I've moved from sea level to 8000 ft, and need to re-jet. I have a Laguna Seca with a Dellorto PHM40.

(I tried dropping the needle one step and that was no good. Then - duh - read the Dellorto tuning manual and they say "reduce the jet size")

I went to a bunch of local shops.. no one is familiar with Dellortos. One guy had a Kehin chart that showed a 25% drop in jet size. All in the end said - just play with it and read the plug.

I'd like to know if there is a chart from Dellorto, and if not, where should I start? down 25%?

How 'bout the idle jet?

Interesting, that the local knowledge says I might have to richen the idle jet some. WTFO?

Right now what's in it is 145 main & 75 idle.

Grazzi!!

Charlie

Hello Charlie, I have no definate answer for you but the Mikuni chart will give you an idea. If it were me I'd try something like 135 and see. At 8000ft if it doesn't work just go a little from there. I don't think the dellorto info makes any suggestions for altitude? Graeme

Here is where I ended up.. not as big a change as I expected, but a 150 mile ride & reading the plugs after showed that this was pretty close.

Slide: 70/1 (OEM = 60/1)
Main Jet Front Cyl: 145 (OEM = 148)
Main Jet Rear Cyl: 152 (OEM = 155)
Needle: K5 (Same as OEM)
Atomizer: 265 (Same as OEM)
Pilot Jet: 75 (OEM = 65)