CNS CARB mounting problem

fugit

fugit

New Member
I purchased the CNS carb and haviing a mounting issue. The manifold tube seats well into the carb ( ~1/8 rubber seal) but when I try and tourqe the screw down to hold it in place it will not get tight. Am I missing something? Even if I could tighten this screw more it stil lseems like there isnt enough to grab to and keep in place securely. What am I missing anyone?
 
The CNS carb should have a plastic spacer in the neck of the carb that fills the gap between the carb and the intake manifold, is that part missing maybe?
 
nightcruiser said:
The CNS carb should have a plastic spacer in the neck of the carb that fills the gap between the carb and the intake manifold, is that part missing maybe?
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Thanks for the reply! Mabey it is missing but not sure i will go look through the parts. If you look into the carb as it is I see a rubber seal piece about 1/4 inch. There is no other plastic piece that would take up the space around the manifold intake.
 
Here is a picture off it as it is. Could not find any plastic peices that would fit into space. Also if you look right below the screw is the part machined correctly or should the gap rest flush when the screw it tight? This motor was a friends who got frustrated and sold it to me for 50.00 so there may be missing parts.
 

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Here is the picture of the part you are looking for. This one is home made to replace one that broke. If you need to make one let me know and I will link you to the details of what I did, but you should look for the part first I would think.....
 

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fugit said:
look right below the screw is the part machined correctly or should the gap rest flush when the screw it tight?
Click to expand...

Without the spacer there is no amount of tightening or closing that gap that will make this carb grab on your intake. It's not gonna happen, you definitely need the spacer....
 
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Here is a link to the thread I posted about tuning up my CNS carb (CNS carbs are reputed to be more difficult to tune than the standard carbs, because they have 3 jets instead of just 1)
If you scroll down to about the 4th or 5th post you will see the details about the spacer, and how I made a replacement for a broken one from a piece of common PVC water pipe which is available just about everywhere...
http://motorbicycling.com/showthread.php?t=32736
 
Yea thanks alot NC! I have used the other carb from the other kit for the meantime. I think I will break it in using the basic carb and later changto CNS carb when I am more familiar with the whole process.

DO you think I am good to go, using spacer, with the milling seen above the screw in the picture?
 
fugit said:
Yea thanks alot NC! I have used the other carb from the other kit for the meantime. I think I will break it in using the basic carb and later changto CNS carb when I am more familiar with the whole process.

DO you think I am good to go, using spacer, with the milling seen above the screw in the picture?
Click to expand...

Although my carb IS completely flat in the gap, there are several versions of the CNS carb so I can't say there is something wrong with the milling I see, it looks to me like that is deliberate and proper.
When I first put the carb on my bike I had to loosen the screw and pry the gap open a bit before it would fit on the intake (with the stock spacer in place), when you tighten the screw it clamps down on the spacer around the intake and locks in place. Some gap will still remain when its clamped up tight, so I think you are good to go if you just get the proper spacer.
Although making one yourself would be pretty easy and cheap, if you dont want to bother making one I might suggest you buy a CNS carb rebuild kit, it should include the spacer in addition to all new jets, float, air filter and the rebuild kit is pretty cheap. Not a bad idea to have some spare jets around any ways...
Good luck to you...
 
There is also a way to make the plastic spacer from copper. I don't know how to send you to the page. But it is in the ( 2 stroke bicycle engine) page section. It is call ( 2 things chain and crab). Keep looking below and you will find it. Thanks
 
there's quite a few horror stories about the cns plastic spacer going defunct in a number of ways, here in the threads. Some, the carb just dropped off the engine!
A couple sections of copper tube will resolve the problems with tightening the carb onto the spigot, yet the rubber seal must still be used. A bit of RTV red gooped on there is not a bad idea!
Best
rc
 
http://www.youtube.com/watch?v=5_K4Hx518AA see Youtube video

It at 5:25 of the 9:32 video information on the fuel pump using crankcase pressure, this so that the carb works inverted or any angle.

I realize you have other information specific to your mounting the carb from people more knowledgeable with that, but thought you might like to see this video.

MT

note continues to part 2 video 8:36 more (this part on the diaphram an fuel jets/mixture)

http://www.youtube.com/watch?v=CC3DnuQD00o&feature=endscreen&NR=1
 
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