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OVERDRIVE P85 PRIMARY

Dr.Notadoo

Dr.Notadoo

Well-Known Member
Messages
805
Age
54
Location
Richmondville
FOR ALL WHO WERE WONDERING WHEN YOU HEAR TALK OF OVERDRIVING UR PRIMARY CLUTCH,HERE IS A PIC ON RIGHT OF THE STOCK CLUTCH OFF MY 16 SKS,FITTED WITH A NEW GATES,NOTE THE HEIGHT.. THE OTHER PIC,ON LEFT IS OFF MY SWITCHBACK WHICH HAS BEEN MACHINED FOR OVERDRIVE,NOTE THE DIFFERENCE IN BELT HEIGHT..

PICTURES ARE COMING HAVE TO UPLOAD FROM MY IPHONE..
 
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Been doing this for years as it gives you that 15-18% over- drive which = more mph

As it sits, the stock primary gives you a 1:1 as doc is showing

You want more mph? Get your primary machined for over-drive .

Machining is basically moving the fixed and moveable sheaves closer together . 0.0020"-0.0040" makes a big difference


Back in the day I've machined my primaries to much and at wot it would flip the belt over, now that's 18%+ over-drive , lol Rofl
 
Does machining for OD cause a loss in Bottom and midrange performance? I have never done it so its a legitimate question lol
 
No the other ratios are not affected, your just pushing the belt further out of the primary. This way you can keep a lower chaincase ratio and still mph.
 
Doc, the Gates belt has a slightly higher cog than oem. Before and after with the same belt woiuld show better imo.
 
So i the assumption if the secondary can/will still fully shift yet then with a closer C to C ratio Doc?
 
OutCast said:
Does machining for OD cause a loss in Bottom and midrange performance? I have never done it so its a legitimate question lol
Click to expand...
As doc said

What your doing is moving your clutch sheaves closer together to force the belt higher in the primary by machining , but still have the same belt to sheave clearance. It just puts the belt further out in the primary which = more mph and over-drive

It's putting/forcing the belt about an 1/8" up and over when at wot

So when you now look at your gearing chart for a 1.73 ratio under 8250 rpm it says 103.5 mph Now that's at a 1:1 ratio. Since you've machined your primary for over-drive , you need to add 10%+(nice easy round #) to 103.5 mph which is now 113.85 mph at 8250 rpm now . This is exactly how I pick my fast trail ratios using this method
 
Got it. As long as you have the HP and all the other factors (secondary setup, track speed and so on). Doc has that new tool to test all this out I guess.Div20
 
That's correct doc.

When a secondary is fully opened the measurement at the bottom is 1.150" roughly. This just happens to be the measurement of the belt at bottom . So yes, there's room in the secondary

So if you force the belt up further in the primary guys, it forces it down in the secondary too. Get the most out of the cvt system Div20
 
When send the clutch out for machining, are we to ask for 0.0020"-0.0040" to be shaved off and that should do it? Is it always 0.0020"-0.0040" or is there a specific way to measure what is required?
 
Rob in Ottawa said:
When send the clutch out for machining, are we to ask for 0.0020"-0.0040" to be shaved off and that should do it? Is it always 0.0020"-0.0040" or is there a specific way to measure what is required?
Click to expand...
I just used those figures as what it usually moves clutch face sheaves in . Others may figure it different , so don't ask for that
You ask for overdrive mostly

Doc knows this too
 
proS800 said:
How much does it usually cost to get it machined and balanced?
Click to expand...

Tom,

Dan @ Indy Specialty charged me $150 for the complete machining/balancing procedure on my '16. He even included a glide washer for in between the spring and spider to prevent spring binding. I plan on utilizing him again for my '17. I'm in IL and it seemed like a no brainer to have a more local guy in MN do the work. Saves me money on shipping costs.

My clutches compared to my buddy's bone stock '16 SWB Pro S 800 ran smoother, cooler and definitely yielded more mph. $150 well spent in my opinion.

Brock and Heath may use a different vendor that does just as good a job as Dan, like CVTech in Quebec for example.
 
P85 clutches will net you 5-10% overdrive from Poo. As you approach 1:1 and especially in overdrive, your cvt gets very inefficient. Most 150hp trail sleds on the trail will not pull very far into overdrive, even with perfect clutching.


Sent from my iPhone using Tapatalk
 
Ya i just talked to indy dan. $200 to service, machine, and balance clutch, $150 if clutch is new. Gonna drop it off friday sinces hes close by where i live
 
On a 1.73 gear ratio at 8250 rpm I have gotten 114 mph on radar and timing system on lake with a little snow covering.
So that's about a 10% overdrive.

I choose my ratios with the 10% overdrive in mind with my clutches machined. 10% is a nice round easy number.
I like to choose ratios for 121"-137" skids with 1 1/4"-1 1/2" lugs in the 1.7 ratios for fast trail.
 
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