doo oil cap related burn down?

Lorduss · Jan 28, 2016

Had a doo oil cap since last year, around 500 miles on it so far
RKtek pistons and head around 200 miles ago, running great

got about 2 miles down the trail today, revved into the motor a bit and it lost power (still running)
hitting det code hard

it started up again but I got a tow back to be safe, the moment I stopped initially I pulled the left panel to check out visually, cracked the oil cap right away and head a solid hiss sound as it sucked air in, to my surprise because I have a doo cap on to prevent these problems, I guess a vent line was the correct option

at the moment I am thinking I squeeked a crank bearing, but I wont rule out a piston either right now, I just got it home so ill be tearing into it tonight or tomorrow, depending on how I feel.

the motor starts and runs and sounds horrible, like its beating it self to death
What are your guesses ?

black z · Jan 28, 2016

Doesn't sound good. I wouldn't run it any more.

wellfed777 · Jan 28, 2016

oh dang that sucks man
don't run that thing anymore ! hopefully your cases are ok
are sure it wasn't air rushing out of the oil tank ?
let us know what you find on tear down

i'm guessing piston issue or rod bearing

Murph · Jan 28, 2016

Lorduss,

Air bubble in the line? Tank looked sucked in? How full did you fill oil tank? What year Pro? How many miles on bottom end?

The duckbill Doo caps will hold oil in tank with oil line disconnected-- they need a little bit of suction from oil pump to open. Disconnect line and put cap on tank-- apply a little vacuum with a mighty vac or something similar and see if it holds vacuum or if it opens duckbill in cap.

Lots of sleds in Tahoe are smoking their crank bearings this year after not being ridden much in the last couple years, and motors not being fogged-- usually we don't have to here but with all the rain we had this summer, rust on bearings could be a factor.

Det code is weird for crank. I broke one Pro crank in half, and shelled another Pro crank bearing-- neither threw a Det code. Injector or fuel filter clogged?

What was the motor temp when it let go?

If you lift up on the primary, is there any free play up or down?

Let us know what you find...

Brian101 · Jan 28, 2016

Doo cap not venting

I too have had some doubt put in me with doo oil cap on my pro. Last weekend I removed the cap while taking a break, there was the infamous rushing air sound and oil tank popped like side walls were sucked in a bit. This is the duck bill style doo cap. I cracked the cap several times after that. The whooshing sound never came anymore. I think the vented passo cap option is definitely the safest option.

LoudHandle · Jan 29, 2016

The Doo cap will not relive thermal expansion. The Duck Bill style vent is one way (air in only as installed in the Doo cap) keeps the oil where it belongs (in the Tank) when inverted. So if it was Capped when cold and then warmed up. The rushing sound will be warm expanded air out.

Possibly you got a set of Kelsey's pistons that were mislabeled and you installed the ring gap to the exhaust side and have grabbed a ring and the engine is eating itself alive? Definitely would explain the power loss.

Or the ring end gap was set too tight and the rings expanded, the ring ends touched and got larger than the cylinder bore, which results in resizing the cylinder. (Read: wiped the Nicasil out, resulting in ring eating the aluminum under the Nicasil and increased friction and no ring seal.

A rod bearing will sound terrible but short term will not be a night and day power loss. Most would not notice it at all until it breaks and punches the case (at least in my experience).

A crank bearing seizing typically kills the engine if the cases have a decent fit on the bearing.

Most likely cause in my opinion is improper piston install, although I'm not a fan of any of Kelsey's products. The items I've mentioned are not specific to any manufacture or vendor. I would never trust the markings, nor the size marked on the box or the part. Everything should be checked and double checked. I have learned from my own mistakes over the years and the ring end gap is far more important than most would think. They are nearly always too long from the manufacturer. The gap should always be to the intake side where there is more support for them. The gap should never cross a port opening. FWIW

Slightly off topic, but reinforces my point; Back in my racing days it was very common for the cheaters to bring big bore pistons to the race in stock boxes. Our tech guys assumed they were a stock bore engine, because the box said so. Yes the tech officials were Idiots and Morons! Not a lick of mechanical aptitude in the bunch. Different Officials today but my sentiment holds true. NEVER ASSUME ANYTHING! If in doubt measure it out!

JMCX · Jan 29, 2016

I lost a big end rod bearing recently on my 15. I pretty much knew what it was as soon as I heard it. No det code from all the hammering. It was a long cold tow out.

Reg2view · Jan 29, 2016

Could be bent crank pin, twisted crank. Your description fits it well, and not unheard of on a poo 800 crank, and nothing to do with oil. Run like crap (until it breaks), bouncing out of phase, will det, sounds like squirrels fighting over a bag of corn.

Don't run it until you tear it down.

TRS · Jan 29, 2016

Here is a picture of the wrong BRP cap installed and the end result. This was this past week. I don't know of one BRP product going down from a BRP duckbill cap. So I question the relation of the BRP cap on a PI product going down.

TRS · Jan 29, 2016

Again the cap, and it took a half day. Tank was sucked in.

TRS · Jan 29, 2016

And for all you doubting Debbie's. Please put your antiquated PI cap back on.

Spaarky · Jan 29, 2016

Whhhhoooooaaaaaa. Some of you guys need to set down the race gas/mnt dew mixture.

There is about 5 things in the first post that led me to think it wasn't the oil cap. Plus there hasn't been one thing TRS has told me to do that didn't work. There is a reason the engineers ask him for help.

Tony any time you want to quit passing out your incredible information to the public, go right ahead. We will just come out riding to get it.

TRS · Jan 29, 2016

Tony any time you want to quit passing out your incredible information to the public, go right ahead. We will just come out riding to get it.

[/QUOTE]

Justin,
Sounds good.

Brian101 · Jan 29, 2016

Thermal expansion

The thermal expansion theory with the duck bill doo cap makes sense with my situation. It was something I had not thought of.

For sale oil cap with vent line

Murph · Jan 29, 2016

TRS said:
Again the cap, and it took a half day. Tank was sucked in.

Wrong BRP cap?!......

Doh!!!?

Lorduss · Jan 29, 2016

Murph:

I actually have allways had a air bubble sitting at my nipple on the oil tank, uses oil for the most part nicely, and has been ran at 40:1 nearly since I got it, went to doo oil cap around 600 miles ago

I did not notice the tank I was looking at the motor as I cracked it, tank was pretty much full
could def be from high pressure in the tank and not low, I really don't see how the basic design of the doo cap could hold a suction, but the hiss did freak me out.

2012 pro, 1500 miles on bottom end
I was crusing down the trail at about 116F for a good mile then it rose up to 125 and popped
I played with the primary at the time, it did not seem like it had any play but ill give it a shot again in the garage here.
I did only happen to get 80 miles last year, and not even 200 the year before that,
so yeah she has barely been ridden and not fogged, I try to run them about every month during the off season, I was busy and did not get around to it, we did have a very wet summer, that is quite a possibility.

LH:
ring end gaps were to the correct side, I took my time on the install and triple checked everything, I just looked at my motor the night before this happened, pulled my plugs to check wash, could still read the lettering on the top of the piston (very rich with RK's fuel numbers) readable from the front of the sled and ring end gaps on the intake side
end gaps were set at .021 on all 4 rings, rings were kept with correct side of engine
one of the reasons I think its a crank bearing is I hear a squeal from behind the primary, while it would run and if I just turn it over by hand. crank seal maybe?

reg2view: somehow you did just describe the way my engine sounds, squirrels fighting over a bag of corn

im trying to get the garage clean so I have room, I have a feeling im tearing it down the crank, might just pull the motor first
come to think I did not pull my injectors when I got this deep a month ago, and my fuel filter is 3 year old spi
would have been good safety measures to do

TRS · Jan 29, 2016

Lorduss said:
Murph:

I actually have allways had a air bubble sitting at my nipple on the oil tank, uses oil for the most part nicely, and has been ran at 40:1 nearly since I got it, went to doo oil cap around 600 miles ago

I did not notice the tank I was looking at the motor as I cracked it, tank was pretty much full
could def be from high pressure in the tank and not low, I really don't see how the basic design of the doo cap could hold a suction, but the hiss did freak me out.

2012 pro, 1500 miles on bottom end
I was crusing down the trail at about 116F for a good mile then it rose up to 125 and popped
I played with the primary at the time, it did not seem like it had any play but ill give it a shot again in the garage here.
I did only happen to get 80 miles last year, and not even 200 the year before that,
so yeah she has barely been ridden and not fogged, I try to run them about every month during the off season, I was busy and did not get around to it, we did have a very wet summer, that is quite a possibility.

LH:
ring end gaps were to the correct side, I took my time on the install and triple checked everything, I just looked at my motor the night before this happened, pulled my plugs to check wash, could still read the lettering on the top of the piston (very rich with RK's fuel numbers) readable from the front of the sled and ring end gaps on the intake side
end gaps were set at .021 on all 4 rings, rings were kept with correct side of engine
one of the reasons I think its a crank bearing is I hear a squeal from behind the primary, while it would run and if I just turn it over by hand. crank seal maybe?

reg2view: somehow you did just describe the way my engine sounds, squirrels fighting over a bag of corn

im trying to get the garage clean so I have room, I have a feeling im tearing it down the crank, might just pull the motor first
come to think I did not pull my injectors when I got this deep a month ago, and my fuel filter is 3 year old spi
would have been good safety measures to do

After reading this post, I now believe it had nothing to do with the 710 cap.

Vincenthdfan · Jan 29, 2016

LOL, I get it... 710 cap. :eyebrows:

diamonddave · Jan 29, 2016

TRS said:
After reading this post, I now believe it had nothing to do with the 710 cap.

Agree Tony. Fully and completely. My Tragically Hip reference today.

Not to mention, it's not uncommon for '11's and some '12's to puke a crank bearing rod bearing. There were 2 diff crank manufacturers in 2012. Consider how much wear and damage not to mention downtime from storage has been occurring over the past 4 years and 1,500 miles to your crank with an antiquated oil cap vent (and other issues I won't mention). I had found their oil cap vents to be an issue back in the Dragon days. Even the experts didn't agree with me at the time.

We can only to address these issues the best we can. Tony found a cheap, easy solution and shared it with all of us. Lucky us!! Before this, I was using fabbed up vents from transmission cases that I scrapped out. Friends thought I was nuts. I began using this cap this year. I did notice the hissing noise while unscrewing my cap today after sled has been sitting for a few weeks. It was holding quite a bit of vacuum. But it's using 36:1 overall. First 3 rides with stock cap and oil pump adjustment was 50:1.

We can't miracle these Polaris motors to live forever. Remember this motor began as a 600. It's the smallest lightest 800 made. I could go on for hours about my beefs with PI (fuel injector/location, electrical) but I enjoy riding and working on their sleds more than the others. Way more.

One needs to really understand there are so many things that can cause a failure in these motors. In a case like this where a new top end has already been installed prior, we should remove the motor from the sled while double and tripple checking everything. Then disassemble it and try to rule everything out before trying to draw any conclusions as to what caused the failure.

Sorry to the OP that you are having these issues. But let's get deep into the teardown and diagnosis of what's happened here.

sledneck_03 · Jan 30, 2016

TRS said:
Again the cap, and it took a half day. Tank was sucked in.

My cap says xps....

doo oil cap related burn down?

Well-known member

Well-known member

Polaris Moderator/ Polaris Ambassador/ Klim Amb.

Active member

Well-known member

Well-known member

Well-known member

Life Member

Life Member

Life Member

Well-known member

Life Member

Active member

Polaris Moderator/ Polaris Ambassador/ Klim Amb.

Life Member

Well-known member

Chilly’s Mentor

Well-known member

Similar threads