flak monkey
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| posted on 2/1/15 at 05:32 PM |
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ZZR 1100 Jetting
My ZZR1100 runs pretty rough at times - it's still in the bike with the stock ram air fitted. It runs particularly badly in gusty head/side
winds, but it feels like it's generally very lean at more than half throttle.
I believe a previous owner has fiddled with it though and fitted flat carb tops, possibly drilled the slides and fitted adjustable needles but it
still has the stock 140 main jets.
I reckon that it needs mains in the region of 160-165 but I'm guessing really. Anyone got any thoughts on it before I start changing stuff? The
carbs are a complete arse to get to on the bike as well 
Sera
http://www.motosera.com
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maccmike
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| posted on 2/1/15 at 06:23 PM |
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Remove the ram air and pipe it into the airbox behind the filter, that way the bowls are equal to the intake pressures.
Part throttle aint the mains but yes I agree 165s are better. I ran 165s on the inner 2 cylinders and 160s on the outer, to keep the #3 cylinder
cooler. Dont know if it worked but I never melted a piston.
Check for leaks, dismantle and clean.
If previous owner has messed about, check pilots and idles etc to ensure suitable size etc. Use vacuum guage to check everything is in sync.
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flak monkey
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| posted on 2/1/15 at 06:37 PM |
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Thanks
They are sync'd ok, I checked them just earlier today  I've had them apart and cleaned them out thoroughly too.
I'll move the breather pipe from the vent at the front to the air box, I've got a spare hole (currently blocked up) where I removed the
PCV hose.
Sera
http://www.motosera.com
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daviep
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| posted on 2/1/15 at 06:49 PM |
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Sounds like previous owner has made a mess of something, I ran mine in the bike and it ran really well when totally standard. It didn't run
particularly well when fitted in the car without the airbox.
Cheers
Davie
“A truly great library contains something in it to offend everyone.”
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davidimurray
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| posted on 2/1/15 at 07:52 PM |
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When you say you've cleaned them, have you blown them through or cleaned in carb cleaner. I spent ages tracing a mid range backfire and it was
due to the pilot jet. I thought they were clean after blowing through but when I soaked in carb cleaner for 24 hours a fine varnish like coating came
out and it cured all my problems!
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
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Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
Duratec Engine Swap https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f " target="_blank"> https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f
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flak monkey
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| posted on 2/1/15 at 08:02 PM |
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Both, they've been stripped and cleaned in carb cleaner and then blown through twice now.
Sera
http://www.motosera.com
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maccmike
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| posted on 3/1/15 at 02:06 AM |
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Make sure the floats are set right too. And they are very sensitive to airboxs. If the previous owner changed the tops, check the diagrams arent split
and the little brass hollow in each corner is clear.
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flak monkey
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| posted on 13/1/15 at 07:51 AM |
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I'm still battling with the jetting on the the bike, its a C1. Unknown modifications by the previous owner to the carbs and I don't have
the stock parts.
Bike has a K&N filter and Nexxus exhaust system with the end cans drilled, so I expect they flow pretty well. Carbs have had full power tops
(flat) fitted. Carbs have been off and been cleaned twice now thoroughly with carb cleaner and compressed air.
It feels lean at cruise - surging slightly. When you open the throttle anything over about 1/3rd right up to WOT it stumbles and splutters from 3.5k
rpm upward. If you close the throttle slightly it seems to pick up marginally, but not much.
It has stock 38 pilot jets, mixture screw 2.5 turns out. It was fitted with stock 140 mains (I expect this was the restricted version) and I've
now fitted 160's to try and sort the higher rpm issue, but it's still just as bad.
It's had aftermarket needles fitted, but I have no idea what they are as they have no markings on them. They have 5 clip positions, clip is
currently in the 4th groove down.
It's a complete  to get at the carbs and I'm getting fed up of pulling them on and off already!
Sera
http://www.motosera.com
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davidimurray
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| posted on 13/1/15 at 12:28 PM |
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By the sound of it, you should have plenty of fuel. I'm sure you've looked at these already but a few thoughts -
Are the slides lifting evenly and dropping in a damped way. When you blip the throttle can you see them opening together.
Under the caps are there little o-rings for the vac passage - if so they can be very easily lost.
Are there any spacers/ washers under the needles and are they all the same (I've made that mistake before!!)
You say they are balance but are all the throttles opening together. I once had a sticky throttle on one carb and when you opened the throttle it
opened, and then collapsed the balancing spring until that got coilbound and then carried on opening. All balanced fine at idle but when on load it
meant 2 carbs were out of balance with the other pair.
Have you checked float levels?
Cheers
Dave
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
Gallery 2 http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319
Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
Duratec Engine Swap https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f " target="_blank"> https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f
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flak monkey
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| posted on 13/1/15 at 12:44 PM |
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Thanks Dave
Slides all seem to lift OK, they have a small brass restrictor in the diapragm which are all in place.
The needles are all set to the same height, clip in position 4.
They all seem to move freely, I'll double check when they are off again.
I checked float heights the first time I took them off, but will check them again as I'm going to have to take them off again anyway.
Sera
http://www.motosera.com
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davidimurray
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| posted on 13/1/15 at 04:32 PM |
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On my ZX6R carbs, below the needle circlip there is a thin metal washer and then a plastic spacing washer about 4mm thick. Have you got exploded
diagrams to check what the needle build up should be.
Can you check the floats on the bike with a bit of tube?
Stupid one, but what about any fuel filters?
Gallery 1 http://www.facebook.com/media/set/?set=a.116893465324.130778.601005324
Gallery 2 http://www.facebook.com/media/set/?set=a.245243755324.181913.601005324&l=a9831a9319
Gallery 3 http://www.facebook.com/media/set/?set=a.440671625324.232627.601005324&l=3f0d42c523
Gallery 4 http://www.facebook.com/media/set/?set=a.490098255324.297598.601005324&l=efb083b7df
Gallery 5 http://www.facebook.com/media/set/?set=a.10150244028550325.366987.601005324&l=583fd5cd3a
Gallery 6 http://www.facebook.com/media/set/?set=a.10150550640070325.430417.601005324&type=3&l=fe779b358c
Duratec Engine Swap https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f " target="_blank"> https://www.facebook.com/media/set/?set=a.10152527759580325.1073741828.601005324&type=1&l=40aae5e72f
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Ivan
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| posted on 13/1/15 at 04:56 PM |
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Totally dumb question - are you sure the problem isn't electrical?
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flak monkey
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| posted on 13/1/15 at 07:51 PM |
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It's always run badly, and I know the carbs have been messed with so it's the first conclusion I drew. I've got another set on the
way that I know run perfectly on a stock bike. So I am going to put them on first and see if there is any difference. If it still runs badly then
I'll know the problem lies somewhere else.
Sera
http://www.motosera.com
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flak monkey
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| posted on 16/1/15 at 07:53 PM |
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Well, I pulled it all apart again this afternoon as the stock carbs hadn't arrived. I put new plugs in a couple hundred miles ago. Pulled them
and they were completely clean, no soot at all. Tells me it's still running mega lean.
Pilot jets are the stock 38 ones.
Just to check to see if I was getting a rich or lean misfire I reassembled the carbs with the original 140 mains, shimmed the needle back up to where
it was and took it for a ride. It's considerably worse over 7k rpm at WOT with the 140's (no power at all, it just dies completely) rather
than the 160's which just have a significant misfire. So I reckon it's still running way too lean at WOT when it's on the main jet
even with 160's. Seems odd, but I have no idea what mods have been done to this bike...
Tomorrow I'm going to drill one of the sets of jets out to 180 and try again. I know drilling isn't perfect, but it saves me buying loads
of jets just to get in the ballpark. Plus I have a set of micro drills in 0.05mm increments just for this job...
While I was in there I also replaced the HT leads, looked like they might have been originals?! Either way they were quite corroded at the ends where
they screw into the coils and plug caps so the new ones should help a bit.
I also backed the idle mixture screws out another half turn, now 3 turns out. It revs a lot cleaner off idle now, no stumble at all. But I think
it's just a touch too rich now, so I'll screw them back in 1/4 turn. I also put the shims back under the clips on the needles and it runs
better in the midrange now.
Also checked the float heights, all spot on at 13mm.
So bigger mains tomorrow and we'll see what happens. I'm getting bored of taking the tank off this thing....
Sera
http://www.motosera.com
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maccmike
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| posted on 16/1/15 at 08:04 PM |
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Mine ran lean for a while.
Remember, the air inlet on the front of the bike is only a couple of inches square and chances are yours is much bigger.
As well as slightly increasing my mains I also made a housing from fiberglass that fitted to the airbox to replicate the size of the motorbikes inlet.
Ran great after that
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Lightning
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| posted on 16/1/15 at 08:33 PM |
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I've still got some various size jets in the garage somewhere if it would help. I had a lot of problems setting up the carbs on zzr1200
Someone had mucked around with mine too had to change the springs back to stock. And adjust the needle height
[Edited on 16/1/15 by Lightning]
Steve
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