DarrenW
|
| posted on 30/1/06 at 05:43 PM |
|
|
Bike Carbs - honest appraisal / advice / help reqd.
I have read a few threads over the months of people fitting bike carbs to a multitude of engines. I have also observed a lack of comments over how
people have found them to use and set up etc.
OK - now to the point. How good are they? Any pitfalls? Performance vs economy vs driveability? etc? etc? Would you do them again? Are they better
than Webers.
Please start reply with summary of application and if poss back up claims with accurate data.
[Edited on 31/1/06 by DarrenW]
|
|
|
|
|
Surrey Dave
|
| posted on 30/1/06 at 06:43 PM |
|
|
Fitted Suzuki GSXR 38mm carbs to my 1800CVH
Made my own manifold from mild steel 'Locost!',
From the outset the car started easier and ticked over very smoothly.
The pilot jets remained standard 35 I think ,and I experimented with the needle position, this effects 1/4 to 3/4 running.
Spoke to Bogg Bros , they suggested I start main jets at around 150 ,they wher 115 standard, being a disbelieving so n so I took the jets up in
smaller increments, by gradually drilling them larger, I ended up at 1.60mm (160) I get a reasonable guide to mixture strength from the onboard lamda
senser with 10 led gauge ,which can be built very cheaply,the car has not been on a rolling road, and would no doubt be improved if it were.
Having said the the car starts and runs fine ,and is quite economical, the mixture gauge and the spark plug colour says the mixture is on the right
planet!!
Would I use them again ? yes , because of the variable venturi they give a very seamless and smooth transition from low to high revs, you get the
tractability of small carbs low down, then they open up to give you the power at the top end, NO flatspots!!
Bearing in mind the Locost element you will never get a pair of Webers for £40 - £60.
The only downfall I can think of is that parts are expensive , so it could be cheaper to just get another set of Ebay ,if you need too much, (main
jets £5 each ,but Weber ones fit! , plastic slides £30 each!!)
[Edited on 30/1/06 by Surrey Dave]
 
Rescued attachment Carbs On Car 6 vvsml.jpg
|
|
|
givemethebighammer
|
| posted on 30/1/06 at 08:21 PM |
|
|
Same comments as Dave - Bogg Bros did my setup for me. Honda Blackbird carbs on to my 2.0L zetec. I bought a second set of carbs from the breakers for
£100 so I have cheap spares!.
The blackbird carbs:
1. use 1/3 less fuel than the weber 45's I had previously.
2. the low speed / off idle problems I had with the webers no longer exist
3. I have connected and calibrated the honda throttle pot to my GEMS ecu for full 3D ignition.
4. They seem to stay in tune (they haven't gone out of tune in 6 months) longer than the weber 45's.
I would definitely use them again.
[Edited on 30/1/06 by givemethebighammer]
|
|
|
DarrenW
|
| posted on 31/1/06 at 09:31 AM |
|
|
Thanks guys, thats exactly what i was looking for.
It looks like you both went the diy route. How did you find them to set up and get running nicely? Have you been restricted on where you can get them
tuned seeing as they are a bit specialist? Im also interested to hear if you have a tangible increase in torque and power.
Do you have pics of manifolds in archives? Im tempted to make my own in steel as well. Im interested how people get the spacing right etc.
As you can tell im in suss them out mode and need to decide if they will be better than twin 40's etc.
Does anyone know much about ZZR carbs and suitability for a now mildly tuned 2.0 pinto - later to be better tuned???
[Edited on 31/1/06 by DarrenW]
|
|
|
jacko
|
| posted on 31/1/06 at 07:08 PM |
|
|
bike carbs
Hi Darren i have fitted zx9r carbs to my pinto 2lt in about 3 weeks i will be going on a R Road i will post how i get on with it . If you look in my
archives under zx9r carbs there is some photos of my manifold etc Jacko
|
|
|
Surrey Dave
|
| posted on 31/1/06 at 08:13 PM |
|
|
Manifold
Manifold
 
Rescued attachment Finished Manifold 4vvsml.jpg
|
|
|
Surrey Dave
|
| posted on 31/1/06 at 08:14 PM |
|
|
Manifold Too
Manifold Too
 
Rescued attachment Finished Manifold 2 vvsml.jpg
|
|
|
DarrenW
|
| posted on 31/1/06 at 09:52 PM |
|
|
this is great info. many thanks.
Ive just been given a set of ZZR1100 carbs (Thanks Guiness). 40mm chokes. Spacing of carbs will be a challenge to get manifold spacing right.
What would stop me just having basic manifold with simple straight stubs sticking out, maybe at an angle then having flexy pipes (bit of Samco?) to
join to carbs? I know carbs have to be held at an angle for the floats but the bodies could be stabilised by a semi-flexy bracket.
Do all bike carb needles have the 5 position tops on them or only dynojet kits?
Does anyone know where i can get 4 K&N to fit ZZR's or a single pipercross from?
Jacko - your manifold has vacuum take offs - is this to suit your carbs or do they all need this?
At the moment things seem to be getting decidedly complicated but this is probs cos my investigations have just started and i have more q's than
answers. Im actually surprised how simple the carbs look compared to webers.
|
|
|
Hellfire
|
| posted on 31/1/06 at 10:23 PM |
|
|
Just have done with it and stick a whole bike engine in. You know thats what you really want. And don't try to deny it................. 
|
|
|
jacko
|
| posted on 31/1/06 at 10:27 PM |
|
|
Hi the vacuum pipes are there so i can balance the carbs and use one for the dizzy vacuum. But you can use a synchrometer if you have one like they
use on webers It is not to hard to make a manifold like mine if you can weld and use a hacsaw Jacko
|
|
|
jolson
|
| posted on 31/1/06 at 10:36 PM |
|
|
Will it work to only use one for the vacuum advance? It's only drawing a quarter of the time.
I've been puzzling over this for a bit. Don't see that you can connect all 4 together either, as you'd just end up with a flow of
air back and forth between carbs. Someone on the forum mentioned using check valves (a long time ago, couldn't find the thread again), but I
don't see that working either.
I thought the approach for bike carbs was to not use the vac advance and then modify the centrifugal advance springs.
Has anyone sorted this out for real?
Cheers
John
|
|
|
Surrey Dave
|
| posted on 31/1/06 at 10:38 PM |
|
|
My GSXR carbs have vacuum take offs built in with blanking caps, I did link them all and use them with the standard ignition at first.
|
|
|
02GF74
|
| posted on 1/2/06 at 09:44 AM |
|
|
quote:
Originally posted by Surrey Dave
My GSXR carbs have vacuum take offs built in with blanking caps, I did link them all and use them with the standard ignition at first.
at first ... so presumably you changed that - why/what probs?
|
|
|
Surrey Dave
|
| posted on 1/2/06 at 10:25 AM |
|
|
The standard 1.8cvh ignition relies heavily on a vacuum feed , but since fitting the Megajolt I have only mapped it for 2D operation so far .
although it has a MAP sensor fitted,
|
|
|
mookaloid
|
| posted on 1/2/06 at 07:02 PM |
|
|
There is no good way to use a vacuum advance with bike carbs, weber 40/45's etc.
if you connect it to just one part of the manifold then the vac advance just gets pulses of vacuum which makes the dizzy sound as if one of the bob
weights is hitting the side of dizzy all the time......
if you connect all the manifold inlets it might just possibly work but I suspect that instead of providing a vacuum to the dizzy it just pull air
from one of the other inlets.
if you have non return valves then the advance won't back off again when it needs to.
So the solutions are to get a properly modded dizzy which is designed to run without a vac adv. or use megajolt or the like.
using a Vac Adv. dizzy with the advance just disconnected will not be a good solution as the advance curve will be all wrong - you will be able to
have it ok at idle but not at speed or vice versa but not both.
Cheers
Mark
|
|
|
jacko
|
| posted on 1/2/06 at 07:22 PM |
|
|
Mark what can you tell me about megajolt? it may be the way to go with my engine Graham
|
|
|
cryoman1965
|
| posted on 1/2/06 at 10:48 PM |
|
|
Manifold
quote:
Originally posted by DarrenW
Do you have pics of manifolds in archives? Im tempted to make my own in steel as well. Im interested how people get the spacing right etc.
I am currently making my own manifold.(ish)
I am having two plates cutIn Stainless Steel). One to fit on the engine and one to take the original inlet rubbers on the Carbs.
Iam using 90% bends cut in half to join the two plates together. This also will sit the carbs at the correct angle to allow the float chambers to sit
level.
See picture of Parts. The plates are currently in 1.5mm mild steel so i can check all the alignment is correct B4 cutting thicker Stainless.
I don't know if this will work as i since i started building this car i have just been following my nose on a very steep learning curve,
although i am probably not the only one. Hope that helps
[Edited on 1/2/06 by cryoman1965]
|
|
|
cryoman1965
|
| posted on 1/2/06 at 11:08 PM |
|
|
PIC
 
Rescued attachment Manifold Bits 001.jpg
|
|
|
mookaloid
|
| posted on 1/2/06 at 11:26 PM |
|
|
quote:
Originally posted by jacko
Mark what can you tell me about megajolt? it may be the way to go with my engine Graham
I'm not an expert on that but AFAIK you need a megajolt kit, a EDIS from some ford or other, a crank trigger wheel and crank position sensor and
a laptop to program your advance curve - I might have missed some stuff too!
Failing that just mod your dizzy or get a points dizzy with ignitor from Aldon
HTH
Mark
|
|
|
