Any tips / experience greatly appreciated........

I have put together an NC35 from a crashed bike that I needed the engine from. I refurbed my engine and replaced. I have the bike back together and I have an issue revving past 6-8k and when pulling away.....

To eliminate I took the carbs from my other bike and there is no issue when using the known carbs with the same air box etc....

Before rebuilding I cleaned up carbs

set float height
pilot screw set at just under 2 turns out
standard jets cleaned and installed
The bike idles ok and I have balanced with vacuum gauges

Seems like fuel starvation but I'm a bit lost after checking the needle valves and float heights over and over. I can replace carbs in < 2mins now

Any input welcome!!!

Are any of your sliders in the carbs sticking? push them up and watch them return back down.. sometimes you can get a stiff slider if there worn or dirty, this will certainly stop your bike revvin up.

If all the internals (including pilot jets, emulsion tubes) are standard and set at factory settings, there shouldn't be a problem. I don't think a sticking slide would give you those symptoms. Are your carb (inlet) rubbers in good condition and sealing properly? Have you checked for fueling issues - vacuum hose, fuel tap?

It may be an aside, but have you checked that it's not restricted after swapping engines (looms?).

One of my bikes wouldn't rev up when the fuel sliders were stiff as they wouldn't open far enough to allow fuel / air into the carbs.

At least you've isolated it to carbs.

It's got to be something :)

Check fuel height, blocked jets / passageways / emulsion tubes / carb rubbers / sliders / even jet sizes may be different

Many thanks for the input

It's not tank/vacuum or carb rubbers (or restricted) as I used the same when testing with the other carbs. I'll check again and let you know.

Thanks again