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Discussion Starter · #1 ·
I was doing some regular maintenance on my bike today and inspected my spark plug at 3400 miles. Are my plugs a sign that I'm running a bit rich ?




I only have a few mods on my bike, full Yoshi system exhaust, two washer under needle, snorkel remove. The rest of my bike is stock.

If it is rich, should I remove one or both of my washers under the needle ? Buy a aftermarket air filter to try to get more air into my engine, or a combination of both.

thanks for your help
 

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Mike,

Yes, Yes, Yes and Yes, but NOT at the same time. Everything you said is correct. If you want more power, buy the aftermarket air filter and see what that does. Also play around with your jetting on both the main jets and the idle jets. This was sent to me by another fellow on another forum:

You need to test the carb 3 different ways,
low range(idle)
mid range (4-6000 rpm)
high range (8-9000 rpm)


High range
In this range the needle is doing nothing, it is wide open the jet is feeding the fuel.
Clean the plug and re-install then run the bike in 2-3'rd gear with the rpm's in the 8-9000 range, steady for 30 seconds.
Hit the kill switch and push in the clutch, let the bike roll to a stop and remove the plug.
If it is white it is running lean and you need a bigger jet(probably not).
If it is milky brown you are right on the money.
If it is black you are running too rich, go to a smaller jet.


Mid range. The jet and needle are working together to supply fuel.
Clean the plug and re-install then run the bike in 2-3'rd gear with the rpm's in the 4-6000 range, steady for 30 seconds.
hit the kill switch and push in the clutch, let the bike roll to a stop and remove the plug.
If it is white it is running lean and you need to raise the needle.
If it is milky brown you are right on the money.
If it is black you are running too rich, you need to lower the needle.

Low range, the bike is getting its fuel thru the pilot jet.
Run the bike in neutral with the rpm's at idle for 30-60 seconds.
hit the kill switch .
If it is white it is running lean and you need to open up the pilot jet.
If it is milky brown you are right on the money.
If it is black you are running too rich, you need to close the pilot jet.
 

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Discussion Starter · #3 ·
Ah thanks for the advice spoogh, I remove one washer later today and install new spark plugs and went for a 30 mile ride with my wife before our 4th of July celebration. I believe my main jet is correct (its the stock main jet), my bike pulls hard well into red line territory without any hesitation or sputtering. So I will work with my needle height and eventually buy an aftermarket filter if it still need more air.
 
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