First ride with P-85'd 800R

[winter brew]

Did 35 miles and tried a few settups today. MUCH more consistent then the TRA....8200 on the flats, 8200 on a climb, better backshift even using a steeper helix in the stock Doo roller. Not completely dialed in yet, but looking promising. Will play more with gearing and trying in different snow conditions.
I was surprised that it still hits as hard as the TRA off the bottom, even with taller gearing. Seemed to pull good in the mid and I havn't had a chance to pull past about 60mph yet. Will play with it more tomorrow.
It does drop 6 lbs off the sled too!!
I liked the TRA when it was "right" but until they figure out how to keep rollers and bushings in them I will run this.

 

[lucky13]

keep us up on this one, id like to know more, my tra days are numberd

 

[summitdude]

when was the tra ever right?....which year?

 

[skidoome]

I had a p85 on my 583 summit a few years back and tried it. It wouldn't keep up with a dialed tra on the bottom but after 55-60 it would pull better. I just couldn't justify loosing the bottom end for more top end with a mt. sled. I was told from indy dan there were things you could do to the p85 to make it better on the bottom but didn't want to invest in the time or money.

Good luck.
jon

 

[nor-cal]

what weights did you decide to use? I'm going to try SLP's 68 gram MTX I just don't know where to start. What color primary spring did you start with?

 

[live2beel]

Where can you get the P-85's with the taper already done? How much? Do you get them balanced? Might have to give one a try.

 

[Bull]

in the spirit of full disclosure.....i ride a poo. was reading an earlier post that talked about a replacement tra cost 2200?? can that be accurate? i had to replace a p-85 a few years back and it ran me 425. have a few buds with doo's that have really struggled with primary problems. curious to see how things work out with the p-85. i always balance mine, cheap insurance. think it is one thing that helps ward off crank problems. are you guys buying the clutch then having it tapered?? where?

 

[Seeder]

I have a brand new P-85 machined to fit the Doo crank for $400 plus shipping. It is the HD P-85 with the wide rollers and large cover bushing. PM me if interested, no weights or spring. You can use your stock bolt and just need to buy the polaris washer.



-Seeder

 

[sanderson]

Winter Brew,
What elevation are you running ?Also what weights and spring ? I am looking at putting one on a XP and normally ride 3000 to 6000.

Thanks

 

[winter brew]

I also ride 3-6000ft mostly. So far I am liking a 140/320, 10-64's. Stock Doo roller with 44/40 and purple. 21/45 gears and 159 track ('07 Summit).
This will sound wierd but it hits harder off the line than the TRA. Pulls hard and smooth past 80mph then I ran out of road.
I do have an issue that I need to figure out. I broke a primary spring (not a good sign!!). I checked runout of crank and of the clutch and all is good. The taper is centered and tight so I am going to have the clutch spin balanced as I don't know for SURE that it has ever been properly balanced. Hopefully that is the issue as it takes some wicked harmonics to break a spring in 1 ride.
Other than that this puts a TRA to shame in alot of ways. Did some 1/8 mile races with another XRS with head, y-pipe (mine is stock) and 2 Polaris 600 turbo's and was able to beat all by a couple sled lengths.
I hope to get this spring issue solved !!!

 

[Seeder]

Doesn't the tra have a plastic sleeve that covers part of the primary spring to help with harmoncis? If so can this sleeve be put on the P-85 to help with the issue? Cannot remember fore sure but just kind of thinking out loud.

-Seeder

 

[sanderson]

Winter Brew,
How was the clutch temps ? I bet they were alot cooler. Were you able to use the stock doo clutch bolt ? Also did you have to have a puller made up to get it off ?

Thanks

 

[winter brew]

Winter Brew,
How was the clutch temps ? I bet they were alot cooler. Were you able to use the stock doo clutch bolt ? Also did you have to have a puller made up to get it off ?

Thanks

Actually the temps are just as hot as with the TRA.... I am hoping to find this particular clutch way out of balance as that would explain the broken spring and probably increase clutch temps as well. Seems odd as this is suposedly a brand new clutch. Could be that it is new parts and was never balanced as a complete assembly. I used a cut down polaris puller, stock Doo bolt and the Polaris centering washer and lock washer. Have to use the Polaris washers as they fit inside the end of the cover plate.

 

[Teth-Air]

Did 35 miles and tried a few settups today. MUCH more consistent then the TRA....8200 on the flats, 8200 on a climb, better backshift even using a steeper helix in the stock Doo roller. Not completely dialed in yet, but looking promising. Will play more with gearing and trying in different snow conditions.
I was surprised that it still hits as hard as the TRA off the bottom, even with taller gearing. Seemed to pull good in the mid and I havn't had a chance to pull past about 60mph yet. Will play with it more tomorrow.
It does drop 6 lbs off the sled too!!
I liked the TRA when it was "right" but until they figure out how to keep rollers and bushings in them I will run this.

With that loss of 6 pounds from the clutch, aren't you worried about taking out the crank? These 800R's will shake themselves apart if you don't dampen them.

 

[winter brew]

With that loss of 6 pounds from the clutch, aren't you worried about taking out the crank? These 800R's will shake themselves apart if you don't dampen them.

I have given that some thought and yes it does concern me. But then I think about Polaris using the same clutch on every engine from 340-900cc, 2-stroke and 4-stroke and their cranks and bottom end are not built any dofferently than the 800R...most not as strong. There are also alot of lightened TRA's being used for many years with no crank related issues that I know of. I also feel the belt itself does a tremendous amount of vibration damping when under a load. As long as the clutch is properly balanced there shouldn't be a problem. I "HOPE" my line of thinking is correct.

 

[oregondoo]

XP Suspension Questions--Help

Did 35 miles and tried a few settups today. MUCH more consistent then the TRA....8200 on the flats, 8200 on a climb, better backshift even using a steeper helix in the stock Doo roller. Not completely dialed in yet, but looking promising. Will play more with gearing and trying in different snow conditions.
I was surprised that it still hits as hard as the TRA off the bottom, even with taller gearing. Seemed to pull good in the mid and I havn't had a chance to pull past about 60mph yet. Will play with it more tomorrow.
It does drop 6 lbs off the sled too!!
I liked the TRA when it was "right" but until they figure out how to keep rollers and bushings in them I will run this.

Appreciate all the information, follow your threads on regular basis. Not happy with the sus on my XP-154. Can't seem to get it dialed in. I have owned 4 other Doo machines, all 800's 2 reg w/ 144 and 2 X w/151. No problems. This one is a challenge. I have tried about everything, adj front shocks 1-2.5 back to 1, adj the strap up one position, 2 turns ( clockwise ) on the middle shock, #3 on the rear. Machine continues to bottom out on rough trails, doesn't come close to handling like my 05. I'am thinking about replacing the shocks? Any suggestions would be appreciated? I ride at 3000'-7500', weigh 200 lbs, boondock, hills and trail. clicker set at #2. Thanks Oregondoo

 

[PTE800]

I have given that some thought and yes it does concern me. But then I think about Polaris using the same clutch on every engine from 340-900cc, 2-stroke and 4-stroke and their cranks and bottom end are not built any dofferently than the 800R...most not as strong. There are also alot of lightened TRA's being used for many years with no crank related issues that I know of. I also feel the belt itself does a tremendous amount of vibration damping when under a load. As long as the clutch is properly balanced there shouldn't be a problem. I "HOPE" my line of thinking is correct.

Winter brew: I have to agree with you on the fact that the P85 is used on so many different Polaris models through the years with no problem. I also have been running a P85 on my mod sled (2001 800) and have had no issues for 500 miles so far. What I will say is how extremely important that proper machining tactics are used when cutting the taper. I'm a machnist by trade and personally cut my own taper so I know how crucial and difficult it is to get no run out when you're finished. I feel that you need to run a tenths indicator on the shaft surface where the belt runs while machining the taper so you can be sure that there is no deflection while cutting the taper. I have a pretty good idea that a lot of guys are'nt doing this because all winter long you hear that they won't work or they shake etc while others have no problem at all. Some are done right while others are not. I believe that when installed on the motor if the clutch is not within .002 -.003 total indicated run out on the end there could be a problem. I was able to get mine .001 TIR so that may be a contributing factor on mine so far. In all fair-ness though, I will add that I did also machine a billet end cover with a custom dampener on my clutch but I'm not so sure that it was needed as I know of a couple others that don't have it and are experiencing no problems at all with more miles than mine. One other thing to note is that all the clutch surfaces should be re-turned while cutting the taper. That way everthing is relative to the centerline of the clutch. It also makes balancing a lot easier...
Just my .02 worth.........

 

[sledhead-also]

I too hope your line of thinking is correct. The TRA has had a plastic dampner on the outside face for years. Polaris has had crankshaft problems on the PTO end for years also, especially in the Liberty 800. One of the fixes for Polaris cranks is the addition of a 2nd PTO crank bearing:

http://www.snowtechmagazine.com/articles/2004/allsprtcrank.php

I have seen harmonics created at certain RPMs do a lot of weird stuff over the years. Everything from clutches that self destruct to carburetors that froth and foam the fuel in the float bowls creating unbelieveable lean conditions. This is one of the main reasons we have rubber carb boot mounts on the Mikuni carbs to lessen engine vibration transfer to the carburetor.

Snowmobile manufacturers have found these issues the hard way, through field testing and sometimes through repeated customer failures. They have done various things to rectify these problems. Doo's fix for the Rotax engines is the TRA dampner.

Years ago I had a Yamaha Exciter that had lots of high RPM issues after modding the engine. PSI built a larger and heavier water pump belt sheave half (mag side) to offset the crankshaft harmonics on the clutch side so they could make their high RPM 570s and 650 big bores work.

I hope your deal works out for you. Anytime you do mod work, it is a crap shoot as to what reaction your sled will have to the modification.

s-a

 

[blksumit]

winter brew,

(not a good sign!!).

Definitely not the way to start. I have been considering a P-85, but am worried about the crank shaft. Sure hope you get it straightened out. Keep us posted and good luck!

BTW, just out of curiosity, have you checked the runout on your crank?

Dave

 

[winter brew]

Thanks for the feedback. I have checked the crank and it's .002" at the center of the taper. I also checked the center shaft of the clutch while on the crank and got .0055". I would say this is pretty good. I will keep you posted on how it does after rebalancing.