700 burned down

M

mx275

New member
Joined
Mar 14, 2009
Messages
6
Location
kindred
cannot find what happened to cause this meltdown. i am afraid to put back together without knowing what was the cause. the pictures show the result of something else that failed with this sled. this is a 2003 viper mountian that has about 1800 miles. was coming off the mountian at a steady cruising speed at about 8500 feet. was running fine untill it started to loose power. took carbs apart to check for loose or plugged jet and everthing look fine. one thing that is troubling is that the oil tank only went down about 1 inch from the full mark.had been riding all day! but doesnt explain why only one cly failed. i dont know how the oiling system distributes the oil but it looks like it feeds into the fuel pump and then mixes it prior to the carbs. from whati have read on this forumn there seems to be a lot of experts on here and hoping someone could enlighten me.
 

Attachments

  • yamaha 700 viper 001.jpg
    yamaha 700 viper 001.jpg
    39.1 KB · Views: 32
  • yamaha 700 viper 002.jpg
    yamaha 700 viper 002.jpg
    40.3 KB · Views: 17
  • yamaha 700 viper 003.jpg
    yamaha 700 viper 003.jpg
    37.3 KB · Views: 34
  • yamaha 700 viper 004.jpg
    yamaha 700 viper 004.jpg
    40.3 KB · Views: 25
I am not 100% sure on this but I think you are running to lean, there is no signs of piston wash on those piston. I am sure someone else will chime in.
 
pto piston looks perfect , but mag one is lean , that is definetly a detonation melt down on the exhaust and intake side aswell .

you may have been working on that melt down prior to the day it happened .

Last ride , stuck , slush , deep snow , very cold ,???????? etc......
 
Last edited:
do not have piston with me today can send tommorow. what are you looking for under the piston?
 
harness racer said:
pto piston looks perfect , but mag one is lean , that is definetly a detonation melt down on the exhaust and intake side aswell .

you may have been working on that melt down prior to the day it happened .

Last ride , stuck , slush , deep snow , very cold ,???????? etc......
Click to expand...

I agree...the piston erosion can occur over a period of time if its just over the edge....That one piston ran hot for awhile for the damage to be all around the piston...it was getting too big for the bore.
 
so if its running lean why only the center cly. jetting is the same on all 3 carbs. should i be concerned about the lack of oil consumption? again why only one cly? how does oil get to the cly. is it mixed at the fuel pump?
 
what do the heads look like,it looks like rings are incomplete,did you break skirt taking out? to me it looks like ring locating pin failer, this is why i think that, if you look at the way the the piston is eroded the thiner point is at the top of the piston and by ring its wider like that part was broken out and then as the motor was still runing all the combustion was flowing past and hiting the next ring, and spreading heat in that area if it was a lean melt down i would think the area by the ring lands would be wide at top and narrow as you go down because the heat starts on top and once it starts it doesnt get cooler only hotter same with detno those points at the top would be gone because of the heat this is just an opinion open to other thoughts i would make sure the bottom rod bearing and crank bearings ok
 
i highly doubt the ring locating pin failed. it was a lean/deto burndown. the exhaust gas was damn hot. look at how it just melted/eroded the exhaust side of the piston.
 
mopar1rules said:
i highly doubt the ring locating pin failed. it was a lean/deto burndown. the exhaust gas was damn hot. look at how it just melted/eroded the exhaust side of the piston.
Click to expand...


X2 ......YES THE PINS ARE BAD FOR FAILING ..BUT THE RING USUALLY SPINS AND LOCKS THE ENGINE UP SOONER THAN LATER .. LOOK AT THE INTAKE SIDE WHERE THE STOCK PISTON PORT IS ,,,FUEL WAS BURNING HOT 1300+ !!!!
 
Last edited:
all im saying is look at the angles that eroded they are / \ if it was melt down they should be\ / heat from the top there should be no sharpe thin angles at the top they would have melted and rolled down (just an observation opinion)
 
thanks for all the feedback it has been helpfull. now does anyone know were i can get a service manual to help with torque specs and such?
 
so far it looks like bad gas cant find anything else. will let you know if i find anything else. still looking for torque specs.
 
are the locating pins there so that can be eliminated? because that cylinder did run lean once it eroded past the ring lands,there was less fuel being drawn into it even while it was eroding just like a jet being slowly pluged over time so the other cylinders were useing more of the fuel, i see some scoreing on mag i think that could have been a fuel issue on oil side and if pto is jetted fatter it was using the most and looks the best, even check fuel lines and fuel pump for restrictions(kinks or real soft where they could colapse) or pin holes where fuel could be leaking and same with oil lines, have seen were a piece of foyal from oil bottle went into tank and restricted oil flow. let us know what you find!
 
You must log in or register to reply here.


Back
Top