Jetting advice for RD400c needed

[ElFuegoBlanco]

I finally got my motor buttoned up and need some jetting advice. The bike is a 78 RD400 barn find.

Expansion chambers of unknown make or model
RD350 y-boot with K&N filter (airbox is long gone)
Stock ignition
Stock porting
Cylinders bored to 65.5

When I got the bike, it had 220 mains. I don't know the pilot jet size as they were trashed in the removal process.

Any advice would be great. Lyn recommended 250-310 for the mains, so that's probably where I'll start.

[quocle603]

After looking at your list, it looks like you're on the right track. I've never messed with a 400, but I've dabbled with a few 350. For your pilot, it should be in between 30~40. Establish a solid baseline and work from there. Just listen and feel what the bike is telling you and may small adjustments.

[ElFuegoBlanco]

Thanks. That's where I'll start. Any advice on the needle jet? Or will the stock size suffice?

Rob

[quocle603]

Sorry man, I am not 100% on the RD400 carbs.

I know that the RD350 needed the Dave F mod to help with the flat spot with changing the needle jet from a bleed to a primary type.