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Old October 5th, 2016, 01:38 PM   #1
Wanderer
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How do you guys check whether one carb is running stronger or more rich/lean? Plugs?

Besides watching the plugs and "syncing" the carbs, is there any other suggestions to determine if one carb is adjusted better or worse than the other?

My background with 1 cylinder "thumpers" makes it easy, but with two cylinders and two carbs, it's not that easy.
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Old October 5th, 2016, 02:10 PM   #2
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It is almost impossible to get a good plug read with modern unleaded fuels.

Let me know what you think of each one of the plugs below.



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Old October 5th, 2016, 02:14 PM   #3
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Quote:
Originally Posted by RacinNinja View Post
It is almost impossible to get a good plug read with modern unleaded fuels.

Let me know what you think of each one of the plugs below.
My guess would be that the top one is running slightly rich and the bottom one is about right.

Yes?
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Old October 5th, 2016, 02:23 PM   #4
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Quote:
Originally Posted by Wanderer View Post
My guess would be that the top one is running slightly rich and the bottom one is about right.

Yes?
Well, nope. Not the answers I was expecting.

Bottom is perfect on 92 No Ethanol. Top is 100LL/92 No-E 50/50 mix perfect tune. Tested both on a dyno.

I always thought the bottom one looked a little lean. Porcelain is perfectly white but the timing is good if you look at the strap. Idle is a tad on the rich side, which the dyno sheet reflects. Base circle is a bit dark.

You're pretty good at reading plugs. Carry on.
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Old October 5th, 2016, 02:32 PM   #5
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Quote:
Originally Posted by RacinNinja View Post
Well, nope. Not the answers I was expecting.

Bottom is perfect on 92 No Ethanol. Top is 100LL/92 No-E 50/50 mix perfect tune. Tested both on a dyno.

I always thought the bottom one looked a little lean. Porcelain is perfectly white but the timing is good if you look at the strap. Idle is a tad on the rich side, which the dyno sheet reflects. Base circle is a bit dark.

You're pretty good at reading plugs. Carry on.
In truth, I would be happy with either plug if I pulled it out of a bike.

I would only be concerned if one was more "sooty" black(rich) or a light tan(lean) or white.

For me, a change in gas brands or the way you ride can make anything else most likely just guesswork.

Thus the reason for my question.
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Old October 5th, 2016, 02:38 PM   #6
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The only other real way is to get an EGT monitor for each pipe, an IR thermometer to check pipe temps or a wideband O2 sensor and computer for each pipe.

Reading spark plugs is easier. A dyno tuner is more expensive but can read the gas output also.
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Old October 5th, 2016, 02:42 PM   #7
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Originally Posted by RacinNinja View Post
The only other real way is to get an EGT monitor for each pipe, an IR thermometer to check pipe temps or a wideband O2 sensor and computer for each pipe.

Reading spark plugs is easier. A dyno tuner is more expensive but can read the gas output also.
That makes sense. Just plug testing for me then.

I just always wonder if one cylinder is carrying more of the load than the other. Much like 2 locomotives pulling a freight train. I wonder how they balance the load between them. *smile*
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Old October 5th, 2016, 03:43 PM   #8
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Quote:
Originally Posted by RacinNinja View Post
The only other real way is to get an EGT monitor for each pipe, an IR thermometer to check pipe temps or a wideband O2 sensor and computer for each pipe.

Reading spark plugs is easier. A dyno tuner is more expensive but can read the gas output also.
This is probably the easiest way to determine if they are even close. You would have to be sure the carbs were synced and the idle mixture screws the the same.

EGT or O2 sensor would be the more accurate way, but obviously more complicated to DIY.
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Old October 5th, 2016, 11:38 PM   #9
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So many outside factors can/do effect the engine, valves out of adjustment, poor carburetors, fuels, etc......

The only true way is to get your hands on a exhaust gas analyzer, otherwise your just shooting in the dark, and taking the best guess you can.
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