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Discussion Starter · #1 ·
About to throw this thing in the creek... Brand new 2018 Icebear fuerza 125cc... 385miles on it, just did a carb swap cause the stock one was a pos, no air/fuel screw, couldn't rejet, needle jet was set to highest level on lean and unadjustable, bike jerked, lurked, sputtered, whatever.. Went with the mikuni vm22 26mm, ran great at first until I started pushing 45mph (top speed originally 65ish) and it warmed up.. I also added a Akrapovic exhaust and mid pipe, figured I needed a bigger main jet like everyone told me I needed to do so, I put a 110 main jet, they recommended 115-125 which i thought was a big bump, stock was a 98.. Figured that was the issue that I was needing more fuel at full throttle with that exhaust and carb and air filter.. No, didn't help, hit 47 and started to jerk and backfire so let off the throttle and took it home. If I pull quick full throttle now it also dies out, I have to slowly roll on the throttle for it to not die. Tried adjusting air/fuel mixture screw, I seated it, went 1 1/2 turns and went from there to probably 3 turns out, didn't really see a difference.. Engine seems to be running hotter now as well which doesn't make sense cause I'm running the mikuni air filter pod so it's getting maximum air flow... where do I go from where. Step by step, lay this **** out for me, be clear and simplify it incase I go full retard, id appericate it. And spark plug seems to be a nice coffee and cream look, so can't get a diagnoses off that either.
 

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Hmm.. I think for kicks I would try to hook up a timing light or spark tester light and take it for a ride just to be sure it's not ignition related while under load.

Have you tried spraying and checking for vacuum leaks?
 
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Honestly I have no idea. It sounds like you aren't getting good enough spark, fuel, air, or any combination, but I wouldn't know where to start.


I've begun working on my Ruckus clone so I'm watching this thread for anything that may be useful. Currently I can get it to run on starting fluid but the engine only stays running at half throttle or above. Of course, it hasn't run in a year and the tank/carb weren't properly drained. Looks like the tank is fine but the carb may be clogged. Still, I was able to get it up to 30 (it's a 150) on its maiden voyage.

I'm repairing it while doing my cafe racer modding. lol

 

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Discussion Starter · #6 · (Edited)
Lol so no ideas other than ignition coil? I'm 95% sure it's fuel/air related. But I'll try for ****s and giggles. I have a brand new ignition coil I can put on and spark plug is brand new. And again it's fine all the way up to higher speeds. Let's say 40mph it starts.
And yes. No leaks.
 

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If I remember correctly you threw a whole bunch of changes to it at once. Go back to stock, get it running there. THEN make one change at a time, get it running correctly before you make the next change.

If none of that works for you google "where is the nearest lake to me?"
 

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Edit: Oof, sounds like going stock would be even worse.
 

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Discussion Starter · #10 ·
If I remember correctly you threw a whole bunch of changes to it at once. Go back to stock, get it running there. THEN make one change at a time, get it running correctly before you make the next change.

If none of that works for you google "where is the nearest lake to me?"
If you remember the thing only ran stock to around 300miles. Stock carb didn't work at all.. couldn't get over 30mph... this carb works up to 45mph and it starts the jerking and backfiring and puddering weird nose from exhaust while the backfiring.. only other mod is the air filter pod for the carb which isn't much of a mod... And the exhaust. Other than that... it's stock. I did put a new cdi chip which is the same as stock just in case a malfunction, that wasn't it. And I have a new stock ignition coil I can try but still think it's the carb tuning and jetting (refer to original post for info)
 

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I'm confused. Brand New bike with a POS carb with no air fuel screw? Isn't this thing under warranty? So you changed the carb cause it wasn't running right and changed exhaust. You know the air fuel screw only affects a small part of the system right? Do what critter said
 

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Discussion Starter · #12 ·
I'm confused. Brand New bike with a POS carb with no air fuel screw? Isn't this thing under warranty? So you changed the carb cause it wasn't running right and changed exhaust. You know the air fuel screw only affects a small part of the system right? Do what critter said
Couldn't even take the float bowl off the stock carb. Needle jet non adjustable. If that carb couldn't push me over 30mph and jerk so hard I got whip lash getting up to it, it's not going back on my bike. This mikuni carb runs it extremely smooth up until 45mph and I start to get all these problems.. If I go back stock, all it'll be is the air box and exhaust. Still don't see how the exhaust could cause this problem or air box delete mod when it did all this stock to begin with x10 and it's running better than what it was with it. Still don't even know why this problem occurred at 297miles stock.
 

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Since the Mikuni carb works good up to 45 mph. It could be the ignition coil, It was not long ago someone here put in new
coils and was like totally amazed. Ignition coils like high voltage magneto coils can and will go bad, start crapping out,
giving one the idea the carb's at fault. I had this happen on a bike some time ago, busted my ass, then I got the idea about
the ignition coil and how at times I stick a hi-voltage mag coil in a 200 degree oven to dry it out and get back the spark...
I just grabbed another ignition coil, re-arranged some wiring and ran battery current through the substitute coil and competed
circuit through the points and the bike ran fine.

Here is the thing. . .Don't ever assume an ignition coil or ignition magneto will last forever and that if the engine runs, the coil
is good, It can be good at low speeds but when the voltage in either a hi-voltage mag coil or ignition coil gets high enough
at higher speeds, it will start to break down or arc over inside the coil and the spark at the plug will be very 'iffy'
 

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Discussion Starter · #14 ·
Since the Mikuni carb works good up to 45 mph. It could be the ignition coil, It was not long ago someone here put in new
coils and was like totally amazed. Ignition coils like high voltage magneto coils can and will go bad, start crapping out,
giving one the idea the carb's at fault. I had this happen on a bike some time ago, busted my ass, then I got the idea about
the ignition coil and how at times I stick a hi-voltage mag coil in a 200 degree oven to dry it out and get back the spark...
I just grabbed another ignition coil, re-arranged some wiring and ran battery current through the substitute coil and competed
circuit through the points and the bike ran fine.

Here is the thing. . .Don't ever assume an ignition coil or ignition magneto will last forever and that if the engine runs, the coil
is good, It can be good at low speeds but when the voltage in either a hi-voltage mag coil or ignition coil gets high enough
at higher speeds, it will start to break down or arc over inside the coil and the spark at the plug will be very 'iffy'
Going out right now to put the new one on then. I'll let you know shortly.
 

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What does it do at WOT, wide open throttle in a higher gear going up a hill?
Before you answer that, imagine someone pored too much beer down your throat. You would gurgle splutter sputter.
Now image you were not getting enough air. You would cough and choke, and stop.

It sounds as if it is too rich. However running hotter than normal sounds like it is too lean.
The main jet is set by running the bike under load. It is not set by other guys on the internet.
Buy some more jets. Stuff in a bigger one. If it gets better then peachy. If it gets worse then go the other way. Lettuce not get frustrated until you have changed the jet about 15 times.
I did that on my XS400 and it has twin carbs.

Also a good plan to check the quality of the spark, and check the timing. And the valve clearance.

UK
 

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Still don't know why this thread is here being it's a 2018. I had to look up icebear. China. No wonder. It's a one year warranty, right?
 

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Discussion Starter · #18 ·
It was the fking ignition coil?!!!!!!!! Wtffffffff it runs like brand new and hit 69!!!!!!!!!!!! I just creamed my ****ing pants. I don't understand how it was the ignition coil....but.... mind blown
 

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Discussion Starter · #20 ·
It was the fking ignition coil?!!!!!!!! Wtffffffff it runs like brand new and hit 69!!!!!!!!!!!! I just creamed my ****ing pants. I don't understand how it was the ignition coil....but.... mind blown
Back up and running nicely?
Perfect. Not a complaint in the world. I've had that ignition coil sitting for three weeks and didn't think that could possibly be it until guy up there said that's probably it... I could kiss him right now. Thank you so much. I'm so fking happy.
 
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