overdrive!

[ROCKRTX]

what is the best real world ratio you can achieve with a primary clutch machine for overdrive? ( 0.89,0.75)

 

[iasledder]

Typically 0.8

 

[ROCKERDAN]

remember just maching primary isnt enough...secondary work needed too,or could be some belts a blowin!

Dan

 

[ROCKRTX]

remember just maching primary isnt enough...secondary work needed too,or could be some belts a blowin!

Dan

is there something else to be done to the secondary?
I have already my helix machine for overdrive whit my ULMER stage 2.

 

[ROCKERDAN]

remember just maching primary isnt enough...secondary work needed too,or could be some belts a blowin!

Dan

is there something else to be done to the secondary?
I have already my helix machine for overdrive whit my ULMER stage 2.

I am always paying attention to detail and like to be sure things work properly...so what i always do with a cut primary,is remove spring,put on sled,then remove secondary spring too...put belt on and physically see if it will shift out fully,so the belt is NOT being stretched by newly machined primary....if the secondary doesnt allow primary to pull belt to were you have it machined to,you could stress belt if you reached those speeds on top end.

I know MOST ALL aftermarket helixs have the shorter HUB on them to let more shiftout happen then stock helix...this is great,and sometimes is enough.

with my setup,i ended up adding the 5/16 lockwashers to the towers,to shim out helix more....this along with my DALTON helix allows me to be CERTAIN the secondary will let primary go to its full shift with ZERO stretch/pull to belt.

it really depends how far your primary is cut...each guy may cut diferently...Our machinist we had him Cut to 1.380",belt rides flush to top of primary when done being cut....I probably could get away without the washers (Shims) in secondary but I wanted to be sure.

hope that helps
dan

 

[KnappAttack]

There is no magic number. Cat used to run about 10-12%, The Ski-Doo runs around 18- 20%. It changes with belt width and length, also center to center on clutches. You are changing the shift ratio when you machine clutches. It seems that too many are putting way to much into a mod as this. I have tested this stuff way more than anybody here ever will, and used data accuasition and timers to test results, and can tell you that there is nothing to be gained by doing it if everything else is right. It takes away track HP by going into overdrive guys. Now you know why the Ski-Doos have no speed for the power they make, can you say Mach Z @ 170 HP? Yes, a good tuner will change that Mach and make that machine fly, but the average Joe just runs what the factory gave him. I don't ever machine my clutches. I also don't run roller covers in the driven. Mike Knapp#17

 

[ROCKRTX]

There is no magic number. Cat used to run about 10-12%, The Ski-Doo runs around 18- 20%. It changes with belt width and length, also center to center on clutches. You are changing the shift ratio when you machine clutches. It seems that too many are putting way to much into a mod as this. I have tested this stuff way more than anybody here ever will, and used data accuasition and timers to test results, and can tell you that there is nothing to be gained by doing it if everything else is right. It takes away track HP by going into overdrive guys. Now you know why the Ski-Doos have no speed for the power they make, can you say Mach Z @ 170 HP? Yes, a good tuner will change that Mach and make that machine fly, but the average Joe just runs what the factory gave him. I don't ever machine my clutches. I also don't run roller covers in the driven. Mike Knapp#17

So you are saying there is nothing to be gain on a primary clutch machine?
How do you explain the gain in MPH off a lot guys here that done this mod here on TY? Explain your theory.

 

[ROCKERDAN]

There is no magic number. Cat used to run about 10-12%, The Ski-Doo runs around 18- 20%. It changes with belt width and length, also center to center on clutches. You are changing the shift ratio when you machine clutches. It seems that too many are putting way to much into a mod as this. I have tested this stuff way more than anybody here ever will, and used data accuasition and timers to test results, and can tell you that there is nothing to be gained by doing it if everything else is right. It takes away track HP by going into overdrive guys. Now you know why the Ski-Doos have no speed for the power they make, can you say Mach Z @ 170 HP? Yes, a good tuner will change that Mach and make that machine fly, but the average Joe just runs what the factory gave him. I don't ever machine my clutches. I also don't run roller covers in the driven. Mike Knapp#17

So you are saying there is nothing to be gain on a primary clutch machine?
How do you explain the gain in MPH off a lot guys here that done this mod here on TY? Explain your theory.

I agree 100% with what Mike is saying..he knows!...

I think we need to not confuse though what we are all talking about here....Mike is totally correct in saying the OD LOSES efficiency...its very hard to be efficient in OD(larger wheel pulling smaller wheel past 1 to 1)

what we need to be clear on is this....machining of the YAMMIE clutches inparticular is ONLY needed for guys who gear down,and when i say NEEDED i mean ONLY if you plan on trying to run over 115 on radar....


KNOW THIS...machining youre clutch will NOT make your sled magically faster at any speeds....the ONLY TIME a machined clutch even would come into play,is IF you...

1-Ran out of GEARING
AND
2-had enough HP to make it to higher MPH then thoeretical gearing allows.


I hope guys understand that the ONLY reason you would NEED to machine a yammie clutch is IF you gear down(like us going to 23 top) and want to get your THEORETICAL ability to do same top speed back,as 24 allowed in theory....this DOES Not mean it will majically go 125mph,but it will be ALLOWED to go to those speeds in theory physically.

a good example would be this...23/38 gearing with UNCUT clutches and a HUGE TAILWIND...or a turbo..would probably run out of gear at 115-118mph or so....IF you had the HP to "RUN OUT OF GEAR" you would see rpms go UP and UP..like a stick shift car in 3rd gear going down hwy before you shift to 4th...rpms keep climbing.

So....dont spend a DIME on clutch machining unless you have geared down....OR have a TURBO with stock gears(most turbos run 25 top min)...cause you simply wont ever utilize that part of the primary with stock gears and stock HP.


Hope that helps guys thinking of machining..this is a MOD that VERY FEW PEOPLE will ever need or be able to utilyze.

Dan

 

[ROCKRTX]

Totally agree whit you machzed,the best ratio efficient is at 1:1 as the book of god and to take advantage of OD,got to gear it lower as i intend to do whit a 40 bottom gear.AS i read my post i realize that i din't give that information.
Thank for reply.

 

[KnappAttack]

You gain shift ratio, yes. As for a performance gain. That is correct, there is no performance gain unless the setup was not good before machining. They are not getting a MPH gain using this mod. It takes more HP or more efficiency to go faster. Using overdrive is less efficient, as it is in a less efficient ratio, however, because it allows the use of a shorter gear, it is that change that increases the performance. The correct way to test is, same day, same condition testing with data acquisition to see results. I have done this on the ice and asphalt till I was blue in the face, and can tell you, that there is no gain to be had using more overdrive. I don't know anyone here that has tested to that degree. My data acquisition cost more than a stock sled, and it is a huge tool that takes massive amounts of time off from the guesswork. This is how I explain it, lack of accurate same day testing, without consistent data to verify their findings. Most guys are gearing down to a 23-38 on their stock machines. They never achieve the additional overdrive anyway. A turbo machine with that gear in it will go 150 on the dreameter with stock belt and clutches. Still think you need overdrive? No, you need more power, better efficiency or better conditions to allow faster speeds. Don't waste your time or money. Mike Knapp#17

 

[KnappAttack]

Dan, Yes you are correct. I see you posted this after I went to relpy and got distracted here. Very nice explanation.

 

[yamadog1]

gearing

i have said this before it blows my mine to have such good info on this site thanks to people like mike and dan and many others, you guys are so advance i'm light years behind. but i know one thing i won't have my
clutch cut. thanks guys

 

[iasledder]

Overdrive has been proven for years to be inefficient. The only time it worked for me was on a 20* down hill slope about a mile long. I am concerned though that a full shift does not appear to occur on the Apex, although it is likely to be @1:1 at less than a full shift on the primary. I'm experimenting with the XS811 belt, which is slightly longer and wider. I have spacers behind the secondary helix as pictured above. No place at this time to run top end or hardly run at all. The belt seems to be a good fit, reduces side clearance on the primary for a very smooth shift, rather than leap frogging at engagement speed. Belt rides right on the cords on the secondary when closed. No belt squeal. Anxious to find out on back-to-back runs between the XS811 And XS805 if there is any noticeable change. I'm running the 23 top gear this year. With the sled stock for clutching (24T) my best run last year on GPS was 109 mph 122 mph on the "GO-FAST" gage. Don't run top end very often, usually when the 'Boys' show up on the lake, after about 2 runs you know who's accelerating best and who has best top end. Then it's trail-riding time.

 

[Sledroll]

Any further test results ?

I am interested to hear more about your testing with the XS811 belt

 

[nate007]

MORE POWER!!!!!!!