550 fan Jetting and burn-down issues....

[Tom400CFI]

My girl friends 550 burn down on the mag side with the iron sleeves. What clearance should I be runing? Should I go with wisco over stock poo? Where does this oil vent tube hook up to and where does it go? Anyone have a pic?

I can take pic for you. I don't know what to recommend and feel good about it (yet). But .007" with Wisecos seems to be working for us so far.

The oil vent tube attaches to the top of the oil pump, in the same orfice as the bleeder screw. Then you drill a hole in the reservoir and plug the hose in to the reservoir.

 

[Tom400CFI]

Anyone have an idea about how much oil the pump should be pumping? When I grab the arm with a hook and pull it all the way the oil line I drained pumps up quickly but in a pulsing action. It pulses up the tube to the carb. about 1/2" to 1" at a time. My question really is, if I disconnect an oil line to the carb. how much oil at idle or at an rpm below clutch engagement should com out? My manual refers to pulling and checking banjo valves on some sleds but I don't see them on the 550 / vm34 carbs.

There is ratio of oil reservoir use vs. gas used. I can't remember what it is though. Your description sounds like it's working right though. It does pulse.

 

[cjgauthier]

Another oil pump question

My Polaris two up/touring manual shows a picture of the pump with two index lines on it, one is just off the stop when lined up with the mark on the pump body and one wide open. My pump only has a mark on the wide open/limit side. Should I sync. the carbs and oil pump so they are both wide open at the same time?
I have put the machine back together and it's running pretty well, maybe a little peppier than before but it's making a fair amount of noise seemingly from the wrist pin bearings. Other than getting two new rods, are there any other fixes for this? I used Polaris bearings and Kimpex Micron piston kits from ALS Snommobile. Did I screw up by mixing parts? It makes a clicking noise when I rock the crank.

 

[richardsb014]

Tom,
After reading your posts, I stopped the boring of my cylinders until I could get a better feel on what I can do to prevent this from happening again. I contacted a reputable mechanic, and his research uncovered a “Polaris Snow Team Tips” bulletin from Sep 04. This tip modified the piston to cylinder clearance requirements for the 04 and 05 550 fan motors. I believe the old requirement were .0035” to .0049”. The tip directed the new clearance to be .0045” to .0053” clearance. Still a far cry from the .007” you seem to have found best, but much more gap then what they earlier called for. He’s researching further to see if there is anything else he can uncover that may have been released by Polaris.

How much time do you now have on the Wiseco engine with the .0007” clearance? Any noticeable performance differences between it and any other good running 550 fan you have?

Man, I hate this quandary. You seem to have done all the quality homework to justify the bore clearance. But with any “normal” two cycle motor, I would never bore to .007” for fear of the piston skirts slapping, etc.

Bart

 

[Tom400CFI]

It makes a clicking noise when I rock the crank.

I'd be concerned about the crank (bearings) itself. If it was still apart, you could try to push/pull on the rods to see if they have play in the bearings, and spin the crank and listen carefully for noise...

We've never used Kimpex pistons here. We used to at the ski resort I USED to work at over 12 years ago, and Kimpex pistons (back then) for Doo 503's were no good for our useage. That's all I know about Kimpex pistons.

 

[Tom400CFI]

...This tip modified the piston to cylinder clearance requirements. I believe the old requirement were .0035” to .0049”. The tip directed the new clearance to be .0045” to .0053” clearance. Still a far cry from the .007” you seem to have found best

Keep in mind, his spec is for a CAST Polaris piston, which should not expand as much as my Wiseco FORGINGS with heat, so the high .04x" clearances would jibe somewhat with our larger clearances and our FORGED pistons. As I've said, we've tried SPI brand CAST pistons and have had little luck. It seems that by the time you get large enough to prevent sticking (~.005" for us) then the piston is rattling too much and the skirt breaks off. The Wisecos are very tough and can manage the larger clearances well.

How much time do you now have on the Wiseco engine with the .0007” clearance? Any noticeable performance differences between it and any other good running 550 fan you have?

We have a few .007"+/Wiseco motors out on the hill now and they're all running great. About the same as any of the good running 550's have ever run. They'll go about 40 MPH up a ~25% grade at 7500' elevation. I think that's about as much "excitement" as you'll ever see from one... The first .007 motor which I put together myself, has 140 mile on it now -which is really hardly anything still.

Man, I hate this quandary. You seem to have done all the quality homework to justify the bore clearance. But with any “normal” two cycle motor, I would never bore to .007” for fear of the piston skirts slapping, etc.

I hear ya. We felt the same way, when we ventured above .005" for the first time...it just seems so "out there". But 5 of us fairly veteran mechanics discussed it at length and we all agreed that it seemed worth trying. Now it seems even more that it was...

 

[ditchrider]

Tom, I am certainly not disputing your problems or findings, but I have to ask why are you having the volume of troubles that you are in such a short amount of time (15 minutes in some cases) vs 400-800 miles depending on iron or nikasil bore from a factory prepped engine. If I've read right, they lasted the 400-800 miles as purchased vs a few minutes with the exception being your Wiseco motors with big clearances...

On a side note, I'm seeing tons of blow by on pistons that have very little time on them. That points to poor ring seal. In an ideal situation you will not see any signs of carbon or brown deposits past the top of the piston, except for small traces around the transfer ports.

 

[d&mraceengines]

from the picks the scored pistons look like lack of oil to me i would look in to the oil pump air in lines issue i sure am curiouis what eventually fixes this problem for you

 

[theultrarider]

Tom, I am certainly not disputing your problems or findings, but I have to ask why are you having the volume of troubles that you are in such a short amount of time (15 minutes in some cases) vs 400-800 miles depending on iron or nikasil bore from a factory prepped engine. If I've read right, they lasted the 400-800 miles as purchased vs a few minutes with the exception being your Wiseco motors with big clearances...

On a side note, I'm seeing tons of blow by on pistons that have very little time on them. That points to poor ring seal. In an ideal situation you will not see any signs of carbon or brown deposits past the top of the piston, except for small traces around the transfer ports.

Tom's sleds are being used as workhorses at a ski resort. It is low speed High torque situations. High underhood heat. Alot like the Alaska bush sleds always pulling huge loads at slow speeds. This creates problems that most people will never see in their sleds.

 

[d&mraceengines]

tom im sorry about the lack of oil post as i had only looked at your frist pics didnt relize you had so many pages of posts sounds like and looks like the heat is the problem so good luck and keep tryin tom

 

[ditchrider]

Tom's sleds are being used as workhorses at a ski resort. It is low speed High torque situations. High underhood heat. Alot like the Alaska bush sleds always pulling huge loads at slow speeds. This creates problems that most people will never see in their sleds.

That I understand but I assume that he used them for the same purposes when they were new??? That's what I'm getting at. It just seems odd that they lasted 400-800 miles doing resort duty at first and now they won't last but just a few minutes?

Again, not disputing at all, just pointing out the weird...

 

[Tom400CFI]

That I understand but I assume that he used them for the same purposes when they were new??? That's what I'm getting at. It just seems odd that they lasted 400-800 miles doing resort duty at first and now they won't last but just a few minutes?

Yes, they've all seen the same duty from roughly the same "rider" since new.

Our problems with them lasting SUCH a short time recently, is a result of:
*Jetting (our sleds needed more fuel this year -for reasons unknown to us)
*Clearances (.003 is way too tight)
*Quality of parts (we now feel that the SPI piston is no good)

The oil pump bubble and way more than that, I believe, the air and engine temps only exacerbated the above, and added confusion to our diagnosis. And I feel that temps and oil pump bubbles (still waiting for an explanation on that one!) are what ultimately limit the life of this engine to a MAX of 4500-5000 miles.

Still, the life we see from even the very BEST of this model is PITIFUL, when compared to the old 440/488 fans used from the mid '80's until '98. Those were GOOD engines. These are junk.

 

[ljbarryiv]

I would still realy like to see the oil vent tude set up on these new 550 fan. I hopfully be putting the sled back together this weekend

 

[gogglefurnace]

Tom, did your sleds have the ataac. my 05 does my 08 doesn't. my 05 is jetted 260/250 and the 08 210/210, i guess because of the nik cylinders. This is for 6000-9000 and i think about 20 degrees. i know you've been through this, i'm just curious. i also have put the slp high flow kit on my air box on the 05 and everything seems still to be okay with no rejetting because i felt this sled was always rich anyhow. i'm just picking your brain. not second guessing what you've done.

 

[ivar]

just some random thoughts:
To me it sounds like Tom is is on the right track - heat is the major issue here.

Having to run richer than previous years - indicates that the gasoline formulation has changed. Maybe much more ethanol than before, making the engine run hotter. And with , at best, marginal cooling, this might be enough to burn down.

Also, many sleds burned down with just a few miles. I'd think with new pistons/rings etc, the break-in also generates more heat. And maybe thats why the sleds with what seems like excessive piston clearance survives longer...?

And nikacil cyl's requires more break-in time - maybe
thats why they have performed worse in this application...?

To test the above theory, you could rebuild a sled with "normal" clearances, then allowing this sled to be run-in doing light duty for a couple 100 miles before putting it to real work.

BTW, have you tested pistons with some kind of thermal coating?

 

[gcmci]

As it has been explained to me the oil is boiling in the pump causing air bubbles which is why again as explained to me they want the cold air hood duct put on low speed ridden 550's which also comes with an oil bleeder kit
On any newer sleds you might get polaris to step up and give you the parts it is worth asking.It would have to be done thru a dealer of your picking.
Hope this helps

 

[Frostbit]

I would still realy like to see the oil vent tude set up on these new 550 fan. I hopfully be putting the sled back together this weekend

You can buy the oil pump vent kits from Polaris. I bought two last spring to put on my '04 and '05 after the '04 burned down. My '06 (I have three) burned down as well, and Polaris provided me with a nicasil kit that included an oil pump bleed kit for it. I then bought the cooling duct kit to put on just last week ($200). I have the part number for the vent kit at work. I can post it tomorrow.

Like Toms, I have had a plethora of problems with my 550 motors. Virtually every unit my dealer now buys (09's) are equipped with cooling ducts and vents, oil pump vent kits, exhaust blankets, and relocated fuel pumps. I believe all the IQ based 550's come this way only. IMO, Polaris still does not have this motor figured out. My dealer told me, far and away, 550 Polaris cylinders and piston kits are his #1 selling parts. That tells me something.

I am in rural Alaska, and there are a ton of these motors in the field. Those that have not had at least one piston and cylinder put in are hard to find. I have done everything I can to try and keep my newest one running for awhile, so we'll play guinea pig. If it blows, I am burning the entire sled on the spot and I will be done with Polaris. There's no way in hell I would ever sell this sled to someone I know...this is a small town. One thing for certain: I will never buy another 550 Polaris!

 

[penguinpoo]

When I used to work on these I had to dramatically increase the pilot jet at higher altitude. I think it was to a size 50, and then adjust idle air mixture screw for best idle and throttle response.

 

[richardsb014]

You can buy the oil pump vent kits from Polaris. I bought two last spring to put on my '04 and '05 after the '04 burned down. My '06 (I have three) burned down as well, and Polaris provided me with a nicasil kit that included an oil pump bleed kit for it. I then bought the cooling duct kit to put on just last week ($200). I have the part number for the vent kit at work. I can post it tomorrow.

Like Toms, I have had a plethora of problems with my 550 motors. Virtually every unit my dealer now buys (09's) are equipped with cooling ducts and vents, oil pump vent kits, exhaust blankets, and relocated fuel pumps. I believe all the IQ based 550's come this way only. IMO, Polaris still does not have this motor figured out. My dealer told me, far and away, 550 Polaris cylinders and piston kits are his #1 selling parts. That tells me something.

I am in rural Alaska, and there are a ton of these motors in the field. Those that have not had at least one piston and cylinder put in are hard to find. I have done everything I can to try and keep my newest one running for awhile, so we'll play guinea pig. If it blows, I am burning the entire sled on the spot and I will be done with Polaris. There's no way in hell I would ever sell this sled to someone I know...this is a small town. One thing for certain: I will never buy another 550 Polaris!

Frostbit,
I could use the oil pump vent kit part number. For some reason the Polaris Dealer I use can't find one linked to my 04 550 Trail RMK. He shows the cooling duct mod and fuel pump relocation kit, but that is all. Any help you can lend would really be appreciated.

Tom,
Did you relocate any of your fuel pumps? I wonder if heated fuel (less dense) could be causing some of the burn down issues???

Bart

 

[Tom400CFI]

I would still realy like to see the oil vent tude set up on these new 550 fan. I hopfully be putting the sled back together this weekend

O.K. Sorry for the delay. Here are two pics of the oil bleeder tubing:

As I said before, it basically screws into the top of the oil pump, in place of the bleeder screw.