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Author: Subject: zzr1100 running rich (I think)
nick9one1

posted on 25/6/19 at 07:37 PM Reply With Quote
zzr1100 running rich (I think)

I'm trying to get my zzr1100 engine running properly and struggling a little.

I've stripped the carbs, ultrasonically cleaned them and rebuilt with a kit.

I've set the fuel level by measuring the floats, set the mixture screw, balanced them and its not running great at idle - kind of lumpy.

I pulled the plugs and they're black and wet (all 4). Running rich?
From what I can gather there are two things that mainly cause this, float level and mixture screw. I've double checked mixture screw and its correct.

The manual covers a secondary way to set the fuel level, but its not quite clear in my head.





initially it seems straightforward

1. hook up some hoses
2. open bleed screw
3. check level against marking

Is it necessary to setup an auxiliary fuel tank? on the car I'm using a bike pump and the tank is lower than the carbs.
I presume I need to turn off the pump before opening the bleed screw?
Surely the pipe length is critical? If there is a set level of fuel in the bowl, a longer pipe will result in a lower fuel reading?

Or am I missing something obvious here!? haha

[Edited on 25/6/19 by nick9one1]

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rusty nuts

posted on 26/6/19 at 06:39 AM Reply With Quote
Liquids will find their own level , once the needle valves have shut the fuel level would show through a clear pipe irrespective of how long or high the pipes are ( within reason) However surely using pipes is not setting the float heights just checking? PS Im not an expert on bike carbs just my observations
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nick9one1

posted on 26/6/19 at 07:02 AM Reply With Quote
Yes youre correct, it's a check of the fuel level, not setting the fuel level.

But if there is an amount of fuel in the bowl, say 40mm. When I open the bleed screw some will flow into the pipe and equalise with what's in the bowl. The level in the bowl is now 30mm and this is indicated by the level in the pipe.

If I use a longer pipe (more of a u bend below the fuel level), when the bleed screw is opened there will be more fuel in the pipe resulting in a lower fuel level indication.

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rusty nuts

posted on 26/6/19 at 08:09 AM Reply With Quote
If the pump is running even with the engine off the fuel level will stabilise when the needle valve shut
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nick9one1

posted on 26/6/19 at 05:28 PM Reply With Quote
I think a previous experience with a bad float valve has confused me.
I briefly tried this method a while ago with the fuel pump turned on - the tube overflowed. I've since replace all the float valves and it no longer overflows

Ok, it looks a little high. Every bowl is reading exactly on the float line
The manual says 4.5mm +/-1mm below the line.

The tube I was using is cloudy so no easy to make out in the picture




Colour of the plugs



[Edited on 26/6/19 by nick9one1]

[Edited on 26/6/19 by nick9one1]

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teegray19

posted on 26/6/19 at 07:55 PM Reply With Quote
Have you got an air box on? that will make a massive difference, ours ran like poo without the air box.





Built Formular 27 with 1600cc crossflow, 1700cc 0 miles crossflow, Kawasaki ZZR1100

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nick9one1

posted on 26/6/19 at 09:30 PM Reply With Quote
No it doesn't have the airbox on at the minute (just the trumpets), but I didn't notice much of a difference when it it did. Good suggestion though, I'll see if there's a difference once the floats are all correct.

I think I'm also going to buy a wideband afr kit to properly check the fueling if I can find a cheap one.

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teegray19

posted on 26/6/19 at 09:38 PM Reply With Quote
Your lack of air box will be chasing you more issues than you know currently. Our engine was rich, lean, hit a rev sealing at about 6k rpm. Our custom Zorst also caused some fuel issues. Running very rich, leaned out with a Dyno jet kit and got in the rollers at day tuner





Built Formular 27 with 1600cc crossflow, 1700cc 0 miles crossflow, Kawasaki ZZR1100

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nick9one1

posted on 27/6/19 at 07:04 AM Reply With Quote
Thanks.
Next time I run it I'll have the airbox installed.

First I need to get the float levels correct. I spent a little time fiddling with it last night and found a method that allows me to get an accurate reading.

Connect pipe to carb bowl
Open drain
Tap and wiggle pipe to remove trapped air
Close drain
Dump the last 2 inches of fuel out of the pipe without creating airlock
Line pipe up with float line
Open drain
Remove carb and adjust as needed

Cylinder 1 is now 4.5mm below the float line. Just need to do the rest.

I also want to clean up the plugs so I can check the condition. I've heard oven cleaner works well.
Once it running well I'll install new ones, but I don't want to put a set in now for them to foul and go black.

[Edited on 27/6/19 by nick9one1]

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nick9one1

posted on 28/6/19 at 07:52 PM Reply With Quote
I managed to spend another hour on the carbs tonight. The fuel level is correct now. All are reading about 4mm below the line on the carb bowls (which is in spec).
Out of interest I measured the float height. 3 are about 17/18mm and the other is 16mm.
If I'd set the float height via just the measuring the floats, the actual fuel level would be way too high.

The mixture screws are set to two turns (I think this is correct).

Then balanced the carbs again. They were quite a way out after adjusting the floats.

Final result is it runs loads better. Easier to start and a much more consistent idle. Previously the idle was quite erratic, but it only varies about 20-30rpm now.

I'm not finished yet but definitely pleased at the progress !

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