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Discussion Starter · #1 ·
I think I have my jetting close to were it needs to be ,but I am not sure what I need to do at this point to fine tune it ?

With my set-up which seems to be pretty common;AI&Air box removed.
Running a Bella air box kit w/K&N's and BC Predator Exhaust.

My jetting is set at 142-40-1shim & 3 turns out.
It seems to run fine,pulls hard and revs to the moon !!When I let off to decelerate there is a small amount of popping nothing to crazy or loud ,but it's there.
The other thing I noticed was when I was at a stop light there seemed to be a bit of hesitation when stopped ? Like it had a small case of the hiccups (I know it's not a mechanical term)

Any help or direction would be greatly appreciated !!
 

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the Hiccups

Hi Redrider

Interesting, although not the same as your setup mine suffers from the dreaded hiccup at idle too. Only when hot and it'll often stop/stall when this happens. Sometimes only 10 seconds after pulling up at the lights.

Was talking to a mech who used to work for my local dealer, he suggested the engine heat was evaporating all the fuel in the bowl and starving it.

I'm running TORs with 115s no shim at 3 turns. Idle at approx 1000rpm

I also get a slight hint of popping, or more of a throaty burble....certainly nothing to worry about.

When I bought the bike new it came with the TORs, they were fitted at about 400km. When the dealer adjusted the carbs they took the idle mix out to 5 turns..... 5 turns!!! and I wondered why it seemed so soggy at idle! When I re jetted I put the idle back to stock and soon after noticed the hiccup/stall. I'm reluctant to go over 3 turns as the response is way worse.
 

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You might be able to go up a size on the pilots and turn your screws in.
That could help.

Check for exhaust leaks too.
 

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Discussion Starter · #4 ·
With the "Popping" on deceleration my understanding is that I am to fat and need to lean out my idle mixture ? correct ??

Currently I am 3 turns out ,should I try 2.5 turns and see what that dose ?
 

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The hesitation at idle is because of a "too rich" condition, the popping on decel is because of a "too lean" condition (or an exhaust leak at the header).

Going up a size on your pilots will help the popping on decel, turning the pilot screw to 2-2.5 turns will lean out the mix at idle which will compensate for richer pilots and the "too rich". You might also find you have better adjustability with slightly oversized pilots.

Turn the screw first, see what happens. If there's it's worse go the other way. If that doesn't help, change the pilots. Then adjust the screw.
 

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I had the same problem. I was running 140/40/1 shim and 2.5 turns out but got popping on decel no matter how many turns on the idle mixture screws.

The solution was to put in a 42 pilot jet, and go down to 2.0 turns out. Problem solved, no more popping.
 

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Discussion Starter · #7 ·
The hesitation at idle is because of a "too rich" condition, the popping on decel is because of a "too lean" condition (or an exhaust leak at the header).

Going up a size on your pilots will help the popping on decel, turning the pilot screw to 2-2.5 turns will lean out the mix at idle which will compensate for richer pilots and the "too rich". You might also find you have better adjustability with slightly oversized pilots.

Turn the screw first, see what happens. If there's it's worse go the other way. If that doesn't help, change the pilots. Then adjust the screw.
Going to try 2turns out this weekend and see what happens.

If I do go up to a 42 pilot from a 40 that is in it know. How many turns out should I start at ?

Thanks Blackstar
 

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Discussion Starter · #8 ·
I had the same problem. I was running 140/40/1 shim and 2.5 turns out but got popping on decel no matter how many turns on the idle mixture screws.

The solution was to put in a 42 pilot jet, and go down to 2.0 turns out. Problem solved, no more popping.
Are you set at 140-42-1shim & 2 turns out ? How is that working for you ? I am going to try 142-42-1shim & 2turns out ,but may have to look at your set up as well.
 

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Are you set at 140-42-1shim & 2 turns out ? How is that working for you ? I am going to try 142-42-1shim & 2turns out ,but may have to look at your set up as well.
Yes, that's what I'm set at. It works great for me. I have not had a dyno yet but the bike is running great. I may go down in main jet size to 135 but haven't tried it yet

if you go up in pilot jet size to 42, 2 turns out should be more than enough. It solved all my popping problems. Sure, once in a blue moon there will be a small pop, but it's hardly noticeable and not an annoyance like before.
 

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Going to try 2turns out this weekend and see what happens.

If I do go up to a 42 pilot from a 40 that is in it know. How many turns out should I start at ?

Thanks Blackstar
Nekkid beat me to it.
Good luck!
 

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I have a similar set up but with 140 mains & 42 pilots - not sure how many turns but I think I set it at 2.5 but the mechanic at the dealer may have adjusted it slightly when I took it in for a tune up after fitting the Preds. I have the popping on decel but that doesn't bother me but never had a "hiccup" or a stall at idle though.
 

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Well, after the weekend I'm pretty sure blackstar1965 has it right. Adjusted the screws to 2 turns from 3, idle was smoother, no noticeable hiccup at all, popping on decel when cold but only slightly when hot. So it seems somewhere around 2 and 1/4 turns is going be spot on for me.

Cheers and thanks for your help!!
 

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Can anyone help?

I just bought an 05 Thruxton (3400miles on it). The previous owner put custom slip-on mufflers and only put a 45 pilot jet in with no change to the main. The airbox and air injection are stock and I get popping when declerating. The bike starts fine and for the first few minutes and it idles fine (1000rpm), but after riding around it idles around 2000rpm and bliping the throttle does nothing. Also, I am located at about 1700 ft. above sea level. I thought I would seek some advice before jumping into the carbs this weekend. Any advice would be great.

-Sloan

Note: I tried posting this in the twins tech talk and could not get any help. Please help as this is my first carburetored bike.
 

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I just bought an 05 Thruxton (3400miles on it). The previous owner put custom slip-on mufflers and only put a 45 pilot jet in with no change to the main. The airbox and air injection are stock and I get popping when declerating. The bike starts fine and for the first few minutes and it idles fine (1000rpm), but after riding around it idles around 2000rpm and bliping the throttle does nothing. Also, I am located at about 1700 ft. above sea level. I thought I would seek some advice before jumping into the carbs this weekend. Any advice would be great.

-Sloan

Note: I tried posting this in the twins tech talk and could not get any help. Please help as this is my first carburetored bike.
I'm certainly no expert but have read hundreds of posts on jetting it seems. I cannot imagine why you would need a 45 pilot in there. How many turns out? If I'm not mistaken, a rich problem will get worse as the bike warms up and a lean setting will get slightly better.

Sandy
 

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I cannot imagine why you would need a 45 pilot in there. How many turns out?
Sandy
I agree - if there are no mods to the airbox it's just making it trun rich although the effect of the altitude will lean it out a bit but by how much I don't know. There's a sticky out on the forum with a whole bunch of good info including the Jenks bolts carb tuning guide which is worth a read.
 

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I agree - if there are no mods to the airbox it's just making it trun rich although the effect of the altitude will lean it out a bit but by how much I don't know. There's a sticky out on the forum with a whole bunch of good info including the Jenks bolts carb tuning guide which is worth a read.
Yeah I've already read the jenks bolts carb tuning guide, I just thought somebody might have had a similar experience. Looks like its time to get my hands dirty. Again thanks a lot for the responses and I am enjoying the forum thoroughly:).

-Sloan
 
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