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Porks bike carbs and boost project

It's quite difficult still to drive,

I have to feed the power in , not pedal to the floor, otherwise it's either not getting fuel or the spark ain't right, and can't get it through the rev range , so have to back of the power, then
Feed it in

It's annoying as hell

Would a proper ignition system help? Or is it jus the fact that carbs is a bitch to get right lol

Don't wanna spend the money on a megajolt, only to find that I should of got a megasquirt and go efi

When it goes right, it's awesome, but getting it to agree with be is difficult

Still slips the clutch a bit too, but havnt got round to putting a spring in clutch lever like frank suggested,
 
It's a bit all over the place really, think it goes from 12 to 16.8 at a glance

Can't keep my eye on it whilst driving, the car is still moving at quite some speed lol
I should try and rig camera up and see
 
It's only every now and then, sometimes I can floor right thru the revs, sometimes I have to feed the power in

I've jus redone all my vac lines too with shiny new (free lol) push fit stuff
 
Il take another look, but quite sure it's all fine tho :)

I have been thinking of going injection route, but it does cost a lot of. Money !!!

Was thinking beings I've allready got a the bogg bros cbr600 manifold, stick the cbr600 itbs on, and turbo those ;)

Should work, right?
 
I've got a gorilla pod, but need phone attachment

Hmmm, might see if I can find a cheapish set of itbs and see what's involved

I would like to stick with the carbs.......I've put all this effort in and would like to see it thru........decisions
 
you just need some form of acceleration enrichment neil, maybe a fuel reg like k11,s that raises the fuel pressure when the vacuum disappears from the mani when you boot it
 
I've got a boost referenced fuel reg fitted allready :)

It's only some times it does it, maybe a ultrasonic bath might help
 
That's what the pitot tube on the inlet of the plenum is for, according to uncle bobs turbo bike page


"Pitot tube



Now that I have that out of the way, lets jump straight to THE most common question I get. What is a Pitot tube? How do you set it up? What sizes do you use? Is it necessary?

Pitot tube is a tube within the charge pipe that acts as a reference to the incoming stream of air, and has an effect of increasing the pressure to the reference. Its an effective method, when using blow-thru carb setup, for improving fueling on boost.

Where does it go? It will go to the float bowl vents on a stock carberator bank. What it does is increase the pressure in the bowls, which thereby, pushes the fuel into the venturi. The more pressure, the more fuel flows into the venturi. This is how you can make the carbs compensate for the increased flow due to boost

Is it necessary? You could instead have a simple reference line coming off the air box, so that the bowl vents see unmodified boost pressure. This does work. But its not as effective. Using this method requires very large main jets, regardless to your carbs, and more importantly, its not as self-compensating for different boost levels. If you change from 5psi to 15psi, this method would require a huge jetting change. It would also cause a overly rich condition as you transition upto that 15psi peak. All in all, I've yet to read about anyone that has gone from this method to the pitot tube method, and not rave about the results. I suggest that is all the evidence you need on why you should use a pitot tube. "
 
worth a try eh :) we had something similar on our junior karts when we fitted new chinese low emission engines to them, they would drive fine if you eased the throttle open, but if you whacked it open it would die like a cold engine does with insufficient choke on.
we had to fit a restricting collar in the intake to cure it
 
I'm assuming having googled CBR carbs and looked at the illustrations that your carbs have a spring pushing the piston down like in an SU. On the SU you have to stiffen the spring if you tune the engine as the piston will rise to the top of its travel (WOT condition) before WOT (due to increased air demond through the revs) giving rich running and reducing the effect metering range the needle has. Softening the spring therefore, might improve the fueling issue at WOT?
 
you need more damping on the dash-pot to increase the acceleration enrichment ideally neil :) stronger spring or smaller airvalve
 
frank said:
you need more damping on the dash-pot to increase the acceleration enrichment ideally neil :) stronger spring or smaller airvalve
Click to expand...
Surely you want the needle to rise faster/sooner, so you want softer springs and dampening?
 
frank said:
my understanding is that the delay increases the vacuum in the needle/jet area :)
Click to expand...
Hmm yeah I just realised I forgot the piston acts as an air restriction as well a the butterfly... softening the springs would mean the piston lifted quickly allowing air into the carb (immediately after the throttle is opened) that is moving too slowly to pick up adaquate fuel, giving lean fueling... Stiffer spring would give less air initially as the piston is still low down but the air would be moving faster (as it has a narrower pathway to travel through) and so will pick up more fuel leading to enrichment.
(It's air velocity that draws fuel eh)
So maybe stick some gearbox oil in the dashpots and see if theres any improvement before playing with springs? :D
 
i,m guessing that bike carbs use an air restriction that dampens the vacuum lift of the dash-pot (rather than the SU type oil damper)
they tend to have a rubber diaphragm eh :)
 
frank said:
i,m guessing that bike carbs use an air restriction that dampens the vacuum lift of the dash-pot (rather than the SU type oil damper)
they tend to have a rubber diaphragm eh :)
Click to expand...
So a diaghram between piston and an air chamber with a release hole, piston rises moves the diaphragm and displaces the air through a sized hole? Simple solution then. Smaller holes :D
 
So driveshaft off, I guess these marks are where it's been binding

jypuvasa.jpg



I've got 10mm of spline left to move it down

ara6aher.jpg


Questing is, do I stick it on lathe and cut in a recess for the circlip, or can I just weld it in place?
 
I don't, but can find one.

The lathe sorts the top clip issue, but not the bottom one.

So I think the grub screw idea will work ok
 
Gunna have to scrap the screw idea , that metal is tough as hell and I'm not spending £100 + on a hardened tap.

I want the spider part here, so shall I weld (if possible) the original bottom clip here....

unajadu3.jpg


Then cut recess for top clip here and trim the excess shaft off?

ede4u7a6.jpg
 
Only 10-13 mm. That should be enough,

I don't really trust my welding enough to mess about with wishbones

If shaft brakes, not as bad as wishbone failing
 
Have you ever had/seen a driveshaft fail.... nasty mannn :p

I still think wishbones is the best and safest option in my honest opinion
 

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