Funky idle, complete bog with any throttle...HELP!

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his196

New Member
Jun 19, 2011
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Thousand Oaks, CA
Hey GearNut,

So, yeah, I had THOUGHT there was a locating pin in there, but upon triple checking, I only saw the air/fuel pin on that side of the carb, so, upon inspection with the air filter off, I was able to see that when I engaged throttle, the sleeve rose up, above the air/fuel pin, and then rotated about 5%, so that when I released throttle, it wouldn't sit back down properly onto that pin, but got stuck in a raised position.

So I filed the opening on both sides of the lower/entry portion of the groove where it's supposed to drop onto the air/fuel pin, and checked it's motion, now it seats properly.

Then, after reading your post, I looked on the OUTSIDE of the carb, on the clutch bar side, and saw a little brass pin protruding right where the locator pin should be, and I pushed it in with needled nose, and yep, it slid in a few mm. I'm guessing that's the locator pin, and it had wiggled out so it no longer entered the carb barrel enough to 'catch' the slide groove.

Crazy that my whole problem was this from day one, improperly seating barrel/slide!

Next time, to troubleshoot this, I'll definitely remove the air filter first to check for proper slide action!

Thanks for all your help.

Chris B.
 
GearNut

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
Well I am very glad to hear that you got it all worked out!
As I said before, most issues are annoying low-buck problems, not expensive parts that need replacing.
Good on you for taking the time to look at every possibility before throwing in the towel!
This was a rare problem.
Now use a center punch and carefully peen the edge of the guide pin hole in 2 or 3 places to make sure the brass pin won't come out ever again, or use a little dab of JB weld, or both.

Ride safe!
 
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his196

New Member
Jun 19, 2011
99
0
0
Thousand Oaks, CA
Yeah, I was able to pop it in, so now it sits about 2mm inside the hole(from the outside) and is holding strong. Gonna JB it shut now.

On another note, now that I've got that all figured out, here's the current state of the motor. I'd love some further tuning advice.

I was on the 2nd notch down, and it idled pretty good. With clutch pulled, I can throttle to pretty high revs for sure, and she sounds strong. Nice 2 stroke poppop out of the SBP Ex. Chamber.

Tuned the idle so she's at a nice low, stable RPM, and air/fuel screw is out about 1.5 turns.

When I go to ride, I get modest, but spotty pull at 20% throttle, but if I go any higher, she boggs. Not nearly as bad as before of course.

So, I though, OK, I'm rich, so I tuned the air/fuel down a bit more to 1 turn, adjusted my clip down to 3rd notch, and then did a plug check at WOT: Looked pretty darn good, in fact LEAN? Nice and tan, no oil, and actually, almost approaching a grey.

In your opinion, do I now need to adjust the float? And if so, allowing more fuel to fill the bowl, or less?

Thanks in advance.

~Chris B.
 
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his196

New Member
Jun 19, 2011
99
0
0
Thousand Oaks, CA
So, went out for another ride.

I've got GREAT idle.

But no mid range or top end for sure.

I'm on the 4th clip.

I'm running 32:1 mix.

If i use 10-20% throttle, I can EVENTUALLY get to about 20mph, but WOT is FULL BOGG!

Just adjusted float to allow MORE fuel, do I need to go the other way?

~Chris B.
 
GearNut

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
If the carburetor is not flooding, which it seems to not be doing, leave the float setting alone.
A CNSv2 carburetor is a "variable venturi" carburetor. All variable venturi carburetors have the same basic fuel/ air circuits and adjust in similar ways.

The low speed mixture screw controls the idle mixture and just off idle slide position only.
The slow speed jet controls just off idle throttle to 1/4 throttle slide position.
The slide needle controls 1/4 throttle to 3/4 throttle slide position.
The fuel jet controls 3/4 to full throttle slide position.

Do not adjust the needle for tuning WOT problems.
Change out or solder/ drill the fuel jet for WOT tuning.
Have you read the CNSv2 tuning threads?
http://motorbicycling.com/f34/omg-i-have-tune-cns-help-30169.html
http://motorbicycling.com/f34/inside-2010-grubee-skyhawk-cns-carb-25062.html
They will give you excellent guidance. Better than I can concerning this particular carburetor in use with these cheap Chinese engines as I do not have a CNSv2 to play with myself. I have a first gen. NT carb.

In addition to the CNS threads, there are also many good tuning guides online catered towards motorcycles. They are very well suited for tuning MB's too.
I have read through this one and it is a good one for noobs to learn from.
Keep in mind that it is for motorcycles with gearboxes. Simply ignore the recommendations for gear selection. You have one gear and it will work perfectly for this tuning guide.
Motorcycle Jet Kits & Carburetion Basics - Motorcycle Cruiser Magazine
 
O

oylavabeer

New Member
Jan 9, 2009
214
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0
Perth Australia
Also had the crank shaft seal on the clutch side blow loosing vacum cuased these probs pull off clutch cover if oil is everywhere thats your prob back then I also thaugth it was carb
 
mixxmilkk1

mixxmilkk1

New Member
Apr 30, 2010
32
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0
55
Mpls Minnesota
You guys are chaseing things now, lol. (Its your seal loop) You can find it behind the magneto. Its will be the part thats just dangling. I had the same problem just a month ago, and i did the same thing you guys are doing lol. They only cost like 3-5 bucks at kingsmotors.com com. (or where ever you bought your motor from) I ordered 10 of them, just in case :) It very easy to change/replace. Good luck! :)
 

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