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

[Tom400CFI]

Were the ring end gaps checked before install??

Yes. At this point, we're checking ever set, on every engine.

Has there been any checking for air leaks?

Yes. Pressure tested and after start up, brake/cleaner spray tested too.

I have worked on a few fan melt downs and most of them were the result of mouse nests blocking the air flow under the motor shroud. Maybe check that on your motors and see if there is a design flaw allowing the air flow to excape before it routes past the rear of that jug?

ALL these motors were completely rebuilt before the season started including cheching a truing cranks. So the shrouds were off all of them. No nests, and they're all installed correctly after.

Next I would find out what the spec is for ignition timing, put a dial indicator on each pioston and make my own timing marks on the engine for each side - start her up and toss on a timing light and see how close each side is to the mark..

We've checked the timing. Not sure the results though. I'll ask the mechanic.

 

[blazer71]

I am gonna rule oil out as the problem on sooooooo many sleds, the odds are just too good.


But lets not forget that if you have a sled with cylinders not firing.....your gonna have "plenty of oil as you can see" just like you stated.

 

[Blokhead]

Sure you don't want to try a richer slide?

 

[Tom400CFI]

Tom, have you got any hair left at all? man I feel for you...the second one that hit deto for sure looks like it overheated.......the other 2 is harder to say since one piston does look pretty good on each motor...I agree doesnt look like fuel or oil problems...looks like it just keeps getting hotter and hotter till the pistons scuff..that one that lost the skirt looks just like it swelled the piston till it scuffed then it tore the skirt off...on the wisco motor that lost compression..whats the ring tension feel like compared to new rings? pistons sure look good for no compression..I have seen bad overheated motors with no ring tension left(ak low compression)and the pistons looked good but I think the reason why was they had good wall clearence and the piston didnt swell enough to scuff the piston ,just took the tension out of the rings....keep us posted..someone is gonna figure this out sooner then later I hope....

Thank you for this post too. The ring tension seemed fine to me.

Since yesterday, we honed the cylinders out to .005", and put new rings on, Since the pics in this post (#36)
http://www.snowest.com/forum/showpost.php?p=1188614&postcount=36
and the machine ran for 20 minutes, then lost compression in the MAG side!! All the time riding it, the WBO2 read 12-13:1 so with our new jetting set up, it wasn't too lean at any point. With the engines with the Wisecos (at least), it HAS to be a heat or mechanical problem. I swear, I question the integrity of the cylinder casting. We've had SPI piston motors do the same thing but right now we're focusing on the two "test" motors which happen to have Wisecos in them.

Yes, we are all pulling our hair out.

 

[gcmci]

If you thinks it's fitment problems have your machine shop build some torque plates for your cylinders to bore and finish hone your cylinders in
Greg

 

[Tom400CFI]

Here's another update:

I personally, took one of the sleds from post number 36 (the first one w/the minor scoring), and put it back together today. Here is the recipe:
Wiseco pistons
.007" Piston to wall clearance (measured 3 times for accuracy)
.012" Ring gap
240 mains
Q4 nozzles,
needle in middle clip
40 Pilots,
Air screw 1 turn out


It ran ~100 lbs compression immediately after assembly, and then 105/110 after a 10 minute on/off throttle break in. BTW, 110 is the absolute higest compression you'll ever see in one of these, at this elevation in our experience. Generaly 100 lbs is about how they turn out after break in.

I ran it about 10 miles so far, and the WBO2 was reading between 11.9:1 and 13.0:1 from 1/2 to WOT. Piston wash was abundant (which I want here) and it was warm today, so...

More data to come tomorrow. I will be putting temp probes all over the motor and fan inlet/exhaust to try to learn more about this little POS engine, and I still need to install a "stand tube" for catching any air bubbles that night be coming out of the oil pump.

I hate these sleds and engines...and I am or was a "Polaris Guy". I can not wait to get this fleet turned over to something that requires damage repair and oil changes only.

 

[Tom400CFI]

O.K. Here's more data. Today I set up my DVOM to use the thermo couple feature to get temp data from various parts of the motor or cooling system. AMBIENT AIR TEMPS WERE AROUND 40*F today.

The first thing I wanted to test was the Fan's INLET air temp, since in this chassis, it's so darn close to the exhaust (?). Running in this mode (see pic below) I observed inlet air temps ranging from ~100 degrees to 170*F

I started by just going about 10 mph constant, on mostly flat ground. That showed temps of about 80-90*F pretty consistently.

Running about 30 mph constant, at about 1/2 throttle, on slight up hill (12-15%grade) resulted in 80*-90*F inlet temps. I was surprised that the temps were that low...but that still isn't very low w/30 mph breeze going through the hood.

WOT up a short 100 yd pitch, about 30 mph, resulted in 90-100*F inlet temps and a idle right after that resulted in 170*F (!) fan inlet temps. How do you cool an engine starting w/100+*F air temps? That air should have been 40*F.

 

[Tom400CFI]

Next, I moved the probe to the air cooling exhaust area to see what the air temps were after leaving the engine...

Putting around at ~10-15 mph resulted in 175*-185* temps

Idle after putt-putt resulted in 220*F temps and high idle w/0 clutch engagment would bring temps down to about 200*.

WOT long climb, Temp climbed to about 230-240*F. Stopping and and idle after climb, air temp spikes to 300*F and a high idle brings air temps down to ~275*-280*F. Cool down takes a while of mild driving after that.


Lastly, I put the temp probe right on the cylinder head, by the plug. Temps ran around 300* mostly, but peaked at 370*F during a hard climb. I don't know what the head temp numbers mean, but the air temps pretty much all seem way too high for my tastes.

I think the motors are running too hot forcing us to run too-large clearances to keep them from sticking. This particular motor (outlined in post #46) now has about 20 miles on it (woo-hoo) and still has good compression and idle/starting qualities.

 

[AKSNOWRIDER]

Next, I moved the probe to the air cooling exhaust area to see what the air temps were after leaving the engine...

Putting around at ~10-15 mph resulted in 175*-185* temps

Idle after putt-putt resulted in 220*F temps and high idle w/0 clutch engagment would bring temps down to about 200*.

WOT long climb, Temp climbed to about 230-240*F. Stopping and and idle after climb, air temp spikes to 300*F and a high idle brings air temps down to ~275*-280*F. Cool down takes a while of mild driving after that.


Lastly, I put the temp probe right on the cylinder head, by the plug. Temps ran around 300* mostly, but peaked at 370*F during a hard climb. I don't know what the head temp numbers mean, but the air temps pretty much all seem way too high for my tastes.

I think the motors are running too hot forcing us to run too-large clearances to keep them from sticking. This particular motor (outlined in post #46) now has about 20 miles on it (woo-hoo) and still has good compression and idle/starting qualities.

hey tom, on the wisco motor that lost compression again how tight was ring gap?am wondering if when it gets hot and swells the piston it isnt touching ring ends?good posibility of that....I agree too hot for my taste as well...how about trying popping a hood off and repeating test? bet your temps come right down..if so then do some side panel vents and some hood vents to get the air flow moving....

 

[Tom400CFI]

hey tom, on the wisco motor that lost compression again how tight was ring gap?am wondering if when it gets hot and swells the piston it isnt touching ring ends?good posibility of that....I agree too hot for my taste as well...how about trying popping a hood off and repeating test?

This particular sled -one of our test sleds now- was assembled with the Wisecos the first time, by one of my mechanics, so I'm not sure what the ring gap was. The piston to wall clearance was .0045" and that motor ran for 20 minutes before losing compression on the PTO side. I installed new pistons and rigid honed the cylinders to .007" clearance, w/.012" ring gap, and that is where it stands now. I think that your theory has merit, for sure.

I bought some drier ducting-like tubing that is 8" in diameter, and heat resistant. I'm going to use it to make a duct to port only cold air to the engine, then re-measure. Results to follow.

I don't know what the head temps should be on a fan cooled engine such as this, and I'm also not positive that my probe got a good reading of the head temp, since really, 1/2 of the probe or more, is exposed to air, not the aluminum. I feel that the head temp may well be higher than the readings I got. More data to come...

 

[Tom400CFI]

Back with more data. I built a very ugly, but effecting intake duct for the fan. See pics.

And here is where I installed the temp probe for this test. Probably a little hotter location than the one yesterday as it's closer to the engine, and after the fan, but...

AMBIENT TEMPS WERE 38* to 40*F today, so about the same as yesterday.

Running about 30 mph constant, at about 1/2 throttle, on slight up hill (12-15%grade) resulted in 60*-70*F inlet temps (compared with 80-90* temps yesterday).

WOT up a short 100 yd pitch, about 30 mph, resulted in MAX 68*F inlet temps (90-100* yesterday) and a idle right after that resulted in 107*F (170* yesterday). High idle after that brought it down to 95*F fast.

Moving the probe to the exhaust side...

...I witnessed these results:

Putt-putting resulted in 130-160*F mostly right around 150*F (175-185*F yesterday).

WOT long climb, Temp climbed to a MAX 175*F (239*-240*F yesterday). Stopping and and idle after climb, air temp spikes to a max of 240*F (300*F yesterday) and a high idle brings air temps down to ~195*-200*F. Cool down after that, to the "normal" (with this set up) ~150*F range took about 20 seconds of driving.

This is a huge, HUGE improvement over stock. I think the motor is getting too hot in this chassis.

 

[Tom400CFI]

MEANWHILE...

ANOTHER sled burned down. This was a SPI piston sled, .003" clearance. Less than 100 miles or 1 week on the last rebuild. Notice that the PTO is showing some wash,...mag side, not so much. 260 mains in this enigne!!! Here are the pics...

The more time I spend w/these, the more convinced I become that they're getting too hot, and/or the clearances aren't large enough for the temps that they're getting up to. This engines rebuild was less than a week old. This is the one which I referenced in post #1 that didn't seem to respond to larger and larger main jets.

 

[AKSNOWRIDER]

MEANWHILE...

ANOTHER sled burned down. This was a SPI piston sled, .003" clearance. Less than 100 miles or 1 week on the last rebuild. Notice that the PTO is showing some wash,...mag side, not so much. 260 mains in this enigne!!! Here are the pics...

The more time I spend w/these, the more convinced I become that they're getting too hot, and/or the clearances aren't large enough for the temps that they're getting up to. This engines rebuild was less than a week old. This is the one which I referenced in post #1 that didn't seem to respond to larger and larger main jets.

looks like you got her figured out tom..hair dresser is gonna be estatic that shes gonna get to start cutting your hair again...congrats..so some impromtu duct work this coming week huh?bet most of those sleds you richened up are gonna need leaned up after you get ducting on them....gotta be the exhaust that is heating the underhood so much...

 

[mccbry]

Hello Tom, I bought a 08' 550 trail and now I'am scared, after reading all of your problems. I wonder if wrapping the exhaust pipe with exhaust wrap would help the problem??

 

[AKSNOWRIDER]

Hello Tom, I bought a 08' 550 trail and now I'am scared, after reading all of your problems. I wonder if wrapping the exhaust pipe with exhaust wrap would help the problem??

I bought my 14 yr old daughter a new 08 550 trail rmk last year..has 800 miles on it now..granted she is a 14 yr old and doesnt ride hard but I will climb on it when I am trying to teach her stuff or when she is having problems getting it to do what she wants it too..I ream the crap out of it and the only thing it has ever been to the dealer for is on the first ride it ate a belt(clutches were out of alignment brand new..dealer aligned it and its never been back for anything...

 

[Tom400CFI]

Well wrapping the pipe (or at least the gigantic can) certainly wouldn't hurt, that's for sure. It's clear to me that having the fan intake in the same air space as a heater (the large pipe and can) is a stupid idea. Especially in a seemingly poorly vented hood like the Edge seems to be. We didn't have problems of this magnitude with the 550 motor in the Gen II chassis. In fact, we loved that model and still have two '99's that run like a top.

But what AKsnowrider said too; some of our machines run and run fine. Other's simply refuse to stay running no matter how many piston kits we throw at them. There is no consitancy from one sled to the next.

 

[ttyR2]

If the cooling duct ends up working, it wouldn't be hard to make a mould out of foam or wood and lay up some fiberglass to make a number of ducts, if you end up adding cooling improvements.

 

[Tom400CFI]

That's a cool idea, and it woudl be fun to do, IMO. I'm not sure if we have time for that though. I'm going to look at one of the "rental" 550 ducting kits and see if that is as good as my make-shift kit is. If it's not, I'll have to go down the road you suggested of fabrication.

I've issued my "test sled" back to it's department (Ski Patrol), with the CAI ducting in place. So far, so good, on that particular machine...

 

[theultrarider]

I think you have nailed it Tom with the air flow. The way in which you guys use your sleds primarly low speeds high torque, creates alot of under hood heat without fresh air moving through to replace it. Thus the "rental" kits that AKSNOWRIDER refered to. Hopefully you "kit" will tame those temps for you and maybe you won't be spending all your time building engines over and over. I sure feel for you but think you are on the right path with this.

 

[gogglefurnace]

i was in front of bad t.v. the other night and read all this thread, plus went to some other sled web sights to see what i could learn about this. i have a 05' trail rmk with 1700 miles and an 08' trail rmk with 600 miles with no problems. i spend about a 1/4 of my sled riding on the 05' lion hunting at a sustained slow speed of 5 to 10 mph for 3-4 hours and sometimes pulling a fold-a sled with dogs. i have spent quite a bit of time hangin with my grandkid on his 120 for 2 -3 hour stretches also. when i read about your problems i thought " boy i must be a lucky s.o.b.". i opened up the hood on the 05' today to see about making an air shroud from the top center air feed on the hood back towards the fan, simular to what you were doing. i compared the 05' to the 08' and everything was the same under the hood so i figured it would be worth the trouble. then i got on this thread to reread and i noticed a major diff between my sleds and the sled engine you were doing the temp testing on. my exhaust is insulated about a foot downstream of the y pipe halfway back to the can, the front half of the pipe in the nose of the sled. also, i have a shield between the can and the fan with a shelf that alows me to mount brackets for a spare belt. i do not have the extra vent that comes with the rental kit. i don't know if these shields have anything to do with the rental kit or if it is a trail rmk thing but when i look at it, it sure does give a lot of protection for exhaust heat being injested by the cooling fan. i'll try to get a pic of it or go check a trail rmk out. i don't think this is a dealer setup, it looks factory to me. i also run polaris ves gold oil. maybe i'll try to get some temps off my sled for comparison to yours. i'll have a beer for ya.