Need help lifan 200cc breaking up

Stolkumfabrication · 08-26-2020, 11:37 PM

I got this mini chopper with a lifan or lifan clone 200cc 4 stroke engine in it, and was told going into it that the carb was out of tune. but it came with a selection of jets so I figured I could at least figure out what direction to go by playing with what I had, and have gotten nowhere.
It currently has a mikuni 22mm slide carb 115 main and 27.5 idle it idles fine but seems to break up at higher rpms and giving it full throttle causes it to give out entirely, ive had the main down as far as a 105, and with the 115 tried putting the choke on at the point that it breaks up to see if it would run if forced to be richer but i have not been able to sort this out. I could really use some advice

Falkon45 · 08-27-2020, 06:00 AM

I think your jet is too small.

franque · 08-27-2020, 07:37 AM

What does your air filter look like? Any air leaks? What about the sparkplug? The exhaust plugged up? Your description is a bit vague about how it runs.

Stolkumfabrication · 08-27-2020, 08:39 PM

It starts and idles fine, and runs well up to about 1/2 to 3/4 throttle at wich point it pops and crackles and if i give it full throttle it dies completely I'll attach a picture of what the setup
I had a duplicate of one of the jet sizes, and a tap and die drill set that goes up in increments of .003 in. So im gonna try drilling it out little by little see where I get

culcune · 08-28-2020, 02:16 PM

Is it the 'lawn-mower' style engine or the vertical style engine? Have you adjusted the valve lash? People drive themselves crazy with their carbs/jets, and oftentimes the problem ends up being their valves.

Stolkumfabrication · 08-29-2020, 10:33 PM

Its a proper motorcycle engine, almost identical to the engines in the lifan gy200 dual sport bikes. I havent checked the valves yet as the bike has only about 400 miles on it, there hasn't been any excessive noise. I would try it as going up .012 thousandths above whatever size a 115 is had almost zero effect on running the bike, but im unsure about what the tolerances should be. I did some looking and somebody said the lifan gy200 that I believe this engine is a clone of are .002 intake and .003 exhaust which seems a bit tight to me.

franque · 08-30-2020, 06:32 AM

That's the correct specs, in inches. It could easily be your valves, check them first.

Stolkumfabrication · 08-31-2020, 09:45 PM

Checked the valves intake was way to sloppy, and the spark plug was coated in suit so my drilled out jet was way to rich so I went back to the 115 main jet and it runs better but still not good, the low end power and throttle response are noticeably improved and it will rev higher than before but it still breaks up at top end and stalls under full throttle regardless of engine load

franque · 09-01-2020, 05:14 AM

I'd try smaller jets, and check everything I said to check before.

bogieboy · 09-01-2020, 07:47 AM

check that your coil ground is clean and tight. also check that the wiring plugging into the CDI is plugged in tight. i have had both issues cause rpm related breakup, more rpm, more vibrations, less contact... had to figure out the CDI wiring 30 mi from home on the side of the road...LOL would take off fine, but as soon as i got into 3rd gear the bike had nothing... bit of a problem when the road you are on is a 55mph speed limit...LOL

Stolkumfabrication · 09-05-2020, 08:03 PM

I checked the cdi connections and ran a wire directly from the coil to the engine and had no luck, im hesitant to tear any farther into the wiring as I already had to redo half the wiring on account that from the factory the battery hung from an open tray on the underside of the bike, and there wasn't a single fuse in the entire harness

08-26-2020, 11:37 PM	#1
Stolkumfabrication Join Date: Jul 2020 Location: Willamette valley oregon Posts: 8	Need help lifan 200cc breaking up I got this mini chopper with a lifan or lifan clone 200cc 4 stroke engine in it, and was told going into it that the carb was out of tune. but it came with a selection of jets so I figured I could at least figure out what direction to go by playing with what I had, and have gotten nowhere. It currently has a mikuni 22mm slide carb 115 main and 27.5 idle it idles fine but seems to break up at higher rpms and giving it full throttle causes it to give out entirely, ive had the main down as far as a 105, and with the 115 tried putting the choke on at the point that it breaks up to see if it would run if forced to be richer but i have not been able to sort this out. I could really use some advice
	0

08-28-2020, 02:16 PM	#5
culcune Join Date: May 2006 Location: Yuma, Arizona Posts: 9,035	Is it the 'lawn-mower' style engine or the vertical style engine? Have you adjusted the valve lash? People drive themselves crazy with their carbs/jets, and oftentimes the problem ends up being their valves. __________________ "They say that life's a carousel, spinning fast you got to ride it well..." TGB Delivery Scooter 150 TMEC 200 Enduro--carcass is sadly rotting in the backyard
	2

08-27-2020, 06:00 AM	#2
Falkon45 Join Date: Aug 2020 Location: Savannah, Ga Posts: 759	I think your jet is too small.
	0

08-27-2020, 07:37 AM	#3
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	What does your air filter look like? Any air leaks? What about the sparkplug? The exhaust plugged up? Your description is a bit vague about how it runs.
	0

08-29-2020, 10:33 PM	#6
Stolkumfabrication Join Date: Jul 2020 Location: Willamette valley oregon Posts: 8	Its a proper motorcycle engine, almost identical to the engines in the lifan gy200 dual sport bikes. I havent checked the valves yet as the bike has only about 400 miles on it, there hasn't been any excessive noise. I would try it as going up .012 thousandths above whatever size a 115 is had almost zero effect on running the bike, but im unsure about what the tolerances should be. I did some looking and somebody said the lifan gy200 that I believe this engine is a clone of are .002 intake and .003 exhaust which seems a bit tight to me.
	0

08-30-2020, 06:32 AM	#7
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	That's the correct specs, in inches. It could easily be your valves, check them first.
	0

08-31-2020, 09:45 PM	#8
Stolkumfabrication Join Date: Jul 2020 Location: Willamette valley oregon Posts: 8	Checked the valves intake was way to sloppy, and the spark plug was coated in suit so my drilled out jet was way to rich so I went back to the 115 main jet and it runs better but still not good, the low end power and throttle response are noticeably improved and it will rev higher than before but it still breaks up at top end and stalls under full throttle regardless of engine load
	1

09-01-2020, 05:14 AM	#9
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	I'd try smaller jets, and check everything I said to check before.
	0

09-01-2020, 07:47 AM	#10
bogieboy Join Date: May 2013 Location: finger lakes NY Posts: 2,045	check that your coil ground is clean and tight. also check that the wiring plugging into the CDI is plugged in tight. i have had both issues cause rpm related breakup, more rpm, more vibrations, less contact... had to figure out the CDI wiring 30 mi from home on the side of the road...LOL would take off fine, but as soon as i got into 3rd gear the bike had nothing... bit of a problem when the road you are on is a 55mph speed limit...LOL
	0

09-05-2020, 08:03 PM	#11
Stolkumfabrication Join Date: Jul 2020 Location: Willamette valley oregon Posts: 8	I checked the cdi connections and ran a wire directly from the coil to the engine and had no luck, im hesitant to tear any farther into the wiring as I already had to redo half the wiring on account that from the factory the battery hung from an open tray on the underside of the bike, and there wasn't a single fuse in the entire harness
	0