Been out for a couple of runs today. The first was just to warm the engine before doing an oil change and then a longer one this evening. Each time i
came in from a run i smell of petrol! I can smell it on my hands. When starting the car the second carb spits back and when i take off the filter the
carbs seem quite wet inside. So i obviously suspect that the carbs are overfueling.
My question is how do i adjust the fuelling on the ZX9R carbs i have? Is it the size of the jets, the amount of turns out on the air screw underneath
or is it the hight of the needle or combination of all of them?
Cheers.
What sort of fuel pump do you have? This sort of thing often happens if you're using a car-style pump instead of a bike one.
Otherwise - no idea!
First and formost are you using a fuel pressure regulator? You need to use one preferably set to 2.5-3 psi definately no more. Bike ones are ideal but
you can use a facet type one (as i do with a adjustable regulator).
Cheers, Sean.
No i have bike fuel pump supplied by Bogg Bros. Is it called an interuptor type?
Another thought - is the car running OK otherwise? If so, have you checked for fuel pipe leaks? (see
this thread. for fuel pipe problems.)
I didn't have a lot of success with a Facet pump and Filter King regulator - if I got the pressure low enough the flow wasn't sufficient.
Changing to a bike pump fixed all of my fuel problems. If you've got a pump from Boggs then I guess that will be fine.
Fit a pump from the same model bike the carbs came from. I had the same problem with a facet and regulator.
Make sure it's not a fuel injection pump.
No fuel line leaks have checked from front to back and back to front. Are none of the things ive mentioned an issue then?
Just to have my sixpennyworth! I have a Filter King, Facet AND a pressure guage in the system on my bike carbed Skoda Estelle engine and dont appear to have any probs. The pressure guage is to accurately check the pressure is correct but you can get a Filter King with a guage.
Combination of all three, the air bleed screw affects idle, lower the needle to weaken the mixture across the range, the main jet is the master in the
equation.
Did they come jetted for the application?
To much pressure should result in the carbs overflowing BTW.
Regards Mark
They came predrilled by Boggs. I think they take them out to 1.8mm. I have the air screw turned one and a half turns. This was set by the mot tester to just get through the emissions test. The needles are one down from the highest setting and i have balanced the airflow today with a flowmeter.
The idle speed is adjusted by that thing you twist thats attached tot he bottom of the carbs.
Did Boggs block the air correction hole ? this can make them run rich, but not blocked can make them run weak at high revs
I have a 2.1 pinto zx9r / E carbs and it has 1.7 mm main jets with air correction hole blocked
The air screws are one turn out
All done on Boggs rolling road
[Edited on 20/6/11 by jacko]
Holes are blocked with snipped off bits of wire by the looks of it. Will try turning in to match your set up and play with the needle setting. Will
look at the jets after that.
Hoping to get the car to Frosts rolling road in ipswich soon. He has an excellent rep. Hopefully he will sort it if i cant 
You say you have E carbs. Thats my other thread im not having any luck with. Dont know which ones i have.
[Edited on 20/6/11 by scoop]
If it has clips on the needles they will be B,s or C,s photos help us
Just be careful if you remove the blocked holes it may make them to week = holes in pistons etc
Every engine is different to set up
ie what cam do you have / what exhaust what pistons etc etc
Make sure you use a carb bike fuel pump
[Edited on 20/6/11 by jacko]
Shant be unblocking them then. Standard cam and exhaust manifold. Just cant get photos to upload. Not sure what im doin wrong.
If std engine i would say the jets are 2 big having said that boggs know what there doing
give them a phone call and have a talk
Is it a 2l engine you have ?
It is 2l
Does the engine 'bog down' around 4000 rpm. that's what I got when I was having the same problem last year, also told that Bogg Brothers (who did mine) do fit oversize jets if they don't have the car to put on a rolling road so as it's not over lean. To be honest BB didn't tell me that but that was the general advice from here.
quote:
Originally posted by norfolkluego
Does the engine 'bog down' around 4000 rpm. that's what I got when I was having the same problem last year, also told that Bogg Brothers (who did mine) do fit oversize jets if they don't have the car to put on a rolling road so as it's not over lean. To be honest BB didn't tell me that but that was the general advice from here.
Okay. Now we're getting somewhere. I understand that webber jets fit these carbs. Which ones do i get, DCOE?
[Edited on 21/6/11 by scoop]
DGAV/DGAS mains fit Mikuni carbs. They will spit back at times, (overrun) especially if the idle is lean, you could try opening the screws another half turn.
Mine are keihin though?
I bought a set of miniture drill bits from the bay and just soldered the jets up and redrilled them.
Cheers
Rich
I made my own jets! 
Quite easy, if you have a small-ish lathe and an existing jet to take measurements from. I made a couple of simple jigs and did a small
'production run'.
They're simple enough if you have reasonable skill with a lathe, but would be a challenge for a beginner.
And to answer the original question - there are a few things to consider when tuning bike carbs...
1. First, get the tick-over mixture right, and balance the carbs.
2. Then get the wide open throttle (WOT) mixture correct - this is governed by the size of the main jet.
3. Then raise or lower the needle (if you can) to get the mid-range mixture correct. My car runs rich at mid-range, but I can't lower the
needles (not adjustable) so I'd have to change the needles. It's not too far wrong so I haven't bothered to take it further, but it
would make a big difference to fuel economy.
4. If you're feeling really swish you could change the needles for ones with a different profile, to get the right mixture at all settings... I
don't know anyone who's done this!
Steps 1, 2 & 3 are the normal sequence though. Ideally you would get all of this done on a rolling road, but I did it with an AFR meter on quiet
back roads.
HTH.
[Edited on 21/6/11 by David Jenkins]
.
Have you checked the slide operation? All move up and down correctly?
Stupid Q? but what state are the air pipes that come out betwix 2&3 and 3&4? Not blocked? free to air?
One previous question you didn't answer (I think!) was - "Is the engine running properly at the moment, ignoring the smell of
petrol?"
The reason for asking is - if the engine's running well then the state of the jets may be irrelevant and the problem's elsewhere. However,
if it's running rough, using petrol like there's no tomorrow, or similar, then maybe fuelling is a problem.
You could try checking the colour of the plugs - get the engine nicely warmed up, give it a bit of welly here and there, then on a quiet road floor
the clutch and turn off the ignition. Once you've stopped whip out a plug or two (hot, hot, hot!) and check their colour. This is a crude and
unreliable test, but if the electrode is black and dripping with petrol you are undoubtedly over-fuelling. If they're a nice biscuit colour then
you're roughly in the right ball park.
A couple of dumb but basic questions
- are there any signs of fuel dripping from the carbs when the engine's stopped but the ignition's on? I'm thinking of stuck and/or
dirty float valves that aren't shutting properly when the chamber's full.
- is your passenger compartment fully sealed off from the engine compartment? You might be smelling normal engine fumes that you wouldn't if
everything was screened off.
(I'm working on the principle that it's worth trying the simple solutions before getting onto the tougher, more expensive solutions!
Have the carbs been stripped before? Float level OK?
Easily the best thing to do is get an afr hooked in... if your gonna home tune.
can get a complete second hand set up off ebay if you keep an eye, or new if you wanna spend 150-170 quid,
I went with the innovate lc-1, quite fiddly to wire up, the uego one looks simpler..
Anyhow- it takes all the guess work out of tuning carbs, idle is easily set then get the main jet right at wot redline and then work back ways through
the revs by adjusting needle height.
I too have ZX9R carbs, C1 jobs, on my 16v 2.0, I have 135 mains with ACs blocked, lift holes reduced 1mm, afr is spot on at all revs. I'm running
red top and filterking with no issues.
Make sure they are positioned at the right angle too... Also just noticed you have a bike pump? They are interrupter type (unlike most fuel pumps
which just whirr away all the time) which means they only tick when the carbs need fuel. So with the engine off and pump working it shouldn't be
ticking at all, if it is there is a leak somewhere.
[Edited on 21/6/11 by Craigorypeck]
The car is running okay otherwise as far as i know. The sierra pedal box ive fitted has left a way for the engine fumes to get into my footwell.
The carbs are only two years old from Bogg Bros and went back to them in march this year for a clean up. Ive only done 350 miles! Everything moves
smoothly and the needles are on the lowest setting barr one. They will insist on setting them with the mixture screw turned out 2 1/2 which is far too
rich.
I think its got to be the jet size from all the information everyone has gratefully passed on.
Rather than guessing what i need ive come to the conclusion that i'll leave it all to the proffesionals and book it into Frosties next week
weather permitting.
Craigorypeck, what do you mean when you say lift holes redused by 1mm?
I changed the plugs yesterday and the ones i took out were more blacker than brown. I will go out and check the new ones now though.
quote:
Originally posted by scoop
Rather than guessing what i need ive come to the conclusion that i'll leave it all to the proffesionals and book it into Frosties next week weather permitting.
Frost Motors in Ipswich. He used to work at Scole Engineering im told. Hes got the only rolling road and the skills in Suffolk to do it im told. Have
a look at www.fmsauto.co.uk
I forget who mentioned that the midrange was basically controlled by the level of the floats and mine did seem hesitant about 3 to 4k so i raised them
a notch and have just been out again. It is improved
The plugs still dark brown/black.
Thanks everyone for your help.
quote:
Originally posted by scoop
Okay. Now we're getting somewhere. I understand that webber jets fit these carbs. Which ones do i get, DCOE?
[Edited on 21/6/11 by scoop]
Cheers for that. The webbers are only a couple of quid each so i look forward to the lowercost items
quote:
Originally posted by scoop
Craigorypeck, what do you mean when you say lift holes redused by 1mm?
scoop's pics
Description
Description
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Just rung Bogg Bros and they tell me the jets are drilled to 1.65mm not 1.8 so seems strange that my carbs are overfuelling?
I have 1600 xflow engine running bike carbs, fitted them and ran them with facet fuel pump and regulater, but it would not rev straigh out.. it
stuttered at 4,700rpm when you put the pedal to the floor, so i took the regulater out and still had the same problem :-s
ive tryed putting a small storage tank just before the carbs to see if its the lack of fuel at high revs but it only made a slight change, it would
stutter at 5,500 rpm then harsh accelerating.
the only time it revs out straight is if u accelerate steady but thats no fun :-(
any idears?? :-/ :'( thanks
"Smell of petrol" isn't so much a clue as a flashing illuminated sign ----- the float bowls are flooding.
Getting the jets a bit wrong won't cause a smell of petrol in the engine bay.
I had a very similar effect when I first fitted bike carbs - accelerating quite well but losing power massively at anything over 4k. When I finally
got an air-fuel ratio (AFR) meter onto it I found that the mixture was far, far too rich at wide open throttle (WOT). After reducing the jet size
from 1.6mm to 1.3mm the AFR was near-enough perfect when accelerating hard (slightly rich).
But it would be wise to get your car onto a rolling road, rather than just try this out, as your problem may not be the same! At least get an AFR
meter and a mate to watch the readings as you go down the road.
quote:
Originally posted by Bowers919
I have 1600 xflow engine running bike carbs, fitted them and ran them with facet fuel pump and regulater, but it would not rev straigh out.. it stuttered at 4,700rpm when you put the pedal to the floor, so i took the regulater out and still had the same problem :-s
ive tryed putting a small storage tank just before the carbs to see if its the lack of fuel at high revs but it only made a slight change, it would stutter at 5,500 rpm then harsh accelerating.
the only time it revs out straight is if u accelerate steady but thats no fun :-(
any idears?? :-/ :'( thanks