OMG I have to tune a CNS!!! Help

I can see thru the hose so no pinch there. I have not had the carb apart to see if the vent tube has an obstruction though. Still runs great and I've put on 8 or so miles since I taped off the hole and put a weedwacker gas line filter on the vent tube.

According to my iPhone app I hit 28 mph on my way home from work. Still have everything original and running heavy fuel/oil breaking mix. Idles, accelerates and maintains top speed no problem.
 
It does make a differance, on my 48cc with a stock air cleaner the engine was drawing fuel from the carb bowl. Was worst when climbing a grade. Hey B/N the differance may be that mine is on a 48cc but its the same carb. that comes in the 66cc kit.
 
Last edited:
This may be a very strange question, but I am getting ready to go through this whole process. My only problem is the drill bits my dad has a set of micro bits but we have no way of telling which size each bit is-extremely old set. he suggest that I ask if one of you guys could use a micrometer and measure the size of each drill bit so that we can make our cns carbs work.

If anyone would take the time to do so it would be much appreciated!

Thanks
 
Floats are set, C-Clip is in the middle (3rd slot), and my first Jet Drilling is completed from #70 to #69. Testing after the holidays.

Drilling the jet one size at a time.
I find this process not only good for checking the performance for the correct size, but also making it easy to drill. I drilled from #70 to #69 by hand with ease. Making a large step, say #70 to #66 would require a more precision method of drilling such as a drill press and vise for example. In steps, it's more like reaming out the hole rather then drilling it out. I used a small aluminum hand drill that came with my micro drill bit set.
Picture and info in link below.
Amazon.com 21 Pc Micro Drill Bit Set $7.75 w/free shipping

Happy Independence Day!​
 
I stoped by a H/F store in Alabama last week but did not see the calipers, did fine a micro drill set and a angle die grinder. I don't know if I need another I allready have two dial calipers, one is metric. Two slide calipers Lyman, Rcbs.
 
Snap On has a real nice drill set for jetting #YA246A .If you dont have access to a dealer you can buy online. My Skyhawk 66 works well with #66 and clip second from bottom. Pulls hills great with slight fourstoking WOT without load.Im still using break in mix.Gonna wait for anymore tuning till after break in is over
 
Helen Weals said:
Snap On has a real nice drill set for jetting #YA246A .If you dont have access to a dealer you can buy online. My Skyhawk 66 works well with #66 and clip second from bottom. Pulls hills great with slight fourstoking WOT without load.Im still using break in mix.Gonna wait for anymore tuning till after break in is over
Click to expand...

Good job. Did your bike run as bad out of the box as most peoples?
 
Yes very poor. my first adjustment was to change needle and discovered I did not have carb pushed on fully, "snapped on "The needle change helped but did not cure. drilling the jet made it come alive. by using the drills as a gauge original jet was #70 I drilled one step larger a time until it could pull the hill that goes from my house to the road. I never worked on many 2 cyc. motorcycles, but many chain saws and always tuned to fourstoking, backed off to lean and find the middle then add a littleto the rich if that makes any sense
 
I notice after riding for about 10mins it starts to bog down. Is this a air issue, I've drilled the jet to #64 and have clip at the middle position. My spark plug is black but it's not gunking up, it's slightly wet but nothing serious. I've been running about a week now still breaking in.
 
droc089 said:
I notice after riding for about 10mins it starts to bog down. Is this a air issue, I've drilled the jet to #64 and have clip at the middle position. My spark plug is black but it's not gunking up, it's slightly wet but nothing serious. I've been running about a week now still breaking in.
Click to expand...

I wouldn't go any futher till you finish break in and start the regular pre mix. What spark plug are you using?
 
Autolite 4093 I believe not sure about the numbers. I did have it drilled to 66, but after I notice it bogging I went to the max it said here. I think it's 4stroking too, I've ran the clip at the second highest setting but it didn't seem to have power and was still 4 stroking, or at least I think it is.
 
droc089 said:
Autolite 4093 I believe not sure about the numbers. I did have it drilled to 66, but after I notice it bogging I went to the max it said here. I think it's 4stroking too, I've ran the clip at the second highest setting but it didn't seem to have power and was still 4 stroking, or at least I think it is.
Click to expand...

These motors seem to be kind of sensitive spark plugs. It might be worth $2 to try a NGK BP6HS
 
So i got my bike going and i feel like it ran really well right out of the box. it does loose power up hills, but is that to be expected im 195 lbs. my clip is on the the stock position i believe secound from the top. if i move that or down will that help? also there is little red gasket i put it between gas can and petcock does it go there?
 
Last edited:
I'm glad I can finally join in this topic.


I am the proud owner of a CNSv2/GenB carb, and I'm even prouder that I got it working.

Everything I did is as follows.

Tightened BOTH jets.
Adjusted float tang.
Chopped choke cable.
Replaced cover with drilled out NT cover.
Replaced intake with MM intake (though I should have tested teflon tape first).
 
droc089 said:
I notice after riding for about 10mins it starts to bog down. Is this a air issue, I've drilled the jet to #64 and have clip at the middle position. My spark plug is black but it's not gunking up, it's slightly wet but nothing serious. I've been running about a week now still breaking in.
Click to expand...


Mine started to bog down too. At first it ran great, then would lose power and bog down when I gave it anything more than half-throttle. Then it would eventually gain power again. Could this be an air leak as well? I bought a new (extra) jet and drilled it to #68 to start and will then make adjustments from there. But first how would I check for an air leak?
 
Spray carb cleaner around the areas you think you're leaking at, primarily the intake and bottom of the carb at the bowl. It's like a buck an a half at wally world.

And to Droc089:

Black and wet is NOT good, break in or not. You need to lean out (not oil, but fuel).

If you bog after a certain amount of time, your fuel bowl isn't staying filled is what I would imagine. Check for pinches in your fuel line, clean your fuel filters and inlets. Adjust the tang on the floats.

If that all fails - there is a RES (reserve) marking on your gas tank petcock, use that in place of on and it will give you slightly more flow.
 
DuctTapedGoat said:
I'm glad I can finally join in this topic.


I am the proud owner of a CNSv2/GenB carb, and I'm even prouder that I got it working.

Everything I did is as follows.

Tightened BOTH jets.
Adjusted float tang.
Chopped choke cable.
Replaced cover with drilled out NT cover.
Replaced intake with MM intake (though I should have tested teflon tape first).
Click to expand...

wait i thought there was only one jet under where the float is. where is the other and which should i drill?
 
To the side of the main jet is a recessed jet - that is the pilot/idle jet. It was loose as a goose when I took a look day one. That is what the two screws adjust. Don't drill that one, it's adjustable with the screws.

The one you CAN (not should) drill out is the larger one in the center. Don't drill until you've adjusted everything else and then decided you MUST due to no other option.
 
You must log in or register to reply here.
Back
Top