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Buell Forum » Old School Buell » Archive through May 24, 2014 » Carb tuning issue: 48 Pilot too lean?! « Previous Next »

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Iamspartacus
Posted on Monday, May 05, 2014 - 11:01 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Ok, so I've done the recommended mods to my carb: 48/200 jets, radiused the slide, removed accelerator pump, drilled out slide hole, shimmed the M2 needle etc. etc. Here's the issue:

When I took the slide apart I realized it had already been drilled out- slightly larger than 1/8th inch. It also had a 50 (!) pilot jet. After putting a 48/200 jets in and putting it all back together with the idle mixture screw set at 2.5 turns out, the bike takes much longer to warm up and Idles between 8-900rpm with the idle adjustment cable maxed out. When fully warmed up it MIGHT hit 950rpm.

So my question is, should I put the 50 jet back in? Is the larger diameter slide hole causing the bike to run a bit lean? How can I remedy this?
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Jim2
Posted on Monday, May 05, 2014 - 03:25 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I believe that the enlargement of the diameter of the slide hole is only intended to modify the venturi affect that lifts the slide up as air starts to rush in. This is supposed to improve off-idle acceleration the same as if you were to install a lighter slide spring. Some one please correct me if I'm wrong. That being said your idle problem lies elsewhere.

Do you have good new, properly installed intake seals(all three)? How about the exhaust, are there any cracks, are the seals good, what kind of muffler are you running and what condition is it in? Lack of back pressure can cause a lean condition.
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Iamspartacus
Posted on Monday, May 05, 2014 - 05:32 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

When I took off the carb I replaced the intake seals. As far as pipes, there are no cracks (I took them off and repainted the headers as well). The muffler is a Vance & Hines that seems to be in good working order- not sure how to check or what to look for though.
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Yo_barry
Posted on Monday, May 05, 2014 - 05:50 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Hey Spartacus,

I have a 99 Sportster Sport, never had an M2. But, my experience with the 1200 and stock CV carb says you are to rich with both jets.

My Sportster is jetted with a 45 and 190 (I think it is 190) and the needle shimmed up with two SS washers. I am running the SE air filter and Supertrapp exhaust.

ymmv

Barry
Hollister, CA
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Ratbuell
Posted on Monday, May 05, 2014 - 07:01 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I agree...45/190 should work just fine on an M2. It's what I run on mine with full Buell race exhaust, intake, and ignition.

I run a 48 on my S1W, same setup, because of the cam difference.

I have yet to run a stock 1203 that's needed a 200.

+1 on checking the intake seals. Just cause they're new doesn't mean they didn't bunch up on installation...
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Jim2
Posted on Monday, May 05, 2014 - 08:20 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I'm on 45/200, radius'ed, drilled, shimmed. Started with idle 2.5 out but turned in to about 1.75 out. I'm at sea level. Runs and idles great. Make sure that your throttle cables are setup right. I think something else is wrong. I'd take the carb apart again and ensure all of the passages are clean and free and that everything is put together right and try again.
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Lakes
Posted on Tuesday, May 06, 2014 - 07:48 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

i think 45 or 46 is right size pilot, i leave slide vacuum hole stock as i found they work better, i like the Bobby Wood needles, also radius slide
main jet depends on the needle you use.
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Cyclonecharlie
Posted on Tuesday, May 06, 2014 - 08:27 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The fact that your idle screw is maxed,makes me think your low speed circuit is stopped up. And your drawing air and fuel across the needle/jet.
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