apex 121 to 144 owner's input please

[evil eagle]

I am very undecided about stretching out my 121 mono apex to a 144. The research I have done seems to say that it might not be a great idea. There is something about the track getting to tight when the suspension compresses and it seems to get worse when it is stretched.
From what i have been told from one of the vendors of these kits was to install extrovert drivers and run a loose track. That may not be so good either. I think I would loose alot of speed with a loose track balloning and the extra drag off the extroverts.
I am sure there is alot of guys on here that have stetched to a 144. I would like to know their before and after thoughts.

 

[jr13322]

I stretched my mono 121 to a tip up 144. The ride is much better, soaks bumps great, but I also got my Ohlins revalved, and heavier spring. Off trail is so much better, I am now going to place where I never ever dared to before. One of the problems I run into is premature hyfax wear at the "tip up" part of the rails, and yes I installed idler wheels at that spot. I run the track loose, but not to loose (2 inch of sag), as I am studed. I went with 1.5 crossover track and 1.45 studs, works pretty good. Put in 8 tooth extro drivers to, geared down by 1, I think from 24 to 23. Nothing done on the clutch yet, not sure what direction I want to go with that. I did have to make new rear mounts out of flat aluminium stock to drop the track 1/2 inch or so as it was rubing on stud protectors. I installed scratchers this year, as I ran into a few times where I would begin to overheat due to poor snow conditions and longer track. I did go with a muffin works rail extensisons and tunnel extensison. I attempted to mount cross shafts between the rail extensiosn to give strenghts but they came loose and fell out, even with loctite. The tunnel extensions, well thats an other story. I got a custom longer one done with a 15 inch deck to mount a bag. After a long sadlebag trip, the tunnel bent from what I supose was the weight of my tunnel bag trashing arround. So I ended up reinforcing the crap out of it. I now run a 1.75 rotapax with a bag, 3000km with no issues. Hope this helps, PM me if you need more info.

 

[evil eagle]

I stretched my mono 121 to a tip up 144. The ride is much better, soaks bumps great, but I also got my Ohlins revalved, and heavier spring. Off trail is so much better, I am now going to place where I never ever dared to before. One of the problems I run into is premature hyfax wear at the "tip up" part of the rails, and yes I installed idler wheels at that spot. I run the track loose, but not to loose (2 inch of sag), as I am studed. I went with 1.5 crossover track and 1.45 studs, works pretty good. Put in 8 tooth extro drivers to, geared down by 1, I think from 24 to 23. Nothing done on the clutch yet, not sure what direction I want to go with that. I did have to make new rear mounts out of flat aluminium stock to drop the track 1/2 inch or so as it was rubing on stud protectors. I installed scratchers this year, as I ran into a few times where I would begin to overheat due to poor snow conditions and longer track. I did go with a muffin works rail extensisons and tunnel extensison. I attempted to mount cross shafts between the rail extensiosn to give strenghts but they came loose and fell out, even with loctite. The tunnel extensions, well thats an other story. I got a custom longer one done with a 15 inch deck to mount a bag. After a long sadlebag trip, the tunnel bent from what I supose was the weight of my tunnel bag trashing arround. So I ended up reinforcing the crap out of it. I now run a 1.75 rotapax with a bag, 3000km with no issues. Hope this helps, PM me if you need more info.

Thanks for your thoughts
It looks like you changed out the drivers when you did the conversion. Two inches of track slack it's alot, I wonder how tight the track would get if you were to compress the suspention to the bottom. I did just that with my sled stock 121 and it gets plenty tight. If what is said to be true the stretched out sleds might stretch out a track prematurely.
I'm hope to hear from somweone that has done this conversion that could tell me if they lost top end speed from this haveing a loose track and extroverts. Most times a longer terck it's self would not loose really any top speed. Example xtx apex's and nytro's.

 

[Yammimodder]

You are right in saying that the extensions cause the track to tighten as the suspension gets compressed. that is one reason why people have to run their track so loose. the key is to keep the parallelogram geometry when you do the extension. If you are to do a 121 to 144 extension, that means that you are moving your axle back 11.5 inches. To keep the parallelogram, the upper rear idler wheel shaft must also be relocated back 11.5 inches. this makes up the extra 23 inches of track and keeps the rear inclined section of you track the same length. The newer mono may be more forgiving than the pro action, but I think that such a big difference in length will cause it to become pretty tight once the suspension is compressed. If you look at the ltx mono compared to the 121 mono, you will notice that they just added a shaft with two idler wheels behind the rear arm chassis mounting point to keep the geometry correct. I just extended the ltx 136 to a 144 and I didn't relocate the upper shaft yet as it seems to be forgiving enough to accept the extra 4 inch extension without the track becoming tight as the suspension compresses. I did install extroverts so I will be able to run my track a little looser this year as well. I would say that you could easily install an extra shaft with wheels for fairly cheap especially if you have some old suspension parts lying around.