicking with it I'll be dropping down to an 18 with a 68 link chain, mainly because most of my playing is low speed and I gained some of my top speed back when I swapped to a P-85
 
19/42 with 8's is really low. Your at a 2.21 ratio plus the correction for the drivers puts you at about 2.48. Personally I think the sled would like to be closer to 2.0 plus the correction so a 21 top would be the direction I would head. That way you can use the 70 and take the dogleg out of it. 21/42 corrected would put you at 2.25 which should work really well in the trees and give you some track speed when climbing straight up the mountain.
 
I see, so maybe gear up on the top. Will I need to do cluthcing changes to match new gearing?
 
Possibly. Would be loading the motor a little more with higher gearing so you may have to lighten the weight a touch. Or the sled might like it and you won't have to change a thing. Have to try it and see. It would be close enough to ride either way so it's not like you'd lose a day or wreck a trip.
 
If it was me I would probably go 1 tooth smaller on the bottom sprocket to fit the other chain. For what you are describing a 2.50 gear ratio is usually really good. That would still get you to a 2.44 ratio and then you wouldn't have to deal with the dog leg in the chain. That would be the route I would take anyway.
 
sometimes you can overthink the efficiency theory. in your application, you would probably never notice the performance difference with or without the bend in the chain. where that typically comes into play is for the straightliners trying to shave a few thousand of a an et.

what you want to shoot for is a constant track speed. somewhere around the 80-85 mph range and keeping it there under throttle and uphill. just for fun, next time your out and going uphill at wfo, look at the speedo. most times your pegging rpm and the speedo will reed about 40-50. its an interesting phenomonon. not something you consider until you actually see whats happening. chain bending has no effect here, its all gearing and clutching.

hard to achieve normally aspirated, but a goal thats fun to try and achieve.
 
Snowdad

Thanks for responding. I am hearing what you are saying about the chain bend and efficiency. So I think i let that go, as far as a concern. My question is then where are you at about the gearing I have? 19-42 for climbing mountains? You said gearing and clutching are where I should be looking at to get better. Thanks for anyone's information :letitsnow
 
testing is underway. so far i have been real happy with the heelclickers. but, whats working for the flatlanders is almost opposite with altitude.

ran a good set up last year on the srx with the 155. found the black hc spring to prevail over the red or gray. straight 43 helix and playing with the wrap, but 70 with the green seems good. using the smaller rollers seems to be a benefit. running 20/42 and seeing track speeds in the mid to high 70's.

just finished setting up the viper with the 151 with heelclickers and testing soon. running 19/42 in that sled, just changed. time and testing will tell.

what i like about the heelclickers is the ability to lower the engagement vs anything oem. problem i always encountered with the mtn maxes, or almost all the yamaha mtn sleds was the higher engagement. read that as a trench. with the lower engagement, your hooking vs spinning. key component when navigating tight terrain.

run your sled wfo on the flat and see what you hit for mph. in theory, you should be able to reproduce this as track speed uphill. just a matter of getting full shift and full rpm under load.

once i dial the viper, the mtn max will get the test using the same components, so i may have more solid info later in the season. had several hours at least last season testing the srx. cool clutch temps and great performance were the end results.
 
Thanks

I have seen heel clickers advertised before, but so many mods so little time, and money. They seem expensive, but from what you say it may be worth it to look at them. Where did you get your heel clickers?.....thanks for the response.
 
one set new, other set used. 40-10y. does require a bit of dedication as theres not alot of info for us altitude guys.

i usually spend the better part of a day just for test and tune. trailer, heater, generator, beer, parts, etc. going to try some different helix options as soon as my test strip snows up some more.

funny part is no one hangs out with me on these days. hmmm.
 
2.5 seems high to me? I'm running about 2.14 and getting 50mph track speed when climbing. 40-21 gears with 8 tooth, but only turning a 144, and have triples.

Snowdad, I'm curious to see how the Viper (triples?) does with that low of gearing, perhaps I have room to go to a 42 driven and still see an improvement. Getting about 85mph on top end, could care less about giving up top end, as long as my track speed climbing increases...I look forward to hearing what your track speed is on that sled...
 
bring that sled up some time and lets play with it. your leaving some clutching and performance on the table if your still using the 43* helix i told you about years ago.

our viper is stock pipe, just the longer track, for the most part. your always welcome to come out and play.
mod-it said:
2.5 seems high to me? I'm running about 2.14 and getting 50mph track speed when climbing. 40-21 gears with 8 tooth, but only turning a 144, and have triples.

Snowdad, I'm curious to see how the Viper (triples?) does with that low of gearing, perhaps I have room to go to a 42 driven and still see an improvement. Getting about 85mph on top end, could care less about giving up top end, as long as my track speed climbing increases...I look forward to hearing what your track speed is on that sled...
Click to expand...
 
19/39

Pulled the trigger on a gear set from a 99mm 600 twin. 19/39. Chain and both sprockets to door 55 scoots. Dropping 4 teeth. Thanks for all the info guys.
 
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