212 predator hemi/big valve non hemi head

#1
I have a 212 predator hemi block withe +.020" billet connecting rod,stock 70mm flat top piston and wrist pin,.275 high duration cam,.045"head gasket 26lb valve springs,1:2 ratio champion rockers,the stock 27mm/25mm valves stock retainers and lash caps,and the head is a big valve non hemi head running 26mm nibbi round slide carburetor stock heating. My problems is at 5900 rpm it start acting like it wants to keep pulling but then it dies out then I can gently apply throttle it will do the same thing over??? Any help please
 
#2
I have a 212 predator hemi block withe +.020" billet connecting rod,stock 70mm flat top piston and wrist pin,.275 high duration cam,.045"head gasket 26lb valve springs,1:2 ratio champion rockers,the stock 27mm/25mm valves stock retainers and lash caps,and the head is a big valve non hemi head running 26mm nibbi round slide carburetor stock heating. My problems is at 5900 rpm it start acting like it wants to keep pulling but then it dies out then I can gently apply throttle it will do the same thing over??? Any help please
What main jet you got in your Nibbi? Could be reaching wide open throttle valve but coming up too lean to sustain?
 
#4
There should be a number scribed in it. My Nibbi came with a #105 main installed, and I wanna say an extra 108 and 110 included in the box. I'm guessing you're running lean. (Just for reference, I'm running a Nibbi 24 on a 120cc Briggs flathead and am currently running a 118 main jet.). Also, do you know your needle position? You might try raising it up from the factory position #3 to 4 or 5 to open the needle jet earlier and more fully. Still, if the main jet is the bottle neck...
 
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#11
So it sounds like you’re running out of fuel. When you get out of it the float bowl fills back up
You roll into it and it empties the bowl, which is leaning it out bad…check the gas cap make sure it’s vented, get a fuel pump. That cam isn’t radical, they usually run 22 lb springs. If I remember right that cam falls on its face about 7500 rpm. Truly setting up any machine depends on gear, cam, fuel system, weight, tire size…..it never ends…and that depends on what youre trying to do.
 
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#15
This has nothing to do with it.
Unless you're on the reddit sub. Torque converter is always the answer there since every bike posted is a big tire Coleman with a stage 1 kit and bypassed governor that gets used off road. 95% of the people there don't want to spend any money to do things the right way.

I hate that place, but can't stay away.
 
#17
So What I need to do is bigger main jet,lift the needle. Add torque converter,my hearing now is 14tooth 65 tooth sprocket and 12" tireso.d.and what put a vent filter on the gas tank right and lighter valve springs when I bought the cam it came off eBay and came with the 26lb springs
 
#18
You said stock valves and retainers but then said it had big valves. Can you clarify what head your using? The fact that it happens exactly at 5900 rpm every time sounds like valve float but 26lb springs should go higher than that unless you're using the hemi specific springs on anon hemi head.
 
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