Spark Plug Colour and Life 650R

I was just wondering how long the stock NGK Iridium plug lasts on average

My bike xr650r has now done 2.7K Miles and this is the first time I have looked at it the colour of the plug is a pinky / brownish / Greyish colour I presume this is the right colour.

The reason why i'm thinking my plug is breaking down is becuse after fitting my new twin can exhaust and headers my bike was running great. 100 miles later the bike is now faultering at 70mph in top gear as if its starved of fuel or its missing. my bike is fully uncorked with cut/airbox opened std. filter and 175mains and 68s pilot altitude approx 1500/2000 ft.

Would this be anything to do with the plug or should i think about re jetting my standard carb?

I have an edelbrock ordered so i'll probably wait

Are you missing or blubbering?

As far as main jetting guidance goes, if it seems to be missing near full throttle then it is lean, go larger and if it seems to be blubbering near full throttle then it is rich, go smaller (in small increments).

Has the temperature changed much in your region with summer coming on? Hotter temps means your mixture will be richer and requires a "leaner" adjustment, go smaller.

I'll order a 180 and 185 main and try that then i think. Will the 68s pilot jet match? :applause:

If you are idling without problems and the airscrew is effective between 1 and 2.5 turns out then there is no need to change the pilot jet.

adjusting the air screw isnt really making an awful lot of difference

I should have said: if adjusting the air screw makes a change in 'off-idle throttle response' then there is no need to change the pilot, simply adjust for the best response. If the air screw has no effect on off-idle response then you should try a 65 pilot.

The 68s works very well in a wide range of temperatures at your elevation.

ok thanks

Quick Update:

Original Plug Still in use

Suck in a 185 Main Jet Now it Rips! :applause::D:bonk::prof::prof:

Congrats on getting your jetting solved.


If you experience any decel popping don't worry about, it can happen even when you run rich. I am currently running rich and experience this on trails. A rich main jet is good in sandy conditions where you are using full throttle.


There is now very minimal popping on deceleration i'm well pleased!

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