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Discussion Starter · #1 ·
hi all. well, it is pretty nice here in ohio, so i have been able to get out and ride quite abit lately. over the winter i added a dynojet kit to my T100. i have posted this before, but for those that might not have read earlier posts i will tell my setup. i have an 08 T100 with epco pipes. it has a kn air filter and the snorkel removed. i also have the ai removed. using the dynojet kit i installed the DJ112 main jets which are the equivalent to 117.5 mains from keihin. i installed the dynojet needle per the dynojet instructions and i turned the a/f mixture screws out 3 turns. after much riding i am still noticing some backfiring and popping on deceleration. it is enough to be annoying to me. now i figured i might have an exhaust leak, so i performed a flame test over the whole exhaust system and everything is tight. also checked for vaccum leaks and everything looks good there. i tried turning out the a/f mixture screws to 3 1/2 turns and the tach is absolutely stable on 1000 rpm, but i am still getting popping/backfiring on deceleration. so...now what? i am turning to you all cause i don't know if i should just leave well enough alone (hard for me to do!) or if i should try something else. the only thing that makes me think that it is a jetting issue still is that when it was jetted before i didn't have the backfiring or popping. this is what it was setup before. i had the kn filter, ai removed, thruxton needle with 1 shim, 127.5 mains, 40 pilots. not sure what the a/f mixture screws were set at. where should i go from here? i am wondering if i should go with 42 pilots. -keith
 

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You're doing great...install the 42 pilots.

How's the full throttle performance? Does the bike pick up after being held at WFO & you then let the throttle close to 7/8ths? If so, you're lean on the main jet.

Regards,

--Rich
 

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over the winter i added a dynojet kit to my T100. i have an 08 T100 with epco pipes. it has a kn air filter and the snorkel removed. i also have the ai removed. using the dynojet kit i installed the DJ112 main jets which are the equivalent to 117.5 mains from keihin. i installed the dynojet needle per the dynojet instructions and i turned the a/f mixture screws out 3 turns.
This is from the instructions that came with my the Dynojet kit:-

Use the Dj110 main jets with stock exhaust. Use the Dj114 main jets with aftermarket header or slip-on with high flowing baffles. If you remove the intake snorkle from the airbox use the Dj124 main jets.
This would suggest that your Dj112 main jets are too lean for your bike and that you should fit the Dj124's.
 

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I agree with BeemerRich - go up a size on the pilot jet and the popping on decel will go away. You may neeed to turn the mixture screw back in and may need to remove a shim from the needle if you are running any. Keep experimenting and you will find the right combination.
 

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Discussion Starter · #5 ·
if i go to 42 pilots what should a starting point to my A/F mixture screws be?
 

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if i go to 42 pilots what should a starting point to my A/F mixture screws be?
I'd start with them about 1 turn out,
Then slowly and equally open them in small increments.
Stop at the point where the smooth tickover begins to falter.
From this point turn them back in 1/4 - 1/2 turn each.
Should be right!!

Often the popping is just a product of the pipes you have fitted, but in your case you say there was none before the DJ kit was installed?
I guess its therefore carb set-up related.
A little popping on the overrun is not a bad thing tho, it gets you noticed and adds to the character!!:):)

I'd be very wary of the apparent DJ advice (as posted above) of fitting DJ124's when having only removed the snorkle.
If this is your only intake mod (apart from a K&N) then you'd run VERY rich with what are the equivenent of Keihin 132.5's in there.
Stick with the DJ112's
The DJ124's are the kind of jetting you'd be looking at if you'd pulled the restrictor and opened the inlet cover.

You could always give that a go while you're at it!
Its worth it!!


V.
 

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If you guys want just a bit of philosophy...I would say about 50% of all motorcycles ever sold pop on decel including my new Bonny...lol. Some attribute this a lean condition but I don't. It is actually an ideal burn condition and why the light explosions in the headers. Richening mixture to eliminate popping maybe detrimental to bike performance. Some believe the strongest running bikes tend to pop a tad on decel. I tend to subscribe to this theory. Why? Oh you can eliminate popping. But how do you do this? By going dead rich. Dead rich won't burn (pop) but dead rich isn't best for performance either. Popping in hot pipes is simply the natural by-product of closing the throttle on a nice and rich A/F mixture tuned for performance and having excess fuel spill into hot headers. If you make it go away but going even MORE rich to keep that fuel spillage from burning i.e. dead rich...you may cure popping but you shoot yourself in the foot for optimal performance. Be careful what you wish for.
My thoughts,
George
 

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Popping

If I dont totally back off on the throttle on decel- the popping stops. Total backoff- a few pops. Not enuff to bother me tho!
 

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If you guys want just a bit of philosophy...I would say about 50% of all motorcycles ever sold pop on decel including my new Bonny...lol. Some attribute this a lean condition but I don't. It is actually an ideal burn condition and why the light explosions in the headers. Richening mixture to eliminate popping maybe detrimental to bike performance. Some believe the strongest running bikes tend to pop a tad on decel. I tend to subscribe to this theory. Why? Oh you can eliminate popping. But how do you do this? By going dead rich. Dead rich won't burn (pop) but dead rich isn't best for performance either. Popping in hot pipes is simply the natural by-product of closing the throttle on a nice and rich A/F mixture tuned for performance and having excess fuel spill into hot headers. If you make it go away but going even MORE rich to keep that fuel spillage from burning i.e. dead rich...you may cure popping but you shoot yourself in the foot for optimal performance. Be careful what you wish for.
My thoughts,
George
I agree, popping isn't a bad thing and if you tune it out you're probably running too rich.
 

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With TORS you get the popping, but it is muffled out, with more open pipes there is less muffling so the popping is more prominent. I have tried to jet it out of my straight through silencers, but as others have said you have to go way too rich and it still pops some. Best to live with it and enjoy it or get quieter silencers.
 

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Discussion Starter · #13 ·
well you all have given me something to think about! do i put in 42 pilots and go with a rich condition or do i live with the popping and probably have a properly tuned engine? i'm thinking for now i am going to leave it alone till i get to a dyno and have the a/f mixture analyzed. probably the only true way to know for sure. as a side note, when i checked for leaks i did what many have said which is to take a lit match at all the joints on the exhaust system. is there a better way to accomplish this? i never got so much as a flicker with the match. either that means that i have a solid system or the test sucks. anybody ever tried lead detector on their system? i am a plumber/pipefitter by trade so i have access to leak detector. would that be worth trying? -keith
 

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+1 on the popping.
I like the way it sounds when I off the throttle and it still sounds like I'm choking a large badger
+2 on the popping.

I actually feel like the light popping I get with my new Dominators is the single best sound I now get. Not sure why but I like off-throttle popping more than the on-throttle roar. I mean, let's face it, the roar out-performs the actual power but somehow the popping makes it seem there is potentially more power lurking somewhere.

Probably a poor explanation but if you feel it, sometimes you don't have to explain it.

Pop on boys...

P
 
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