121" to 144" conversion recommendations

[vanderrules]

Hey Folks

I am looking for opinions and suggestions in regards to an upcoming project. I currently have an 07 FX and an 08 GT. I got my hands on an 07 MTX parts sled that just happened to have a fully rebuilt skid and a new 1" Camoplast track. My plan is to put that skid and track on my 07 FX.

I have done a lot of looking around on here and my understanding is I am in a pretty good spot. Seems everyone who goes with the long track conversion also wants the FX suspension to go with it.

So my questions are as follows:
-Would you use the 8 tooth or 9 tooth drivers?
-Are anti ratchet drivers necessary?
-What top gear would you recommend and with what drivers?
-What clutch kit would you go with after the conversion?

I don't mind throwing some money at this thing as i go along. I was considering the Schmidt Brothers Stage 2 Clutch Kit and upgraded sway bar when I am done. Any other must haves?

My riding is 95% trails with lots of lake crossings in my area here in Northern Ontario. Because of this I'd like to keep the top speed as high as possible.

Let me know what you think!

 

[maim]

welcome to the site!

you already have a good start with the mtx skid and track. having built a 09 rtx into an xtx i can give you a few tips.

as you have a 1" x 144" track already, i would personally try it with the stock 9 tooth drivers from that sled with the mtx skid before getting 8 tooth drivers. do not need extroverts as with 8 tooth drivers and a 1-1/2" track it will not skip/ratchet at all. worry about the gears after finding out if you need to replace the drivers. stock the mtx has the 8 tooth drivers on the axle.

we are using the stock rtx clutching and like it.

with the 9 tooth drivers, use the rtx clutching of 18/41. this ends up withing a decimal point of the final ratio as the below combo.

with 8 tooth drivers, use the xtx clutching of 19/41. this is the best fuel economy/power ratio. still hit 70 mph on the rail grade in muni.

we did run it with 18/41 and the 8 tooth for a season and while it was snappy as heck, the fuel milage sucked.

i do reccomend a ski up grade as when i got the 09 it had snow trackers on the stock skis, i was not impressed with them as i tend to run over a lot of trees. had a set of curve xs skis and they work pretty dang good on it all around. they shine on the trail and are workable off trail for keeping the bumper on top of the snow.

 

[vanderrules]

Thanks for the info maim!

I do have a set of Yamaha Tuner skis to go on there as well that came with the parts sled. I am curious to try them out as i have been running the stock skis on my 07FX which aren't so great. Girlfriend's sled is the 08GT and she has the snowtrackers on hers which make a huge improvement.

 

[blueironranger]

I think 8 tooth drivers are a must IMO, My MTX is almost totally loose on the adjustment and there is no way I could loosen it more to clear 9 tooth drivers. 8t+18/41 gears are a hoot but I can run mine up to the limiter in under 1/4 mile (87 on the speedo) with that. I could even hit the rev limiter with the 8t+19/41 combo under great conditions which showed ~91mph (81-82 GPS)

 

[maim]

blueironranger, he might have enough stretch with that 1" track to run the 9 tooth drivers and keep the rolling resistance down. cannot hurt to try.

 

[vanderrules]

Thanks for the input guys. Currently the 07FX is stock and I have all the MTX parts available (stripped down and in boxes) so all options are available. The MTX had a 19 tooth top gear and 8 tooth drivers in it.

I am no expert in regards to gearing, but what i gather is the 9 tooth drivers and a 19 tooth top gear would keep my top end as high as possible?

 

[maim]

yes it would but it would turn into a belt burner as it would not have enough grunt in the stock clutching witch is pretty much the same for all the 121" sleds and the xtx. the only difference is with the mtx clutching in all of the phazers.

 

[vanderrules]

My plan is to do the Schmidt Brothers stage 2 clutch when I am done. Would this give it enough grunt?

 

[maim]

idk as we are still running the stock 09 rtx clutching in it and it is easy on belts with good grunt out of the hole how we have it. heck it took 4 seasons to finally go through a belt on it and it has been pulling a sleigh and powder riding for most of that.

 

[vanderrules]

I'm thinking start with the 9 tooth drivers (if they fit), and 19 tooth top gear and clutch kit. If it isn't able to pull it I can drop a tooth on the gear.

 

[vanderrules]

I finally got a good chunk of this project done. Ended up modifying the 08 GT instead as it needed a new track. The 9 tooth drivers did fit but she is a little tight. A little track stretch this winter will definitely help. I have way too many hours into this thing...

As a bonus I found the perfect tunnel bag to fit the new extension at Royal.

I haven't taken it for a rip yet and I am expecting some clutch work ahead of me. I am contemplating a Powerbloc 80 clutch instead of a SBR or other clutch kit. If anyone has any experience with the PB80 I would love to hear about it.

I have uploaded some before and after pics.

 

[StinkyFingers]

Vanderrules - that's awesome. I'm thinking of converting my 09GT to a 136 or something. (Also in north bay half the time)

 

[MikeWalters]

I threw in a MTX skid into my 121 FX. stock drivers. 17t top gear, ulmer clutch kit and YVX secondary. 1.5" doo track.

Pulls very hard with all that traction and gearing now, overall easier to drive.

 

[vanderrules]

I took it out for a good ride and it pulls great with the 20T top gear and 9T drivers. I have a Powerbloc 80 clutch coming next week and I am hoping to see some mild improvements to what i currently have.

 

[MikeWalters]

I took it out for a good ride and it pulls great with the 20T top gear and 9T drivers. I have a Powerbloc 80 clutch coming next week and I am hoping to see some mild improvements to what i currently have.

Flat out what rpm are you holding at? Why the Power Bloc clutch? (Are you having problems with yours, or is it worn out?)