YamahaSXR700
Member
ok, here it is, yesturday morning was going for a ride to make some ice on the lake, leave from home like 20 min from here engine stops. i restarted it, it ran good left with it again, then stop again in not even 5 min then after i tried pull start it the engine was like seized a bit u know then it turned good after it was ahrd then easy could this be a crank bearing guys? umm i opened up the plugs all redish brownish im think has a crank bearing
warx22
New member
is your oil injecter working and adjusted properly check it out
YamahaSXR700
Member
well it was good after i fixed the carbs i checked it oput it was running okay but like my plugs would be white man no? if that wouldnt worked?
PZ 1
Member
- Joined
- Mar 12, 2005
- Messages
- 987
warx22 said:
Yea, sounds like like it was oil starved.
You will have to look inside. Score marks on the pistons will tell what the cause was.
YamahaSXR700
Member
i got some pics clutch side piston melted down, i loks like it was dry on oil oil inject pump might of let go
YamahaSXR700
Member
buddy had it before had did the top end on it, not sure about the bottom end but the top end was done by someone, and on top of the piston is says 25 on it i beleive its bored out and i havent mention that it has 23233 kms on it thats alot,
YamahaSXR700
Member
YamahaSXR700
Member
second piston
YamahaSXR700
Member
iu found the problem what cause the piston to melt down, theres two little oil inject lines from the pump that goes to gas lines, and one line on the pump was cracked big i got pics i will post later
Brit44Aldo
New member
your pictures show a typical lean mixture seizure. If it were oil related the seizure would be at the bottom of the skirts. oil lubricates the bearings, fuel cools the piston crown.
The question I ask when seeing this type of piston, is where were you holding the throttle the first time it quit. The leanest jetting is a 1/3 maximum speed. Your butterfly carb regulates this area by the holes drilled in the body (under the welch plug) and not by any of the fixed jets (unless you count the fuel that must pass throught the pilot jet).
Also, poor fuel quality (old gas) will cause this same "4 corner" seizure as it does not vaporize well, thus the heat is not disipated. Top of the piston, heat. Bottom of the piston, lack of oil or snow injestion.
I see from your pictures someone used RTV. RTV should NEVER be used. That was OK in the 70s, but even tephlon (sp) tape can plug an oil passage on a modern 4 stroke.
"The Works" toilet bowl cleaner and a Qtip will work well to remove the aluminum from your cylinder. Do this before you take it to your local shop to have the bore checked and #1 they will have a better estimate of the damage and #2 they will not charge you for acid washing out the aluminum. If the aluminum is there, it will tear up there honing stones, so they will charge you to remove is with acid first.
The question I ask when seeing this type of piston, is where were you holding the throttle the first time it quit. The leanest jetting is a 1/3 maximum speed. Your butterfly carb regulates this area by the holes drilled in the body (under the welch plug) and not by any of the fixed jets (unless you count the fuel that must pass throught the pilot jet).
Also, poor fuel quality (old gas) will cause this same "4 corner" seizure as it does not vaporize well, thus the heat is not disipated. Top of the piston, heat. Bottom of the piston, lack of oil or snow injestion.
I see from your pictures someone used RTV. RTV should NEVER be used. That was OK in the 70s, but even tephlon (sp) tape can plug an oil passage on a modern 4 stroke.
"The Works" toilet bowl cleaner and a Qtip will work well to remove the aluminum from your cylinder. Do this before you take it to your local shop to have the bore checked and #1 they will have a better estimate of the damage and #2 they will not charge you for acid washing out the aluminum. If the aluminum is there, it will tear up there honing stones, so they will charge you to remove is with acid first.
YamahaSXR700
Member
yea i know about the RTV i bought the sled like that that was only on one side of the head that they put that, and the piston should be bored if they have a 25 on top of it,