Ski-Doo Snowmobiles Forum banner
1 - 20 of 31 Posts

·
Registered
Joined
·
127 Posts
Discussion Starter · #1 ·
'04 600 SDI 5k+ Miles. Boots are excellent, Y pipe excellent. Sled was completely functional, meaning starting, reverse etc. This happened going a consistant 55 MPH. First one side then the other. Thinking crank seals as this thing looks like it has 20K miles on it. Meaning it's an oily mess. What do you think?
 

Attachments

·
Registered
Joined
·
127 Posts
Discussion Starter · #3 ·
oily mess from say exhaust gaskets being junk or a cracked Y-pipe? It would melt down that side but dont know if it would do it that bad.
Oily mess from Y pipe not tight, leaking. The mag side looked to really oily, the PTO side pretty bad too. The Y bolts were pretty loose as well. Pipe in excellent shape though, no cracks. So leaky Y would cause this?
 

·
Registered
Joined
·
2,562 Posts
Leaky y pipe won't cause your issue. Both sides show a symmetrical breakdown. A leaky crank seal would only affect the side with a leak. I doubt both side failed simultaneously.

I am not a piston expert. Luckily I have not had enough failures to know all that stuff. But given that both sides have what looks like the same issue, I would guess it may be a fuel related problem. Not enough, or contaminates, etc.

Others will chime in on this.
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #6 ·
Combustion definitely got hot, but the motor wasn't. I was running I think BR 9's, like people suggested. I wonder if the SDI/Injectors are the issue? Any known problems with the injection messing up like this? To me it looks like I was running to hot of plug, but don't think that's the case. And yes, now the entire motor will need to be done, but curious about what the cause was.
 

·
Registered
Joined
·
9,622 Posts
I have seen too lean/not enough of fuel burn holes thru pistons,,possible clogged fuel filter or weak fuel pump or 2 dirt injecters

Also have seen a crankcase vacuum plug missing cause a hole,,but unlikely both cyls

Timing advance can cause it also

Haven't seen 2 even holes like that either,,lol

So you say the one side melted and you continued riding till the other side went??
 

·
Registered
Joined
·
4,667 Posts
I would think the first one went down from injector failure then the other went do running it while one side was already gone once you don't have enough fuel for the motor to burn the spark plug will burn the hole do to high internal temps, just like it would with too hot spark plug range or too much timing. - Bill
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #9 ·
What happened was I was on Oneida Lake just cruising along around 55MPH, wasn't racing or WOT when it backfired and died. Engine temp was normal, maybe a tad bit high but nothing significant, by the gauge and by hand. At that moment I knew it wasn't good. Pulled the plug and the end was burnt right off with no compression. Meanwhile I'm alone. Luckily 2 guys saw my side panels open and stopped. They offer to tow me back. I was like well I might be able to nurse it back on one cylinder. Well I did and that didn't last long, that's why booth pistons have holes, and they towed me back.

I too thought possible fuel issue etc, but was hoping this has been seen before to lead me to a successful repair. Due to the condition of this sled, I wouldn't be surprised if it's something with the injectors/fuel filter etc.

How do I get the timing checked? Is this something that is through the ECM or manual?
 

·
Registered
Joined
·
9,622 Posts
Carbed engines with a leaky y pipe will lose exhaust back pressure that holds the intake charge(fuel and air) in the top end when both ports are open at the same time,,when if the charge dumps out the exhaust port,,more fuel will be pulled thru the carb

Now the SDI is programmed/calibrated to inject X amount of fuel depending on throttle position,,,so with a big back pressure loss at the manifold it might cause it to run lean

Just a thought?? Like when you alter the exhaust on fuel injected stuff and it won't run rite till you program more fuel?? Or add more fuel with bigger jets
 

·
Registered
Joined
·
137 Posts
Glad Oneida was frozen up enough that you weren't watercrossing at the time!.surprised there is enough ice.

Have one friend whose y pipe loosened up twice he hasn't burned down yet but have another had a y pipe crack ( after I told him to ck it because mine cracked) The only thing we found wrong was the y pipe. Fixed that rebuilt it and it was fine after that. So I believe they will lean out a motor enough in certain conditions ( part throttle mid range lean) ?
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #14 ·
I'm wondering now if it was a fuel issue. Gonna pull/replace the filter and see if that tells any tails.
 

·
Registered
Joined
·
66 Posts
You can Doo alot of guessing. When they burn up like that,start from the ground up to cover all your bases.Check crank.New seals,ALL new gaskets.get her sealed up again and perfom a fuel pressure test before firing.If pressure is good fire it up! Also replace the O rings on the fuel injectors for piece of mind. Once its running again have it scanned for fuel trim. if its fuel ijected it has a O2 sensor!! dont forget about that!! it will go lean or rich it it goes bad! good luck
 

·
Registered
Joined
·
127 Posts
Discussion Starter · #20 ·
I've only run non-ethanol 91 octane in it and Ski-Doo Synthetic, but no idea what was in it before

In talks with my engine re-builder, he said it would be extremely rare that it was a fuel issue due to each cylinder having 2 injectors along with the engine light never came on as well. He actually went into much more detail than I can remember to re-type and leads to believe it's the outer seals that went. He also said that if it were the center seals/bearings that the motor would have smoked more than normal due to oil build up, which it didn't seem to but it did seem to go through more oil than I expected. Either way I'll be dropping the motor off in the next couple of days for a complete diagnostic and full repair. In the mean time I'll be cleaning up the engine area, new fuel filter, injector O rings etc etc.....The part that kinda sucks is that the sled isn't worth anything not running, and will only be worth what I'll end up having into this motor rebuild. But in the end should be good.
 
1 - 20 of 31 Posts
Top