Blown motor help please

[Snowshovel]

Well the day started off perfect, we started up mountain and by the time we got to the trail head there was 10 inches of fresh powder on the trail and more falling in buckets. About 5 miles in I was in the lead and as we started to go up an incline i gave my (new to me, bought used last week) 03 Mountain Viper more gas. The result was bogging and the sled dying... hmm i thought bad gas from last year? fouled plugs? improper jetting as the altitude increased? So after inspecting the plugs the center one looked like it was burning lean, hardly wet at all after running for at least 45 minutes. Swapped in new plugs, and tried to start it, the crank would not turn, i pulled on the rope and she would come out about 5 inches and stop dead.

Fearing i had somehow seized the engine up I pulled the clutch shroud off and tried turning the primary by hand. At first it seemed stiff but then gave way and was turning fine. After many attemps the sled would not start so i hooked up my snatch strap and towed her out using my sons 600 Mountain Max. Once we got back to the trailer, i figured wtf lets give it another go before we try to drag the sled up the ramp into the trailer. Couple pulls and she fired right up, but something didnt sound right. It was almost like a piston was knocking, and the engine was shuddering.

I gave her some gas got it 1/2 way up the ramp and heard the sickening sound of the center piston rock going through the bottom of the case. A mad dash after moving everything off the floor to avoid the coolant that was leaking everywhere we popped the hood open to survey the damage. First thing out of my buddy's mouth "Rob we got debri" you dont want to know the first thing out of mine. The center piston rod had come loose and popped a hole right in the bottom of the case. I just bought this sled 8 days ago, the guy i bought it from said it was awesome for him and other than some minor "kissed a tree" repair he had no issues. It had 7000 miles on it and after looking it over had no visable defects other than a minor oil leak.

I had all fluids full, I was using oil the reservoir had gone down some from where we started. Only maintenance i have done on it was clean the power valves yesterday, which after pulling the top end off looked fine. So no way the powervalves caused this, di i just get the $hitty end of the stick and it was me the engine happened to fail on? Those of you who have owned these sleds please weight in and give your opinions. I am attaching photos of the damage, and am looking for a new motor if anyone has one.

Also is there a way to test your oil pump with the motor tore apart? A way to energize it and watch it pump to ensure it is working before i get a nerw motor and do it all over again?


Top end damage

looking in to the center piston

another of the center chamber

 

[aopdahl]

i 've got a 700 mountain max motor up for sale

_______________________________________________________________
2000 mm 700, triple pipes,156'',mpi transfer enhancement,boss seat and reed spacers.

 

[Snowshovel]

You might be the guy my fried was in here talking to earlier, is it out of an 04 Viper has about 700 miles on it? My only fear is buying it, installing and BOOM i get another present. Kind of looking for a newly rebuilt one

 

[thinksnow]

I think 7000 miles on a 2-stroke is good. I worry everytime I start my MM700 and it only has 4500 miles. My buddy took his motor out at 4000. Another one made 6000 before parts went out the bottom.

These motors are fairly bulletproof, but when they start getting a bunch of miles check them out. I have heard of alot of piston skirts cracking with time. It's fairly cheap to drop in new pistons/rings before the whole motor goes down.JMO

 

[Snowshovel]

Too bad im past that point the top end was beat to $hit by the piston smacking it and the lower end has a hole in it. Not to mention the scoring the cylinder wall took

 

[roughrider99]

I really don't think you can garuntee that your gonna be safe with any 2 stroke motor thats used. my mtn max 600 twin blew up at 4500k then after being rebuilt at a dealer the motor blew up again after 400k.both times required a new pot. just make sure you get a motor from someone with good reputation even if costs an extra buck.

 

[MM800]

motor

In my experience, you wanna make sure you have good fuel. Last years fuel does not cut it. I've see issues where the sled ran flawlwsly one year, jerked on the rope and went for a ride-Boom. A little low in elevation or a little colder than usual, bad fuel (looses octane from sitting), motor starts detonatiang and boom. I cant tell ya how many times I've seen this. Not knowing what your jetting is and what elevation u are set up for, coupled with old fuel spells trouble.

 

[aopdahl]

no it not one out of a viper its a spare one for my 2000 mountain max laying around and iam trying to sell it

 

[Alaskan]

Do some research

I would recommend doing some research and being patient....one will turn up or perhaps you can have yours rebuilt....this would save time and probably money in the long run! You would then have a new motor good for another 5000 miles! You might call Dustin @ OUtlaw Motorsports and quiz him on a replacement motor or where to have it affordably rebuilt the RIGHT way! Tom Hartman from Hartman Inc is another awesome guy to deal with and worth calling! use google to find their home pages and contact info....I'd go with Hartman over OUtlaw, Hartman Inc. is more experienced with older sleds and not so Turbo focused. Almost forgot Totallyamaha.com....wealth of information on your sled and probably the place to go and find one on classifieds or another member!
cheers....

 

[Yammerhead]

There are definately better two stroke piston experts than me, but I will take a stab at it.

The squish band on the head has much more damage than the top of the dome. So, to me, it would indicate that you had some serious detonation going on. Deto can be caused by a few things.

Too high of compression for the fuel used
Bad fuel with lower octane than you thought
Too high of engine temperature which brings on deto earlier
Too lean of jetting
Too lean of jetting due to dirty carb

Were the carbs cleaned this fall? Was there last years gas in it? Had there been any head work done to the motor? Stock Yammie engines have quite a bit of tolerance for bad fuel, so I doubt only that would have been the only cause. Plugged up carb is the usual culprit, but the piston will usually show the exhaust port side melted more than the rest of the piston. It's hard to tell from your pic. My guess would be that it was some combination of the above that caused the piston to stick. Your attempts to run it after probably then broke the rod which then punched the hole in the case. Check the carbs for sure and make sure there isn't something up with the cooling system.

I don't think it was lack of oil. When Yammie pumps wear out, they inject too much oil, not too little.

The 2 stroke forum at Totallyamaha will be the best place to find more info.

 

[aopdahl]

this engine has an extreme port job shaved head brand new stator ,oil and water pump comes with a set of carbs.

 

[M-Max]

In the classifieds.
AOPDAHL he needs a viper engine. 700 powervalve triple
You MM engine is a 700 non powervalve, so it will not work for this application.

http://www.snowest.com/forum/showthread.php?t=170935&highlight=viper

 

[schmitty53]

Buy my mountain Max and then you have a good motor and tons of parts.

 

[twincam88]

i bet it was a plugged jet from not cleaning the carbs. the old man has 16000 km(10,000 miles) on his 97 700 sx and not a problem. the jets are like your heart...got to keep it clean.

 

[RIDECATS]

I had a viper with 3-4 years hard riding and I lost a crank also - took the case with it. I was luck to find an engine very good shape and fair price for sale here on snowest. I feel mine went down from many 3-4 years of hammering the engine