broken plug?
- Thread starter 76FOMOCO
- Start date
Detonation!
E
Ex-Member
ACCOUNT CLOSED
that was my thought.
Did you check it before it broke off? Usually det will mash the spark gap closed before it just busts it off.
I would pull the jugs and check the crank bearing and the wrist pin bearings. Just to be sure there is no extra play in them. Also check your reeds and reed cages to make sure no pieces broke allowing them to be caught between the plug and the piston. From the looks of that piston I don't think detonation will be your problem.
D
diggerdown
Well-known member
I think you had it right...it just broke off! No sign of deto or water ingestion. I used to see that way back in the early '70's when ngk first started selling plugs in the US.
Is it a possibility a brass drift or a rivet stem some how migrated in there?
Nope, no thanks needed, try to help out wherever I can..
Nope, no thanks needed, try to help out wherever I can..
How come you paint those spark plugs black?
X 2. Check your rod bearing for play.
if play was the issue she would have more off an impact in center of piston..???...i think she just broke..could have been weakened gapping back and forth a few times to get it right originally..
BRP had NGK build a plug with a beefer ground because they were getting breakages. That also why BRP says not to gap them, make sure they are the right gap when you buy them.
Autolite plugs are real very reliable from my mechanic experiences for many years. Usually something else cause the plug problem regardless of brand due to detonation (number one problem), person bending tip back and forth while gapping, weaking the tip which will break off later on. I have not seen a single plug go bad by itself on good tuned motor.
the few i have seen from deto were totally gone, that one snapped right where ya bend em to gap them, could just be a bad plug with a tad bit of stress from gapping it made it not last.
It could have hit anywhere and then broke of causing the worst of the damage. Something I'd check for if it were mine...
G
Gimpster
Guest
Anybody ever have this happen? what is the cause?
it's not burnt just broken off.
so lets hear all the pros answers.
plug had about 1k in mountain miles on a 900 based cat twin with slp twin pipes
Almost looks like too cold of a plug. Yes, It broke off, but I believe it broke from heat. The jetting change may have brought out another issue as some have mentioned. Possable reaction with the fuel where the rejetting raised the tip temp160 to 210 degrees. This could have caused a weakened bend to heat up and easily break off.
Too cold of a plug will show signs of black. I think the heat had to dicipate through the negative electrode and was increased when rejetted, enough to burn off the weak spot in the bend.
I have seen this in higher performance engines I have built, altering timing and compression, a hotter spark plug has to be ran or what happened to you will result, on dyno pulls.
I know it sounds bass-ackwards, when you get this motor back together, throw a hotter set of plugs in it and make a run and do a plug check, in case you do not come to a resolution for cause of that plugs electrode breaking off. After a short hard run, pull the plugs and check them before riding too much more and confirm the plugs are correct before riding on.
My thought is that the center electrode was not taking the increase in heat dicipation from the rejet. A hotter plug would have directed the heat more to the insulator and not the tip.
----- Gimpster -----
