Dellorto Carb float needles

[fredperrybruce]

Hi all long story short!!! "maybe"

For a while I've been getting a flat spot while opening up the throttle in 3rd & 4th gear (when opened right up)

Thought fuel starvation so brought fast flow tap (SIP) ,, been out last few days thought I had cracked it but flat spots back again???

pulled out carb today (24/24) and opened up the float chamber pulled float out and something didn't seen right?

Pulled out my spare (20/20) carb and pulled float out,, held them both up together and the 20/20 float hung much lower by 5mm maybe more!!

Played with the (24/24) float and didn't really have much play in it,, "maybe dodgy needle"??

Anyway swapped the (20/20) float/needle for the dodgy (24/24) one ...not been out yet for a burn but what's your take on this??


Don't no if it make's any difference but the 24/24 needle was black and the 20/20 was red???

[sime66]

This takes me back to when I stripped my Dell'Orto 24/24 when I bought it 2nd hand. (There's a thread here somewhere -  about a year ago)
The very sound advice at the time (Kru, I think it was) is that the old black ones don't like modern fuel, so always, when overhauling/checking a carb, if you have a black one, swap it for a new red one, even if the black one looks OK - ditch it.
I can't be doing with going back through your threads at the moment, but did you give your carb a thorough going over?

[fredperrybruce]

Hi Sime66,,


When I brought the carb few months ago (yes second hand) no offence to the seller!!! I gave it a real good going over stripped,cleaned,gaskets replaced!!

I did the same this afternoon but as mentioned already I also changed the needle to a red one!!

Very good advice Sime66 Cheers

[vespasco]

My spider senses sense sensi, sorry, I mean, a flat spot at wot to me suggests main jet is too small.if it had no effect from 3/4 to WOT then its likely too small.
Unless of course, by a flat spot you mean, its bogging at this throttle range, then its too large!!
Proper plug chops at WOT is a good starting point to get it finely tuned at this stage.

Edit: Yeh. I think the red ones are dellorto. Ive read (and as such use) the red ones, as they're the best..

[henri]

must of been a well old needle to still be black tip ,havent seen em sold for yonks (years) ,H

[fredperrybruce]

I see where your coming from,but.......I have brought so so many different jets over the last few weeks ranging from 112-126

I've played with the jetting over and over and over doing plug chops for bloody day's but still couldn't get rid of the flat spot in high rev's!!

The engine never ever bogged down but always wanted to go flat!!

I had some not bad results with plug chops mostly nice brown only when I stick a stupid high jet like a 125 it would look like a wet fart and wan't to die.

I'm going with a 120 main now will hopefully try within next day or 2.

[fredperrybruce]

To describe my flat spot more easily,,

When I got to high rev's in 3rd/4th it would just die,,, I would have to let off throttle give a second or so then open back up on throttle which "maybe" tell's me the Carb bowl need's that second to refill with fuel

[vespasco]

You could also help a larger main jet from fouling by swapping to a hotter plug.
What are you looking for and what have you learnt from your plug chops?
Its also possible you could advance you timing very slightly to see if that has any positive effect on your motor.

Edit: I.just saw ya post....
Yes, you're quite right! this could also be fuel starvation!! These symptoms can lead to the top end ovet heating, detonating and more. Which can be heard by spider senses.
In that case id try setting.up the 24/24 nicely if thats not what ya got in already. For more fuel supply if nothing else.