broken plugs

dvav · Feb 13, 2011

i keep having the porcelan break on my plugs ngk br 9es and they come loose also i know that this can happen when you get detonation but how can i tell for sure what is causing this i run supreme and at the begining of the year i drained the tank because i thought water might be the reason for the plug issue i had 142 psi compression on both cyl is that to much for supreme do i need more octane? the sled is a 99 xc 700 with slp twins and powerdome head when i bought this sled 8 years ago i always ran supreme no problems so i dont see why its not enough now any input is appreciated.

sledmasterr · Feb 13, 2011

Are you riding lower elevations? Colder temps? Starting to see the beginning off a hole starting in the top of the piston? You have det issues that need to be resolved. I had this same set up on one of my older twins, ran 3 gallons of av gas per tank of nonethanol premium. Ran down to 5,500', no problems...

dvav · Feb 13, 2011

i just put the motor back together for 2 time this year first time to change a seal and the had to redo the crank the second time . so i was driving it around my yard a bit to test it out after putting it back together. im at about 3300 ft and then when we go riding we probably are at 5000 to 8000 there are no holes starting yet and i would prefer not to have any . sled seems to run fine almost a bit gurglee in the mid range but rips wide open. woudl det happen more at high or low rpm or even at idle. also i have never checked the timing physically just always line up the points when putting the stater in which i was told was 16deg and i set it a c hair to the left which i thought would be about 15deg or am i going the wrong way thanks for any info temp was pretty mild today +4deg celcius and sunny

RMKSinner · Feb 20, 2011

i would say bad fuel. i had this same problem this year. and it was all becasue of bad fuel. they are putting to much ethanol in the fuel, i was talking to Millennium Tech. in Plymouth,WI great people. but they told me alot fuel is up to 20% ethanol, even thou there is only supposed to be 10% ethanol in the fuel. just my 2 cents. hope it help.

AKSNOWRIDER · Feb 20, 2011

if you turned the stator a hair to the left..you advanced the timing...check the timing with a timing light....

mike taylor · Feb 20, 2011

AKSNOWRIDER said:
if you turned the stator a hair to the left..you advanced the timing...check the timing with a timing light....

Agree X2
And you might try half jet size fatter.
my 98 700 ported,twin piped would do it lower alt @ WOT
on av gas back in the day. so check fuel for ethenol
good luck !

dvav · Feb 20, 2011

i think i will take a little bit of timing out just to be safe i have twins and powerdome heads i think i need to be at 15deg and stock is supposed to be with the notches lined up 16deg so a little to the right i guess. i dont see how your supposed check timing at 8000 rpm

X2Freeride · Feb 20, 2011

When you say power dome heads whose heads are they? SLP or PSI?

142 PSI of compression is quite a bit for a otherwise stock engine running premium if you advanced the timing.

dvav · Feb 21, 2011

they are the slp heads and pipes and v force reeds anyone know how to figure out what the compression ratio would be with 142 psi compression

X2Freeride · Feb 21, 2011

Whats the CC on the heads, or at least the part number on them?

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broken plugs

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