Sorry, sorry, and sorry.

I know there are plenty of posts about pre-mix and jetting but after browsing alot of them, I'm still not too sure about what I should start with. I'm mostly stock so hopefully this should be easy:

Stock pipes and chambers
Stock airbox & filter (with 4 big holes drilled)
Powerjets are retained
lost the injectors so full pre-mix
Did both wire splices
Located pretty close to sea-level (Virginia, US) but pretty humid.
It's a track-day bike but on a tight course so midrange will be welcome.
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The carbs right now have 42 SJs and 142 MJs and stock needles (no washers).

The bike boggs on the low end, especially riding from a dead stop, but the top is great!

Should I go down to a 40 SJ and maybe go up to 145 MJ, and maybe even add a washer to the needles?

Thanks in advance and again, sorry for the millionth pre-mix jetting question but I couldn't find a topic that matched my scenario close enough...

Jae (PekingDuc)

You won't find many willing to advise in much detail but this is what I would do, bear in mind however I have wreaked multiple barrels though jetting too lean.

Presuming you're happy it's not lean at the top I'd try the 40 slows with the needle and MJ as it is to see if that cleaned it up a bit, if not bring the main down a size or 3 several people have run '21s on o.e. pipes with the splices done and the airbox opened up on standard jetting I wouldn't be surprised to find that 142's are a bit rich.
Here's where having the jet kit really pays off.

That said the only way to find out what's going on in there under real load is to plug chop it.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

Sorry, I should have stated that this is for a '21.

With the jetting comments you made, is that assuming its pre-mix? Given everything else is the same, does just going to pre-mix usually mean a 1 or 2 size increase in jets?

I'll try and see if I can find a long enough straight to do a proper plug chop in the meantime.