IF YOU HAVE HAD YOUR 850-pDRIVE PRIMARY MACHINED TRUE... A FEW QUESTIONS.

[mountainhorse]

You make a good point...

But to remove 0.025" in truing operation... Not sure if that going to cause too many issues though.

Maybe the 6OO race pDrive is the the one to try then... without the "D" shaped key and without the "wobble" ... So long as the taper and depth are the same between the two.

So the question would then be... is the the taper of the 2017 MXZ 600 RS sheave (PN 417224196, Fixed Flange Assembly) the same as the G4-850 sleeve except, of course, for the D shape.

There would be no need to index the sheave with the D-shape-key if the vibration system is negated by using this sheave... and the balance of the clutch is done well.

if it can be confirmed that the taper is the same... then the 600-RS sheave (or entire pDrive) is the way to go...


Things to ponder.
.



.

 

[revx827]

I'd be willing to buy a pdrive and have it machined true, just to see if it made cooler clutch temps, but I really don't want to ship to Canada and back.

Doodoctor should be able to machine it for you.

 

[powdermuncher]

In theory you would have to true out the belt side and the backside, that should get it close to balanced.

However a proper Balance job would be great just to make sure we are not messing stuff up instead of fixing.

 

[fredw]

If I had a G4 this would be my first step to see if this could work, maybe just use the entire race tra and forget all the crap with the pdrive.. Suppoisingly there is a turbo G4 that is running this way after ha eyeing problems tuning pdrive.. But I have never seen it!!

You make a good point...

But to remove 0.025" in truing operation... Not sure if that going to cause too many issues though.

Maybe the 6OO race pDrive is the the one to try then... without the "D" shaped key and without the "wobble" ... So long as the taper and depth are the same between the two.

So the question would then be... is the the taper of the 2017 MXZ 600 RS sheave (PN 417224196, Fixed Flange Assembly) the same as the G4-850 sleeve except, of course, for the D shape.

There would be no need to index the sheave with the D-shape-key if the vibration system is negated by using this sheave... and the balance of the clutch is done well.

if it can be confirmed that the taper is the same... then the 600-RS sheave (or entire pDrive) is the way to go...


Things to ponder.
.



.

 

[mountainhorse]

So the big question then is....Does the 850 pDrive have the same taper as the 600-RS?...
BESIDES, of course, the D-shape 'key'.



.

 

[revx827]

So the big question then is....Does the 850 pDrive have the same taper as the 600-RS?...
BESIDES, of course, the D-shape 'key'.



.

No. Taper is different.

 

[fredw]

So can it just be machined out to fit, are is it to big to start with??

Waiting on a reply from the guy that suppoisingly has done it.. Nothing yet

 

[mountainhorse]

No. Taper is different.

If you have a moment ... What are the specs/dimensions on both tapers ?

 

[mountainhorse]

I've been contacted by an 850 owner that is machining his pDrive from his G4-850 'true', this week ... he has also ordered a RazorBack temp sensor... I hope we hear some results back before the end of the season. He claims his sled is a belt eater and wants to have more confidence in the sled that he is otherwise thrilled with. I think he will have a 'cut' pDrive and the Stock for direct comparison.

In light of the press release from BRP today...I feel that mfg inconsistencies of the anti-vibe system, not the actual design or validity of the system, in SOME sleds are pushing the belt temps, over the edge... again... in Some units.

I'm interested in the results.

The CVT on the 850's run hot in general on all of the sleds.... enough that a cooling fan and ducting are being included in the 2018 models to deal with the symptom of high CVT temps. The ACTUAL cause of the heat is what I am most interested in.




.

 

[nickbeann]

I've been contacted by an 850 owner that is machining his pDrive from his G4-850 'true', this week ... he has also ordered a RazorBack temp sensor... I hope we hear some results back before the end of the season. He claims his sled is a belt eater and wants to have more confidence in the sled that he is otherwise thrilled with. I think he will have a 'cut' pDrive and the Stock for direct comparison.

In light of the press release from BRP today...I feel that mfg inconsistencies of the anti-vibe system, not the actual design or validity of the system, in SOME sleds are pushing the belt temps, over the edge... again... in Some units.

I'm interested in the results.

The CVT on the 850's run hot in general on all of the sleds.... enough that a cooling fan and ducting are being included in the 2018 models to deal with the symptom of high CVT temps. The ACTUAL cause of the heat is what I am most interested in.




.

Just wondering if you had any updates on this ?? Thanks

 

[mountainhorse]

Not yet.


/

 

[revx827]

If you have a moment ... What are the specs/dimensions on both tapers ?

I don't know specs. I know a couple guys that are running tra on their 850s.
Haven't been able to get specs out of them.
They are claiming better performance.
No mention of any added vibration.

Please update if you get any feedback on machined pdrive

 

[graham_r]

I machined mine down to be true. The sliding half came out beautifully. The fixed have I had to remove to much material to make it true. After machining it true it was no longer safe to run at 8000 rpm


Sent from my iPhone using Tapatalk

 

[mtncat]

What company is cutting the tapper on the TRA's so they fit the 850

 

[1Mike900]

If it was me, I would try to make a P85 Polaris clutch work? With the added fins of the new clutch I am sure it will be heavier? Maybe to counter balance the longer crank and not have to machine cockeyed? This is why I hate a long stroke above 3.00" in a twin with a thin alum. block, causes all sorts of bearing problems and fatigue! At least with the lighter P85 you will see if the stroke is the problem if vibration goes out of control? But then again it may respond in the lower revs like nobody's business, but may numb your feet and hands in the upper? I am sure some of the guy's that still run the 900 Polaris with a P85 clutch are still surviving to this day! Mike

 

[sledhead_24_7]

My 900 RMK broke the crank stub off with the stock clutch still holding on, first and only season I ran that pile.

 

[caper11]

I don't know specs. I know a couple guys that are running tra on their 850s.

Haven't been able to get specs out of them.

They are claiming better performance.

No mention of any added vibration.



Please update if you get any feedback on machined pdrive

I find it interesting that guys are ditching the Pdrive for the tra.

Did they try taking the runout out of the fixed sheave??? If it was me and I still had access to a lathe I wouldnt of trued it up. I would of taken maybe .010" out and tried it first.


Sent from my iPad using Tapatalk

 

[madmax]

I took my infrared temp gun with me last time I rode and was surprised how much hotter the primary runs than the secondary clutch on my 850. Mines not a belt eater, one belt in 700+ boosted miles. Primary runs consistently 50-120 degrees hotter than the secondary. Hottest primary temp I saw after 600 vert foot climb through 2-3feet pow, was 280 degrees primary and 160 secondary.

 

[BIG JOHN]

OK

I need to visit here more often...

taper is the same...
CANT put any other clutch on a 850 UNLESS you cut the "key" off the crank...
SHR tip adj weights solve most of the tuning issues (doo is off several grams)...
blu/blu QRS spring has been wrong since day one...
proper calibration for elevation is critical (just like any sled)...
SHR motor mount shim helps center/center...
old skool shim kit helps alignment...
proper belt deflection is important (doo video is WRONG)...
venting helps (not sure why they are sealed so tightly)...
cutting the wobble out is the least of your concerns (I dont agree with said wobble and will cut a clutch to see but ran outa winter)...

NO different than the 2008 XP (poor alignment, wrong belt, poor calibration etc)...

DEALERS failed miserably too, sending sleds out with little to NO PDI or set up for riders elevation...

I have been posting info, tech tips, clutching all winter-BJ

 

[dave@trygstadmotorsports]

G4 850

Big bores tend to run smoother because the builder generally takes the time to fine tune the balancing, buuut, I've ridden a 920 cat that had so much vibration that my hands and feet hurt afterwards. I can't say if the skidoo big bores create more vibration or not.

Our new TMS 927 runs much smoother than the stock bore 850 at all rpm ranges with a lot of development work to make this happen as with the 872 build also is much smoother running.

Machining the 850 P-drive and installing it on the 850 will vibrate way more than an untouched P-drive as we have tested that last season several times while developing our line of products for the G4-850 and the TMS 927. And yes we balance all of our drive clutches in house on all of our custom builds.

Anyone looking for a 600RS P-Drive let me know as we have a few for sale with very low use.. Work well on 800-872 Etec and R but will not sell for 850 or 927 use.

Dave Trygstad
Trygstad Motorsports
Your Leader in Rotax Performance and Development!