locosaki
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| posted on 14/6/10 at 07:28 AM |
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Bike Crab Fuelling
I've got zzr1100 bike carbs on my 2.0 16v vauxhall engine.
Now I thought I had the fuelling quite close but after a trip to the rolling road the operator tells me it's running mega rich on wot from
3000rpm until 5000rpm but I thought with bike carbs this would be the norm.I.E sinking the boot at full throttle puts you on main jet and that will
obviously over fuel low down as the main jet is set for higher up the rev band !!
Have I got this correct or am I needing to rejet and alter needles.
I'm running 160 main jets with needle on 2nd clip from top.
At 3000rpm AFR was 10 - 1
At 4000rpm AFR was 11.5 - 1
At 5000rpm AFR was 13 - 1 to the redline
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coozer
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| posted on 14/6/10 at 07:45 AM |
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I would say its running rich lower down and 13 isn't too bad at the top. 13.5 being ideal.
The rolling road not able to set it up for you while you where there?
1972 V8 Jago
1980 Z750
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RazMan
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| posted on 14/6/10 at 07:54 AM |
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I would suggest lowering the needles one notch - main jets are probably about right. I would like to see between 13-14 under power so your mid range
is looking a bit rich.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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locosaki
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| posted on 14/6/10 at 07:59 AM |
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The guys at the rollers I went to don't know much about bike carbs,I'm more than happy to alter them myself though.
So if I lower the needle 1 notch to the top will this still lean the fuelling out even if I'm in 4th gear and give it WOT from 3000 ?
I was under the understanding that this would only alter the fuelling on part throttle ?
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GaryM
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| posted on 14/6/10 at 05:07 PM |
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Not familiar with these carbs....but does the throttle cable operate the butterflies (CV carbs) or the slides?
If they are CV carbs then the slide/needle position is determined by the 'load' on the engine not just the throttle pedal position.
Get yourself a wideband Oxygen sensor and keep on adjusting until you get the mixture as close to perfect as you can.
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craig_007
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| posted on 22/7/10 at 02:30 PM |
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I always thought that 12.5-1 was the perfect afr for power anything above was a bit on the lean side and could sap power,saying that I certainly
wouldn't go richer !!
Your 13-1 is probably close enough.
Regarding needle jet,I would try clip on the highest setting and see if it leans out enough. On mine I got top end set at approx 12.5-1 from 4k
through til 7300 rpm but my needle settings were way off. I ended up using different needle jets that were fatter than the ones bogg supplied as I
couldn't get mixture right at wot from 2000rpm.
All of this was done using a wideband lamda though,absolutely no way of guessing this and I've not been on the rollers since but car feels good.
HPH
[Edited on 22/7/10 by craig_007]
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flak monkey
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| posted on 22/7/10 at 02:38 PM |
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12.5:1 is peak power as it is the fastest burning mixture. I dont know where the 13.5:1 myth comes from....
14.7:1 under cruise and light acceleration is good for fuel economy.
Aim for around 13:1 at idle to keep it stable.
Sera
http://www.motosera.com
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atspeed racing
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| posted on 22/7/10 at 02:53 PM |
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quote:
Originally posted by flak monkey
12.5:1 is peak power as it is the fastest burning mixture. I dont know where the 13.5:1 myth comes from....
14.7:1 under cruise and light acceleration is good for fuel economy.
Aim for around 13:1 at idle to keep it stable.
Flak Monkey is correct. However altering the needle height will alter the whole mixture range from above idle to peak RPM. If you cant get the mixture
"spread" correct with the jetting, then you have to re-make the needles to get the mixture right. This is the most difficult area to get
correct.
Find a dyno operator that knows about bike carbs.
Alan
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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craig_007
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| posted on 22/7/10 at 04:13 PM |
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Alan (at speed)
Where are you based mate ?
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locosaki
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| posted on 23/7/10 at 02:15 PM |
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I have re jetted yet again,When I had the car flat out in 5th gear afr was dropping to 13.8-1 which I thought was a little weak,I'm now running
170 mains and afr is around 12-1 but midrange is reading 10-1 on afr gauge (thats as low as it will read !!) I've got the needle at the highest
setting so it looks like I need to try different needle jets or put another few washers on top to drop needle further down !!
Anyone got any other sugestions ??
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flibble
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| posted on 23/7/10 at 03:54 PM |
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When you say "I've got the needle at the highest setting " do you mean the circlip is at the highest setting or that the needle is
riding as high as it goes (ie, circlip in lowest groove)?
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locosaki
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| posted on 24/7/10 at 05:17 PM |
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I've got the circlip in the higest sitting (Right at the top of the needle) Which in turn puts it in the leanest position.
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locosaki
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| posted on 27/7/10 at 07:59 PM |
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OK guys,
Looking for a little info here.
I have my circlip on the highest setting and the fuelling is still to rich at full throttle at 2k rpm up to around 4.5k rpm.
Is it possible to put washers above circlip which should in turn should lean the mixture further ??
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Ahdammit
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| posted on 28/7/10 at 12:32 AM |
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Would going slightly smaller on the main jet and lifting the needle work?
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RazMan
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| posted on 28/7/10 at 07:38 AM |
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Looks like you need a 'straighter' needle (one with less of a taper) This carb lark is very fickle sometimes.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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locosaki
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| posted on 28/7/10 at 08:11 AM |
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Yep I agree, very fickle !!
I have four standard needles that appear to be straighter than the dyno jets ones already fitted.
I might try them and see what happens.
I don't want to go with a smaller main jet as Im close enough with the topend fuelling and I agree changing the main will affect the midrange
but it will also lean out the topend.
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locosaki
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| posted on 31/7/10 at 10:20 PM |
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Well I have tried different needles but to no affect.
I'm thinking about going down the way with the jetting now and see if I can get the mixture correct with altering the needle height.
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Ahdammit
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| posted on 1/8/10 at 10:03 PM |
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Just a thought-I'm unfamiliar with the ZZR 1100 carbs,but do they have progression holes on the front face and are they plugged?
What I'm wondering is-if you set the jetting for full throttle and have the main jet correct for that,then
set the midrange opening up any plugged progression holes by a tiny amount til it's right?
Does that make sense?
There'sthis device which seems to allow a degree of tuning too,but I dont know if it works
http://www.flo-commander.com/
[Edited on 1/8/10 by Ahdammit]
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locosaki
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| posted on 3/8/10 at 07:37 AM |
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Hi there,
The ZZR1100 carbs are the same as the ZX9R carbs (c model)
There is one hole on the front of each carb blocked,I'm led to believe it's the main air jet(centre hole blocked)
Could this make the midrange rich ?
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Ahdammit
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| posted on 3/8/10 at 10:52 AM |
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Yeah,it's blocked so there's no air getting through it making it rich.
That flo-commander seems to be a small plenum with a tapered insert I'm guessing,allowing a degree of adjustment to the midrange.
I suppose,for a locost solution,a small drilled hole would work the same?
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