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Dellorto Air Bleeds

A

azzad

Joined Jul 2009
31 Posts | 0+
Excuse my ignorance if this is covered somewhere but I cant find it.

I am after identification of the 2 air bleeds that are drilled when moding the Dellorto.

I have made my 40 slide into a 45 and now I want to try the rest of the changes.

Thanks
Dazza
 
Drilling

Wild guessing
I guess if you dismantle the carb and take away the venturi from the back of the carb and blow with compressed air in the place were the pilotjet shuld be and feel in the back of the carb and find out witch hole the air is coming from then you have found one hole at least ;-)

Or is it in the airmixture screw hole you should blow air in?

The other i suppose you can find the same way if you put a finger in the needlehole and blow with not to high pressure in the mainjethole and find the hole.

I`am home this week with the flu and are so sick a just a man can be ;-) and have nothig else to do than wild guessing and speculations.
So if i`am wrong please give us the truth about those secret holes............

Regards
Jampe
 
RE: Drilling

the air bleed at 6 o clock is for the MJ and the one to the left at 7 o clock is the pilot air bleed.

regards

Taffy
 
Good answer as usual

Thanks Taffy for the input, going to drill one of mine carbs to see if it makes any difference.
And make the 45 slide modification.
Regards
Jampe
 
Azzad

Some of my previous threats might be of use to you.
I did the mod cause could not get the idle and low end snap perfect. It seemed too rich. And also to try cure my intermittent high idle speed. It never really worked on the idle, but I DID get a lot more low end power/snap.

http://www.husaberg.org/index.php?name= ... ic&t=10768

http://www.husaberg.org/index.php?name= ... c&start=15

Back then, Taffy refused to tell me where to find them bleeds and what to drill. I'm telling you, I was on my knees and didn't know what I was looking for. Is he getting softer on he's older days ??? Did he finally get laid ??

My bleeds where however already bigger than what JoeUSA recommended as drillsize in the original threat about this mod & The doc. Dont know why, they did not look drilled out in any way. Could it be that the bleeds are already big on the 650 dellorto setup ?? JoeUSA was working on a 501 cc.

My impression is that this mod can be necessary/beneficial when runnnign a cam with big overlap such as Taff Hi Tq cam. And that this mod can get rid of the rich build up.

Correct me if i'm wrong here

Anders, DK
 
Thanks for the help, I knew what and where they were, I just wanted to 100% before I do anything.

When i posted last night i had only just done the slide mod and hadnt ridden it. On my way into work this morning I noticed a big differance on my a/f meter. No matter what size primary/idle jet I put in before has made the same differance as taking 0.5mm of the slide. I am still a bit rich but I am a lot closer than ever before.

Most ppl rubbish these carbs on the KTM and swap them out for others but i think that it is purely that they were poorly setup in the first place and no matter how much jet swapping was done it just wouldnt run right. I know I was getting close to that mind set, thinking that it couldnt be that far out from STD, but thanks mainly to the information found on this website I have perserved and am now getting close.

Mine is on a KTM 620 SC which is the super competion model that I believe is the fully opened up model, head, cams etc.

Thanks again.
Dazza
 
Ok I have the carb out again and have drilled the main air bleed but I dont think there is a pilot air bleed well what I mean is it is way bigger than 1mm or 1.5mm for that matter.

I am wondering if the CD1(I) jet is supposed to take care of metering the air in the absence of a pilot air bleed?

The CD1(I) has 4 small holes approx. 0.75mm, I am not real keen on drilling these out any bigger?

Dazza
 
well lets remember that you are on about a KTM for a start here.....! not sure its identical. if you were really keen you would get a tap and tap out the hole for a keihin air jet ala dale lineaweaver!

if you have lots of air going in it means you must use lots of fuel to balance it out so start thinking in those terms.

regards

Taffy
 
So far the other mods and jetting have been so similar its not funny.

It runs rich down low and slowly leans out to a near perfect mixture at 1/2 throttle.

I did read on this forum (I think) of someone else that didnt seem to have the primary air bleed as well?

Dazza
 
I have flicked eurocarb an email asking for some clarification on the CD1 jet and primary jet air bleed.
 
there are no air bleeds available to buy, they are pressed in at the factory and that's that. can't unscrew them/can't replace them. the CD1 jet is the only one, there isn't a CD2 etc.

you only have to ask.

regards

Taffy
 
I realise that what I am looking for is the purpose/functionality of the CD1 jet.

Why do some carbys have them and others dont?

If Iam missing the primary air bleed which should restrict the air flow what is restricting the air flow and making it so rich?

Dazza
 
lots of air grabs lots of fuel. i have said it before. suggest you fill the hole and re-drill. don't try and reinvent the wheel.

regards

Taffy
 
I understand what you have said. I still think the primary jet would have metered the fuel still.

I will find a way to reseal and then redrill the primary air bleed.

Have you seen dellortos with out the primary air bleed before? or are you suggesting mine may have fallen/vibrated out?
 
Sorry to brake in here..

As described in my above post also:

With my dellorto I was always rich in idle. Did the slide mod that gave me more snap. When wanting to drill the air jets I found that they where allready bigger than the proposed drillsize (Can't remember the sizes) This would explain why I could not get rid of the richness, cause the airbleeds where too big.

It makes sense to me anyway...
But I moved on to FCR instead, thats another story.

Anders, DK
 
i have found occasionally the holes to be way larger too. rarely but yes once or twice. you shouldn't think they are all like that! i found the MAJ to 2mm on both occasions but the pilot to be around the 1mm mark as suggested by DL/joeusa.

the slide cutaway lift from 4.0mm to 4.5mm sends a weaker signal so that less fuel is drawn up. so all it is doing is correcting the situation and as you know, the correct ratio means more power.

regards

Taffy
 
my name isn't anyone. it's taffy! :twisted:

of course!

the point is, you can buy a;
/30
/40
/50
/60
/70

but the /45 you make yourself.

all you are trying to do is get to the point where you can go for a PJ, a PJ below, and a PJ above whereas the 33PJ you are stuck on the leanest PJ they do and even then its rich! once you have got to around a 35 then you are a happy chappy! a /45 brings you to that.

a /50 would need say a 38PJ and a /60 would need a 42PJ etc etc.

regards

Taffy
 
Ok, I appreciate everyones time and patience, I knew I had read it somewhere Husaden, I will work out away over the weekend to replace the PJ air bleed.

I guess I am only looking at 1 carby where as Taffy has probablly seen 100's and that is the reason I am here asking all the novice questions; you guys are very lucky too have people like Taffy, who knows his stuff and is willing to spend the time to share and help others understand.

Here is the response from Eurocarb (Dellorto UK):
The idle emulsion tube helps hold the fuel up in the carb. ready to be picked up and it atomises it better before the mixture is passed into the venturi.

So what you have said makes 100% sense, too much air through this passage means too much fuel, simple really ;)
 

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