Scooterotica

Have you run this motor before on a smaller carb?

remember that the recommendations are a starting point, not a definitive setting.

The recommendation for mine was d26 on 2nd notch from bottom, 266 atomiser and 102/105 main. This is for 25mm Dellorto, iron Stage 4 and MB Clubman.

I was panicking last week getting ready for Kelso as I couldn't get rid of a massive flat spot at 3/4 throttle. Friday and I find that by dropping the main jet to 98 the flat spot was easier to work on as the over richness on the main seemed to distort any needle adjustment. I ended up going to Scotland flat out with as above but needle on 3rd slot from bottom. during the journey I could still detect a small flat spot if I rolled off the throttle. Just dropped the needle all the way (top slot) and it now revs and no flat spot.

I'm now thinking even 98 is too big, but I'll need to set aside some time for plug chops to be sure.

mag, wilky ran a 95 main jet on his 25mm phbl on his Honda 205 with clubman.

I've got the same setup, but have had to go down to a 40 pilot jet to get it set up right and also start when warm, gave up on the drilled air box in the end and went to a remote filter, didn't make loads of difference though, D22, 264, second clip from top, 60 choke, 100 main.

I've had good success with the 266 atomiser & a D29 needle in 25mm carbs. It's similar to the D26, but has a different final taper. Always seems to work better for me.
I also make a point to be sure that the needle seat is a 300, not a 200.

Did any of you run a std 20mm before and then replace with the 25mm?

Yes.