Burn Down, need some advice

[BrentMartell]

Sooooo it began last year: 2003 800 HO Summit. The engine has been stock from day one with the addition of a HPS can. With the can I ran my needles 1 clip leaner and all else remained factory.

I pulled the can off and installed my stocker to decrease the noise. The sled ran great until one day it burned down the mag side. We thought the atmospheric conditions that day coupled with the 1 stage leaner needle setting might have caused the burn down. I put a new cylinder and pistons in the sled, parked it until this year.

This year: first ride the engine ran very well and the plugs looked dark but dry, SAFE. Next ride, the engine was fine until we got to elevation and was running rich. Plug check indicated wet plugs and the engine really struggled to clean up and run consistently. We thought it could be fuel related but I decided to check everything I could think of. I drained the carbs, checked the needle, choke, floats, main jet, and DPM hoses. Checked everything I could think of except the reeds. The tank was dang near bone dry but I did check for water as well.....put in fresh fuel. Next ride: -11 degrees, engine ran great until I got to elevation...ran like sheet! Very rich and would not pull r's. Checked plugs and mag side was wet. Installed new plugs...it helped but not the cure. As the day wore on it would good one minute and crappy the next. END of the day, we are headed out and I get 2 miles on the trail and Burn the SOB down again. Mag side, burn down from exhaust port.

What in the heck is going on? Big John and I decided it could not be a bad seal. He doesn't think it is the DPM or MPEM. What else could cause this? Not enough oil would create a rich condition to a point most likely a seize vs burn down. I am very frustrated and leary of rebuilding it for fear it might just do it again unless I find the problem. I just taint smert enough to know what to do. HELP!

 

[winter brew]

Have you done a compression check?

 

[BrentMartell]

For what?

Compression was 150 each side taken the day before the burn down when I had a ski doo tech buddy over drinking a little barely pop and problem solving, we found nothing at the time.

 

[DiVo]

****ing sounds like what my non ho is doing right now
Now I have it in a shop so they can try to figure it out and hopefully waranty a rebuild incase they don't get it right.
Mine is so bad that it actually fouls the plug though not just makes it run like ****, I have stock carb settings also. Rebuilt it and ran fine for a while then just burnt down right out of a parking lot.

 

[DiVo]

They also are going to split the crank and look at everything to make sure its not anything in there. I would like to know if it was the DPM or MPEM ****ing up but I don't know if there is anyway to test those

 

[BrentMartell]

A buddy has the same sled as I and I am thinking I might pull his dpm and mpem and stick it on mine to see if the problem is related to one of those. Of course I have to install a new cylinder and piston first, FN stocker. Should have mod'd the sheet out it and at least have something to blame this on.

 

[DiVo]

I feel the same way, you should try switching them out and see if it solves the problem. God knows I'de like to know.
do you know if the dpm and mpem are the same on a 01 summit x 800 as all 01 summit 800's?

 

[BrentMartell]

They are the same. The X really only was a package option for the chassis type stuff. The engine and electrical are the same. I miss my 01. If had kept it and done all the light weight crap I did to my 03 it would still be running!

 

[Idaho Slim]

I had to run staggered jetting in mine Brent, ended up 2 sizes different
Mag side was my nemesis also.

Just spend the coin on a 840, listen to John about setup, Mine is still screaming (Neighbor bought it).

Its the only way to get around the $hitty DOO 800 motor. If you rebuild it stock again, it'll get hurt again.........

 

[BrentMartell]

What jetting do you run, 430 and 450? Of course, that won't help a rich condition.

My 03 was always strong stock. I never had any issues with it until now. 2000 miles of trouble free pull the rope and go. In fact I have not had an issue keeping up with any other brand stock for stock. Since I added the lightweight seat, hood, and bigger track the sled is right there with the new iron too.

Soooo back to the problem of why it is going from rich condition and not running to a lean condition? There was a group of 13 on the hill Tuesday and I was out troubleshooting and headed toward the group. When I pulled up the sled would only pull 6000 rpm. It sounded like I was running on one cylinder. I poped the hood and pulled the plugs. Mag side was wet, pto was dry. It looked like the mag side was not firing at all.

So, does that mean I have a faulty coil, plug wire, dpm, or mpem? Do I also have a lean jetting issue? 2 problems not one. If the lean jetting on the mag side w/stock can is causing the burn down and the faulty firing issue is causing a rich condition (actually just a mis-fire or weak fire) then I am chasing my tail.

Any thoughts on the improper firing issue?

 

[Wheeline]

Sounds like DPM to me. Also check your carb boots for cracks. A little extra air can cause lots of trouble.

 

[outlaw11j]

This may not apply here but I have seen rich jetting burn down with a bad base gasket seal.

 

[Motley Doo]

You CAN check the DPM on those, it involves a water column and a couple of hoses, kind of a pain, but Ski-Doo does cover it in there manual. It would probalby be something for a shop to do, though!

 

[hymark860]

Sounds like DPM to me. Also check your carb boots for cracks. A little extra air can cause lots of trouble.

What he said. ^^^^^^^^^

 

[BrentMartell]

I did check and will check the boots again, however, a carb boot leak would not cause a rich fuel to air issue.

I did remove the DPM and test with a 9 volt battery. The little plunged moved in and out. However, these probably is best tested while hooked up to the mpem and while sled is running.

I also tried to test the resisitance to the mpem probes and compared the results to a mpem that is know to be working correctly. There was differences in the resistance, however they were small diff.

Last, I found the black wire with yellow stripe that feeds the mpem box was rubbed and the wiring exposed. I removed it from the coupler and heat shrinked and taped. It is possible this wire is a feeder and when wet was experiencing enough resistance to mess up the mpem to the point of messing up the signal to the coil and dpm. One of the reasons why I THINK this exposed wire may be the problem is the fact the first ride of the season the sled ran very well and there had not been any moisture under the hood yet. The second ride the sled ran fine for about 3 miles and started acting stupid again. The sled sat in the trailer for a few weeks and had not been inside to dry out. The third ride started out in -11 F temps and the sled had been stored in my heated garage for several days while I was problem solving etc. The sled ran fine until we got off the trail and started playing in the new fluff. IF moisture is the problem then it makes some sense.

Next ride out I am planning to take the known good mpem with me and if the problem shows up I can test it. If not.....I will be parting out a 2003 800 with 2000 miles on it.

 

[Crasher]

On the Mag side, there is an unused port that is capped with a rubber cap. My buddies 03 800 burned down because the wiring harness was zip tied to the port. The wiring rubbed a hole in the cap and it sucked air in the mag side. Just a thought.

 

[Teth-Air]

Are your needles tight? just would explain the dark plugs not the lean burndown. I had an 01 and one needle retainer came loose and the needle was floating around changing the fuel/air mixture. Also my 03 did have the carb boots delaminating causing a hole on top edges.

 

[BrentMartell]

The 03 has adjustable needles and they are in the #3 slot and the clips are good.

I have the cylinders off and did not see any damage to the boots. I will, however, double check. The reeds look good too.

Crasher, I am not following you on this. A unused port where, on the block? I will look tonight and see what I can find. Once again though, it does not explain why this sled was running rich then lean.

In fact, I almost burned the other side down. It was real close, the plug is clean and white and the top of the piston shows ZERO wash and is gray. The underside of the piston does not show heat but it was close! I am hoping that blakc wire with yellow stripe is the problem. Does anyone have a wiring diagram or know where I can find one? I am curious about that wire.

 

[diamonddave]

Why not just bypass the dpm and see if yor runnability issues go away. One other thing that I could say is I had a similar problem about 5 years ago and after chasing it for weeks, I found black plastic pieces rolling around in the dpm and they actually were plugging the vaccum ports of the dpm on the mag side. It might be worth checking this. If memory serves me, you can take of the actuator by removing the 2 phillips screws. My sled did this at 2,400 miles.

 

[BrentMartell]

2 philips screws? What year was your sled? Also, that is a good idea that I am planning to do once I put a new cylinder and piston in it. The dpm only works once power is supplied and that means the sled has to be repaired first. I did, as I already mentioned, test the dpm selonoid and it seemed to work correctly. Inspection of the dpm does not indicate any obvious issues, such as damage, holes in the vent lines, etc.