That Stinks!
I think the Chinese motor bike engine kit manufactures should send every one that got a CNS carb a replacement Dell Orto or the old "speed" carb free of charge.
The CNS a hunk of junk, not only were they never field tested or tuned properly, next to NO tuning instructions exist in the first place.
You have to do it the old fashioned way, by trial and error.
Then IF your lucky and didn't get a lemon, you can get it started.
Just for comparison, I took a Dell Orto SHA carb off one of my Morinis, tightened it up, hooked up the throttle and fuel line, primed it and it fired the first, time every time.
Even one of my old rebuilt "speed" carb works like a champ.
Since the CNS is a knock off of a knock off of the popular Mikuni flat slide/built in choke small carb, some but not all the tricks used on a mikuni MAY work on the CNS, or may not.
Why should you have to re jet a carb just to get the engine running?
Unless your at extream elevation, way above or way below sea level, or extreams of heat and cold or racing situations should re jetting be necessary.
I've found WILD fluctuations in the sizes of needles jets and floats
missing or broken gaskets and seals stock from the factory.
Its almost like they throw in what ever size jets and needles they have laying around.
Metallurgical speaking, the aluminum alloy they use is inferior, and there casting techniques are awful, full of inclusions and porosity.
If the Chinese manufacturers ever read these forums-
How about building some decent parts and ACTUALLY learn how to cast small aluminum parts better?
Make mine Italian or Japanese please (I'd love an American made alternative)... im tired of the china girls hit or miss, slap shod reputation.
The quality is just not getting any better.
Just my 2 cents worth.
FR
While I'll not in any way try to defend the "quality" of these motor kits, their retailers or manufacturers - or even say the stock CNS doesn't have it's issues... I do want to mention a few things.
The crack in the above pic has little to nothing to do with "inferior" aluminum or even the carb itself - but the mismatched intake manifold and the resultant plastic spacer. Many will tighten/overtighten the clamp to try and help prevent movement issues, but as the spacer is comparatively resilient it will squash a bit, resulting in cracks as the clamp has been overtightened. This is a hazard regardless of brand/type or alloy if a plastic spacer/shim is used. A better solution is to scuff the manifold/spacer and seating surface in the carb to gain some grip, 'SealAll' fuel resistant adhesive may help if there's still movement problems.
Both poor quality and jetting has
always been an issue with
all of the various carbs offered with these kits, the NT and Speed carbs were no exception with many finding them so rich as to need a replacement jet/solder & drill with damaged/missing floats and/or gaskets more common than not. Previous to the introduction of the CNS, both the NT and the Speed received just as many complaints, for as many reasons. Regardless of which carb you get, you'll need to at the very least adjust the fuel/air for your local elevation - it's not even a matter of "extremes" as only a few thousand feet may require a clip adjustment for optimum preformance. BTW, just as an interesting side note - I live at sea level, never had to rejet any of my carbs (speed, CNS or NT) and after some time spent tuning - the only one I hate is the 'Speed' carb, and that's because of the "extra" fuel petcock as it's unnecessary, ported way too small, the internals degrade in ethanol & it leaks like a stuck pig.
"I think the Chinese motor bike engine kit manufactures should send every one that got a CNS carb a replacement Dell Orto..." That I have to say is not even vaguely reasonable, it's like saying "I bought a Yugo, it's a piece of junk, you should give me a Ferrari"
Again, I'm not in any way try to defend the "quality" of these motor kits, far from it - in many ways I agree, but their flaws are well known and documented, easily fixed and upgraded with parts cheap and plentiful - a replacement carb NT/Speed is at most like $20... when you buy these low end cheap motor kits, why would you resent it when you find you've gotten cheap, low end parts? If you expect quality, decent parts and good cast aluminum - you're just not going to get it penny pinching, if you want Italian or Japanese or American made alternatives - you're going to have to pay for it, it's out there - but not for less than $200 for an entire motorized bicycle kit.
Buy what you will, but don't be surprised or angry that you got cheap when you bought cheap, don't demand champagne on a beer budget - just fix the silly thing or spend the extra so you don't have to.
