Fastest gear on snow....21/38...22/38...23/40

[ROCKRTX]

Hey, You still running the stock clutching? If you are going for broke all out top end, bring it up to 11,000RPM. Ulmer keeps adding fuel and timing up to 11,250, then the rev limiter kicks in after that. I pulled 111.3 on my GPS in 2000ft on a groomed trail in pretty much the same condition as you on Saturday. Temps were 28-30 degrees when I started playing and 32-34 when I was done. Are you running 23/40 or 23/38 gearing?

So what do you think of the 23/40 gearing vs 23/38? do you like it?

I really do like mine

 

[ReX]

Mike,

Is there a simple trick to add a little extra tip weight on the stock setup?

My 07 RTX's drivetrain is bone stock and I wanted to keep it that way - at least as close as possible.

Off the line it's revving at about 10,600 (edit: I just checked, instead of what I "thought" it was doing and found it starts off at around 9800). It quickly pulls to just under 11,000 (edit: more like 10,400) and slowly climb from there. At a top speed of about 200 kph (125 mph) on the speedometer, it will sometimes be turning close to 11,150. I know it hasn't quite run out of gear because if I back off on the throttle a little at these speeds, the rpms will instantly drop by at least 250-300 rpms. When there is an inch or so of fresh snow on top of hard pack (so the track is always transitioning between spinning and gripping), the rpms run roughly in the 10,500-10,700 range while accelerating (pretty much ideal).

I'm very pleased with the performance as it is. I'd just prefer the engine to spin a little slower so it will hopefully maximize its life. With the rpms the way they are now I won't hold it wide open long and I'd feel more comfortable under 10,900 rpm. At the same time I definitely don't want to hurt the performance at all (and better performance would be a bonus...). I did talk to Yamaha and my dealer about this and their answer is it won't hurt it to run stock. All of the 07/08 RTX run like this because of the lower gears.

I tried backing off on the secondary preload from 70° to 60° and all this did was hurt my off the line acceleration and make the low speed throttle response not quite as snappy. My fuel economy also seemed to drop. In fresh snow on top of hard pack conditions, the acceleration dropped off the most and the rpms here dropped down into the 10,400-10,600 range (quite a bit lower than that off the line too). The rpms still quickly climb to about 11,000 and still climb to close to 11,200 at top speed when on hard pack.

I'm back at 70°, but ideally I'd like to find a way to add enough tip weight to bring the rpms into the 10,800-10,900 range (I'd prefer to keep it a "little" on the higher side to handle varying conditions).

Are there any "extra heavy" rivets that can be used instead of the stock ones or is my only option to install an aftermarket clutch kit in order to get the rpms to stay below 10,900?

BTW, this sled has run these rpms since the first time I opened it up over 12,000 km ago. To be honest, the reason I didn't do anything before was I expected the rpms to drop as the miles got on the sled and the clutch springs weakened. I'm amazed that the rpms haven't dropped off at all after 13,000 km. I also went over the clutches a couple of weeks ago and they are still in great shape. There is a little stop in the weight bushings, but not much. The worst wear, again not much, is in the spider slides. Almost all of the miles are "highway" miles. The main bushings are still in very good shape too. I have a clutch rebuild kit, including weight bushings, but didn't end up installing it.

 

[pro116]

Yes hauck sells boldts/nuts up to 6 grams to replace your stock 4.5 grams.
He has
5grams
5.5
6

 

[SledFreak]

You could try the 5.5 from hauck OR spend the money and tune the drag and fly weights that seem to really help performance from what I have read so far. At 11,000 on a stocker is too high and it's actually starting to pull back timing @11,000, so it's not helping you at all. It's hurting you... You need to be at 10,800-10,900 max on a stocker on a long pull.

 

[SledFreak]

Hey, You still running the stock clutching? If you are going for broke all out top end, bring it up to 11,000RPM. Ulmer keeps adding fuel and timing up to 11,250, then the rev limiter kicks in after that. I pulled 111.3 on my GPS in 2000ft on a groomed trail in pretty much the same condition as you on Saturday. Temps were 28-30 degrees when I started playing and 32-34 when I was done. Are you running 23/40 or 23/38 gearing?

So what do you think of the 23/40 gearing vs 23/38? do you like it?

I really do like mine

Yes, it seems to pull better to around 105... I needed my buddy to race to find out if it really worked or not, but his F1000 has issues. They now have to crack the motor. It might be sucking antifreeze. Piece of #*$&@ CAT.... I need a road to run on, to verify top end numbers.

So far I like it.... It will stay in for now.

 

[ReX]

Yes hauck sells boldts/nuts up to 6 grams to replace your stock 4.5 grams.
He has
5grams
5.5
6

What's your best guess as to how much weight I'd need to add to drop the top speed rpms by about 250 rpm?

It would probably be best to slightly lighten up the inner rivet and use a slightly heavier tip rivet (to make sure the low speed rpms are closer to peak hp)? I wouldn't want to go to far though since I like the low ~3400-3500 rpm engagement.

How much weight is there at the low speed rivet location stock?

Have any of tried this with 22:38 gears? How well did it work?

 

[ReX]

You could try the 5.5 from hauck OR spend the money and tune the drag and fly weights that seem to really help performance from what I have read so far. At 11,000 on a stocker is too high and it's actually starting to pull back timing @11,000, so it's not helping you at all. It's hurting you... You need to be at 10,800-10,900 max on a stocker on a long pull.

I do have a complete stage III (I think it was III - top of the line kit anyway) clutch kit from Ulmer for an 05 RX-1. It includes tunable weights, primary & secondary springs as well as a helix. The only thing I don't like about it is it doesn't use the heavier weights that the Apex kits use. I'd need to add a lot of weight (washers) to get enough weight, especially with 22:38 gearing.

I wonder what rpms it would run with just the Ulmer helix and secondary spring? High or lower than stock? My guess is it would lower the rpms.

 

[pro116]

The ulmer helix and spring would work really good.Put that in and see where you rpm's are at.

 

[pro116]

If you want to stay stock try a 6 gram from hauck.

 

[KnappAttack]

Rex,
add a 1.5 gram washer to the tip of the stock rivet. I drill a small washer and grind a flat on one edge so that it just slides over the tip rivet, and just tack weld it to the rivet with a wire feed welder. Grind the weld down slightly and your good to go.


One more thing,
depending on the belt you are using and the amount of miles on it. Best performance can be had with the new 8DN-01 belt and keep it below 1000 miles or so for max performance and racing. Even though they last and run forever. Newer belts work best and tend to keep the RPM lower. I've personally seen 4 MPH difference from a 1500 mile belt and a 50 mile belt comparison on the trail with no other changes. Thats huge!

 

[ReX]

Rex,
add a 1.5 gram washer to the tip of the stock rivet. I drill a small washer and grind a flat on one edge so that it just slides over the tip rivet, and just tack weld it to the rivet with a wire feed welder. Grind the weld down slightly and your good to go.


One more thing,
depending on the belt you are using and the amount of miles on it. Best performance can be had with the new 8DN-01 belt and keep it below 1000 miles or so for max performance and racing. Even though they last and run forever. Newer belts work best and tend to keep the RPM lower. I've personally seen 4 MPH difference from a 1500 mile belt and a 50 mile belt comparison on the trail with no other changes. Thats huge!

I did recently install a new belt and right away the rpms dropped right down into the 10,950-11,000 range max, with it revving in the 10,600-10,800 at WOT typically (lower speeds).

I also saw a noticeable improvement in both acceleration and speed.

Unfortunately it only really lasted 1 long ride or about 500 miles. By the next ride I noticed that the rpms were back into the 11,000+ range and climbing into the 11,100+ range at high speeds.

We'll often put on over 2000 miles in a week of sledding, so I really want a solution that will work with a belt in the 500-6000 mile range - not 0-500 mile range. I always take it easy for about 50 miles on a new belt, breaking it in, so changing the belt every time the rpms get too high would mean a new belt every 450 miles of real riding.

I expect the belts I've been running are the original 8DN though (I bought the last one last summer and I only changed the original belt for it at around 6000 miles - I still have one more new 8DN belt to go; the spare). Will the 8DN-01 keep the rpms down for good? If so, I could always run the other belt on my wife's Venture 700 and pick up a new belt for my sled.

 

[ROCKRTX]

Hey, You still running the stock clutching? If you are going for broke all out top end, bring it up to 11,000RPM. Ulmer keeps adding fuel and timing up to 11,250, then the rev limiter kicks in after that. I pulled 111.3 on my GPS in 2000ft on a groomed trail in pretty much the same condition as you on Saturday. Temps were 28-30 degrees when I started playing and 32-34 when I was done. Are you running 23/40 or 23/38 gearing?

So what do you think of the 23/40 gearing vs 23/38? do you like it?

I really do like mine

Yes, it seems to pull better to around 105... I needed my buddy to race to find out if it really worked or not, but his F1000 has issues. They now have to crack the motor. It might be sucking antifreeze. Piece of poop CAT.... I need a road to run on, to verify top end numbers.

So far I like it.... It will stay in for now.

I put the pink spring at 6-1 and solve the over shifting.

Try a couple run today,pretty warm day ( 8 degree ) everyting was melting but have a bit off traction ( icy and soft snow ) and a lot off bump in the trail ( no more groomer ),3 pass at 106 MPH and one at 108 MPH.

Pretty happy with the performance off this gearing

 

[Grunter]

I'm just waiting for Ulmer to call me back so I can order that tool,

I use two 12" crescents with the key put back in on the shaft at the brake.
One crescent engages with the key - the other I use to crack the nut....works real well, fast & easy!!!!

 

[rehm70]

.

Spec rtx,
Are you running the 1.325 in a 1" track?
I haven't ordered my studs yet. I ordered a 1" predator and want to stud it with as long a stud as I can. Can you run 1.325 or 1.450 in a 1" track? I believe that I can only run 1.175. Any feed back on this guy's.

You definately do NOT want to run anything taller than a 1.175" woody's in a 1" track. Anything longer will be WAYYYYYYYYY too long.

Just to let you know, I run 1.40" installed length(1.72total length) in a 1" Predator.
I used the mid height nuts and it hooks like a mutha with NO scratch marks on muffler.

 

[SledFreak]

What's a 1.72"?