benlg924
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| posted on 10/1/09 at 11:34 AM |
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bike carbs
Hi All
i have been put your way as the best place to discuss bike carbs so here goes.
I am currently planning on running cbr900 carbs on my 924 2ltr n/a.
i am getting a manifold base made by short track and then plan to weld the inlet tubes to the base and match to the carbs,
first off will mild steel be acceptable for this application?
what is the ideal length on the inlet tubes to gain good torque power ect?
with regards to the carbs am i best off using the fuel pump that the original bike uses? or best to use a facet pump and filter king regulator?
what are the ideal jet sizes need to run the size of engine. mains and others?
also can you buy bigger jets or are they a drill out job?
and also what sort of gains are people seeing with this over the old injection or old carb ect?
cheers
Ben
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BenB
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| posted on 10/1/09 at 12:04 PM |
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Inlet length isn't a one size fits all parameter. It depends on lots of factors including whether you want a broad power range or a peaky (max
BHP) power curve.
Best use the fuel pump from the bike the carbs came from.
Jet sizzing is also something that requires a trial+error approach.
Welded mild steel is fine for a manifold....
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UncleFista
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| posted on 10/1/09 at 12:31 PM |
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quote:
Originally posted by benlg924
Hi All
i have been put your way as the best place to discuss bike carbs so here goes.
I am currently planning on running cbr900 carbs on my 924 2ltr n/a.
i am getting a manifold base made by short track and then plan to weld the inlet tubes to the base and match to the carbs,
first off will mild steel be acceptable for this application?
Yes, no problems at all, it's what a lot of people use (me included).
quote:
what is the ideal length on the inlet tubes to gain good torque power ect?
The ideal length for me was whatever would fit under the bonnet 
Errr, sorry, can't help with that one.
quote:
with regards to the carbs am i best off using the fuel pump that the original bike uses? or best to use a facet pump and filter king
regulator?
We had lots of problems using a normal Facet "carb" pump at 3psi, it was much too high pressure for the carbs which just squirted fuel out
of every hole
We fitted a 'blade pump and it's been perfect since.
quote:
what are the ideal jet sizes need to run the size of engine. mains and others?
All I did was to drill the mains out to 1.65mm, I bought a set of mine drill bits off ebay and started with the smallest then tested the car, drilled
the next size, tested etc. 1.65 seems about right.
quote:
also can you buy bigger jets or are they a drill out job?
Much cheaper/easier to drill out, but Weber carb jets are meant to be "screw-in" replacements.
quote:
[and also what sort of gains are people seeing with this over the old injection or old carb ect?
I can't help with this one either, we changed engines at the same time as fitting the carbs, all I can say is it runs "very" nicely,
no popping, farting etc. it runs much better than the crossflow on a weber ever did.
quote:
[cheers
No problem
If you want a copy of the part of the Honda workshop manual concerning carbs, I have it
HERE
[Edited on 10/1/09 by UncleFista]
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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benlg924
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| posted on 10/1/09 at 01:42 PM |
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thanks for your quick replies.
mild steel it is then, did you treat it with anything or just leave it natural?
i will get some tiny drill bits then and maybe a few spare jets just in case.
did you have to build a supporting hanger/bracket to take the weight of the carbs?
are you using a air box or filter/sock option? i plan to use the original fireblade air box
ireblade fuel pump it is then although they are hard to find at the moment for some reason.
dont suppose you have any pics of your set up?
cheers
Ben
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snapper
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| posted on 10/1/09 at 01:51 PM |
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Paint your steel manifold on the outside to prevent rust and it looks better.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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will121
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| posted on 10/1/09 at 03:04 PM |
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quote:
Originally posted by benlg924
i will get some tiny drill bits then and maybe a few spare jets just in case.
did you have to build a supporting hanger/bracket to take the weight of the carbs?
are you using a air box or filter/sock option? i plan to use the original fireblade air box
ireblade fuel pump it is then although they are hard to find at the moment for some reason.
dont suppose you have any pics of your set up?
cheers
Ben
i made my last one out of mild steel as easier to fabricate and me to weld and sprayed it externally.
air box options will depend a bit on wether you are going to respace the carbs to suit your port spacings or keep the carbs standard and form tubular
bends in the manifold. what do the port spacings look like?
as for support brackets a lot will depend on your filter options and weights. i set my jet sizes with basic use of narow band lamba sensor and basic
meter, different size jets available from some bike shops about £4 each, ideal use matching fuel pump but any simular capacity sports bike pump should
be ok like say a ZX9.
attached couple pictures
this is set up with standard carb spacing for a 1600 CVH
[img] [/img]
this time i respaced the carbs to suit ports 2 litre zetec
[img] [/img]
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jacko
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| posted on 10/1/09 at 04:00 PM |
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Have a look in my photo archives under zx9r carbs & manifold
Jacko
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David Jenkins
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| posted on 10/1/09 at 04:02 PM |
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I've recorded my experiences on my website - see 'www' button at the bottom of this post, & follow link for bike carbs.
Not saying that it's the way you should do it - just the way I did it!
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benlg924
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| posted on 10/1/09 at 05:59 PM |
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quote:
Originally posted by David Jenkins
I've recorded my experiences on my website - see 'www' button at the bottom of this post, & follow link for bike carbs.
Not saying that it's the way you should do it - just the way I did it!
great website and full of interesting reading cheers for that.
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benlg924
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| posted on 10/1/09 at 06:02 PM |
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i plan to keep the original spacing and make the manifold match with bends in tubes. so will probably use the standard air box for a while until i can
either make another or go down the sausage filter route.
i am now about to attack ebay on the hunt for a 900cc fuel pump
cheers for all your help so far
great images and information
Ben
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David Jenkins
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| posted on 10/1/09 at 06:48 PM |
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Any pump for one of the larger bikes with carbs will do the job...
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benlg924
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| posted on 20/1/09 at 09:05 PM |
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hi
found this pump
http://cgi.ebay.co.uk/Honda-CBR900-RRN-F....parms=72%3A1301|66%3A2|65%3A12|39%3A1|240%3A1318
just wondered where I would wire the wire into and also what is the other pipe coming from the bottom, I take it the two top ones are the inlet and
outlet?
sorry for stupid questions just trying to get my head around it all.
the manifold is being made as we speak so nearly there!
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benlg924
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| posted on 21/1/09 at 09:15 AM |
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also anyone know of a garage or rolling road that can set my car up i am in the west midlands area.
cheers
ben
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benlg924
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| posted on 15/2/09 at 06:15 PM |
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got my fuel pump eventually just out of interest what colours are what on the wiring on pic below
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benlg924
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| posted on 15/2/09 at 06:20 PM |
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benlg924
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| posted on 15/2/09 at 06:22 PM |
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benlg924
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| posted on 15/2/09 at 06:23 PM |
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just to let you know i have started a build thread at
http://retrorides.proboards86.com/index.cgi?board=readersrides&action=display&thread=54569&page=1
if you want to follow it online
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benlg924
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| posted on 26/2/09 at 07:33 PM |
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little thursday update
these arrived through the post today,
they guys at short track motorsport knocked me iup two after my first one was lost in the post cracking guys so if you need any manifolds or metal
work give jason a call they are ace.
now all i need to get is the tubing now in around 40mm internal diametre and i am away.
still need to get the chock and accelerator cables and then a little silcon to connect them together.
looking forward to getting cracking now
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les
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| posted on 1/3/09 at 03:55 PM |
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hi,
this is a bit off at a tangent , but there seem to be lots of bike carb experts on this thread- I have a fuel starvation problem with my r1 carbs
through left hand bends on the track- i am running a competition spec facet solid state fuel pump- but the carbs run fine without any regulator- no
fuel leaking. could this mean there is some other blockage or problem causing the starvation? from one of the posts- this pump should have fuel
leaking everywhere?
LEs
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benlg924
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| posted on 9/3/09 at 08:52 PM |
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hi all
my tubing should be here tomorrow to get cracking on the manifold and i was wondering if peopl ehave made the extra tube for the vacume?
do i just run 1 vacume feed from #4 or all 4 or is it not really needed?
all help would be great so i can get started
cheers
Ben
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