givemethebighammer
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| posted on 12/9/06 at 08:50 PM |
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One for the BEC people or bike carbs on CEC people
I fitted some dynojet needles to my blackbird carbs (on 2.0L zetec engine) this evening. It has made a big difference to the mid range torque but I
now have a rich spot at 1500-2500 rpm (AFR 9-10 to be precise). The Car bogs down as you pull off junctions etc. So do I lower the needle a clip
position or lean the idle jets out 1/4 of a turn. AFR at idle is 12-13. I can't adjust the float level so that option is out.
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trikerneil
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| posted on 12/9/06 at 09:14 PM |
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It's always bin a bit of a black art to me  
Does this help?
 
carb_tuning
[Edited on 12/9/06 by trikerneil]
ACE Cafe - Just say No.
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givemethebighammer
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| posted on 12/9/06 at 09:22 PM |
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Thanks, I have already diagrams like that. It seems that at the point I have the rich spot I could either lower the needle or lean out the idle jets.
The car pulls fantastically everywhere else so I am more inclined to just lean the idle screws out a bit than mess with the needle height. I may call
someone like Holeshot or TTS in the morning for their opinion. Then I guess I could also just add a little more ignition advance at that point in the
map too?
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TangoMan
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| posted on 12/9/06 at 11:49 PM |
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I have the same problem. The first option is to lean off the mixture screw. If that fails, as it has for me, the only option appears to be to source
smaller pilot jets.
This is as far as I have got because they seem very hard to get hold of!!
I am on R1 carbs, how about you.
Summer's here!!!!
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givemethebighammer
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| posted on 13/9/06 at 08:53 AM |
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cheers Tangoman
I have Blackbird carbs, the idle screws are currently 1 1/2 turns out on a 42 pilot jet. I have some 40's and 35's to change them to if I
need to but I suspect that 1/4 to 1/2 a turn back in on the 42's should be enough. Mine were not hard to get hold of, all Honda Keihins from
(97-99) seem to use the same type of pilot jets
Blackbird = 42's
Fireblade = 40's
CBR 600 = 38's or 40's
CBR400 = 35's
Allens Performance should be able to help you or a motorbike spares place (if you know what model of bike you want jets for)
http://www.allensperformance.co.uk/
not cheap though pilot jets are £5-7 each.
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givemethebighammer
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| posted on 15/9/06 at 08:00 PM |
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Solution found:
After talking to Bogg Bros and TTS, I lowered the needles a clip position to lean out the rich spot. This improved but didn't cure the problem.
It also made the top end feel "flatter" than it had been. I ended up putting the OEM needles back in but with an extra 2 washers to shim
them up and richen the mid range. The results are good the car pulls hard from 2000rpm right to the redline at 7000rpm. It doesn't feel like it
is pulling quite as hard as when the dynojet needles were fitted, but I can't live with the car bogging down every time I pull off a junction. I
think I may talk to Allens Performance about buying some needles with the same top end profile as the dynojet ones I have but with a slightly leaner
profile at the lower end.
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TangoMan
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| posted on 15/9/06 at 09:53 PM |
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I will be driving past Allens tomorrow so I will drop in, if they are open, t see if they have some pilot jets for R1 carbs.
Going back to my SU days it was failry standrad practice to use a needle file to reduce the needle at any piont where a richer mixture was needed.
Maybe you need to remove a washer and then file as required to thin the needle to richen up where required.
I am trying to use the TPS and MJLJ software while driving to plot how open the throttle is when rich so I can then remove the air filter to work out
where the needle is at each of the plotted points. Not an exact science but near enough to give a good start for the rolling road.
Summer's here!!!!
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