Need help on the CNS Carburetor

[oldsub]

Hello all,
Because I have a small lathe, not quite what you would call a watchmakers size, but small enough to do the following project. I am going to turn out some jets for the CNS carburetor. But one problem I have encountered, is I don't know what the thread size of the thread on the end of the jet, which I have removed from the CNS carb which I have. The CNS carb I got has a red air filter on it. I have tried to insert a 6M X 1MM bolt into the threaded hole in the carburetor, it kind of starts then quits. Measuring the threads on the jet that was removed, it appears to be a 6M X 0.75MM, but this thread is very rare and very hard to find. Once I find a bolt preferable a brass one, which will screw into the hole of the carburetor. The hardest part of making the jet is over, just a matter of cleaning it up and drilling a hole.

So therefore if anybody has replaced their main jet on their CNS carb, and know the thread size I would certainly appreciate hearing from them.

Back to these CNS carbs, I got 3 engine all got CNS carbs and they all seem to have one problem. Here is the problem I have with this CNS carb. Take a car carb for example, if you press the accelerator, the engine jumps into action immediately, give it some more and the RPM's will climb accordingly. Now the bike works like this, if climbing a grade, the engine will slow down, turn the throttle for full gas, and there is some seconds pass before it jumps into action and once it's get completely open, it gains speed on the grade. That hesitation does not spoil the ride but I'm going to play around and see if I can improve it and get rid of it.

Going see if I can pasted some images of the jet etc..

Very Best and Good Luck

Oldsub

 

[socialdistortionkid]

Answer #1: 5mm from what ive been told. Replacements can be found on Dellorto`s website

Answer #2: 2 strokes have no bottom end power and make their power in higher up rpms. Your car performs is different because 4 strokes have a wider range of power, there is nothing wrong with your bike...These little 2hp motors dont climbs hills well

 

[oldsub]

Thanks for input, I saw on Sick Bike Parts web site, they had some jets for the NT carb. The jets were 5mm. But this is too small for the hole in these carbs. If you look at the image of the measurement of the thread by the micrometer it is 229.5 of an inch. Convert this to metric it is 5.829mm. So a 5mm will not fit it, takes an 6mm with the right thread.

The question is what is the right thread?

Its strange but I just bought these engines this year, maybe this is an upgrade or ???

Have a pleasant day.

 

[haste]

I actually just downgraded to the nt carb. Had these issues with cns
1. Carb would never stay on. Messed with tons of options and it always came off.
2. Tuning it was a huge pain. It was either more top end or great acceleration to 15 mph and bog out.
3. Never would idle right.

Switched to the simple nt and all these issues are gone. With an expansion chamber exhaust, it pulls all way up to 34mph with ease, and idles perfectly. Saw 0 difference in power change...

 

[biknut]

I ended up drilling my main jet out with a #64 brill bit

 

[oldsub]

Greeting all.

If I ever find out what thread size is used, then I want to make up 4 jets. I will save the original, because it does a good job for me. I will make the jets #73, #74 and #71, #70 for starters. Then I can just drill the ones out that don't help and experiment some more. I'm just having some fun.

It's my opinion, there is no way to defeat the real enemy for this carb. The real enemy is using a single cylinder 2 cycle engine and adding a carburetor with a float system. Too much vibration is develop from the single 2 cycle engine, which will never let the float system carb to do its job. The day they add a diaphragm carb to these bike, is the day you will see some great performance.

By using a diaphragm metering system, the atmospheric pressure controls the diaphragm and the right amount of fuel is available at all times. Plus by adapting the pulses created by the up and down strokes of the piston into the carburetor, this will signal the carburetor when to send fuel to the orifice and venturi for the incoming air to be pick up and deliver to the engine.

In my way of thinking the needle valve is history. I took the 3 needle valves in my carburetors and junked them and used my own needle valves. No more flooding, no more gas running out of the drain hose.

Have attached an image of such a case, flooding carburetor and a very wet bike frame of gas and a pool of gas on the ground. All this right between my legs, one spark and I would lose all of my skin right up to by balls.

Have a nice time

oldsub