CNS V2 Main Jet Size?

skrew37

skrew37

Member
I can find "sort of" answers but nothing exact. I have adjusted the e (or c) clip on my needle up and down a notch which adversely affected performance, so I'm sticking with notch #2. I've adjusted my idle and air/mixture screws to where I'm satisfied with the idle. The only thing is it 4-strokes really bad (in my opinion) at high rpms. I think I need to go down a jet size, but I have no idea what stock size is for these new carbs and no way to measure it. My plug is black and oily. Oh another thing, after making adjustments to the needle, when I put it back to the way I had it, I lost power. On the straightaway in front of my house I go 24-27mph now it is 17mph. Please help. I keep thinking of Bike Guy Joe's quote, "If it ain't broke, and you mess with it long enough, it will be." That's what I fear I might be doing...
 
I forgot to mention that I was using the "pantyhose air filter mod" (worked great, looked a little funny though.) and switched back to modified stock air filter and I stuck the vent tube back in the hole. I'll pull the tube out tonight and readjust the screws and see if I can get it back to "normal". Also since I'm running rich and 4-stroking at high rpms no matter what I do, I want to switch to a smaller jet?
 
skrew37 said:
I can find "sort of" answers but nothing exact. I have adjusted the e (or c) clip on my needle up and down a notch which adversely affected performance, so I'm sticking with notch #2. I've adjusted my idle and air/mixture screws to where I'm satisfied with the idle. The only thing is it 4-strokes really bad (in my opinion) at high rpms. I think I need to go down a jet size, but I have no idea what stock size is for these new carbs and no way to measure it. My plug is black and oily. Oh another thing, after making adjustments to the needle, when I put it back to the way I had it, I lost power. On the straightaway in front of my house I go 24-27mph now it is 17mph. Please help. I keep thinking of Bike Guy Joe's quote, "If it ain't broke, and you mess with it long enough, it will be." That's what I fear I might be doing...
Click to expand...

I tuned a SkyHawk 80 that had a CNS V2. The main jet in it was = to about a
#71 drill bit, which is about the exact same size as the jet that comes in a NT carb.

I suggest you check your muffler, and make sure it flows enough air for the motor to run at high RPM.

I had to run the needle in the richest position, and drill the main jet out to a #64. That was still a little on the lean side.
 
If your CNS is running rich, it's one of the first ones I've heard of doing so. Everybody else has white spark plugs.
 
Yeah well I guess it may be one of the first. it's definitely rich as the only time I saw white was when it was brand new. I took it out today for a while and after pulling the vent tube and readjusting the side screws, it ran great. No 4-stroking. I still want to go faster though and I think if I properly rejet and get an upgraded cdi, there a possibility of at least a few more mph's...
 
skrew37 said:
Yeah well I guess it may be one of the first. it's definitely rich as the only time I saw white was when it was brand new. I took it out today for a while and after pulling the vent tube and readjusting the side screws, it ran great. No 4-stroking. I still want to go faster though and I think if I properly rejet and get an upgraded cdi, there a possibility of at least a few more mph's...
Click to expand...

What do you think it's getting up to now?
 
Well, I got a cheap "bicycle computer" from Dealextreme and it says at top speed I'm hitting 31mph. BUT, it reads 31.0 and won't go over that. I think I may be going faster. I know I'm complaining about nothing, but if I can get the mixture right with a few more mph's, that would be perfect. I bought a #74 jet and a cheap set of mini drill bits that go from a #80 to a #61. I figure I wouldn't need anything smaller than the #74 as a starting point and I can go bigger from there. When I do the plug chop, the bottom few threads are oily and the rest of the plug is black and wet. I'm using full synthetic and premium gas. And oil drips from my muffler. That's rich right?
 
Sounds like it's running pretty good. If you're running a 44T then 31 mph is fast. You'll be turning way over 7000 rpm.

Oil dripping from your muffler is probably a different issue than jetting. That's more related to your pre mix ratio.
 
I'm using a full synthetic from sears. It doesn't say what the ratio is, but it's a 3.2oz bottle. I guess that makes it a 40:1 ratio? (128 / 3.2 = 40) Should I use less than that seeing as it's dripping and it's synthetic?
 
Right now the only way I know of to lean out a CNS is to solder up the main jet, and drill it out.
 
You might want to make sure your choke is fully open. If it's slightly closed the motor will run rich. I learned by making this mistake.
 
You must log in or register to reply here.
Back
Top