800r spark plug de-gapped

[snoking]

Ive got an o7 summit 800. I rode it on saturday and suddenly lost a cylinder, i pulled the plugs and one was ungapped as if the piston hit it. I put a new plug in and rode it fine all day. Any idea what would cause this?

 

[polarice]

Ive got an o7 summit 800. I rode it on saturday and suddenly lost a cylinder, i pulled the plugs and one was ungapped as if the piston hit it. I put a new plug in and rode it fine all day. Any idea what would cause this?

one of two things i think

either some crap got on top of piston
or somethings fishy on bottom end

 

[Polarblu]

ussually a crank bearing on its way out. In dirt bikes you see it more. Is there strange marks on the piston dome?

 

[TROLLCAT]

that,s weird there is alot of room between piston/spark plug on those motors

 

[rusty]

its your engine detonating or knocking..

 

[Polarblu]

it isnt caused by the piston hitting its foreign material traveling at high speeds hitting perfectly on the red hot electrode which bends super easy.

 

[snoking]

Could this happen from running low octane gas?

 

[tukernater]

Could this happen from running low octane gas?

its all starting to make sence? yes never run low octane in it 91 min

 

[team dirt]

its all starting to make sence? yes never run low octane in it 91 min

Detonation is your issue. Save a major headache and pull your head. You will have piston damge wich if left will turn into a catastrophic failure. Always use premium at minimum.

 

[Polarblu]

when you pull the head and see small cylindrical marks in the piston post picks so people can see that its not detonation.

 

[snoking]

I was using 87 octane from a gas station in the middle of nowhere, i had no choice. I guess I'll probably pull the head tomorrow and see whats happening.

 

[team dirt]

when you pull the head and see small cylindrical marks in the piston post picks so people can see that its not detonation.

Actually with detonation you will see marks in the top of the piston and the four corner seizure marks. As you detonate your ring alignment pin being steel will get red hot and start pitting away at the aluminum causing small peices of aluminum to come off the piston and close the plug gap. Also look inside the dome of the piston and i bet it has alot of burnt oil on it.

If you were riding a mountain sled in the prairies on 87 octane you were for surely detonating. Also did you happen to notice if your water temp light ever came on.

 

[snoking]

I honestly thought that 87 octane would just make it run a little weaker, I had no idea it would physically damage it.

 

[Polarblu]

Actually with detonation you will see marks in the top of the piston and the four corner seizure marks. As you detonate your ring alignment pin being steel will get red hot and start pitting away at the aluminum causing small peices of aluminum to come off the piston and close the plug gap. Also look inside the dome of the piston and i bet it has alot of burnt oil on it.

If you were riding a mountain sled in the prairies on 87 octane you were for surely detonating. Also did you happen to notice if your water temp light ever came on.

I have to disagree. yes pitting does happen with detonation and if compression is too high with low octane fuel this is a posibility. I have never seen those tiny pieces of aluminum smack a plug and close the gap. The locating pin can come out and hit the plug and that part is the only way detonation can be a factor of the initial problem. The plug gap is only closed by foriegn material in the combustion chamber period. Detonation happens when two flame fronts meet at the side of the piston. pre-ignition and the flame fronts meet @ the center of piston. Niether of those shockwaves happen near the plug. Any aluminum that is shocked off the piston is molten, its not hard enough to close the gap. You may see what looks like a silver coating on the plug and thats it. What i am trying to point out is small cylindrical marks in the piston dome which are bearings that have cracked in half and have been sucked up with the fuel from the bottom end. I mis-diagnosed this same problem once and it cost me, put on a new top end and made sure everything was good to go just to have another bearing pass to the top and cause the same damage.passing on the knowledge.

 

[maxwell]

polarblu is right there is some debris flying around in their. happened on my friends 01. put a new plug in and it ran fine for 2 more rides and then the crank went out. and you have an 07 this is not a suprise

 

[TABSTER]

spark plug....... yup, its forshadowing!

 

[Polarblu]

polarblu is right there is some debris flying around in their. happened on my friends 01. put a new plug in and it ran fine for 2 more rides and then the crank went out. and you have an 07 this is not a suprise

ah shucks we agree on something!!!!! I feel warm and fuzzy like you just gave me a hug!!

 

[knee deep in it]

polarblu is right there is some debris flying around in their. happened on my friends 01. put a new plug in and it ran fine for 2 more rides and then the crank went out. and you have an 07 this is not a suprise

i have seen the dreaded zero gap plus twice in my life. Both times, the crank followed. Once, it was my 07 rev 800r.

I have read about this quite a few times on forums and, always, the crank is about to go kaboom. I have no idea why a failing crank would close the gap on a plug.

 

[teeroy]

i have seen the dreaded zero gap plus twice in my life. Both times, the crank followed. Once, it was my 07 rev 800r.

I have read about this quite a few times on forums and, always, the crank is about to go kaboom. I have no idea why a failing crank would close the gap on a plug.

pieces of the bearing get sucked into the combustion chamber. seen it before as well on a 2001 summit x....

 

[Polarblu]

i have seen the dreaded zero gap plus twice in my life. Both times, the crank followed. Once, it was my 07 rev 800r.

I have read about this quite a few times on forums and, always, the crank is about to go kaboom. I have no idea why a failing crank would close the gap on a plug.

On the con-rods there is a slot for the oil to get in. When the bearings start to fail one or more disinigrate and this gives room for pieces of the others to turn sideways break in half and fly out of the oiling slot. These get sucked up with the fuel and air coming in and head up top to fly around the combustion chamber. This typical. However a chunk of reed can do this as can other foreign crap like sticks or a chunk of belt when there isn t a screen on the intake.