Bike starts up as if it ant to start!

T james

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Nov 6, 2017
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Hi guys I have a motorized bike and it work fine stock going 27 tops bone rattling tho. But I decided to adjust carburetor and after a few test runs. It bogged out on me! Now it won't fully start. Its like it comes on but doesn't fully get going. Then does studdered bogging as if its struggling to get gas or air. It has a lazy hum if I fight the motor without clutch to pedal as if it want to start. And when I pull throttle its like its overwhelmed with air and boggs out as well! Where as when it was untampered stock except spark plug NGK B8hs started with no problem. Please help!! 1st bike and it ran fine til adjust c-clip.
 

Greg58

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May 1, 2011
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Welcome to the forum, from your description it sounds like a fouled plug or something went wrong when adjusting the c clip. Go back and check everything you've done.
 
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T james

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What engine do you have? How many miles on it? Which way did you move the c-clip? Does it run fine with the clip back in the original position?
80cc chinese engine. Everything stock except spark plug. NGK B8hs was brand new when I put it in yesterday. It started up fine just bogged a little when pulling throttle and a little sluggish picking up speed. So i moved c-clip with 4 notches from notch before richest mixture. To notch before lean mixture. Still ran ok. But I proceeded to try other slots and idle adjustments because chop test wasn't tanish brown. Last run it was on original position 1 notch above richest. Heard a pop before it bogged out. And couldn't get it back started no matter what position c-clip is in. Sounds as if it wants to start but no firing up from piston. Spark plug was brand new and have spark...fuel bowl was full as well.
 

T james

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Less than 200 miles on it and 3rd gallon mixed 8oz to a gallon. Still in break in period.
 

T james

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Ok replacing spark plug and carburetor. And will give it a try. Also I have a lil gap between gask and cylinder head. I put 2 gaskets there still a gap. Do you think this could be the problem. It still ran fine with the gap at first...
 

Chaz

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Jun 3, 2012
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That gap is from the cyl head gasket not being the full size of the mating surfaces. They all have that gap. Go back to one gasket and tighten the head down to spec.

good luck
 

T james

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**** yea, man I'm kick my self in the ass. It worked great stock everything smh! Being greed for speed...
 

Chaz

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Jun 3, 2012
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**** yea, man I'm kick my self in the ass. It worked great stock everything smh! Being greed for speed...
You have lots of company in this regard. Most of us can't help but fiddle with these things. One of the many things I have learned from the experienced builders here is to make one adjustment at a time and observe the results. I've noticed that small adjustments need a good run to full operating temperature to evaluate. Take your time and take notes for reference. I am terrible at this but it's a good habit to adopt.
 
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Greg58

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May 1, 2011
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Someone here has their signature to that effect, something like "if it ain't broke keep messing with it and it will be". Keep at it and you'll figure it out, simple little engines can drive you crazy.
 
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T james

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Ok after a few videos. I've narrowed the problem down to either a blown cdi (which might explain loud pop before it bogged out and never started again) or the magneto has slipped out of alignment. Because I unplugged my cdi and tried to start it and it sounded just the same as it did without cdi. Also the drive crank gear and clutch are in working order. It has a new NGK B5HS spark plug in it which it had a B8HS in it when it stopped operating. Wires are set correctly. Everything set back to original position when in working order (such as c-clip 1 notch above richest mix, 1 head gasket, and tension in throttle). Haven't tried to start it since setting everything back because my chain broke during last attempt. So I have to order another master link. But soon as I do. I will post results. If it doesn't start I'm assuming it must be the cdi since magneto is correctly aligned.
 

T james

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Nov 6, 2017
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I keep a spare Mag coil and cdi, I would order these while getting the master links
Ok, but my diagnostic sounds bout right correct? If engine sound the same when clutch released with or without Spark plug hooked up. Its most likely cdi or magneto...
 
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Chaz

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Jun 3, 2012
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Ok, but my diagnostic sounds bout right correct? If engine sound the same when clutch released with or without Spark plug hooked up. Its most likely cdi or magneto...
I don't grasp why the engine would sound any different whether or not the spark plug is connected or not. Unless you mean the difference between not firing at all and intermittent firing. I've pedaled around like a dope for five minutes trying to start mine once and then noticed I'd forgotten to re-connect the plug after making a gap adjustment but I don't recall the engine sounding any different.
 
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crassius

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Sep 30, 2012
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I built a CDI tester to do free tests when someone brings in a CDI, but for a no-start bike, it is easier to just use alligator clips to hook in a 2nd CDI to see if it starts.
 

T james

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I don't grasp why the engine would sound any different whether or not the spark plug is connected or not. Unless you mean the difference between not firing at all and intermittent firing. I've pedaled around like a dope for five minutes trying to start mine once and then noticed I'd forgotten to re-connect the plug after making a gap adjustment but I don't recall the engine sounding any different.
I don't grasp why the engine would sound any different whether or not the spark plug is connected or not. Unless you mean the difference between not firing at all and intermittent firing. I've pedaled around like a dope for five minutes trying to start mine once and then noticed I'd forgotten to re-connect the plug after making a gap adjustment but I don't recall the engine sounding any different.
Ok, I'm going to test cdi and magneto with multimeter tonight. i re adjusted magneto. The notch in it should be at 1 o'clock position when piston is at top of chamber correct? And that is what signals cdi to initiate spark right?
 

Chaz

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Jun 3, 2012
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Vancouver, British Columbia
Yes, one o'clock is right.

Another thing I've learned from the experts is that you can break in your engine safely at a ratio of 32:1 I noticed that you are using a 16:1 ratio which is really heavy and may be a part of your issue. I know that the manual says 16:1 but that is only to make sure that folks don't squeak the piston. You can research this here on this forum if you're feeling nervous about it.