fuel, and clutch engagement?

[mariner12]

I,ve been following for a year on here and usually find answers I need. Now however I'm stumped and in need of advise.
Engine:
Predator 212 w/
Billet rod
Black mamba Jr cam
14cc head w/ stainless stock valves
26lb springs
1:3 rockers
Cone intake
Robertsons H pipe
Fuel pump

Issues: I run a very small auto cross style dirt track. Short track, lots of turns I need a carb that will make low end power and I can't find it. I've tried a gx390 carb and a mikuni 24mm. No matter the jets or tuning, I lost bottom end and gained rpms I didn't need. Any ideas?

Second does anyone know a good clutch engagement rpm for the black mamba Jr?

Thanks
Dave

 

[rmm727]

A bigger carb is exactly what you Don't need for low end. Try a blueprinted or cheater stock carb.

 

[Camjamsdad]

I gave up with all the different carbs and went back to a bored stock carb. Rejetted and a 140 etube. The motor likes it.

As for the clutch you could switch to a black spring or buy a box stock clutch which is set to 2800 rpm if I recall

 

[astrowrench]

I,ve been following for a year on here and usually find answers I need. Now however I'm stumped and in need of advise.
Engine:
Predator 212 w/
Billet rod
Black mamba Jr cam
14cc head w/ stainless stock valves
26lb springs
1:3 rockers
Cone intake
Robertsons H pipe
Fuel pump

Issues: I run a very small auto cross style dirt track. Short track, lots of turns I need a carb that will make low end power and I can't find it. I've tried a gx390 carb and a mikuni 24mm. No matter the jets or tuning, I lost bottom end and gained rpms I didn't need. Any ideas?

Second does anyone know a good clutch engagement rpm for the black mamba Jr?

Thanks
Dave

Gear it Lower and go back to a smaller carb run 32* ign. timing and you will have more low end than you will ever need!!!!

 

[Norcalputput]

Velocity is key with a stock bore and stroke motor you will not need a carb bigger than 22mm anything beyond that is not needed till the motor has more swept volume


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[Txpowdercoater]

Gear it Lower and go back to a smaller carb run 32* ign. timing and you will have more low end than you will ever need!!!!

agreed, smaller carb with small intake runner and you will have more torque deluxe.
after all of my searching and research I found a clutch called the "mongrel" , it is an affordable 6 shoe clutch based on a max torque base, and has bully gear set up, roller bearing and a machined hillard drum and engages around 3,200 out of the box with black spring. that should be a happy spot for a medium rpm motor with torque, clutch cost $100.

 

[mariner12]

Thanks to all for the info, just had a pretty fun two days of racing. Ended up buying a Dover Performance "holy moses" carb. Torque has picked up over the larger carbs. I'm still not getting off the line as well as I would like. Have a friend with same kart set up but stock motor getting me off the line. Gear ratio is 1:6, running a Hilliard extreme duty clutch. Looks like I'll try the mongrel next.

 

[mariner12]

What is the best way to advance the timing to 32*. I see the offset keys but I'm not sure which one to use.

 

[davidlamb78]

Call Dover and ask what they recommend. They're really cool, and they'll tell you what they think is best for your setup. I bought a couple keys off of them when I bought my stuff just in case I wanted to swap around.

 

[minibikin']

Setting the thing with a light is the most accurate way. Lap the flywheel with mild valve lapping compound. The key really isn't needed other than getting the timing correct. Once you torque the flywheel down where you want it, you'll be fine.


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