LCGB Forums

Hi All,
question is if I change the slide I have in my 30mm phbh from 40 to 45 would this have a dramatic affect all through out the range and dan
gerously weak...?

why are you changing it first?
do a plug chop thru the 4 rev ranges

the slide only affects just coming off idle up to 1/4 throttle so to answer your question, no it won’t make it weak across the full range

Simon_T wrote:Hi All,
question is if I change the slide I have in my 30mm phbh from 40 to 45 would this have a dramatic affect all through out the range and dan
gerously weak...?

It depends upon interpretation.

Although the slide affects the lower part of the range, from which point, in the upper range, the atomiser, needle, main jet & power jet (if fitted) take over in the upper range, any engine has to get through the lower range to get to the upper range & back down again.

If you get my drift, the lower range is, therefore, fairly critical.

Because a 40 slide is fairly common with all non-SH type derivatives of Dell’Orto’s utilised on Lambrettas, have you considered modifying what you have?

By removing material from the lower edge, a 40 slide can be converted to a 45, or even, say, a 42.5. Knowledgeable tuners, such as Taffspeed, used to carry out precisely that modification @ times.

Side by side comparisons enable measurement with a Vernier to calculate the amount of material to be removed.

(Do be aware that for the cost of a new slide, a brand new PWK with all likely jet kits can be purchased that some of us consider far superior…..)

hullygully wrote:why are you changing it first?
do a plug chop thru the 4 rev ranges

the reason why I was gonna change the slide from 40 to 45 was a friend has same setup with 30mm phbh Avanti ex box exhaust he had it dynode and I thought 40 was the norm and thought his would be lean, he doesn't do a lot of miles in paticular motorway miles so I copied his setup I thought maybe mine would go bang on the motorway and in particular when rolling off the throttle.

On my GT 186, I took a small file to my 40 and made it 42/43. Was spot on. I’d tried a 45 beforehand but it was too lean.

Personally, I don’t think I have heard of anyone successfully running a 45. I still have the 45 if you want to borrow it.

Storkfoot wrote:On my GT 186, I took a small file to my 40 and made it 42/43. Was spot on. I’d tried a 45 beforehand but it was too lean.

Personally, I don’t think I have heard of anyone successfully running a 45. I still have the 45 if you want to borrow it.

cheers stork foot I have both options available but like I said a friend has the same setup and had it dynode and has a 45 in but it don't sound right to me I would rather err on the side of caution and go 40, to witch ill test it and do plug chops rather than depend on his setup although dynode by a reputable tuner.