crackle from STD 350LC exhaust and rough running

[firmstools]

Hi all,
My 81 350LC is standard, freshly rebuilt motor and just run in.
Been running fine up to 7000 rpm with 4L0-00 carbs,(balls removed, cleaned, all new internal parts) Yamaha mod done, 170 MJ and 27.5 pilots but had to drop needle from middle to second groove from top to get a smooth mid range.
Bike was perfect to ride with lots of torque and felt crisp although plugs were bit black.
First time I gave it full throttle and high revs it refused to go above 8000rpm.
Plugs were black so new set fitted,  160 MJ and 25 pilots fitted (Yamaha option), needle put back to mid position and it is almost un rideable.
Loud crackle from STD exhausts with STD baffles, sounds like it has race pipes on! splutters up to 5000 rpm and will eventually pull through to red line and beyond but seems to have no power.
Is anyone else running 4L0-00 carbs with early cylinders?, if so what jetting/settings did you end up with?
Thanks as always.
Pete.

[mangocrazy]

I don't know where you are in the country, but before you go any further I'd give Dave Whattams (Muttsnuts of this parish) a ring and book time on his dyno (he's near Wetherby/York). I took my LC to him (see current thread) and he transformed it. Before you do anything else I'd put a bigger main jet in. My 1980 4L0 has 200 mains.

And has your oil pump received the Arrow treatment? If not, I'd wholeheartedly recommend it.

[firmstools]

I think that is the way forwards! Just no way I will have the time to make that trip this year.
Oil pump was sorted by Arrow
Not convinced the jets I bought are a quality part, put needles and pilots back to where they were and it runs better low down but wont rev past 7000 now.
Will try a spare coil and windings later to eliminate that as well as putting old plugs and caps back on.
Ain't old 2 strokes fun?

[bezzer]

I appreciate it’s an old thread now, but do you have any update on your running issues?, just curious to see if you cured it and, if so what it was!?.