98 Msrx 700 gearing down for the deep stuff

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Gerryjackman

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Anybody familiar with gearing down a 98 Msrx 700. I,d like to do it up as best I can for the deep stuff and hill climbing. I don't know what's in it right now but I know it's not stock it has a dropped and rolled chain case and for some reason they looked a bit different in size but appeared the same ratio. Do you guys know of a good gearing set up for real deep powder ? Riding ranges from 5000 to 8000 ft sometimes mainly 6500 ft. Clutches are stock as far as I know and other mods are listed below. Thanks guyys
 
I'll be taking my Mountain viper to West Yellowstone this weekend. Stretched it out to 159" x 2 1/8" series IV track. I am running 19/42 gearing. From my testing last weekend in the UP, I think it will work out good for me. The stock Mountain viper comes 21/40 gearing with a 2"x144" track. I think that would be a good starting point for you. Maybe a 20/40. I'm assuming you are making more HP with MSRX than I am with a viper so you wouldn't have to gear it as low as I did.
 
Ok so a 20 40 you think? What about ratio change does that matter and Should my stock chain still work with that?
 
My manual says a 20/40 takes a 68L chain. Not sure what came on your MSRX. A 21/40 requires a 70L chain. These charts are from a SXV70MH Supp. manual. (Mountain Viper)
 

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The short answer is yes. Anything you do will affect clutching. The longer answer... Let me start by saying there are a lot of others on ths site who are much more of an expert with clutches than I am. That being said, here's my 2 cents worth.

By lowering your gearing (numerically increasing your gear ratio), you are reducing the load on the engine for a given RPM, speed, loading condition. Basically you are using a slightly lower gear. In theory, this would decrease your top speed. I have read many times on this site and others that the yamaha's are geared too tall from the factory anyhow. I.E. the engine (stock) doesn't have enough power to have the secondary fully shift out under normal riding conditions. By gearing down, you can potentially fully shift out your secondary clutch. My simple answer is gear it down and you'll be just fine. Watch your Maximum RPM. There is a lot of fine tuning you can do with both the primary and secondary if you're looking for every last ounce of performance but unless you're racing, you'll probablly never notice the difference. I generally use the factory clutching and jetting recommendations from the manual for my sled. I went with a taller gear ratio, but I am running a much longer track. I also like to think of it this way, by gearing down a little I am decreasing clutch temperature slightly, all else being equal. Keep in mind, with your drop and rolled chain case, the gear/chain chart is no good. Meaning you probably have a longer chain for a given gear combination than what is listed in the manual. Just count the links on your existing chain, and look at the chart, specifically where a change in ratio dictates a change in chain length. Just use the same increase or decrease at those jump points. Also, the chart I attached earlier is for factory gearing available. You can get smaller top gears and larger bottom gears from aftermarket suppliers such as Hartman. if you look at the gear chain chart, there is not an option for a 19/42 combination, yet that is what I and others are running.

In summary, if you drop 1-3 teeth on top or increase 1-3 on the bottom, I would think you'll run just fine without messing with clutching. Sorry about the long winded answer.
 
That's awesome man appreciate it, so basically find my chain size and ratio, then do I stick with the same change on both sprockets and keep the same gear ratio or does that matter. Should I drop two and increase two or one or the other ?
 
first thing you want to do is verify what you currently have foe gearing along with the tooth count on the drivers.

your msrx came stock with 9t drivers and 21/29 gearing, along with a 70l chain, although the 68l will work.

in grizzly1's sled, it came with 8t drivers, already an 11% reduction in final gear ratio. on the drop and rolls i have done, we kept the 9t drivers. important factor to consider when re gearing is calculating for the drivers.

seeing how your set up has possibly been altered, figure out what you have in there. theres a few tricks and shortcuts to save money. for instance, if your still using the stock 15 plate chain, it will run on the less expensive and more readily available 13 wide gears. depending on 68l or 70l will dictate your gear options so you wont need a new chain.

i am running 19/42 gearing with 8t 2.86 pitch drivers on my 155 srx with a drop and roll.
 
Right on man I will get at it hopefully Tomorow And get back to you with what I have in there as soon as I can. If im understanding right 9 tooth drivers would make it so you dont have to gear down as much? Kind of off topic but what would it cost me to convert from 144 to 155". Thanks
 
Ok gotcha, I'm going to tear it down tonight and get the info, one thing I was wondering last time I took the chain case apart was how much chain oil to put back in, with it having a drop and roll do I still run stock quantity of chain oil being as though the dipstick does not work with my drop and roll. If it is not stock quantity do you know how much I should put back in?
 
Ok thanks That's what I'm unsure about I bought it as is it has inverted drivers and a ekholm tunnel that fits a 144" ill post pics soon. What are things I need to look for to see how to get to 155"
 
Okay this is what I found
9 tooth drivers
Small sprocket is 21
Large sprocket is 42
70 link chain

Where do I go from here I would like to go fairly low top speed isn't everything I want the jam low end. And for ordering purposes do you know if thiese are hyvo or not or what do I have to order exactly I don't know what hyvo means an I've seen 13W around but don't know what that means either! Thanks
 
hard to tell the width, but the gears are for sure non-hyvo. count the plates side to side on the chain, they appear to be 13w.

from what i can tell on the skid, looks to be simply rail extensions to get to 144, your leaving alot of off road performance behind running the skid in that configuration and you have some performance to gain by re-thinking the gearing. 19 or 20 on the top will still work with the 70.

back to the skid, some closer shots would be helpful, especially where the front bolt on the skid is positioned at the tunnel.
 
Ok. Why do you mean by performance engine or handling ?imnot sure what you mean by that configuration what is done here ? I will take a pic soon of the bolt what do you think about bottom gear 40? Will that work with 70l chain?
 
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