Another jetting a/f mixture thread.
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Outstanding HDF Member
Joined: Jul 2013
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From: Houston, TX
Another jetting a/f mixture thread.
Ok, I'm running a 45 idle and 180 main, A/F mix screw out about 2 1/4 turns. I get a little bit of decel pop, and my pipes have minor sooting in them... not heavy. My front plug just has one spot on it that is starting to show some tan coloring to it. I have about 200 miles on these plugs now... should I richen it up some, or am I good to go? Just don't want to burn a hole in these pistons. I don't see how that could happen though, considering from the factory this sucker came full advance, with a 42 idle and a 170 main jet.
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Joined: Jul 2010
Posts: 853
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From: Melbourne
Your in the ballpark....If the Electrode, Earth tag or Porcelain were all black then I would be telling you your too rich.
Your definitely not too lean so thats a plus...too lean and you would not see as much carbon.
Its always going to be a trade-off on the Pilot jet to get a balance between minimising exhaust popping on deceleration and running at perfect mix - I choose to run richer and cut down on the popping.
Your main jet is in the right ballpark as well, so I would just ride it!
Your definitely not too lean so thats a plus...too lean and you would not see as much carbon.
Its always going to be a trade-off on the Pilot jet to get a balance between minimising exhaust popping on deceleration and running at perfect mix - I choose to run richer and cut down on the popping.
Your main jet is in the right ballpark as well, so I would just ride it!
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Outstanding HDF Member
Joined: Jul 2013
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From: Houston, TX
Your in the ballpark....If the Electrode, Earth tag or Porcelain were all black then I would be telling you your too rich.
Your definitely not too lean so thats a plus...too lean and you would not see as much carbon.
Its always going to be a trade-off on the Pilot jet to get a balance between minimising exhaust popping on deceleration and running at perfect mix - I choose to run richer and cut down on the popping.
Your main jet is in the right ballpark as well, so I would just ride it!
Your definitely not too lean so thats a plus...too lean and you would not see as much carbon.
Its always going to be a trade-off on the Pilot jet to get a balance between minimising exhaust popping on deceleration and running at perfect mix - I choose to run richer and cut down on the popping.
Your main jet is in the right ballpark as well, so I would just ride it!
Road Warrior
Joined: Jul 2013
Posts: 1,476
Likes: 5
From: Florida
Does it stumble and choke out when you turn the idle mix screw in past the 2 1/2 turns and bog down when you turn it out past the 2 1/2 turns? If it does, you probably have the right slow jet. If it doesnt choke out when you turn it all the way in you probably are a size too large, if it doesnt bog down/out when turn it out 3-4 turns you probably are a size
too small.
As for the main jet, get the bike out on a road you can run at speed safely on. Get it in 4th gear and run it up to redline, then slightly back off the throttle. If the engine wants to run faster when you ease off it's probably too lean. If it responds accordingly your probably gtg.
How is your throttle response? How is your needle set up?
too small.
As for the main jet, get the bike out on a road you can run at speed safely on. Get it in 4th gear and run it up to redline, then slightly back off the throttle. If the engine wants to run faster when you ease off it's probably too lean. If it responds accordingly your probably gtg.
How is your throttle response? How is your needle set up?
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Outstanding HDF Member
Joined: Jul 2013
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From: Houston, TX
Does it stumble and choke out when you turn the idle mix screw in past the 2 1/2 turns and bog down when you turn it out past the 2 1/2 turns? If it does, you probably have the right slow jet. If it doesnt choke out when you turn it all the way in you probably are a size too large, if it doesnt bog down/out when turn it out 3-4 turns you probably are a size
too small.
As for the main jet, get the bike out on a road you can run at speed safely on. Get it in 4th gear and run it up to redline, then slightly back off the throttle. If the engine wants to run faster when you ease off it's probably too lean. If it responds accordingly your probably gtg.
How is your throttle response? How is your needle set up?
too small.
As for the main jet, get the bike out on a road you can run at speed safely on. Get it in 4th gear and run it up to redline, then slightly back off the throttle. If the engine wants to run faster when you ease off it's probably too lean. If it responds accordingly your probably gtg.
How is your throttle response? How is your needle set up?
No cough, no stumble... run up to redline, chop the throttle, and it immediately decelerates, no hesitation, nor surging... wack the throttle and she just goes, ZERO hesitation like it had with the stock cam and the jetting set up I had.
EDIT: I forgot to add that it does kind of bog a little when you run the A/F mixture past the magic number of turns, and coughs a little when you turn it in. But as far as riding performance, like I said, no cough, no stumbles or hesitations.... it just goes and decelerates.
Last edited by tmanbuckhunter; Mar 2, 2014 at 10:37 PM.
Grand HDF Member
Joined: Apr 2007
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From: Brighton, MI
My plugs look about the same as yours, my jetting is the same as yours. The only difference is I don't have the needle shimmed (but have the cvp needle for big twins), and I don't have a cam.
I get the decell pop as well, but only after I really get on it and then let the throttle drop to idle position. I have replaced manifold O-rings, and exhaust gaskets, along with using silicone to seal up the muffler to head pipe connection point.
I think the decell pops is the nature of the beast with the mufflers I run. I run the cycle shack mt-129 mufflers and they are short.
What kind of exhaust are you running? YD
I get the decell pop as well, but only after I really get on it and then let the throttle drop to idle position. I have replaced manifold O-rings, and exhaust gaskets, along with using silicone to seal up the muffler to head pipe connection point.
I think the decell pops is the nature of the beast with the mufflers I run. I run the cycle shack mt-129 mufflers and they are short.
What kind of exhaust are you running? YD
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Cruiser
Joined: Aug 2010
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I had decel popping on a friends bike as I had set the idle a little low,adjusted it back up and ok.
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Thread Starter
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Outstanding HDF Member
Joined: Jul 2013
Posts: 2,874
Likes: 36
From: Houston, TX
My plugs look about the same as yours, my jetting is the same as yours. The only difference is I don't have the needle shimmed (but have the cvp needle for big twins), and I don't have a cam.
I get the decell pop as well, but only after I really get on it and then let the throttle drop to idle position. I have replaced manifold O-rings, and exhaust gaskets, along with using silicone to seal up the muffler to head pipe connection point.
I think the decell pops is the nature of the beast with the mufflers I run. I run the cycle shack mt-129 mufflers and they are short.
What kind of exhaust are you running? YD
I get the decell pop as well, but only after I really get on it and then let the throttle drop to idle position. I have replaced manifold O-rings, and exhaust gaskets, along with using silicone to seal up the muffler to head pipe connection point.
I think the decell pops is the nature of the beast with the mufflers I run. I run the cycle shack mt-129 mufflers and they are short.
What kind of exhaust are you running? YD
I think I'm just going to call it good and fine tune the timing and jetting later when I can get it on a dyno.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,070
Likes: 2,115
From: Ohio
Showing a plug set with a AFR reader at some good numbers. You are still slightly lean but in the power range, heat can be your friend but can also be your enemy. Most likely need a little more needle because that is where it spends most of it's time and more color needed on the electrode.
Your timing heat line should be in the center of the strap bend also, can tell if timing is advanced or lazy.
Your timing heat line should be in the center of the strap bend also, can tell if timing is advanced or lazy.
Last edited by 1997bagger; Jan 26, 2019 at 11:57 PM.