Carb needle recommendations for DM 10HP in SoCal

I did a search and although there are many carb jetting recommendations listed, they're mostly for Cags. I would rather take the advice of someone that owns a DM or other high end PB.

Anyhow, as some of my prior posts have stated, I plan to order a DM 10HP midi in a few weeks and wanted to get parts ahead of time so I can get to riding and racing when it does eventually show up.

I went out to the Fontana CA race this past Saturday and it reminded me how desert dry it is out there and most likely at the Rialto, Grange and Adams Kart tracks too. I did some research and the average daytime (racetime) humidity around these tracks is 40%.

In contrast, I'll be doing 95% of my riding near the LAX airport which is right on the ocean. The average annual humidity for LAX is 77-80% at night (that's when I ride). So a few questions arise.

I think the vast difference in humidity between LAX and the inland kart tracks would require a carb needle change. Am I right or do people not bother changing needles for humidity changes? I speculate motors are best setup to run richer in arid environments and leaner in humid environments. Or is it the other way around?

Either way, I want to break in my motor nicely here in the humid LAX area so can any of the SoCal riders recommend which carb needle to run in a 10HP stock DM motor near the ocean at night or around 80% humidity?

Also what do people run in arid environments?

Sure I'll experiment with needles, but for breaking it in it would save my engine if I just set it up with the best jet for this humid LAX area. Any feedback would probably help many people.

Thanks in advance, T

for starters, a 10 horse DM utilizes a Dellorto 14/14 which doesn’t use an adjustable needle like a Cag does. Adjustments to the carb are primarily done by changing the jets. In my motor (the same hp) I have found that jetting ranges between 74 and 88 depending upon the type of fuel used and climate conditions. Right now mine is I think at an 84, but that is due to my NW weather and fuel choice. It will likely arrive with a 68 jet in it, and that could be a quick way to seizing it. Best way is to start with a big jet that won’t go lean and destroy your motor. Check your plug for color…if black and wet go down 2, if white go up. For this bike, if you are interested in carrying spares, get a couple of spare clutches and spare PMT T41s, maybe a spare starter ratchet plate…etc.

I forgot to mention...I am not giving you a number for a jet because it varies from day to day, from bike to bike, from climate to climate. I can't tell you what will end up being right for your bike. But at least I can give you a range...

higher humidity the smaller the jet. dry day i usaally run from 76-78 maybe even 80.. when it rains i run from 72-75

This is a good explanation:
http://www.rscycles.com/tech_articles/air_density.htm
Hope this helps you out.

...from 0% to 100% humidity might require a change of 1 size on the main.

(not-so)noob