Mark O
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| posted on 15/11/20 at 10:09 PM |
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Running rich
Gents
I have Zetec 2.0 blacktop mated up to ZX9R CVK carbs. I have the following set up.
Checked needle jet - it is shimmed by one 0.5mm shim. This is standard.
Airscrews turned 2.5 turns out.
Main jets are 165.
Air corrector holes open.
With this set up, it starts fine enough, but on blipping the throttle when warm it does emit black smoke. Not alot, but definitely some there and it
does leave a residue of black against a piece of cardboard at the tailpipe. It is also a bit smokey at idle.
No tuners up here know about bike carbs so it's a policy of try it and see.
First things
Air screws - is it out to richen or vice versa?
Air corrector holes - I believe 0.7mm is about right. I have some brass inserts en route. Not sure if this will make much difference.
To lean it out, what do you recommend?
Will a smaller main jet -155? make a difference? I thought main jet only acted on the final 3/4 throttle.
Many thanks
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robertst
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| posted on 16/11/20 at 01:43 PM |
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quote:
Originally posted by Mark O
Gents
I have Zetec 2.0 blacktop mated up to ZX9R CVK carbs. I have the following set up.
Checked needle jet - it is shimmed by one 0.5mm shim. This is standard.
Airscrews turned 2.5 turns out.
Main jets are 165.
Air corrector holes open.
With this set up, it starts fine enough, but on blipping the throttle when warm it does emit black smoke. Not alot, but definitely some there and it
does leave a residue of black against a piece of cardboard at the tailpipe. It is also a bit smokey at idle.
No tuners up here know about bike carbs so it's a policy of try it and see.
First things
Air screws - is it out to richen or vice versa?
Air corrector holes - I believe 0.7mm is about right. I have some brass inserts en route. Not sure if this will make much difference.
To lean it out, what do you recommend?
Will a smaller main jet -155? make a difference? I thought main jet only acted on the final 3/4 throttle.
Many thanks
My Pinto on R1 Carbs was running stupidly rich until I found out the Air corrector holes were blocked. Yours are open and it's still quite rich
by the looks of it. I think it's your idle circuit. Check your needles, you'll probably have to lower them one or two notches, then your
idle screw. Out to richen, In to lean. Check the diaphragms on each carb to see if there are any cracks or tears. Also check out your float levels
(this had a massive impact on mine, as they were too high)
As you say, the main jet is irrelevant until 3/4 throttle and beyond so it's not that.
Are you sure it's not burning oil? have you checked the plugs? Mine was leaking in two valve stem seals. It was a right bummer to fix, but she
ran sweet after all that.
Hope it helps
Atb
Tom
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Mark O
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| posted on 16/11/20 at 02:49 PM |
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Yes -I too think it is idle circuit - they are actually CVR carbs by the by..... Airscrews were well out - certainly over 4 turns, so I think that is
what I will try first. Any recommendation as to what to set them to as a good first start - 1.5 out? Float levels - not checked them. Will do so.
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robertst
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| posted on 16/11/20 at 05:39 PM |
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quote:
Originally posted by Mark O
Yes -I too think it is idle circuit - they are actually CVR carbs by the by..... Airscrews were well out - certainly over 4 turns, so I think that is
what I will try first. Any recommendation as to what to set them to as a good first start - 1.5 out? Float levels - not checked them. Will do so.
whoah 4 turns out! that's your ticket right there then!  yeah 1.5 turns out from fully closed is ok as a starting point.
Normally, if the idle screw is more than 2 turns out you need to change to a smaller jet, less than 1 turn out change to a larger jet. But you need to
adjust everything in the right order:
1: Make sure carbs are balanced
2: Main jets - your's seems to be fine at 165
3: Adjust needle jets
4: Adjust Idle circuit
just in case, you need to do this with the engine at operating temperature. Don't bother doing it on a cold engine 
Do you have a wideband? If not you could use an infrared thermometer aimed at each exhaust branch to get the temps roughly equal and a visual
inspection of the plugs straight after shutdown. That is a rough and dirty method to get the engine running acceptably well, but by no means will it
be spot-on without a wideband.
[Edited on 16/11/20 by robertst]
[Edited on 16/11/20 by robertst]
Tom
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Mark O
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| posted on 16/11/20 at 07:16 PM |
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Yes - many thanks for that. Just an aside, why should airscrew settings matter so much ref running rich? I understood they affected about 1/4
throttle, so I can understand them the affecting idle, but after that? I guess they are still leeching fuel through all the time the engine is
running? It's actually using fuel like a drag racer! I stuck 5 litres in from empty just to test in on the road - all gone after 10 miles! Goes
well though!
Carbs balanced by the kit supplier - not actually checked them though.
Main jets agreed are OK
Needle jets - now reverted to stock with just the one shim
Idle - will set all at 1.5 out
Pump is a bike pump which came with the kit
CVR carbs - float heights all checked - all now around 4mm - a couple were low - and therefore possibly contributing to the rich mix - at 2mm or
so.
Air correctors now 0.8mm hole.
Agreed about the plugs as a check. Pity. They were brand new Motorcraft for the Zetec put in yesterday - now 'orrible, sooty and black.
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Mark O
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| posted on 19/11/20 at 05:26 PM |
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Nope - no good. Car still runs way too rich with airscrews 1.5 turns out. Black smoke and it stinks.
Any further advice as to how to lean it out considerably would be greatly apppreciated.
Many thanks
Mark
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Wildnz
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| posted on 24/4/21 at 07:55 PM |
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I have an identical issue and a very similar setup - I would greatly appreciate any additional steps or advice here...
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