Am6 new 17.5mm carb problems

[JensonP]

Hi there having some problems with my new carb 17.5mm dellorto phbg i think it’s called.

I’ve got an unrestricted cdi and a naraku 70cc kit and a dellorto 17.5mm carb and lastly carbon reeds.

so the problem i’m having is that the new carb came with a 90 main jet and it barely wanted to run with that so i put my old 86 jet from my old carb in and it was better but only with the air fuel screw all the way in and sometimes it still boggs but it runs a lot better when the choke is in. After that i bought a jetting kit 70-88 one and i tried and 82 to see if it needed a smaller one but it barely wanted to rev with that so i popped the 88 in and it’s a lot better but still quite boggy at full throttle. I was testing it out earlier almost flat out in 6th gear and it didn’t bog down but just stayed at 8k rpm at full throttle.

Any help would be very appreciated thank you very much.

[stinkwheel]

It's not all about main jet. Sounds like you've dialled that in for now. You want the biggest jet that doesn't bog at wide open throttle, if it picks up a bit as you wind off slightly, you want to go bigger.

The size of the throttle cutaway determines running at 1/8 to 1/4 throttle.

For 1/4 to 3/4 throttle, the needle position, needle profile, and needle jet determine the fuelling with the throttle valve cutaway. If it's hesitant at this throttle opening, you might need a larger cutaway

A slide carb is about throttle position, not rev speed. It can help to mark 1/4, 1/2 and 3/4 throttle positions on the twist grip.

My next step would be trying the needle in a different position. Go rich first to be safe (raise the needle), if it gets worse, try dropping it a notch. If that's worse, go back to where you were. If it's hesitant, you might need a steeper angled needle. If it's rich, you might need a more paralell one.

Every thing you change affects every other thing so once you're happy with the needle position, have another look at the main jet. Then go back to idle/slow running again. Then slide cutaway, then needle position, then back to main.

There's no magic wand for this unless you have access to a dyno and exhaust gas analyser and years of experience. It's trial and error and lots of plug chops.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[JensonP]

i’ve tried it with the needle one notch down so richer and it was worse will try the needle in the leaner position tomorrow and will let you know how it goes thanks for your help very much