What d'ya reckon?

Just post charts and set up details.
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VTRDark
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Re: What d'ya reckon?

Post by VTRDark »

Stick with the 48's, leave needles as are and try tweaking the fuel mixture screws a bit. Maybe a 1/4 turn richer and see if this gets rid of your cough/stutter. Have the carbs been balanced/synced since making changes.

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Stephan
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Re: What d'ya reckon?

Post by Stephan »

I really don´t want to argue, but first dyno with 158/160 shows good AFR in high revs IMO, when only size of jet is playing. There was no reason to change this, maybe one size down to 156/158. If you had problem only between 2-3k, pilot screw setting could handle it, or going one size up on pilot jets.

Now you need to handle rich bottom end with 48 pilots, going to lean mid range with small jets. It is hard to say how much is size of pilot jets affecting AFR through rev range, but is is likely close to 100% in low revs, and close to 0% in top end. But you cannot just sum size of pilot and main and say that one will replace another.
Phil_H
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Re: What d'ya reckon?

Post by Phil_H »

Interesting responses guys :)

However, I feel the bottom end (sub 2.5k) is fine & top end (5k+) is fine also. Would pilot screw setting really have a significant affect on 2-3k rpms?

With the 158/160 mains the top end was quite rich bar the last 500rpm where it picked up a bit, which is why I reduced the mains while fitting the larger pilots.

Hopefully get chance to try lifting the needles this eve :)
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VTRDark
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Re: What d'ya reckon?

Post by VTRDark »

Now you need to handle rich bottom end with 48 pilots
It's lean on the bottom not rich. The higher the AF ratio the leaner it is. I agree on the mains though.
Would pilot screw setting really have a significant affect on 2-3k rpms?
It sure will. As Stephen said it's hard to judge exactly how much it affects AFR but will start at 100% bottom end tapering off to 0% top end.

Lift your needles and this will also have an affect on your pilot screw setting as this crosses over to both the top end of the pilot circuit and bottom end of the main circuit as they overlap each other.
FUEL SCREW/MIXTURE ADJUSTMENT

Start off on the lean side of things (better performance/rideability) and getting richer as you go up through the revs. It's better to be too rich (a little flat) up top than too lean (not that you are) as the extra fuel helps with engine longevity as it has a cooling and lubrication affect.

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Stephan
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Re: What d'ya reckon?

Post by Stephan »

Cybercarl: i only guess it is rich with 48 pilots, because it was slightly lean with 42. Just talk about revs where pilot jet is dominant. Let's say up to 3.5 rpm?? But it is likely that this bottom end is not lean anymore after this change.
Phil_H
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Re: What d'ya reckon?

Post by Phil_H »

Cheers for the ongoing information guys, I have successfully done a bit with carbs over the years but never had a problem chasing my tail like with this setup, as I inderstood it, pilot screw opening only affected tickover & very small throttle openings, above which the pilot jet size itself took over until the needle started to lift?

Anyway, another day, another fiddle and another test run....
48 pilots & 150/152 mains still now with 2 extra shims under the needle (1.5mm now).
2-3 1/2k the bike pulls better than it ever has done.
3.8 - 5.2k the bike pulls pretty well (and an improvement over yesterday withjust 1 shim) - if I chase the revs with the throttle. Wack the throttle open, it coughs & stutters going nowhere fast, back it off & you get a surge then usual acceleration.
If I pull the choke full on, things improve markedly.
5.2k+ feels good with the usual big twin punt up the butt to the redline :)

I'm happy with the sub 3 1/2k & 5k + delivery, still feel it's lean in the middle. I don't think shimming the needle to death is the way to go either.....

My head hurts now!
Phil_H
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Re: What d'ya reckon?

Post by Phil_H »

Ok, left the 48 pilots in, fitted 158/160 mains, needles std 1x .5mm shim.
Bike generally feels very good, still a roughness/labouring feeling between 3-3.8k, topend is great.
This has not addressed the rich 5500-7500 rpm or lean 3000-4500 areas.
I feel lifting or lowering the needles will help one area at the detriment to the other & vice versa.

Not sure where to go now. As far as I can see the needles are not ideally profiled for the application.
I'll leave as is for the mo :)
Phil_H
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Re: What d'ya reckon?

Post by Phil_H »

Ok, left the 48 pilots in, fitted 158/160 mains, needles std 1x .5mm shim.
Bike generally feels very good, still a roughness/labouring feeling between 3-3.8k, below 3k & topend is great.
This has not addressed the rich 5500-7500 rpm or lean 3000-4500 areas.
I feel lifting or lowering the needles will help one area at the detriment to the other & vice versa.

Not sure where to go now. As far as I can see the needles are not ideally profiled for the application as anything I do seems to chase the lean spot around the rev range!
I'll leave as is for the mo :)
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Stephan
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Re: What d'ya reckon?

Post by Stephan »

Phil_H wrote:Not sure where to go now.
I would go to dyno for next AFR chart to see how 48 pilots are performing.
Phil_H
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Re: What d'ya reckon?

Post by Phil_H »

I'll probably get a dyno done in due course, however, I feel the 48's are an improvement over the oe 42 pilots.
Will report back with any developments :)
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8541Hawk
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Re: What d'ya reckon?

Post by 8541Hawk »

Phil_H wrote: This has not addressed the rich 5500-7500 rpm or lean 3000-4500 areas.
I feel lifting or lowering the needles will help one area at the detriment to the other & vice versa.
IMHO these two RPM ranges are controlled by different circuits. If I were working on this, my next step would be to drop the needles one and open the pilot screw 1\2 a turn to start, but that is just me.
I'll let the other guys get into the long discussions, well unless I get bored.....lol :angel:

:beer:
Loud pipes don't save lives, knowing how to ride your bike will save your life.
Phil_H
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Re: What d'ya reckon?

Post by Phil_H »

I have openet the pilot screws by 1/4 turn to 2 full turns out. As I suspected, all it has achieved is to make the bike struggle to run when on choke & cold, tickover when warm has reduced - obviously too rich.
I really can't see how pilot screws have a significant impact on 3k + running.

Off with the carbs again!

Seriously thinking a dj kit & try their needles.

Phil
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Varastorm
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Re: What d'ya reckon?

Post by Varastorm »

If I were you Phil, I would put it back to the very first Dyno run settings & set the pilots to 2 1/3 out front & 2 2/3 out rear :thumbup:

The A/F ratio is fab after 1/3 throttle, your barking up the wrong tree changing needle height & mains :thumbup:

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