Opinions on plugs readings

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thumper580
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Joined: Wed Jul 12, 2017 3:34 pm
Location: Virginia

Opinions on plugs readings

#1 Post by thumper580 » Mon Sep 04, 2017 5:29 pm

Like some educated opinions on the following two plug readings. One is BR8HS and the other BR9HS. Carbs are clean and synced. Smooth idle, nice off idle response. Mikuni 34mm round slides, Wilson Performance stage 3 porting.

What you should be looking for.
1. dark ring on first 2-3 threads, indicate correct heat range
2. brown ring around the base of the plug, indicates good jetting
3. color change at the 90 degree bend of the grounding strap, indicates proper ignition timing
4. the three color bands on the ceramic insulator to read idle, needle and main jetting

what I'm seeing....
BR9hs looks to be on the cold side, very minor darkening on the first 2-3 threads.
BR8hs looks to be a better temp plug with thread darkness.

Timing mark on both plugs look good....on the bend of the grounding strap

BR8hs has better color around the base of the plug...jetting. The BR9hs has partial color around the plug base??? Same jetting.

Given the poor cell phone lighting the insulator color on both are about equal.
BR9HS on top followed by BR8HS. .....I'm leaning towards the BR8HS plug..... Comments, opinions??? Thanks.
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plug br8hs.jpg
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silverstrom
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Re: Opinions on plugs readings

#2 Post by silverstrom » Mon Sep 04, 2017 11:03 pm

BR9 plugs are 70*C to 100*C colder than BR8 plugs. Unless you plan to ride at full WOT all the time or live where the temperature is 100*F every day you don't need a BR9 plug. With normal use you may foul BR9 plugs.

To properly verify jetting you must do a proper plug chop.

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