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

mountainhorse · Mar 22, 2017

With all of the talk about the BRP/ROTAX factory built-in pDrive 'wobble' (aka 'offset')...

There are surely some of these pDrives out there that have been machined true, with no factory wobble/offset.... what kind of vibration are you feeling?

It would also be nice to have some before and after machining readings of temperature, IN USE, especially since this year brings us a new affordable monitoring system perfect for just such an occasion. :face-icon-small-win

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salmonbum · Mar 22, 2017

Most gals will pay extra for a sled to vibrate. Doo just needs to market the sleds differently.

When I am pulling a big climb, the last thing on my mind is "man the sled is vibrating". But I do wonder if the belt will grenade.

mountainhorse · Mar 22, 2017

Aside from the misogyny... Ride a sled that vibrates badly and you'll feel it and it will make a difference.

An out of balance 2005 900 RMK would make your feet numb!
Same stroke and similar light rotating assy on the POO 900 if the primary is cut on the pDrive G4-850 (with the pDrive being heavier than the P85).

It's the COMBINATION of the long stroke and trying to keep the rotating mass as light as possible that causes the vibes in these sleds.

You'll note that the 800 ETEC has a full circle crank, which for the stroke of that engine... has enough mass to damp vibes and no "offset" in the primary to keep vibes at an acceptable level.

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mountainhorse · Mar 23, 2017

Back on topic.

This is not a thread about the corrective vibration control system used by BRP on the G4/850's... That is covered nicely in another thread.

This thread is about those with clutches that have been machined true (A machine shop has removed the "BRP Factory wobble") and HOW Much is vibration increased, if any, by negating the system and cutting the clutches so they turn with ZERO run-out?

I'm sure there are some that have tried this machine operation on their sheaves of their G4-850 .

From another thread:

This innovative tech may be great once dialed in... but for the meantime.....

What does a standby/experimental fixed sheave cost?
What does the machining cost?
How much do a few belts cost?
How much 'fun-time' is burned up with a sled that goes down in the field and used up spare belts?
What wear and tear does a belt, that has violently blown, cause on crank/clutch/sled?
What does a sled cost that hit a tree after loosing control from no fwd momentum when you loose a belt? (Warranty does not cover this )

So.... with this in mind... How much is the 850-G4 Actually vibrating after the sheave has been cut... and is it acceptable in terms of cost and vibration felt?

Most importantly... are the belts generating less heat after the cut has been done and the clutch runs true to axis. ??

In the end... the short term solution for the 2017 850-G4 sleds that ARE belt eaters for specific owners... MAY be to have the clutch machined true... and live with some vibration :face-icon-small-con

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d1100t · Mar 23, 2017

Machine shop

mountainhorse said:
Back on topic.

This is not a thread about the corrective vibration control system used by BRP on the G4/850's... That is covered nicely in another thread.

This thread is about those with clutches that have been machined true (A machine shop has removed the "BRP Factory wobble") and HOW Much is vibration increased, if any, by negating the system and cutting the clutches so they turn with ZERO run-out?

I'm sure there are some that have tried this machine operation on their sheaves of their G4-850 .

If your refering to the shop in Alberta I don't think they've tried it yet.
He said he was to busy.
I'd be surprised if there's a lot more vibration after being machined flat.
In my mind that high of a runout would cause belt heat.
Do the big bores have a vibration problem?

rulonjj · Mar 23, 2017

d1100t said:
If your refering to the shop in Alberta I don't think they've tried it yet.
He said he was to busy.
I'd be surprised if there's a lot more vibration after being machined flat.
In my mind that high of a runout would cause belt heat.
Do the big bores have a vibration problem?

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.

d1100t · Mar 23, 2017

rulonjj said:
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.

A guy I ride with use to have a XM with a trigstad 872. He never complained about his vibrating.
That same guy is going through lots of belts on his 850. He's more than a little frustrated.

Ski-doo#1 · Mar 23, 2017

I thought we all already knew that a big bore wasn't comparable to the 850. The 850 is a big stroke not a big bore. People get worked up about the 850 supposed to be smoking everyone cause it makes more power. It does but if it was a big bore 850 it would put out 180HP. Well it isn't, it is a big stroke.

The big stroke is what causes all the vibration, the extra vibration they claim. This has already slightly been discussed in other forums. Like the Poo 900 which had a longer stroke as well vibrated to beat hell and couldn't hold belts. Well probably because of too much vibration. Ski-doo claims this design is to counteract all the added vibration of a longer stroke something Poo didn't manage on the 900. Now all my info on Poo here is only what I've read from guys who seem knowledgeable about them.

Regardless, people need to stop comparing big bores to the 850 "big stroke"

And to keep this on topic MountainHorse, it seems as if nobody has taken their clutch in to get machined except for one guy who maybe hasn't visited the forum since he posted about it. I thought he did say that it was still blowing belts after being machined but I'm not 100% sure.

Good job to Ski-doo for catching it in time before people got too carried away. They even had to sacrifice the publicity of their patent to do it, wow.

d1100t · Mar 23, 2017

Big bore

Ski-doo#1 said:
I thought we all already knew that a big bore wasn't comparable to the 850. The 850 is a big stroke not a big bore. People get worked up about the 850 supposed to be smoking everyone cause it makes more power. It does but if it was a big bore 850 it would put out 180HP. Well it isn't, it is a big stroke.

The big stroke is what causes all the vibration, the extra vibration they claim. This has already slightly been discussed in other forums. Like the Poo 900 which had a longer stroke as well vibrated to beat hell and couldn't hold belts. Well probably because of too much vibration. Ski-doo claims this design is to counteract all the added vibration of a longer stroke something Poo didn't manage on the 900. Now all my info on Poo here is only what I've read from guys who seem knowledgeable about them.

Regardless, people need to stop comparing big bores to the 850 "big stroke"

And to keep this on topic MountainHorse, it seems as if nobody has taken their clutch in to get machined except for one guy who maybe hasn't visited the forum since he posted about it. I thought he did say that it was still blowing belts after being machined but I'm not 100% sure.

Good job to Ski-doo for catching it in time before people got too carried away. They even had to sacrifice the publicity of their patent to do it, wow.

Are you saying that BRP should have kept the 800 stroke and used a bigger piston?

I hope you get that job at BRP your trying to get.

Ski-doo#1 · Mar 23, 2017

d1100t said:
Are you saying that BRP should have kept the 800 stroke and used a bigger piston?

I hope you get that job at BRP your trying to get.

No, I'm not saying that.

I also don't know if they should've done that. I think they did what they did for a reason, and it works for the most part. I thought a big deal right away was that the added stroke actually created an increase in torque vs an increase in power. Pretty sure their purpose was to achieve more torque, not more power. They clearly were well aware that the added stroke was going to add vibration hence the patent-pending clutch design.

Yeah I hope I get the job someday too, unsure if you're being sarcastic but I'm obviously serious haha, thanks no matter.

mountainhorse · Mar 23, 2017

I moved some of the other posts to keep this one on topic.

I like to keep this Thread On Topic and get some feeback on the results IF someone machines the primary true....

Not the merrits or demerits of the Doo Vibe-management System, the merits/demerits of the proposed machine work or a comparison to other sleds or big bores...

Any help you guys can lend in this is much appreciated.

I think that some G4-850 owners will try this cut and then we'll be able to get some good intel on this.

It is quite possible that vibration will not be an issue.

I'm very well versed in the Polaris 866cc (aka 900)... similar rotating mass and same stroke with a hair larger bore.
They would vibrate... but it was definitely acceptable to all but the most sensitive...I've been on bikes and other sleds that vibed more.

The cost to find out would be a pDrive fixed sheave and the machine work related.

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powdermuncher · Mar 23, 2017

Maybe the redline guys can chime in.

If this works I will consider having mine done this summer.

I like to do clutching once get it right and ride the sled that

way till I sell it.

Nikm17 · Mar 23, 2017

I think it's going to be unlikely that someone will machine their clutch now, since doo has said that they will not warranty clutches that have been machined

powdermuncher · Mar 23, 2017

If it works there will not be any need for warranty.

If I brake the bulkhead and they see my gripe and rip brackets -- most likely no warranty either.

No warranty does not worry me if stuff works perfect.

rulonjj · Mar 23, 2017

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.

mountainhorse · Mar 27, 2017

Someone will machine their pDrive

lots of places in the US that can do this too I'm sure.

I'm sure not too long before we see one or a few on here that have machined their pDrive on their G4-850 in short order... and let us know the results.

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Hardass · Mar 27, 2017

powdermuncher said:
Maybe the redline guys can chime in.

If this works I will consider having mine done this summer.

I like to do clutching once get it right and ride the sled that

way till I sell it.

Yes i hope the redline guys do chime in im sure they machined some since they were advertising it on here. Im pretty sure thats what caused BRP to come out of the closet.

mountainhorse · Mar 27, 2017

I've messaged them on FB.... They say they have not yet machined one.

If I had a "belt eater" that was ruining my season.... I'd invest in this to see if it alleviates my issues.

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Hardass · Mar 28, 2017

I wonder if BRP them selves have machined one down to see what the difference might be.

geo · Mar 28, 2017

mountainhorse said:
I've messaged them on FB.... They say they have not yet machined one.

If I had a "belt eater" that was ruining my season.... I'd invest in this to see if it alleviates my issues.

.

Don't know if I would try it MH. It appears that Doo offset the whole sheave not just machined an offset.
That's a lot of sheave thickness to remove in one spot, leaving a lot of holes to be drilled to balance in another spot, and a thin on one side sheave that may end up, too thin?? And,,, I heard the Doo sheave is curved to boot.

Definitely an "experiment".

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

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