all the "anti-bottoming" blocks are, is a roller placed on the rail behind the torsion spring retainer. when it gets to the roller, the spring stiffens up.
as far as anti-bottoming, it will still bottom if you are large in size and the bump, jump is large enough. in my opinion it is just a band aid for those needing stiffer springs due to weight and riding style.
at that point you will need to revalve and re-spring your shocks. the engineers can only send out a generic shock/spring package based on the majority of riders. if you are bigger than their specs, you will need to upgrade. unfortunately, sad but true.
for those wanting the blocks they can be had at your dealer for about 72.00 retail (alot cheaper than a spring and revalve upgrade). the most expensive thing in the part list is, the rollers. they are about 21.00 each. the only critical part besides the roller that you cant buy over the counter at your local hardware will be a collar for the roller. everything else is nuts, bolts and washers.
for another avenue of help, there is a guy on dootalk named bc3 he makes torsion spring spacers that slide over the upper cross shaft that the springs ride on. their premise is to keep the spring from rocking when loaded by coiling over the larger delrin spacer taking up the gap between the spring and the shaft.
i have them on my 02 zx chassis 440 and they took the place of 2 spring adjustment clicks on the spring adjuster. we also had them on the wife's rev renegade and they did the same thing there. we had to run hers in the 3rd or 4th position to get her sled not to bottom with her light weight body on it. with bc3's spacers, we ran them on 1-2 depending on conditions.
grape ape sent him dimensions for his mountain apex last year and so far he hasnt had the call to make any for the yamaha guys. i talked to him a few weeks ago wondering about the nytros, and bc3 said he still needs full closed specs on the springs to be able to machine the spacers for that particular yamaha (needs fully closed to prevent spring bind on the delrin). if guys live close to him, maybe they could take sleds over to him and help him develope this for us too. they cost the guys on dootalk about 50.00 per set. and they do work. ski
as far as anti-bottoming, it will still bottom if you are large in size and the bump, jump is large enough. in my opinion it is just a band aid for those needing stiffer springs due to weight and riding style.
at that point you will need to revalve and re-spring your shocks. the engineers can only send out a generic shock/spring package based on the majority of riders. if you are bigger than their specs, you will need to upgrade. unfortunately, sad but true.
for those wanting the blocks they can be had at your dealer for about 72.00 retail (alot cheaper than a spring and revalve upgrade). the most expensive thing in the part list is, the rollers. they are about 21.00 each. the only critical part besides the roller that you cant buy over the counter at your local hardware will be a collar for the roller. everything else is nuts, bolts and washers.
for another avenue of help, there is a guy on dootalk named bc3 he makes torsion spring spacers that slide over the upper cross shaft that the springs ride on. their premise is to keep the spring from rocking when loaded by coiling over the larger delrin spacer taking up the gap between the spring and the shaft.
i have them on my 02 zx chassis 440 and they took the place of 2 spring adjustment clicks on the spring adjuster. we also had them on the wife's rev renegade and they did the same thing there. we had to run hers in the 3rd or 4th position to get her sled not to bottom with her light weight body on it. with bc3's spacers, we ran them on 1-2 depending on conditions.
grape ape sent him dimensions for his mountain apex last year and so far he hasnt had the call to make any for the yamaha guys. i talked to him a few weeks ago wondering about the nytros, and bc3 said he still needs full closed specs on the springs to be able to machine the spacers for that particular yamaha (needs fully closed to prevent spring bind on the delrin). if guys live close to him, maybe they could take sleds over to him and help him develope this for us too. they cost the guys on dootalk about 50.00 per set. and they do work. ski
I updated my first ride report so I cut and pasted that review into this one. Main things people were concerned about in this review was MPG and ride. In my opinion the Nytro needs a 10 gallon Trail Tank (no they don't sponsor me) otherwise you are stuck with a 100 mile range. I go into more detail below.
For ride, I've been doing some research and learned that Yamaha lowered the front ends in '10 or '11 by using shorter front shocks. This will improve cornering but reduce big bump absorption ability.
The biggest thing is the twitchy handling. I'm really interested in the new AC Procross F1100 so I've been researching if anyone has figured out how to make the Nytro handle. I know I'm not happy with the Nytro's lack of high speed stability and I believe that is primarily caused by the abundant bump steer present in the front end. Even if you set the front end up to not dart at high speed on a smooth, hard packed trail, it still won't track through the bumps straight and true. Get into the bumps and the sled will become a handful and not stay planted. In big whoops the sled moves from side to side. I rode a Polaris Pro-R 600 after my last race and could not believe how easy it was to go fast on! It was stable, the front end just soaked up the bumps and it went through the big whoops without me having to do much of anything. That simply is not the case with my Nytro.
I've run all kinds of different skis - stock, stock with Duece Bars, stock RTX, SlyDog Race, Ultra Flex III (C&A copies) and Curves. None of the skis made the sled more stable through the bumps. Duece bars tuned out darting, but caused the sled to push in corners, especially when the trails were not packed and set up. So, after doing testing this spring with an open mind and a desire to buy a new sled, it appears bump steer is the big culprit in why our Nytros do not handle. I don't think the aftermarket can easily cure it because it involves altering where the tie rods mount and their length. You then have to modify either the spindle mounting points or the steering frog or both. Anyhow, I think it would be expensive for them to do that and that's why no one has. Below is the review I posted on the other FAQ ride report.
DEPENDABILITY
I've got about 3600 miles on it now, which isn't a lot, but over 700 of those miles were from cross country races, and the rest from lots of practice and ditch banging. The sled has held up very well. I never experienced a DNF in any race and the motor still runs perfect. I've never blown a belt or had the electrical issues I've read about on TY. I've also only had to replace the hyfax once.
PROBLEMS
My lower ball joints became sloppy in the first 400 miles. I replaced them with some greasable units my dealer made up. They have held up well. The a-arm bushings were loose and I replaced them with oil lite bushings my dealer made on his lathe. They are still tight with no slop and have around 2600 miles on them.
One issue I've had is bashing in the side panel on the clutch side which allowed snow to pack the clutches and make the belt slip. This happened due to snow pressure from deep whoops pushing the panel into the clutch causing the clutch to knock a hole in it.
I've not had the hyfax issues guys complain about and my idler wheel bearings have done okay. I repacked them with grease two seasons ago. I've also not had my oil tank crack (I always check to make sure my mounting bolts are tight) nor have I tweaked my subframe, but then again, I've not hit anything and ride the sled in good snow conditions. I did cartwheel the sled once into some wind drifts and that twisted the a-arms a little but I was able to bend them back using a big pry bar as nothing had been creased and the mounts were not bent either. It is disconcerting to see how much the a-arms flex!
I replaced the stock rear shocks with those of an RTX and had them rebuilt/revalved along with those on the front. I was able to get a Yamaha racing reinforced front torque arm so I never broke the stock one. I was priding myself on not bending a-arms or spindles but I discovered that is due to two things: one I ride smooth, but the main reason is the bump steer and lack of high speed stability has caused me to go slower than the competition so I'm not as hard on my equipment. That's NOT a good thing for racing.
The lack of high speed stability was really apparent this season. I got to ride a Polaris Rush Pro-R 600 and could not believe how stable and in control that sled felt at high speed through rough terrain. My Nytro does not compare... period.
ERGOS
I installed an OFT steering post relocator and WRP Seat and they made a huge difference in the ergos. By last season my stock seat was getting sacked out and I noticed it was more difficult to go from sitting to standing than it should have been. The taller seat makes it more comfortable and easier to stand up and the relocator makes it easier and more natural to steer the sled, plus it allows you an easier time to get your weight forward for cornering as you don't fight the weird angle of the bars.
The handwarmers don't work that great when it is cold and the hand guard brackets break way too easily when you roll the sled in deep snow.
FUEL ECONOMY
If you ride hard,fast or in deep snow, the stock tank is not big enough in my opinion. The 7.4 gallon tank is only good for 100 miles and that's pushing it. The 10 gallon Trail Tank is a must have, especially now that most of the 2-strokes come with 12 gal tanks and are tuned to provide better MPG than was the case back in '07 when the Nytro came out. I've routinely gotten between 14-16 for play riding and 13 for racing, all depending on snow conditions.
RIDE & HANDLING
I've got my sled to handle better than stock but its a compromise. Lower the front end for better cornering and you lose travel for the big bumps and holes. Raise the front end for rough conditions and the sled feels more top heavy in the corners and wants to lift the inside ski but isn't predictable about doing so. You can also lower the rear skid which helps improve handing and stability but takes away from the ride quality. It's really frustrating because the other brands of 600's don't require such compromises to deliver predictable handling and a good ride.
SUMMARY
Overall I still really like the sled but in my opinion, the front end is holding it back. Between the bump steer and twitchy high speed handling it just doesn't compare to a Polaris Rush 600 Pro-R. On paper, the revised front end geometry (FXG2) that came out in '09 should have cured the issues but I see lots of the same complaints about the handling of the '09 -'11 so it doesn't appear the changes were enough. I've not been willing to spend over $1000 on the parts to find out for myself. The rear suspension design doesn't seem to have the same amount of travel as the other 600cc sleds. That is probably due to the need to tighten the limiters to get the Nytro to handle which takes away travel. In any case, I was very impressed with the Pro-R and the Sno-Pro 600 I got to try back in March. To bad they were two strokes because I really love the Nytro motor. I love that the Nytro will run on cheap gas, makes great power and doesn't make you worry about the engine burning down or letting go when holding it to the bar across a lake or down a river.
For ride, I've been doing some research and learned that Yamaha lowered the front ends in '10 or '11 by using shorter front shocks. This will improve cornering but reduce big bump absorption ability.
The biggest thing is the twitchy handling. I'm really interested in the new AC Procross F1100 so I've been researching if anyone has figured out how to make the Nytro handle. I know I'm not happy with the Nytro's lack of high speed stability and I believe that is primarily caused by the abundant bump steer present in the front end. Even if you set the front end up to not dart at high speed on a smooth, hard packed trail, it still won't track through the bumps straight and true. Get into the bumps and the sled will become a handful and not stay planted. In big whoops the sled moves from side to side. I rode a Polaris Pro-R 600 after my last race and could not believe how easy it was to go fast on! It was stable, the front end just soaked up the bumps and it went through the big whoops without me having to do much of anything. That simply is not the case with my Nytro.
I've run all kinds of different skis - stock, stock with Duece Bars, stock RTX, SlyDog Race, Ultra Flex III (C&A copies) and Curves. None of the skis made the sled more stable through the bumps. Duece bars tuned out darting, but caused the sled to push in corners, especially when the trails were not packed and set up. So, after doing testing this spring with an open mind and a desire to buy a new sled, it appears bump steer is the big culprit in why our Nytros do not handle. I don't think the aftermarket can easily cure it because it involves altering where the tie rods mount and their length. You then have to modify either the spindle mounting points or the steering frog or both. Anyhow, I think it would be expensive for them to do that and that's why no one has. Below is the review I posted on the other FAQ ride report.
DEPENDABILITY
I've got about 3600 miles on it now, which isn't a lot, but over 700 of those miles were from cross country races, and the rest from lots of practice and ditch banging. The sled has held up very well. I never experienced a DNF in any race and the motor still runs perfect. I've never blown a belt or had the electrical issues I've read about on TY. I've also only had to replace the hyfax once.
PROBLEMS
My lower ball joints became sloppy in the first 400 miles. I replaced them with some greasable units my dealer made up. They have held up well. The a-arm bushings were loose and I replaced them with oil lite bushings my dealer made on his lathe. They are still tight with no slop and have around 2600 miles on them.
One issue I've had is bashing in the side panel on the clutch side which allowed snow to pack the clutches and make the belt slip. This happened due to snow pressure from deep whoops pushing the panel into the clutch causing the clutch to knock a hole in it.
I've not had the hyfax issues guys complain about and my idler wheel bearings have done okay. I repacked them with grease two seasons ago. I've also not had my oil tank crack (I always check to make sure my mounting bolts are tight) nor have I tweaked my subframe, but then again, I've not hit anything and ride the sled in good snow conditions. I did cartwheel the sled once into some wind drifts and that twisted the a-arms a little but I was able to bend them back using a big pry bar as nothing had been creased and the mounts were not bent either. It is disconcerting to see how much the a-arms flex!
I replaced the stock rear shocks with those of an RTX and had them rebuilt/revalved along with those on the front. I was able to get a Yamaha racing reinforced front torque arm so I never broke the stock one. I was priding myself on not bending a-arms or spindles but I discovered that is due to two things: one I ride smooth, but the main reason is the bump steer and lack of high speed stability has caused me to go slower than the competition so I'm not as hard on my equipment. That's NOT a good thing for racing.
The lack of high speed stability was really apparent this season. I got to ride a Polaris Rush Pro-R 600 and could not believe how stable and in control that sled felt at high speed through rough terrain. My Nytro does not compare... period.
ERGOS
I installed an OFT steering post relocator and WRP Seat and they made a huge difference in the ergos. By last season my stock seat was getting sacked out and I noticed it was more difficult to go from sitting to standing than it should have been. The taller seat makes it more comfortable and easier to stand up and the relocator makes it easier and more natural to steer the sled, plus it allows you an easier time to get your weight forward for cornering as you don't fight the weird angle of the bars.
The handwarmers don't work that great when it is cold and the hand guard brackets break way too easily when you roll the sled in deep snow.
FUEL ECONOMY
If you ride hard,fast or in deep snow, the stock tank is not big enough in my opinion. The 7.4 gallon tank is only good for 100 miles and that's pushing it. The 10 gallon Trail Tank is a must have, especially now that most of the 2-strokes come with 12 gal tanks and are tuned to provide better MPG than was the case back in '07 when the Nytro came out. I've routinely gotten between 14-16 for play riding and 13 for racing, all depending on snow conditions.
RIDE & HANDLING
I've got my sled to handle better than stock but its a compromise. Lower the front end for better cornering and you lose travel for the big bumps and holes. Raise the front end for rough conditions and the sled feels more top heavy in the corners and wants to lift the inside ski but isn't predictable about doing so. You can also lower the rear skid which helps improve handing and stability but takes away from the ride quality. It's really frustrating because the other brands of 600's don't require such compromises to deliver predictable handling and a good ride.
SUMMARY
Overall I still really like the sled but in my opinion, the front end is holding it back. Between the bump steer and twitchy high speed handling it just doesn't compare to a Polaris Rush 600 Pro-R. On paper, the revised front end geometry (FXG2) that came out in '09 should have cured the issues but I see lots of the same complaints about the handling of the '09 -'11 so it doesn't appear the changes were enough. I've not been willing to spend over $1000 on the parts to find out for myself. The rear suspension design doesn't seem to have the same amount of travel as the other 600cc sleds. That is probably due to the need to tighten the limiters to get the Nytro to handle which takes away travel. In any case, I was very impressed with the Pro-R and the Sno-Pro 600 I got to try back in March. To bad they were two strokes because I really love the Nytro motor. I love that the Nytro will run on cheap gas, makes great power and doesn't make you worry about the engine burning down or letting go when holding it to the bar across a lake or down a river.
