problem with a pwk 24 carb

so i ported my airsal 70 cylinder on my derbi senda, got a new intake manifold for a pwk 24 carb, slapped the pwk on there and it ran fine when it was idleing, it revved to the max and all but when i went for a test ride, it just had a lean bog at high rpms, the engine just shut down and i still havent figured out what it could be, i tired literally everything, bigger jets, smaller jets, raised the needle, raised the float, checked for leaks in the manifold, tried multiple new reed valve and manifold gaskets, even drilled out the holes on the valve seat, tried blocking off the powerjet and other random holes that didnt have a fuel hose on them and lead nowhere. even tried the old carb with the old manifold, ran fine, test ride was fine, no bog. so i know it cant be an air leak in the engine, also the carb is not seated with an extreme angle at all so the needle valve should have no problem opening. does someone have an idea what it might be ? im considering just getting another one and seeing what it does.

 

Sounds like jetting to me.
What air filter are you using?

 

using an aftermarket mesh filter, as i said, i tried many different jets, i went as high as 125 main jet, the 125 was clearly too rich but it still bogged down at high rpm. also tired a 95 main jet, no difference

 

Use a foam filter.
Those mesh ones are just trash.

 

yeah but it couldnt be a filter issue

 

also the foam filters restrict flow quite a bit, i dont ride in muddy or dirty conditions, i just ride it on the street

 

You need a filter to protect the engine, a filter won't restrict airflow if set up correctly. Maybe the carb is to big ? It's only 70cc !

 

but it revvs fine when its idleing, it bogs when you ride it, i dont think its a size issue then. also a 24mm is fine for a ported 70 with a widened exhaust port. people run 28s on racing 50s...

 

Trust me, I've seen this more times than I can count, I run my 30hp bike with a foam filter, no problems.
But yeah, the carb could be too big for a 70. Does it bog down if you give it like 95% throttle?
It's hard to explain this in writing

 

And is the ignition standard? And have you set the squish?

 

lets just get rid of the filter thing for now it runs and rides fine on my old 19mm so the ignition and squish is not the issue. it doesnt bog at all when im giving it gas on idle but yes, when i go on a test ride it bogs once the rpms get high and the throttle opens at about 80-95%

 

So use the 19mm carb !

 

I ran a 24mm PWK on my 172 runner, far better than an agricultural 25mm Dellorto carb, it maybe a velocity problem with the 24mm carb on a 70cc ?

 

Yeah I'm with Marsh.
Don't fix what ain't broke.

 

It doesnt rev that good and that high with the shitty 19 dellorto with no powerjet or a tapered venturi for faster airflow and i absolutley agree, its definetly not a carb that is meant for going fast. Also you mean that the air moves slower through the carb body therefore it doesnt pick up enough fuel ? Is a 21mm pwk worth a try ?

 

Wait but if its a velocity problem and the carb is too big, wouldnt there be a problem at low rpms and be fine at high rpms? If you can get the revs up it should suck enough air through to pick up fuel and i got the revs up to about 10k and the acceleration was really good until it bogged down

 

Try a 20.5 runner carb.