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Discussion Starter · #1 ·
I have just purchased a 2021 xrs 900 turbo, installed a tune, dalton adjustable clutch arms, stock primary spring, dalton byr torsion spring with stock helix. I didn't change the gearing as I wanted to try stock first. I mainly ride corner to corner trails and few friendly 500ft drags. Rarely due we top end on ice or fields so top speed is low on priority list. In short drags in grass the sled launches hard then hits a wall around 400ft. I was wondering if anyone has tried say a 47/42 or 47/44 helix instead of regearing. Surely don't want to create belt heat on the clutches, they run quite cool, but after launch you can feel when the clutch is transitioning to the 40 degree part of the helix and shift slows right down. Seems on the 800's I used to have 42 and 44 were very common helix numbers that worked good. Please stay on topic with info you've tried, not what you dreamt about or read on a cereal box.
 

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What do you have that spring at 18 lbs?
How much weight in the arms?
What belt are you running OEM?
What max RPM?
 

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Discussion Starter · #5 ·
Friends, my question is has anyone tried something besides stock helix on these turbos with a tune. Yes I understand the tuner gives their clutching, but as in all clutching their is different stuff that works for different types of riding. Clutching for top speed is much different then 500ft run or corner to corner trail where backshift is equally important. I'm mainly looking for others experiences with other helixes with this sled
 

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I ran a 46/36 that helped maintain rpms as the power dropped with intake temps but performance dropped. It didn’t maintain rpm better but it was slower. I was also running a 38 gear which will be different than your 45.
 

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Testing on grass probably not a great indication of what you will see on snow, also power will be way down playing around on grass, which is probably the main reason you hit a wall at 400’.
 

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The true answer to this can only be answered by you. Test, test and test some more. Not many running the 900 in the grass that I know of.

If you want help to improve on grass then post some details. There are many members here with clutching exp. that would be happy to offer you good advice.
 

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Discussion Starter · #9 ·
Yeah, testing is key, in our area we normally start playing in the grass in oct. When temps cool down. Everybody tunes their trails sleds for 2-3 months of grass racing, then switch for snow riding. Normally 200 miles or so a year in the grass. Can't bear to spend 15k for only 12 weekend rides a year. I haven't had a doo since 2016(800), bought yami winder-quite fun amount of power, bought doo 900 because winder was like driving a lumber wagon thru the trails.
 

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To start with your gearing ratio is way too high for a 400 ft run.

Older grass sleds set up for 500 ft with 220-230 hp run a much lower gear ratio than the stock 900T.
 

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thats because they ran much higher rpms
 

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Waisting your time running stock gear after tuned. Is Hurricane selling the Dalton Yamaha weights or the Dalton doo. The wall you are hitting is probly IAC temps pulling timing . I tried lots of helix, with 215 hp stock was best but loaded the tips very heavy. Got 5000 miles out of a belt also . Hope this helps but you seem to know more than the people replying lol
 

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boost junkie
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race weight of imp turbo was 750 lbs
 

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Waisting your time running stock gear after tuned. Is Hurricane selling the Dalton Yamaha weights or the Dalton doo. The wall you are hitting is probly IAC temps pulling timing . I tried lots of helix, with 215 hp stock was best but loaded the tips very heavy. Got 5000 miles out of a belt also . Hope this helps but you seem to know more than the people replying lol
So if you are trying to help why not grace us all with your vast amount of knowledge. What gear do you suggest for 400 ft grass on grass????
 

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Discussion Starter · #17 ·
Friends, who cares about pro grass sleds and 2 stroke info. Simple question in post was helix info for 900 ace turbo base on your experience thru trial, not former professional grass racing knowledge. Stay on point, surely with much money you could turn sled into grass animal and have to then buy trail sled. I understand the 41 gear recommended which changes speed and torque and different shift points vs stock. Question I have is if anyone has left the gearing alone and changed the shift points thru a helix with the doo turbo. Used to do it all the time with 800 etec, even different setup for differing trail conditions, same with my winder. The problem with 41 gear i grass is losing so much on take off you don't have time to run em down. Understand we are running mid 80's in 500 feet. Its just fooling around here, but we give lotta time and effort to the fooling. My neighbor runs a indy xc 850 that right now is hard to beat, only 1 850 doo all decked out for drags has been able to beat him. Please don't start bashing the poo either, else you gain an open invitation to come show us what you got any given weekend.
 

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JFYI ,Won't make Any difference what helix you use on grass with a 750 lb sled if you don't put 25/49 ,or close gears in it .It's that simple !race a car 1/4 mile with 410 gears and you have 272 gears .See what happens .
 

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JFYI ,Won't make Any difference what helix you use on grass with a 750 lb sled if you don't put 25/49 ,or close gears in it .It's that simple !race a car 1/4 mile with 410 gears and you have 272 gears .See what happens .
Apparently Ken you and I are the only ones who agree that a 900 turbo needs to be geared down for such a short distance on grass. We must both be idiots! :rofl
 

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Discussion Starter · #20 ·
Well sounds like question answered, no one has messed with helixes as you all are spatting about gears. Km sled is 530 not 750, lol. Thanks all for help, ill leave some info about different helixes tried once I get time over holidays
 
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