Helix angles/STM/BDX,SSI/Yamaha

[max rolph]

STM SECONDARY sooo as has been reported, STM angles are diff than Dalton as advertised, but using a dalton helix on an STM sec clutch also creates an issue as the roller cover bottoms out on base of dalton helix limiting the secondary from opening up all the way and belt will not go to bottom, also the rollers start/ hit the ramps .250 down from top of ramp and will not go the whole way dwn ramp because daltons are not under cut as deep as STM and the rollers hit base before full shift..... soo on a helix of 46/36 you are actually starting at 43deg and going to 37deg

the stm helix base is .565 thick and dalton is .710, i have just machines off .130 from base of Dalton helix, making thickness of .575, this allows roller now to start at the 45deg and go to the 37deg of 46/36 helix, and starts the roller within .120 of top.
i also did cut a helix that 48/34 and now do get the 46/36 with rollers. and clutch opens up all the way.

so if you use a Dalton helix on STM... either shim roller cover up or machine base of helix.

 

[Srxspec]

The STM secondary uses Arctic Cat helixes, those helix angles are very close between STM & Dalton. The STM stock secondary Yamaha helixes are where the big difference in helix angles is.

 

[Trailleader]

Run a helix and stick with that company
Always had good luck with stm and cat stuff
Seems that all cuts differ a bit
That’s a lot but that straight 38 stm is a good angle meaning the angle it actually measures
I liked the 46/36 or 46/38 stm on trail

 

[Srxspec]

Run a helix and stick with that company
Always had good luck with stm and cat stuff
Seems that all cuts differ a bit
That’s a lot but that straight 38 stm is a good angle meaning the angle it actually measures
I liked the 46/36 or 46/38 stm on trail

Depending on tune level I use the STM 39/35 or 42/36 which works very very well.