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Old 07-21-2017, 01:05 AM   #1
XenoMorphicRex   XenoMorphicRex is offline
 
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Misfire in the hole!

As the title of this thread humorously says. I dealing with an odd occurrence of My 2008 CF Moto Fashion 250-T

I've owned this Scooter For 2 years. Bought it from a Local collision shop owner who had, bought it for his wife. She put about 900 miles on it, and then it sat in the shop for 3 yrs. collecting dust. When I saw it, I bought site on seen for $1100.00 USD. I've lovingly Maintained this sweet little scoot, I even nicknamed Her Matilda, Since I bought her, the odometer has reached just north of 3500 Miles, with few problems, until recently that is.

Anyway, The issue is that at Idle, and at low speeds (25Mph or less) she runs buttery smooth, but at higher speeds she starts Misfiring, and starts jerking and bucking, and sputtering, Sometimes even stalling.

What I've done to my scoot since getting it:

(1) 32mm Performance Carb
(2) K&N Pod Filter (Stock Air box removed and junked) "No tuned Pipe yet"
(3) replaced Melted Junction Box (Don't Ask how that happened)
(4) New Tires, Vacuum, Coolant, Fuel Lines with filter
(5) Oil Changes Every 1000 Miles (I know "Overkill, read my Signature") I use Royal Purple 10w 40 full synthetic.
(6) Final drive lube changed with "Lucas Oil Gear lube" once since purchase
(7) New front 4 Piston Brake caliper, disc, and Pads. New Rear Brake Shoes
(8) Laid it down Once (rookie Mistake)
(9) CDI upgrade (No rev limiter)
(10) Performance Coil, and NGK iridium sparkplug (Hotter plug)


Anyway, aside from some Cosmetic Damage, It's been super reliable (Unusual for a Chinese scooter in my experience) I've checked the usual suspects for hesitation and misfires, CDI is find, Ignition Coil is fine, put a new Sparkplug in it. Checked Oil levels, and Gaskets, seals, Timing chain, Valve lash, and seats. and Compression tested it. As far as I can tell, There should be absolutely no reason for the problems I've been having at Higher speeds.

But yet She's been acting like she running lean, or the ignition system have been cutting out or something.

Now I'm a Mechanic by trade, and its also my hobby. So I know a thing or 2 about Engines, But I am thoroughly stumped. Anyone have this issue or have a Solution? I'll answer what questions I can, If I know the Answer. My memory hasn't been all that good these days. (Getting old) So Some things I should know by heart, may slip my mind from time to time.
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Old 07-21-2017, 06:13 PM   #2
Roscoe   Roscoe is offline
 
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Obviously carburetor icing ... just kidding... I'm also in Oklahoma and it's 105F right now. If you still have the original carb you might try putting it back on and see what it does. Fuel filter of course. Partial clogged main jet, gummed up float valve? Intermediate wiring problems if it's that they can be bear to find. Tug and pull on the wires with a multimeter connected? Does this have fuel pump or gravity feed? Wondering if you can bypass the vacuum switched petcock if you have one.
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Old 07-25-2017, 05:17 PM   #3
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Have you done anything with your fuel pump yet? Their diaphragms don't last forever....especially if you run an ethanol blended fuel, and 9 years is a long time.

Runs fine on the pilot jet.....crappy when the main kicks in, sounds like a restriction somewhere in the fuel system.

How is the new carb jetted, compared to the old one? Too much main jet will cause big problems when operating past half throttle also....but being a mechanic, I'm sure you're aware of this.
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Old 08-12-2017, 12:50 PM   #4
XenoMorphicRex   XenoMorphicRex is offline
 
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Pissed

Since I started this thread, I have recently solved the misfiring problem. But a new one has cropped up. I did a test ride yesterday, and she purred like a kitten. I parked her in the garage overnight, and now I can get my scooter to start. The motor turns over, and she's getting fuel, because I smell it coming out of the exhaust. I thought "Ok she's either flooded, or there's no spark."...I pulled the plug out, and put a spark tester on the plug lead. and it's getting a good strong spark. Changed the plug again, thinking I may have a defective Plug, But it still sparked with a strong blue arc. So it's not ignition. I checked all my vacuum lines, because the fuel pump is vacuum powered. The pump itself is working, because I got a strong spray of fuel. The timing seems to be correct.

But this Chinese POS still won't Start. when it was running fine yesterday.

I'm dreading the next possibility, But Could it be Rings?
If so, This engine it mounted in such a way that I'll have to pull it out of the bike for tear down. I'm not afraid of the work, It's the expense I'm worried about. If its the rings, the cylinder may be scored, and pieces of Piston ring may be in the crankcase. Which all us mechanics know that this can utterly destroy an engine. If this is the case. then it will be a long time before I cant ride again. I've been out of work due to a back injury. and I'm on temporary disability, so money is not coming in at the moment.
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Old 08-12-2017, 12:55 PM   #5
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It's an exact duplicate of the stock carb. she was acting like she wasn't getting enough fuel. Found out that problem was an air leak in the intake manifold. I replaced the manifold, and she ran like new, until today. Now I can't get Her to start. Look at my reply above for more details.
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Old 08-12-2017, 07:02 PM   #6
Roscoe   Roscoe is offline
 
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I'd give a shot of carb cleaner into the carb and see if it fires. That's how I check for fuel problems and sometimes starting balky small engines.
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Old 08-12-2017, 10:24 PM   #7
XenoMorphicRex   XenoMorphicRex is offline
 
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It's getting fuel, and spark. yet it won't start.
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Old 08-13-2017, 12:38 PM   #8
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do a compression test first before a tear down. maybe carb flooded cylinder wiped oil from rings and loss compression. maybe sitting over night kept getting gas?
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Old 08-13-2017, 04:12 PM   #9
XenoMorphicRex   XenoMorphicRex is offline
 
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Quote:
Originally Posted by crawford View Post
do a compression test first before a tear down. maybe carb flooded cylinder wiped oil from rings and loss compression. maybe sitting over night kept getting gas?
Ring wiping is a good thought. The "Continuing to get gas" However is Highly unlikely, due to the fact that the fuel tank and fuel pump are both below carb level, And the fuel pump requires a vacuum impulse from the engine to function, I've check to vacuum lines that run the pump, using (and you're gonna laugh) a turkey baster bulb, It works really good for creating a vacuum if you squeeze the bulb before putting it to the vacuum line. When I did this, It pumped a little gas into my drain pan. So the pump works and the lines are good.
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