RT225 jetting set-up

[Psychedelicropcircle]

Hi could any of you running this kit guide me into the thereabouts area of carb settings!

RT225 30mm PHBH ancillotti zaurst

Scott.

[foremanbob]

Running with a JL3 Curly

choke 70
X13 Needle
AV264 Atomiser
52 Pilot for summer 55 for Winter
300 float Valve
122 main

[Scooterdude]

In my opinion the av264 is to small for this kit. To prove the point take out your main jet and see if it revs through cleanly, mine did am now using an av268.

[foremanbob]

In my opinion the av264 is to small for this kit. To prove the point take out your main jet and see if it revs through cleanly, mine did am now using an av268.

Its sorted all the way through the rev range... been running that setup for over 3 years now, doing long motorway runs to rallies. The only thing that I've had to change is the pilot from a 55 in this hot weather.. was struggling to get away from lights....

I'll bear your feedback in mind though... Chiselspeed recently dyno'd a mate RT195 and put a AV268 in it with an X7

[Warkton Tornado No.1]

In my opinion the av264 is to small for this kit. To prove the point take out your main jet and see if it revs through cleanly, mine did am now using an av268.

Its sorted all the way through the rev range... been running that setup for over 3 years now, doing long motorway runs to rallies. The only thing that I've had to change is the pilot from a 55 in this hot weather.. was struggling to get away from lights....

I'll bear your feedback in mind though... Chiselspeed recently dyno'd a mate RT195 and put a AV268 in it with an X7

We all hold different opinions & some may be borne out through experience over many years. My belief is that any two stroke setting should err on the cautious side, but proving the suitability of the atomiser is something that is done with no main jet fitted, commencing with the smallest likely atomiser & moving up a size @ a time until the best minimum size is established.

The reason that I stick with that principle is because the variation in needles has a greater effect running in a smaller atomiser & the range is therefore more 'tuneable'

The consequence is that the optimum needle is likely to be better in terms of response being utilised in a smaller, (but safe!) atomiser than a larger one.

This rule of thumb applies to racing or road engines because for the engine to respond as well as it should, the carburettor needs setting to suit the limitations that a four speed gearbox impose as well as allow the engine to over-rev if the exhaust allows. Up until about four years ago, our Group Four engines were mainly running (DQ) 264's, with the largest tried being 265.

I also believe that the smallest safe float needle valve should be chosen as the level is likely to be more consistent with the float being fed lots of little sips rather than a few large gulps....

[Psychedelicropcircle]

Same setting as foremanbob other than an AV266 & a 55 pilot.

I holed a piston on an imola with a 264 in & have been cautious of them since!

I appreciate the reply team

[Warkton Tornado No.1]

Same setting as foremanbob other than an AV266 & a 55 pilot.

I holed a piston on an imola with a 264 in & have been cautious of them since!

I appreciate the reply team

An atomiser of adequate size, with the correct needle & other settings, will not be the cause of an engine failure.

More likely though, is the tendency for different sized atomisers to be fitted without then fitting the appropriate needle to suit. With the Dell'Orto in particular, there is a vast range of needles, yet most Lambrettas with the PH range fitted, tend to have the X7, IMHO simply because many others do so.

For the record, there are needles of the same tip size as the X7 (1.8) that have different single tapers: X2, X12 & X13.

My point is, though, that an AV264 fitted with any of the needles mentioned above, should cope with a main jet up to about 190. I doubt many road tuned Lambrettas are using such a large main jet.

[Leotech]

RT225 60 x 110 crank and LTH reed
Varitronic
BGM pipe

Was on 4.7 final gearing but revving out on motorway, dropped it down to down to 4.43 and did a few miles today but still bit revvy on motorway. Just dropped it to 4.35 tonight. will try it tomorrow.

Been doing a few miles and got mine to this, 10.5 miles per litre of petrol, mixed riding.
Jetting
30 PHBH
Slide 40
Pilot 55
Atom AV268
Needle x7 2nd notch up
Main 145
Choke 70
Float 350

[ULC Soulagent]

Jetting
30 PHBL
New type of carb or spelling typo

[Leotech]

Jetting
30 PHBL
New type of carb or spelling typo

Sorry it was a typo, there is a PHBL carb also though. Its the smaller bodied version, similar to the PHBH.

[ULC Soulagent]

Jetting
30 PHBL
New type of carb or spelling typo

Sorry it was a typo, there is a PHBL carb also though. Its the smaller bodied version, similar to the PHBH.

Yip using a 25 phbl on my rt225 reedvalve
My setup is
115main
70 choke
45 slide
50 idle set 2 turns out
D22needle
AQ 266 Atomiser
300 float jet
Mighty impressed with it

[rossclark]

In my opinion the av264 is to small for this kit. To prove the point take out your main jet and see if it revs through cleanly, mine did am now using an av268.

Sorry if this is obvious, but, if you take out the MJ and it revs all through, are you saying you should up the atomiser size until it doesn't and then adjust the MJ / needle / clip till it does or something different?

I understood that there were certain combinations of needle / atomiser that were 'optimal', with the needle circlip providing the fine tuning, but that there might be exceptions depending on other factors. So for example AV264/X7, AV266/X13, AV268/X2, and then you tune the atomiser / needle / taper / clip position from there.

[corrado]

Check for an air leak ........... between your goalie's gloves ...

[Scooterdude]

In my opinion the av264 is to small for this kit. To prove the point take out your main jet and see if it revs through cleanly, mine did am now using an av268.

Sorry if this is obvious, but, if you take out the MJ and it revs all through, are you saying you should up the atomiser size until it doesn't and then adjust the MJ / needle / clip till it does or something different?

I understood that there were certain combinations of needle / atomiser that were 'optimal', with the needle circlip providing the fine tuning, but that there might be exceptions depending on other factors. So for example AV264/X7, AV266/X13, AV268/X2, and then you tune the atomiser / needle / taper / clip position from there.

Sorry i missed this. Yes forget the needle and main jet to begin with and just think about the atomiser, the needle passes through it and the main jet feeds through it so it is important to get the atomiser right before you move on to the needle and main jet.

So yes take out the main jet and go for a spin, if it revs through as mine did it’s obvious then that the atomiser is to restrictive so in effect you could put the worlds biggest main jet in and it should still rev cleanly.

[Adam_Winstone]

Jetting
30 PHBL
New type of carb or spelling typo

Sorry it was a typo, there is a PHBL carb also though. Its the smaller bodied version, similar to the PHBH.

Yip using a 25 phbl on my rt225 reedvalve
My setup is
115main
70 choke
45 slide
50 idle set 2 turns out
D22needle
AQ 266 Atomiser
300 float jet
Mighty impressed with it

Did you stick with this jetting or modify it after posting this? Interested as I'm also trying to jet in a reed 225 at the moment.

Ta

Enjoy the weather

[ULC Soulagent]

Stuck with it Adam

[Adam_Winstone]

Thanks for confirming.

[Psychedelicropcircle]

See’s thread & wonders why I posted as I’ve never had an RT

Then remembered I fitted one for a team member