66cc NT Air Leak / Run Away Engine

Kioshk · Feb 6, 2013

So, I have my very first vaccuum leak, and it's driving me insane. I have done absolutely everything to determine where it might be (short of splitting the case), and have actually sealed the magneto and clutch covers SIX DAYS TO SUNDAY and short of splitting the case (jinx) to inspect the seals. Took the head off and the gaskets are pristine. As is the intake....tore everything down and inspected the gaskets...all good. Sooooo...I've never had to deal with this issue, and I'm about 10 miles from home (having a couple of beers right now). Engine's running great otherwise, and the temperature's acceptable. I cut the engine when I need to idle since it's running-away when I release the clutch. It's actually run-away while the kill-switch was on a couple of times...dropped the clutch @ stop to remedy that (how the **** does that happen?).

Am I safe to get home provided I don't allow the engine to run-away, and keep the temp down?

The engine's running excellently otherwise...I'd hate to destroy it.

PS: I used WD & Carb Cleaner to check fer leaks. No dice.

2door · Feb 6, 2013

Are you sure your throttle isn't sticking partially open? Maybe a kink in the cable, or the cable is pulling the throttle open a little?

Remove the air cleaner and look down the throat of the carburetor( you didn't say what carb you have) to watch the position of the throttle. Does it close when you release the throttle grip?

Tom

Kioshk · Feb 6, 2013

Thanks Tom,

I did check that out, I thought that might be the culprit...oiled the cable-sheath, toke the carb apart and cleaned everything...no go.

Kioshk · Feb 6, 2013

Oh, and it's an NT Speed ("NT" in the message subject).

BigBlue · Feb 6, 2013

Check and make sure your the slide is seated properly. Take the slide and needle out and reassemble.

Good Luck,

Chris
AKA: BigBlue

Groove · Feb 7, 2013

BigBlue might be on to something there. It's possible for that C-washer to get caught funny in the spring.

KCvale · Feb 7, 2013

NT carbs are pretty simple, as mentioned with the air cleaner off verify the needle goes in the jet hole and the barrel goes all the way down to the idle screw stop and open at the bottom only a couple of milometers at no throttle.

The other thing to note is poor fuel flow.
When we break in new builds part of the process is run them around some, turn off the tanks gas valve, then leave them to idle outside the shop.
When the float bowl fuel level gets very low the engine races up as it is sucking bubbles of air up the venture until the last of the fuel is sucked up.

In short, if your fuel supply line is restircted or float level is set way too low you will get the same symptom.

Kioshk · Feb 7, 2013

Hey guys,

Thanks for the advice; just to cut off speculation, the carb is operating properly. I'm also having a problem with dieseling...in neutral, the engine will sometimes run-away even with the kill-switch on. I've been running a 20% castor mix and it looks like I had a good deal of carbon buildup. I have cleaned the head and piston so that problem has been resolved, but I still have what seems to be an air-leak. I've jetted to 76mm, and clipped it to its richest setting...more 4-stroking, but still RPMing like it's lean. I RTVed the magneto and clutch plates airtight in an attempt to rule out seal leaks...no good. I have the engine on my bench now and will be splitting the case. I can only imagine it may be a defective case gasket between the crank and clutch axel. We'll see.

KCvale · Feb 7, 2013

Ohh for crying out loud....

When you can get a brand new 2012 Skyhawk motor only delivered for $109 what the heck are you doing spending more than that trying to make a POS knock off go with BS RedNeck temp fixes again?

Sorry to sound harsh but reading all your 'Performance Mod's' like re-jeting, electrical work on the magneto and who knows what else did you really think it would be cheaper or better than than just starting with something good?

Just a tip from a guy that meets the standard for what other smart dogs set to lay up on the porch with the big dogs, and the dumb dogs that have to go lay out in the yard.

Not my best analogy but the best I can do at the moment with this topic and it's author.

Bikeguy Joe · Feb 7, 2013

A Skyhawk is better...? LOL. They're all pretty crappy.

Kioshk · Feb 7, 2013

Holy CRAP! Where's all this come KCvale? I HAVE a Skyhawk. And what the **** makes you think I've made 'Performance Mods'? I have a standard 66cc that I've made minor adjustments on based on a lean-condition and a mysterious run-away issue. Hence, my positing a query based on an unusual condition which I'm confident a few very intelligent mechs on here have come across and can share a solution with me on.

In any case, you knuckle-head, I COMPLETELY disassembled by baby this afternoon and checked all her seals and gaskets, as I did to the NT. For good measure, I replaced the head, head-gasket, base-gasket, and while I has the case split, I replaced the flywheel-bearings for good measure. I STILL have the lean behavior as well as the deiseling (thought I'd solved it). Anyway' the engine temperature has been within nominal limits, and I'm still running it; and it's running superbly except for the run-away. In fact, I' on the road nw.I am baffled but want to figure out WHY it's doing what it's doing. If your answer to engine problems is "just buy a new one, you're on the wrong site. Also, I can get a new engine for $89 delivered, so suck it.

wing nut · Feb 8, 2013

hello have you checked your fuel valve (petcock ) for debris? the stock petcock filters arent that great do you use an inline filter ?
i have a clear one so i can tell if im getting gas
that is what happened to my engine & that was what the fix was ..clogged filter , no gas ..screaming engine
best of luck to you

Bikeguy Joe · Feb 8, 2013

Kioshk said:
Holy CRAP! Where's all this come KCvale? I HAVE a Skyhawk. And what the **** makes you think I've made 'Performance Mods'? I have a standard 66cc that I've made minor adjustments on based on a lean-condition and a mysterious run-away issue. Hence, my positing a query based on an unusual condition which I'm confident a few very intelligent mechs on here have come across and can share a solution with me on.

In any case, you knuckle-head, I COMPLETELY disassembled by baby this afternoon and checked all her seals and gaskets, as I did to the NT. For good measure, I replaced the head, head-gasket, base-gasket, and while I has the case split, I replaced the flywheel-bearings for good measure. I STILL have the lean behavior as well as the deiseling (thought I'd solved it). Anyway' the engine temperature has been within nominal limits, and I'm still running it; and it's running superbly except for the run-away. In fact, I' on the road nw.I am baffled but want to figure out WHY it's doing what it's doing. If your answer to engine problems is "just buy a new one, you're on the wrong site. Also, I can get a new engine for $89 delivered, so suck it.

Sometimes KC gets his panties in a bunch.

Kioshk · Feb 12, 2013

OK, I'm a dope. Seems my "run away" engine was not due to dieseling or carbon-deposits, and I think the lean-behavior was not actually an air-leak. First off, one of my kill-switch leads severed...I believe this contributed to my intermittent inability to kill the engine. The racing however was caused by my throttle-cable being sluggish. I believe that since the cable-sheath was gunked up and restricted, the engine vibration caused the carb-barrel to creep up, and the spring was unable to overcome that trend. This came to light the day after the Blizzard: my throttle-cable was frozen due to the extreme cold that day. I used a propane torch to loosen it. I was glad i brought it with me on my ride because when I came to a stop-sign, my throttle was frozen OPEN. Since my kill-switch wasn't working and I was on ice, the wheel freespun as the engine screamed. I was able to find a patch of sanded asphalt though, and stalled the engine. I have a new cable assembly on order, but in the meantime, I put my old one in a toaster-oven @ 200F for 1/2-hour, then saturated the sheath with WD40. I didn't realize how tight the throttle had become over the last 8-months I've had the kit! Lessons: don't assume that the kill-switch is actually connected properly if it doesn't work, and OIL THOSE DAMNED CABLE SHEATHS!

Bikeguy Joe · Feb 12, 2013

Just be sure to follow it up with some kind of lube, the WD-40 will dry out and you'll be back where you started.

crassius · Feb 12, 2013

I have one of these that works well.

NOTE: this link was just the first that came up in a search for 'bowden cable oiler'
http://www.passion-parts.com/produc...ER&WTP-BOWDENZUG-OELER_html=&products_id=979&

Groove · Feb 12, 2013

Hey Kiosh - Now you're like one of the smart dogs set to lay up on the porch, not like the other dumb dogs settin' out in the yard. Woof!!

Great job with the fix. Thanks for letting us know what the issue was.

2door · Feb 12, 2013

Glad you found the problem, Kioshk.
Some guys like grease for lubing the cables but I prefer a heavy oil. I know this will start a firestorm, but I've been using Opti-2 in my cables for a couple of years. In fact I've been using it for quite a few things around the house.

I use a small hypodermic syringe to inject the oil down between the cable and housing then let the oil drain down while moving the cable in and out.
I don't ride in extreme cold weather, freezing temperatures, but my guess is that oil will be less prone to gumming up the works as opposed to grease under those conditions.
And like Joe said, WD-40 is not a lubricant. It can cause you more problems eventually. It has a lot of uses but lubricating isn't one of them.

Tom

Kioshk · Feb 12, 2013

Thanks again guys!

I have a new throttle-cable on the way, and I picked up a set of other cables at Walmart this afternoon. Gonna lube 'em up REAL good.

KCvale · Feb 12, 2013

2door said:
Glad you found the problem, Kioshk.
Some guys like grease for lubing the cables but I prefer a heavy oil. I know this will start a firestorm...

Naw, but the need to put any lubricate in a cable must be weather related I would think.
Rain, cold, humidity, whatever as I never lube any cables here in the desert and even on my oldest builds the throttles still snap right back closed when you let go.

I just put a light coat of grease on the handlebar where the throttle barrel oes with my finger and use a Q-tip to put a thin smear inside the throttle housing plastic pieces where the white cable wheel rubs against them but that's it.

Seems to me some fine powder graphite lube like this would work better if you need something in a cable.
http://www.supercheapauto.com.au/on...hite-Powder-Lubricant-35g.aspx?pid=1173#Cross

Or not. Maybe getting wet would ruin it, but you can read about Graphite Powder as a lubricant here.
http://www.buzzle.com/articles/graphite-powder.html

66cc NT Air Leak / Run Away Engine

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