posted by ANGE on 5/16 12:58 GMT

mik try the reg i have here, as i told you its been modified to accept a vacuum line that drags the fuel pressure down when
vacuum is present. with it i used to run around 1.5psi on idle and up to around 6-7psi at full noise (when theres no vacuum)

if its a pressure problem it should do the trick

posted by unfamilia on 5/17 3:09 GMT

Cleaned out carb passages and jets etc with guitar string and carb cleaner. Also reset float.

Must be fuel pressure.
Got it idling for 5 mins now no leaks but gave it a rev and once it settled fuel only came out by the overflow now not the carb jet and breather hole. Also noticed few drops out rear overflow but not as much as front one.

Can that fpr just sit at 1.5psi without ramping up to 6 psi ange?

posted by racer135 on 5/17 5:42 GMT

Did you ever get that mystery of the fuel supply to the front 2 carbs of your CVK's sorted out Chris or did you sell them and continue with those Mikuni ones?

I have a set of CVK's from a 2001 ZZR600 with 90-something model ram tubes (rubber ones about 100mm long, look sweet) and when I eventually get around to making the manifold I'm going to flange it to suit the flanges on the intake manifolds from the 90-something model ZZR.

The intakes from that model also have 3/16" outlets on the top for vacuum reference and piping which goes between them to help them balance (could also tee into them somewhere to hook up to the fuel reg ANGE mentioned).

I also thought they were mounted on an angle from intake to outlet so the flange on the bowls was level but I read your old thread about yours last night where you said on the bike you got yours off the intake paths were level (which would make the bowl flanges on an angle)

posted by unfamilia on 5/17 8:19 GMT

Looking at mine the bowls arent quite flat so closest to the motor is slightly lower than the outer. So im thinking I may need to adjust the floats lower so they cut off earlier.
The pilot and main jets would be more submerged now.

im going to try a different fuel pressure reg with guage so I know what its doing 100%.

If that fails will try floats if that fails will try gravity feeding (would need to get something made to get this working).



the overflow hole is at the top left corner. That should be at the higher point of the bowl. Thats why im trying fpr first.

posted by unfamilia on 5/17 10:31 GMT

Well looking at a bike, the carbs sit almost verticle (about 10 deg off verticle) so I think the floats on wrong angle massively.

posted by unfamilia on 5/18 8:24 GMT

Ok reset floats to try and work with the angle mounted on.
Ran for 10mins idling no issues so took for drive in lane. Low to mid range much more responsive to 4.5 to 5k rpm. Then pulled into drive and checked.... fuel out overflows again but not as much at all.
So after a run seems to overflow again.
Will get a better fuel pressure reg and try at 1.5psi constant.
Keeps about 50ml fuel in bowls now so should be enough per cyl seeing weber only holds about 100ml for all 4cyl.

more playing needed but will speak to sikyne first I think.

posted by unfamilia on 5/20 4:34 GMT




anges old fpr. Modded with vac port to increase pressure as vac signal increases with revs

posted by clyons8 on 5/20 8:45 GMT

That's a rising rate regulator, not really what you need. As for the reservoir of fuel just use a large filter off a wrecker which holds enough fuel to handle a decent dose. Fabricating a special little box is what you do once you know what volume you need.

The manifold looks to be spot-on on 15 degrees which is relevant to the format of the carburettors. The top line of the bowl where it meets the body is typically the indicator of the pitch they are to be fitted. Please upload an image of the almost vertical ones you speak of, they may be a semi down draft version in which the fuel bowl and bowl flange is at a much steeper angle.

Your problem might be debris on the needle and seat, or a bad float or float adjustment. Have you tried swapping floats and needle valves around to see if the problem remains on the carb or moves with the float or needles?

Also, please upload pictures of where the fuel is coming from.

In my experience used carburettors said to be in good running condition are rarely ever that. I have had as new looking crabs with detrimental corrosion on the inside. Of the carbs I rebuild approximately 6 in every 10 require a comprehensive clean out, ultrasonic clean and media blast.

You're very close to having it solved, just get into it.

posted by unfamilia on 5/20 9:19 GMT

That's how they sit in the car. Fuel only comes out the overflow pipes now chris. Stuff all and only after about 5-10mins idling.
Cleaning pilot jets and passages solved the weep out main air jet passage.

posted by unfamilia on 5/20 10:07 GMT

Just bought the wrong adapter for fpr. Got 3/8 bsp fitting needs 3/8npt. I just read 3/8 and they screwed in. But now im home I realise wrong ones. Another day wasted. Well wont be able to til sat most likely