David Jenkins
|
| posted on 11/5/08 at 08:52 PM |
|
|
My bike carb saga continues...
Managed to get a session with Doug (garage19) and his AFR meter on Saturday... very helpful (and much appreciated) and I'm making steady
progress.
On tick-over and mid-revs I'm running a little rich (about 12.5 AFR) - I'll have to live with that until I can get some adjustable
needles, but the engine runs well at that point. However, with the throttle wide-open the reading goes to 25 or higher, so It's running far too
weak. It's no wonder that the car sounds strangled at high revs!
The engine's a 1660cc crossflow with Honda CBR600-FX carbs, re-spaced to match the cylinder head ports. Currently I've drilled the jets
out to 1.6mm - I was wondering what size other people have drilled their jets for a similar sized engine?
Apart from the jet size, what else could cause such a lean reading at WOT? Have I missed a trick or forgotten something somewhere along the line?
cheers,
David
|
|
|
|
|
daviep
|
| posted on 11/5/08 at 08:55 PM |
|
|
It maybe worth checking your float height, if the carbs are mounted at a radically different angle the fuel height in the jet maybe too low.
Davie
|
|
|
Guinness
|
| posted on 11/5/08 at 08:58 PM |
|
|
quote:
Originally posted by David Jenkins
Apart from the jet size, what else could cause such a lean reading at WOT? Have I missed a trick or forgotten something somewhere along the
line?
Apart from jet size, I would point to either fuel supply, or slide lift.
Are you using the matched fuel pump from the bike?
Can you have a look into the mouths of the carbs while someone else floors the peddle to see if the sliders are opening (thus pulling the needles out
of the jets and allowing the fuel out)?
HTH
Mike
|
|
|
daviep
|
| posted on 11/5/08 at 08:58 PM |
|
|
Sorry meant to say when setting up carbs it's normal to setup WOT first since this will dictate your jet size. No point in setting the needles
for low/mid as the setting will be wrong if you change main jets.
Davie
|
|
|
whitestu
|
| posted on 11/5/08 at 09:58 PM |
|
|
I'm running 1.6mm jets in my 1.8 Zetec [ZX6R carbs] and they seem fine, so the same in your crossflow should be OK.
|
|
|
garage19
|
| posted on 12/5/08 at 05:24 AM |
|
|
quote:
Originally posted by daviep
Sorry meant to say when setting up carbs it's normal to setup WOT first since this will dictate your jet size. No point in setting the needles
for low/mid as the setting will be wrong if you change main jets.
Davie
If he increases the main he will also richen up his already rich needle range hence the two changes you see.
|
|
|
will121
|
| posted on 12/5/08 at 07:28 AM |
|
|
my bike carbs (zxr600 on a 1600cvh) are mounted at the origional angle to keep the float bowl level motorbike fuel pump. i actually brought sets of
replacement jets from a motorbike tuner at £4 each as didnt like the thought of drilling them out. went up from the orignal 135’s to 165’s. it
started with these first time!
I had also fitted a lambda sensor into the exhaust manifold and brought a magic box to monitor and indicate the fuel/air mixture, which indicated it
was running too rich. (so did the 15mpg I initially got!).
Ive subsequently on the road and with the aid of the fuel/air monitor continued to tweak the fuelling, its now running with an air box, smaller 150
main jets (for full throttle fuelling), needle jets position 2 of 5 (mid range) and air screws two turns out (tick over fuelling) which seems to suit
my engine and pulls strongly.
|
|
|
BenB
|
| posted on 12/5/08 at 07:55 AM |
|
|
What's your fuel pump doing when you're at WOT (presumably you've fitted an electrical bike one rather than sticking to the original
dodgey car one 
It could (probably isn't- but could be ) be that your pump isn't up the job hence going lean @ full chat....
|
|
|
jacko
|
| posted on 12/5/08 at 03:36 PM |
|
|
If you do a serch under my name [ jacko ] you will see some posts about this it may help this is for zx9r/e carbs
Graham
|
|
|
