Wanted!!! 2009 Polaris RMK 700cfi engine....or any help and ideas to fix the problem

[Nelson]

My buddy keeps burning down his Mag side piston, same failure in 3 rebuilds....Polaris mechanic's are stumped so he just wants to replace the engine. Let me know what you've got.

Thanks

 

[Chuck D7]

I have seen this happen. The ecu gets partially burnt from a voltage spike. You can not tell anything is wrong. Replace the ecu and good to go. I have been a polaris tech for 7 years. Easy to do at the dealership. When you run the sled with the track of the ground you should be able to here the popping and detonation. Sometimes you really need to get it up in the Rpms. Replace the ecu and see if it goes away.

 

[Nelson]

That's kind of a pricey experiment tho isn't it? Polaris has rebuilt the sled 3 times and each Mag piston has had the same scoring on the Exhaust side when he squeaked it, looks like a lean burn down. Polaris has reflashed the ECU twice, wouldn't if the ECU was partially burnt it not take the reflash? All factory OEM Polaris parts were used in the rebuild, pistons and cylinders mic'd good before install, injectors flow tested good, fuel pressure good, reeds are stock (good), TB boots were brand new. Its weird and he doesn't want to rebuild it just to have it blow up again so he wants to replace, first seeing if there's a used engine for sale before ordering a new crate engine. The only mods to the original is an SLP pipe/can, he runs Polaris Gold oil and non ethanol fuel.

Any thoughts???

 

[gcmci]

Test for Crank seal leak on mag side ????????????

 

[Chuck D7]

I'm sure they have tested the crank seal. That wood be an obvious problem. I don't understand, the dealer told you they can't fix it? Wow, I wish I could give up and say we can't fix it. The dealer should have a ecu they can flash and test. If it works, great. If not put it back on the shelf. I have never tried to reflash a ecu with the same flash. So I wouldn't be able to tell you if a bad ecu would take a reflash or not.

 

[BB454]

motor

Why replace the motor? If you do and use the same electronics and fuel system, you may still have the problem unless you replace everything. Take that ECU off and look at the back of it for melted area. Usually you will see some discoloration. What does the piston look like when it fails? If it is pounded on the top then you are lean. If it sticks in the cylinder then you have a oiling problem. I just did a Cat that had the piston pounded and a cup in the dome starting. Come to find out the guy was running 88 fuel.

 

[sethmp6]

I would bet on the mag crank seal. Have seen at least 25 engines with that seal leaking. Very common problem, especially in 2009. It is hard to tell by looking, you might see some oil seeping around the crank stub. Polaris upgraded the seal in 2011 to a high tolerance part. If you replace it order the newest seal number from an 800, they are all the same seals. Have your crank true checked while it is out also.

 

[Nelson]

It isn't my sled, its a buddy of mines sled. Polaris didn't say they couldn't fix it, they're just stumped....They want him to buy a brand new crate engine and he's reluctant to spend that kind of cash if it doesn't fix the problem. Changing ECU's won't help because then engine doesn't run(blown up), he'd have to rebuild it again and if it's not the ECU then he's out the money for an ECU and the cost to rebuild the motor a 4th time. He'd rather see if there's a used engine out there that he can swap into his sled and go from there.

Polaris pulled the engine out of the sled on the 2nd and 3rd rebuild so I'm sure the crank seal was checked but don't quote me because I wasn't there when they did it. I'm stumped because this is literally the only 700cfi motor I know of that's had any kind of issue.

 

[Chuck D7]

They should be covering the bill if they said they fixed it and it burns up again. That is there fault for not fixing the problem. They shouldn't charge you if wasn't fixed right the first time. If the motor has been gone threw and everything is within service limits, it's not the motor. Sounds exactly like a case I had a few years ago. Checked fuel pressure, injectors, timming, stator, no air leaks, good fuel, stumped. We had seen a lot of bad regulators taking out ECU's. You could tell by looking at the back of the ecu and or smell. But this one looked and smelled fine. Finally I just decided to grab a new ecu for sh*ts and giggles. Fixed the problem. Same case. one cylinder burnt down twice.