30mm Delorto carb idle mix screw?? (and jets)

[ericthered]

Hi all, I just fitted a 300mm (PHPB) delorto to my GP200, the basic instructions I got about the idle mix screw for my set up (see below) were 2.5 to 3.5 turns out, that seems a lot to me and at idle on onlt 2.5 its really rich and really smokey up to about a 1/4 throttle!
Has anyone got a similar set up and what turns out are you using please?
also what main jet? It came with a 128 fitted (for my set up) but it was quite weak.

Indian GP200.
Standard stage 4 indian barrel (but cleaned up and opened by about 1 or 2 mm).
Matched inlet and exaust manifolds.
Matched transfer ports (barrel to casing)
AF 42mm Clubman.
30mm delorto round slide with mesh bell mouth, (PHPB, I think)

Thanks and regards,
Eric.

[col68]

I had a 200cc on a 30mm phbh with a 53 idle, av266, x7 2nd notch form top , 125 main and a ramair filter on a rubber elbow facing back over fan cowl and a fresco exhaust. Mine did not like bell mouth took it off and went to this set up. On a phbh screw mix out richens up mix . Have you tryed it with out bell mouth to see if it cleans up at 1/4 throtle . col

[B-Race Tuning]

Eric, was the carb bought NEW from a SCOOTER dealer? You say it's a phbh, it'd be useful to know all the letters of the code cast into the body of the carb.
Do you know the pilot size? and the slide size? I'd be more inclined to think it's pilot/ slide cutaway than airscrew if evidently rich to 1/4 throttle. Simon.

[ericthered]

Sorry I made a mistake the carb is a standard PHBH. I got it new from AF Rayspeed and they jetted it for my set up before sending it.
Acording to the sheet they sent with it it has a AV266 needle jet, X7 needle (2nd from top), 55 pilot, and it came with a 128 main jet (too weak). I dont know what the slide is, is there a number I can check on it?

I wanted to fit a K+N cone to it as I dont like open mouth stuff but AF talked me over to a bellmouth, I still want to go K=N cone though (fitted directly to carb and sticking out of panel). I used K=N on a couple of my scoots years ago and like the set up.

Thanks,
Eric.

[cgt75b]

Have a look on the Mb site under tech info, some great info on there regards carb set ups.

www.lambrettaspares.com

Best of luck with it.

[ktmh5]

I would be very surprised if a 128 main jet was too weak on a stage 4 200 setup. Are you sure you don't mean too rich?

[Architecten]

I run 118 main on my RT200 with a 28mm PHBH. All other jets similar apart from 48 idle. Ramair filter to bellmouth. I'm currently on 1 turn out... running very nicely...

[B-Race Tuning]

I would agree with the others that a 128 is probably too rich, as is the AV266, but I think you're talking about the idle circuits here. The Slide has to be removed to see the number underneath it but would be surprised if supplied with anything other than a 40. The pilot is most likely cause here. If you can borrow (or buy) smaller jets, go down incrementally (I normally drop two then assess and either go up or down, it's quicker). I would expect you'll end up at somewhere between 51-48 on that set up. Oh, 40 slide should be fine.

EDIT: Purely based on your posts, is their a club/ knowledgeable friend/ dealer NEAR you? Without being condescending your experience of carbs seems limited, and I would advise that to get it wrong could be dangerous at worst or expensive at best if got wrong. And with ALL the experience available to you via forums, there is no substitute to hearing/ feeling carburation. Which obviously can't be done on the net.
Every dealer no matter how good or reputable can supply a correctly jetted carb and will err on the side of "caution, but runs". Every engine IS different jetting wise, even identically built ones.
We try to help, not take the pish.
S

[ericthered]

Thanks for the help chaps.
I'm an ex mechanic (used to restore classic cars for a job) and I used to be pretty carb savy in my first time round scooter days (early 80s) but most of what I used to know has been pushed out the brain to make way for more useless stuff! lol.

AF were suprised at the 128 being weak too, and it went like stink with the 128, but it is weak (almost white for a WOT plug chop and 1/4 plug chop. Did not try the other positions as it was needing a bigger jet for WOT anyway). Although its about a standard stage 4 it is very cleaned up and streamlined inside and everything matches perfectly, I dont want to burn pistons etc out hence playing with the jets.
The 128 might be ok if I fit a cone filter but until I get one I cant try it.
I was running a 130 on my old 26mm (bored out Jetex) and it went very very well, people were quite surprised at how it could keep up with the GTS's and up to about 65mph I gave a Targa twin a good run for its money once (I think the owner was very surprsed when he looked back to see how close I was! lol)

The way I used to work was to get it to its best performance and plug looking bang on, then jet up by one or two for safety.
I'm in the Woolybacks SC (near Northallerton) but mostly they're running standard stuff or Vespas, a few have tuned stuff but they only come in summer.
All I want to do is get it as near as I can by ear then perhaps take it to get done on a dyno at some point, but be able to use it until I do.
The main thing at the moment I'd like to resolve is how many turns out for the idle screw, the AF sheet says 2 1/2 to 3 1/2 out, but thats really rich, about 1 to 1 1/2 seems nice but I'm just wondering if I'm missing something here and it might hurt it somewhere else at cirtain revs? (long deceleration down hill type thing?).
Best regards,
Eric.