Piston Burnout.

[Pappillion]

I have a 2002 Rev 800 that cooked a piston so i went out and bought a small block to replace it. Did one trip and on the second day that motor blew up on me with the exact same problem.

The inside piston ran to hot and blew a hole in the top of it on the front side. As well the outside piston's rings had worn down and the piston itself showed signs of being to lean.

I originally thought that the first motor had just went due to age but having the second motor do the same thing within 200 km makes me think that there is another problem. Some people have told me that it could be the computer and some have told me that it could be jets or even DPM. No changes to the motor had been made prior to the blowouts.

Any advice would be great.

 

[POWDERSLUT]

what size jets are you runnin,where did it blow up,in the mountains or flatland.If u run only in the mountains then u should be good with 420-410 ,but if you flat land it you want to be 460 maybe 480.when you put in new motor did you bleed oil injection?What is your primary clutch set at,?

 

[Pappillion]

what size jets are you runnin,where did it blow up,in the mountains or flatland.If u run only in the mountains then u should be good with 420-410 ,but if you flat land it you want to be 460 maybe 480.when you put in new motor did you bleed oil injection?What is your primary clutch set at,?

Nothing had changed. Just put the new motor in. Everything should be OK for jetting. It blew up in the mountains both times on the trail once coming down and once going up. I don't think that the oil injection was bled though. That might be the problem.

Could it be a clogged line or something?

 

[Modman]

Could be a clogged main jet or something as well if its lean. I would pull carbs and check everything and all lines to DPM. Sounds like both sides are almost getting too lean?

 

[Pappillion]

Could be a clogged main jet or something as well if its lean. I would pull carbs and check everything and all lines to DPM. Sounds like both sides are almost getting too lean?

The inside cylinder is definately lean but the outside one isn't bad. Could the outside cylinder be effected by the heat if the inside cylinder is getting too hot?

 

[Modman]

The inside cylinder is definately lean but the outside one isn't bad. Could the outside cylinder be effected by the heat if the inside cylinder is getting too hot?

OK, then if one side is lean and the other isn't, there is even more reason to suspect carbs. My mistake, thought that it sounded like both sides were lean.

Not sure about the oil line as it would not have been "bled" before the first burndown and should have been fine, not sure why it would be fine for a few thousand kms and then all of a sudden just get airlocked, which is why I suspected jetting. Oil line could be the issue if the oil pump has failed, usually not a common thing though, but may explain things. If you mixed oil into the first tank after the rebuild, then on day 2 you might have been on just gas (no premix). The oil in the premix from the first day may have been enough to get you through to the second day. You could also have an air leak somewhere. This would be my other suspicion, maybe you have a crank seal leaking. It would not have been replaced on the rebuild unless you split the cases. Did you split them?

When you say "inside and outside" cylinders, they are both on the outside, so I'm confused. Magneto or PTO (power-take-off) side (as you are sitting on the sled)?

Just throwing some ideas out there.

 

[Pappillion]

OK, then if one side is lean and the other isn't, there is even more reason to suspect carbs. My mistake, thought that it sounded like both sides were lean.

Not sure about the oil line as it would not have been "bled" before the first burndown and should have been fine, not sure why it would be fine for a few thousand kms and then all of a sudden just get airlocked, which is why I suspected jetting. Oil line could be the issue if the oil pump has failed, usually not a common thing though, but may explain things. If you mixed oil into the first tank after the rebuild, then on day 2 you might have been on just gas (no premix). The oil in the premix from the first day may have been enough to get you through to the second day. You could also have an air leak somewhere. This would be my other suspicion, maybe you have a crank seal leaking. It would not have been replaced on the rebuild unless you split the cases. Did you split them?

When you say "inside and outside" cylinders, they are both on the outside, so I'm confused. Magneto or PTO (power-take-off) side (as you are sitting on the sled)?

Just throwing some ideas out there.

I had good oil mixed into the tank so i know it isn't an oil problem. Motor popped on the first tank. I have broken in motors before so i know that i didn't run it to hard. The PTO side did show signs of being lean. Compression was at about 115 when i checked it after the second motor flopped on the PTO side. On the MAG side the piston had a big hole on the front side of the top(exhaust side). Rings were gone too. I will check the jets when i get home. I'd feel really dumb if it is a clogged jet. I will also check the DPM to see if all the lines are in good order.

Is there any way to check DPM modules to see if they are running properly?

 

[POWDERSLUT]

Nothing had changed. Just put the new motor in. Everything should be OK for jetting. It blew up in the mountains both times on the trail once coming down and once going up. I don't think that the oil injection was bled though. That might be the problem.

Could it be a clogged line or something?

jetting i would think now...down low it is runnin lean (to much air),air gets thinner the higher you go,so less air.I have to baby mine down low elevations,then i can pin it all day , 5000 ft and up,my plugs look like cinnamon ...You always here about the guy who cooked his motor 3 kms up the trail ....
You definatly want to bleed the oil lines........

 

[Modman]

I had good oil mixed into the tank so i know it isn't an oil problem. Motor popped on the first tank. I have broken in motors before so i know that i didn't run it to hard. The PTO side did show signs of being lean. Compression was at about 115 when i checked it after the second motor flopped on the PTO side. On the MAG side the piston had a big hole on the front side of the top(exhaust side). Rings were gone too. I will check the jets when i get home. I'd feel really dumb if it is a clogged jet. I will also check the DPM to see if all the lines are in good order.

Is there any way to check DPM modules to see if they are running properly?

Might not be a clogged jet if both sides were lean. Possibly air leak somewhere to be that lean to smoke a piston. DPM usually defaults to extreme rich if it fails, that's the way its built and designed.

 

[CrankShop910]

I would check for air leaks. Really check your carb boots.

 

[Pappillion]

I would check for air leaks. Really check your carb boots.

Other than pulling everything apart and manually checking, is there a way to check for leaks when the motor is running?

 

[YellowMissile]

Other than pulling everything apart and manually checking, is there a way to check for leaks when the motor is running?

A trick I use for checking for intake leaks on automotive engines is to have them running and spray a combustible fluid on the suspect sealing surfaces (WD40, Brakekleen). If the rpms pick up then you know there is a leak there.

 

[Modman]

A trick I use for checking for intake leaks on automotive engines is to have them running and spray a combustible fluid on the suspect sealing surfaces (WD40, Brakekleen). If the rpms pick up then you know there is a leak there.

Use Ether (diesel starter spray), it works the best. New WD 40 isn't flammable so its useless and most of the newer Brakleen type products are also starting to be non-flammable as well. Ether works the best.

Do what YM said though and spray around the base and crank gaskets. Hope you get it worked out.

 

[YellowMissile]

Use Ether (diesel starter spray), it works the best. New WD 40 isn't flammable so its useless and most of the newer Brakleen type products are also starting to be non-flammable as well. Ether works the best.

Do what YM said though and spray around the base and crank gaskets. Hope you get it worked out.

If you want the good flammable brakekleen, it's behind the parts counter at auto value.. Might take a little sweet talking but you can get it without an account. Stuff just works better than the new non-flammable crap they have out on the floor..

 

[boondockin]

I have a 2002 Rev 800 that cooked a piston so i went out and bought a small block to replace it. Did one trip and on the second day that motor blew up on me with the exact same problem.

The inside piston ran to hot and blew a hole in the top of it on the front side. As well the outside piston's rings had worn down and the piston itself showed signs of being to lean.

I originally thought that the first motor had just went due to age but having the second motor do the same thing within 200 km makes me think that there is another problem. Some people have told me that it could be the computer and some have told me that it could be jets or even DPM. No changes to the motor had been made prior to the blowouts.

Any advice would be great.

what plugs are you running? may sound off but i had a 670 that wnt b/c one side had the stock plug and the other side had the split tail plug and the side with the split tail was lean and threw the piston... just an idea