Pilot screw tip position - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 15 (permalink) Old 09-11-2019, 05:33 PM Thread Starter
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Pilot screw tip position

Hi.As you know the most often recommendation for pilot screw of Keihin on TB 2-3 turns out. Definition of starting point is quite vague for me : gently turn as long as seated in, then turn out somewhere between 2-3 turns....I have tried to do it without looking at the tip of the pilot screw several times on each carburettor..(new O-rings, screws etc) and almost each time on each carburettor little diferent tip position in the hole...maybe not the same gentle fingers on each turn? So my final position I got most often was like this.
I would appreciate your photos of the hole/tip when you will/did
rebuilt your carbs....My conclusion?: carbs mounted on the bike must have set pilot screw position in advance and carefully notice every partial turning to have it set the same on each carb?( I know some in the middle carb got minus 1/2 turn than on the rest)
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post #2 of 15 (permalink) Old 09-11-2019, 10:04 PM
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Forget about what they look like. It's the distance from the seat that matters. Lightly seat each screw then back out 2 3/4turns, or whatever your magic number is. If they're vastly different someone may have manhandled one or more of them. Still, same number of turns from seated is what you want.

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post #3 of 15 (permalink) Old 09-12-2019, 12:04 AM Thread Starter
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Ad WSC: so you mean no matter there is different opening of the hole? different Iddle mixture? I mean when I looked at the orifice while turning screw out even small partial turning makes quite big difference in how large portion of the hole you get opened. Previously I usually counted quaters or half- turns, but now I take every even small movement of screw into account. And if I did all procedure ( full in and 2.5 out) just after carbs on, I would get different result on each carb....

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post #4 of 15 (permalink) Old 09-12-2019, 06:08 AM
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Not all your carb mixture screws will need to be exactly the same amount of turns out.I went with the thumb screw's on my carbs which made it easier to tweak out each carb while it was idling.
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post #5 of 15 (permalink) Old 09-12-2019, 08:40 AM
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If the needle protrudes more or less, it means the screw is seating at a different level in the housing. The fuel is metered based on the space between the needle and the hole, so, if the holes have not been enlarged, the number of turns should still work. If the holes are not all the same size then you've got a problem. Adjustments will be imprecise and the only way to really get it right is to use a CO meter or Colortune type device.

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post #6 of 15 (permalink) Old 09-12-2019, 03:17 PM
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Not all your carb mixture screws will need to be exactly the same amount of turns out.I went with the thumb screw's on my carbs which made it easier to tweak out each carb while it was idling.
I went with the exact setup on mine. Because of the tip being different and tapered the best adjustment is just off fully seated.
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post #7 of 15 (permalink) Old 09-12-2019, 03:32 PM
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Originally Posted by Snakepit View Post
I went with the exact setup on mine. Because of the tip being different and tapered the best adjustment is just off fully seated.
Wow
Mine is about 3 1/2 turns out.
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post #8 of 15 (permalink) Old 09-12-2019, 06:28 PM
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Quote:
Originally Posted by turkpet View Post
Hi.As you know the most often recommendation for pilot screw of Keihin on TB 2-3 turns out. Definition of starting point is quite vague for me : gently turn as long as seated in, then turn out somewhere between 2-3 turns....I have tried to do it without looking at the tip of the pilot screw several times on each carburettor..(new O-rings, screws etc) and almost each time on each carburettor little diferent tip position in the hole...maybe not the same gentle fingers on each turn? So my final position I got most often was like this.
I would appreciate your photos of the hole/tip when you will/did
rebuilt your carbs....My conclusion?: carbs mounted on the bike must have set pilot screw position in advance and carefully notice every partial turning to have it set the same on each carb?( I know some in the middle carb got minus 1/2 turn than on the rest)
The pic is of the throttle screw not the pilot screw, you need a 3x gauge set or vacuum set to balance those. The pilot screws need to be set at recommended start about 2, 1/2 turns out ( hard to get at while on the bike unless you have one of those right angle gear screwdrivers ) and then use vacuum gauge to synchronize carbs by adjusting 2 of the throttle screws at about 2000 rpm,. then linked throttle knob to adjust to idle. If I have miss read please ignore this post.
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post #9 of 15 (permalink) Old 09-12-2019, 07:44 PM
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Quote:
Originally Posted by Muzz Bird98 View Post
The pic is of the throttle screw not the pilot screw...
That's what I thought at first, too, but I think he was trying to show the needle of the pilot screw sticking in the hole of the idle jet.
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post #10 of 15 (permalink) Old 09-12-2019, 09:11 PM
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That's what I thought at first, too, but I think he was trying to show the needle of the pilot screw sticking in the hole of the idle jet.
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