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

Hey there here's a new idle/throttle problem for you!

Skyhawk GT2 48cc;
SBP Expansion Chamber - tuned;
CNS 2 Carb with Slim SBP AirFilter;
Boost Bottle (proven to work great for me);
On 3rd notch on clip, and float is level;
Piston clean, jug smooth, brand new spark plug;
Great spark, no shorts anywhere;
No air leaks - checked everywhere with WD40 while idling;
All gaskets tight, again no leaks;
Muffler clear, not clogged;
Running 32:1 mix and have about 300 miles on the bike.
Southern California, warm weather, about 500 above sea level.

And sooo....

Had this bike running great up until a couple days ago.
I could idle fine (1.5 turns out on screw).
I could throttle right up through to top end (30mph) no problem, nice and smooth with a LITTLE bit of bog at about 10-15mph, then it would power out of it.

Put a new jug on (cuz' I broke the old ones exhaust flange), and noticed after puttin' her all back together, that I seemed to be running lean (bogging at WOT), so I adjust C clip down a notch, made it worse.

So I went back to middle position, and still no good.

Then, I realized that with the choke up about 1/2 way, I could get it to run fine at WOT, but deduced that that meant I was still running lean.

So I messed with the screws, and viola, with the air/fuel screw in almost down to it's 'seat', (90% screwed in), it idled fine, and I could get her to run though the whole band, for all of 2 rides, then bog, bog, bog, bog.

Then the backfiring began, let off throttle while riding and POP!!!

Then, no throttle response at all, just Bog, bog, bog.

Checked the plug and it was all crusty black, carbon fouled, but NOT wet black. That told me way to lean again!

So, I went through the entire checklist at the top of this post, and put her all back together with a new plug, and fired her up without the muffler on, and she idled to HIGH RPMS out of control.

Threw the muffler back on, and she calmed down a bit, but still out of control idle, and when I engaged the motor, she would just bog, bog, bog.

When I pulled in the clutch...Revvvvvvvv out of control.

Then, she calmed down a bit, and I was able to once again, keep her idling like this:

run, RUN, run, pop, p'pop, p'pop run, RUN, runrun, rrruunnnnnnn, p'pop, and when I gave her the tiniest sip of fuel with throttle, booooggggggggg, til dead.

Ok, there's a mouthful.

Throttle cable is tight/good from top to bottom, and I haven't a CLUE what's going on.

Here's a link to a video, Poor throttle... - YouTube
(sorry, you'll have to turn your head sideways!).

Listen for the idle pattern, and then at the end, I'm only revving it with about 10-20% throttle, and then it dies.

Thanks for your time!

Sincerely,

Chris B.

Ok, took it out for another ride.

It'll idle VERY sporadically, and then, once warmed up, I can get her going about 8-10 miles per hour using the IDLE only, ie: Not giving it any gas, then, it slowly grinds and sputters UP to about 15 mph without me doing anything, but then, when I pull the clutch in and disengage the motor, RRRRRRRRRR right on up to HIGH RPMS!

So, I use the electronic kill right away and it goes away.

If I try to give it throttle at all, it bogs til dead.

Crazy...

Hey thanks GearNut...

Yeah, I'm down with the colors, and I was running an NGK actually.

I found this cool chart from NGK and my plug looked like #3 (see description of #3 as well on the link), it was carbon fouled, ie: too rich.

Anyway, I changed out the sparky to an old original 3 pronger laying around (unused), and I got great spark...but same idle probs.

A motorcycled dude I chatted with while riding says by the sound of it, the bike wasn't getting enough fuel (currently)...so I don't know where to turn next!

Carb was totally cleaned out, float set level, pin pushes fine on tab, no air leaks etc., 32:1 mix, messed with idle and air screws and still stuck on out of control revving when the clutch is pulled, and boggy/poppy/jerky riding with motor from low speed on up to mid speed WITHOUT even giving it any throttle!?

Weird....stuck man!

Any other thoughts?

Thanks in advance.

Hey there GearNut, thanks for that.

I'll double-check the needle and also, I attempted to get at the magneto, but couldn't pull out the magnet. What's the trick?

I opened the case, no debris, wires/soldering look good (again, I have great spark), I used pliers to gently tug at the magnet after removing the nut and lock-washer, and was able to pull it out about halfway, and then it simply wouldn't budge any more.

What's the trick to pulling it out to check on the wooddruff key?

Thanks.

I double checked the throttle slide inside the carb, it MAY have not been 100% seated on the pin on the idle screw side.

Also, I'm now on the 2nd notch on the needle with the clip.

Carb is NICE and clean for sure, and no air leaks.

I'll let you know!

Thanks.

Ok cool, doing that check tonight.

What are your thoughts on the motor revving off the charts when I pull in the clutch?

I rode it again today, fires right up, idle's poppy, sporadic, but holds idle, pulls slloowwwllyyy up through to about 18mph, on it's own! Giving it zero throttle, then, if/when I do give it ANY throttle at all...bawwwwgggg.

Then, in this condition, (no throttle), but cruising jerkily, if I push the choke on up to about 50%, it rides much smoother, but still won't take even a hint of throttle without bog, and then, if I pull in the clutch (with choke) off, its ZOOOM up to full RPM.

Weird.

BINGO!

Pulled the magnet/rotor.

I have no Woodruff key! It's simply gone!

Not sure if this is my problem, but going to try and figure out a workaround.

NOW, where do I turn for a new Woodruff that's the right size?

~Chris B.

Back to the drawing board!

Found the woodruff key, of course it's best when working on these things at night to have good light...I didn't last night!

But today, there she was, hidden on the ground and in good shape.

I'm reinstalling the whole magneto/coil today.

The engine seal looks great, but I'll check for leak once I get coil/magnet back on just to be sure.

Assuming there's no leak, I'm back to all the details as described in the above posts.

Anyone want to help troubleshoot?

Thanks again!

Thanks GearNut,

Great vids. thanks. Gotta get some tools to accomplish the pressure test.

Meanwhile, on this one specific issue:

How in the world could the bike get up to 20 mph, without me even giving it any throttle?

And in this condition, what would cause it to race up to HIGH RPMS when I pull the clutch?

Finally, I noticed that when I tilt the bike waaayy over while idling, it idles way smoother/better.

Gonna troubleshoot this thing one more time, top to bottom, starting with the float.

~Chris B.

Oylavabeer, you mean the screw that holds the carb onto the intake manifold?

This is a CNS2 carb, not an NT.

Let me know...

OK all, found the problem! Woo Hoo!

The slide inside of the carb was hanging up and not dropping correctly onto the air/fuel pin.

It was somehow twisting when I pulled the throttle and then not re-seating properly back down onto the pin. Twisting inside the barrel.

I was able to see this with the air filter removed and looking inside the carb while pulling the throttle to see the 'action' of the sleeve, which showed me that it was not re-seating back down completely as it should.

So, moral of the story:

I got it running/idling fine tonight.

I'll do some fine-tuning/float/idle/needle setting in the next couple of days.

But that's ALL IT WAS...needle/slide not seating properly.

By the way, I FILED down the 'entrance' to the slide and opened it up to 'receive' the pin much better. This fixed the problem of 'twisting' while engaged.

Thanks to all for help.

~Chris B.