ProjectSi
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| posted on 2/11/17 at 05:46 PM |
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Zetec bike carb issues
Just fitted my zzr1100 carbs on danst inlet to my Zetec 2.0. It idles really well, but out in the road not so good. If I rev it from stationary, it
struggles to go above 4K then when I’m the road it is very lumpy and bogs down a lot. Any ideas what could cause this? Carbs were ultrasonically
cleaned and then balanced so that shouldn’t be the issue plus I believe they have 1.6mm jets fitted.
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David Jenkins
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| posted on 2/11/17 at 06:13 PM |
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I used to have similar problems when I fitted CBR600 carbs to my 1600 x-flow. I followed all the guidelines, drilled out the jets to 1.6mm, and got
all the symptoms you describe. Eventually I got hold of an AFR meter and found that the mixture was seriously rich at wide-open throttle, and quite
rich at normal running speed.
I ended up with 1.3mm jets that gave me a close-to-ideal mixture at WOT and over-run, but slightly rich at mid-range. I couldn't improve things
as it's not easy to fix needle issues on CBR600 carbs, so the only way I could go further was to take the car to a rolling road.
[Edited on 2/11/17 by David Jenkins]
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gremlin1234
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| posted on 2/11/17 at 06:19 PM |
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bike carbs require really low fuel pressure.
what fuel pump and or regulator are you using?
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ProjectSi
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| posted on 2/11/17 at 06:40 PM |
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I’m running a factory fiesta rs1700 fuel pump with malpassi injection to carb regulator, unfortunately my fuel pressure gauge is playing up though
which isn’t helping when trying to set the pressure bang on. Can you damage the carbs running too high pressure?
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r1_pete
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| posted on 2/11/17 at 06:49 PM |
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Way too much pressure, you need a bike pump or an SU type pump, any carbed bike pump will do, fitted close to the tank as on a bilke they are gravity
fed to you need to replicate that.
Also check the carb diaphragms are sealed properly in the plastic lids, its a good move to fill diaphragm locating recesses with rubber lube, that
stops any leakage.
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ProjectSi
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| posted on 2/11/17 at 09:22 PM |
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Been playing with the fuel pressure a bit, got it revving up. Pulled really hard in 1st, not too bad in 2nd then begins to big around 4K in 3rd and so
on. Go half throttle for a bit then gets better, if anything feels like it’s being starved of fuel?
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chris
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| posted on 3/11/17 at 02:12 AM |
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Could be fuel vaporisation or tank not breathing
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ProjectSi
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| posted on 3/11/17 at 07:48 AM |
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quote:
Originally posted by r1_pete
Way too much pressure, you need a bike pump or an SU type pump, any carbed bike pump will do, fitted close to the tank as on a bilke they are gravity
fed to you need to replicate that.
Also check the carb diaphragms are sealed properly in the plastic lids, its a good move to fill diaphragm locating recesses with rubber lube, that
stops any leakage.
Does this sound potentially like too high fuel pressure? I’m not really experienced with bike carbs to know how they respond if the pressure is too
high
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chris
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| posted on 3/11/17 at 08:03 AM |
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If your fuel pressure was to high wouldn't there be fuel pissing out of carbs
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SJ
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| posted on 3/11/17 at 08:51 AM |
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Float valves can stick open or closed so worth cleaning them if you haven't already done so.
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ProjectSi
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| posted on 3/11/17 at 08:54 AM |
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quote:
Originally posted by chris
If your fuel pressure was to high wouldn't there be fuel pissing out of carbs
Yeah I wOuld have thought so, if anything it feels like it’s starving. Yesterday after having a play I got it to rev really niceley, I gave it a hoot
full in first and it pulled mint, pulled really well in second then started to die again in 3rd gear and onwards. Pulled over tried revving it and it
wouldn’t go over 4K again....
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40inches
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| posted on 3/11/17 at 08:57 AM |
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quote:
Originally posted by r1_pete
Way too much pressure, you need a bike pump or an SU type pump, any carbed bike pump will do, fitted close to the tank as on a bilke they are gravity
fed to you need to replicate that.
Also check the carb diaphragms are sealed properly in the plastic lids, its a good move to fill diaphragm locating recesses with rubber lube, that
stops any leakage.
This ^. If you use a pump that was designed for bike carbs, it removes that as a possibility 
You need around 2psi. 4psi as a max.
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ProjectSi
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| posted on 3/11/17 at 09:34 AM |
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quote:
Originally posted by 40inches
quote:
Originally posted by r1_pete
Way too much pressure, you need a bike pump or an SU type pump, any carbed bike pump will do, fitted close to the tank as on a bilke they are gravity
fed to you need to replicate that.
Also check the carb diaphragms are sealed properly in the plastic lids, its a good move to fill diaphragm locating recesses with rubber lube, that
stops any leakage.
This ^. If you use a pump that was designed for bike carbs, it removes that as a possibility
You need around 2psi. 4psi as a max.
What does too high fuel pressure cause though? As I say if anything this feels like it’s losing fuel, it starts popping when it begins to big down and
backfiring which is normally because it’s too lean?
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redturner
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| posted on 3/11/17 at 02:29 PM |
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I have 1.8 jets in a set of R1 carbs and and air correction jets plugged and redrilled to .075mm. I run about 2psi fuel pressure with a small solid
state pump.
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ProjectSi
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| posted on 3/11/17 at 05:02 PM |
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Cheers guys, one thing I have found is the carbs won’t seal perfectly with the hoses, there are small air leaks not enough to be able to hear audibly
but if I spray brake cleaner the engine begins to labour. Anybody recommed best way to get them to seal? It’s on the carb end
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avagolen
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| posted on 3/11/17 at 06:12 PM |
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Hi, I had a problem with the 'basic' carburettor mountings. They kept falling off, so I doubt they were air tight.
I eventually replaced them with some 'proper' carburettor mounting tubes from ebay.
This is an example. Mine were in a pack of 4 for about the same price.
Ebay 222594342467
Hope this helps.
These look more like what I ended up with.
Ebay 391895376916
[Edited on 3/11/17 by avagolen]
The Answer for everything, but never the last word....
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ProjectSi
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| posted on 4/11/17 at 09:57 AM |
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quote:
Originally posted by avagolen
Hi, I had a problem with the 'basic' carburettor mountings. They kept falling off, so I doubt they were air tight.
I eventually replaced them with some 'proper' carburettor mounting tubes from ebay.
This is an example. Mine were in a pack of 4 for about the same price.
Ebay 222594342467
Hope this helps.
These look more like what I ended up with.
Ebay 391895376916
[Edited on 3/11/17 by avagolen]
Did these fit your manifold okay? I assume internal diameter is 40mm?
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avagolen
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| posted on 5/11/17 at 06:27 PM |
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Hi,
I can confirm that my carbs are 40mm diameter, but what I cannot confirm is that the tubes are exactly the ones I purchased.
It was a long time ago.
I have carbs from a ZX6R and the Kawasaki mounting tubes from a ZX9 definitely fitted.
391895376916 look very familiar.
They fitted the carbs and the jubilee clip holds them firmly where as the silicone tubes just 'squeezed' off when the clips where
tightened.
I am sorry I cannot be more helpful.
Len.
The Answer for everything, but never the last word....
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SJ
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| posted on 5/11/17 at 08:59 PM |
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The ZX9 carb rubbers I have have a flange on the head side to bolt them up so wouldn't work with an aftermarket manifold. I'm not saying
all are like this but worth checking you are ordering the right thing if you buy some.
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avagolen
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| posted on 5/11/17 at 09:14 PM |
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Yes, be careful.
The ebay number I put in my last post is of the non flanged variety.
The Answer for everything, but never the last word....
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ProjectSi
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| posted on 5/11/17 at 11:46 PM |
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Nice one guys, took carbs off today as they had vacuum leaks so took them off and reseated them properly with new clips. Also rerouted my fuel pipes
to prevent any vapour lock but sill bogs down, very weird one minute it revs up and goes brilliantly, then all of a sudden still bogs down and then
begins to backfire and miss until I lift off for a min, seriously considering dropping the tank and fitting the bike pump just to see....:/
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