2015 RTX LE (Blue/White) with 1.7 track GEARING

[shagman]

Received an email from ALLEN ULMER last night with the following info in it which was news to me, other purchasers, and my dealer.

"I have done about 15 MPI turbo installs now and have everything spot on with the clutching. On the trail MPI kits you should have no problems. The fuel controller may be set a tad on the rich side, but nothing major. i think you will be close enough that riding on the trail will be no problem whatsoever." (KICKER HERE). "They have thrown us for a loop on the Viper RTX SE 1.7 though, as they have changed the gearing drastically over what was in the 1.25 track RTX models. They have gone from 24/50 gearing in the 1.25 track sleds to 21/49 gearing in the 1.7 track sleds. This is going to keep us at 105 mph on top end with the stock gearing."
"21/49 Stock = 105 mph
22/48 (uses stock chain yet) = 111 mph
24/49 (requires use of a new chain) = 119 mph"

Your MPH is high.
21-49 @ 9000 RPM = 94 MPH
22-48 @ 9000 RPM = 100 MPH
24-49 @ 9000 RPM = 107 MPH

these are figured with 9 tooth drivers and 2.86 track.

 

[NOS-PRO]

I know TD and weasel33 are havng the same situations and we all need to figure out what is happening to their sleds.....

1- Can't creep up rpms with the throttle (using thumb slowly...sled rpms just from 2,700 to 3,800)
2- No top end speed (Gearing/drive axle size by the way I am seeing it)
3- Anyone else using this track on an RTX LE? Speeds?

 

[TD Max]

I was happy to hear that we were geared down. It was a bonus to me. By my thinking it would help bottom end and the extra OD would get us solidly to 105mph plus. I was hoping to run out of gear on top. That may still happen, but for the moment, it appears there is something in the clutching causing the speeds to pause or slow down. This may well be affecting most or all machines in some way, shape, or form. Only time will tell.

 

[Srxspec]

Your MPH is high.
21-49 @ 9000 RPM = 94 MPH
22-48 @ 9000 RPM = 100 MPH
24-49 @ 9000 RPM = 107 MPH

these are figured with 9 tooth drivers and 2.86 track.

My MPH figures quote the capability with fully shifted stock clutches taking into account overdrive without any machining.

 

[cannondale27]

8t on cat 7000rr

 

[number1kyster]

Bingo! I bet this is the real issue!

 

[Srxspec]

Cannondale, a RTX LE has 9 tooth drivers. Sure looks like your 7000 Cat has 9 tooth as well. Arctic Cat part number 2602-771 is a 9 tooth driver which is stock on a RR I believe.

 

[cannondale27]

I will count again. I looked and part # is definitly saying 9 tooth but 2602-762 which is on the Viper is also a 9 tooth. What is the difference?

 

[cannondale27]

Srxspec can you do the math if 8t 2:86 drivers were used with stock RTX LE gearing? Thanks

 

[shagman]

Srxspec can you do the math if 8t 2:86 drivers were used with stock RTX LE gearing? Thanks

84 mph without overdrive. 9000 rpm.

 

[cannondale27]

So it's worse with 8t?
Looked again RR is 9t. Will check gearing on 600 XC which for sure has 8t and does 90mph+

 

[shagman]

Track pitch and number of teeth sets the diameter of the driver. You have to have both to compare vs gearing.

 

[cannondale27]

It's 286 pitch on 600

 

[TD Max]

OK just wanted to clarify. 9 tooth 2.86 drivers in both Cat and Yamaha.

I also just verified my 2.33 (21-49) ratio. To verify I marked a tooth on the drive roller noting it's position. I then rotated the secondary 7 turns and the marked tooth was in the same position. I could have done a single revolution or the roller, but multiple revolutions helps to eliminate error. 2.33 x 3 = 6.99 so 3 full revolutions of the drive roller requires 7 of the jackshaft.

I would be interested to see if the LE with the 1.25 lug track got the same gearing or not?

 

[500champ]

OK just wanted to clarify. 9 tooth 2.86 drivers in both Cat and Yamaha.

I also just verified my 2.33 (21-49) ratio. To verify I marked a tooth on the drive roller noting it's position. I then rotated the secondary 7 turns and the marked tooth was in the same position. I could have done a single revolution or the roller, but multiple revolutions helps to eliminate error. 2.33 x 3 = 6.99 so 3 full revolutions of the drive roller requires 7 of the jackshaft.

I would be interested to see if the LE with the 1.25 lug track got the same gearing or not?

It has 24-50 gearing