125cc runs like cra* after rebuild

Bbdiddy · 10-11-2015, 06:40 AM

Hey everyone, hope you guys can help out here. One of the 5 Chinese atvs that I have is a 2004 toatao 125cc 3 speed sa and for the past two years has been the benchmark leader in reliable starting and riding. It was bought for the gf for that exact reason. It has the pz 19 factory carb on it with open filter and slightly punched out muffler. Recently had to completely disassemble because the three bolts that held revers gear in place came loose. As I had the thing apart I decided to clean up the casting in the intake and exhaust ports, no hogging just smoothing. I've done this many times to automobile heads as a teen. Now all back together and I can't get it to start and run without numerous difficulties. The odd time I can get it to ride nice and strong after I putt around till its warmed up but still can't get it to idle. When I do get it to idle alone it's a little high on the rpm then when I shut it down it will not start again the idle screw it holding the carb open witch made me think my air screw was too rich. Changed the carb to one with the factory sealed air screw only to go through all the same bs as before with it being almost impossible to start and run again... Please anyone. I've tried so much I'm lost now and need to hear advice from another set of eyes/ears. Thanks Brian

Mudflap · 10-11-2015, 08:35 AM

First things I would check is ignition and cam timing since it's been apart. One tooth off on the cam timing or a few degrees in the ignition timing could have the effect you describe. Also be sure the valve lash is set properly.

Bbdiddy · 10-11-2015, 09:24 AM

Ya, today I'm going to check timing first! I checked it once but I'm going to check again. Has lots of spark.

Bbdiddy · 10-11-2015, 11:56 AM

Yup! Timing was retarted one tooth! Runs great now thanks.

Bbdiddy · 10-11-2015, 11:57 AM

Also I need to figure out how to post pics on here from iPhone to show you guys my fleet

Weldangrind · 10-11-2015, 08:27 PM

Glad to hear that it runs!

Try hosting your pics on Photobucket, and then sharing them from there.

Weldangrind · 10-11-2015, 08:29 PM

Quote:

Originally Posted by Mudflap

First things I would check is ignition and cam timing since it's been apart. One tooth off on the cam timing or a few degrees in the ignition timing could have the effect you describe. Also be sure the valve lash is set properly.

Excellent guidance! I'm not sure I would have thought of the cam chain so quickly.

Mudflap · 10-12-2015, 09:30 AM

Getting the timing chain off by one tooth is pretty easy, something I've done a few times or a few dozen times as a motorcycle mechanic.

10-11-2015, 06:40 AM	#1
Bbdiddy Join Date: Oct 2015 Posts: 16	*125cc runs like cra after rebuild** Hey everyone, hope you guys can help out here. One of the 5 Chinese atvs that I have is a 2004 toatao 125cc 3 speed sa and for the past two years has been the benchmark leader in reliable starting and riding. It was bought for the gf for that exact reason. It has the pz 19 factory carb on it with open filter and slightly punched out muffler. Recently had to completely disassemble because the three bolts that held revers gear in place came loose. As I had the thing apart I decided to clean up the casting in the intake and exhaust ports, no hogging just smoothing. I've done this many times to automobile heads as a teen. Now all back together and I can't get it to start and run without numerous difficulties. The odd time I can get it to ride nice and strong after I putt around till its warmed up but still can't get it to idle. When I do get it to idle alone it's a little high on the rpm then when I shut it down it will not start again the idle screw it holding the carb open witch made me think my air screw was too rich. Changed the carb to one with the factory sealed air screw only to go through all the same bs as before with it being almost impossible to start and run again... Please anyone. I've tried so much I'm lost now and need to hear advice from another set of eyes/ears. Thanks Brian
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10-11-2015, 08:27 PM	#6
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Glad to hear that it runs! Try hosting your pics on Photobucket, and then sharing them from there. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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10-11-2015, 08:35 AM	#2
Mudflap Join Date: Sep 2014 Posts: 1,871	First things I would check is ignition and cam timing since it's been apart. One tooth off on the cam timing or a few degrees in the ignition timing could have the effect you describe. Also be sure the valve lash is set properly.
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10-11-2015, 09:24 AM	#3
Bbdiddy Join Date: Oct 2015 Posts: 16	Ya, today I'm going to check timing first! I checked it once but I'm going to check again. Has lots of spark.
	0

10-11-2015, 11:56 AM	#4
Bbdiddy Join Date: Oct 2015 Posts: 16	Yup! Timing was retarted one tooth! Runs great now thanks.
	0

10-11-2015, 11:57 AM	#5
Bbdiddy Join Date: Oct 2015 Posts: 16	Also I need to figure out how to post pics on here from iPhone to show you guys my fleet
	0

10-12-2015, 09:30 AM	#8
Mudflap Join Date: Sep 2014 Posts: 1,871	Getting the timing chain off by one tooth is pretty easy, something I've done a few times or a few dozen times as a motorcycle mechanic.
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