Yz125 sputtering in mid range

Related:
Create New Tag

7/4/2017 12:05 PM

Happy 4th all!
I have a question about the ignition on my bike. Its an 01 yz125 all stock. However it has started sputtering at half throttle right before powermand. I tested the stator and that is whithin spec. Reeds are good. Crank seals amd top end are good. Coil is good carb is clean and jetted properly. Plug is brand new. I even disconnected the kill switch. I feel like ive narrowed it down to a bad cdi box but would like a second opinion. Any help is greatly appreciated!

|

7/4/2017 3:24 PM

Are you 100% sure that it is jetted properly? Have you jetted it or did you take it somewhere? I know a guy who there CDI box was bad and they actually couldn't tell when they were riding it. He kept burning holes in the top of his piston and that's how he found out. idk much about the electrical parts of a bike but I don't know that you can tell when a CDI box is bad. I would buy one or two leaner main jets and see where that takes you. Like 6$ a piece

|

7/4/2017 3:41 PM

Blackjack31 wrote:

Are you 100% sure that it is jetted properly? Have you jetted it or did you take it somewhere? I know a guy who there CDI box was bad and they actually couldn't tell when they were riding it. He kept burning holes in the top of his piston and that's how he found out. idk much about the electrical parts of a bike but I don't know that you can tell when a CDI box is bad. I would buy one or two leaner main jets and see where that takes you. Like 6$ a piece

Positive. I have been running this jetting for about 2 years now with no problems at all and ive always made sure the carb was spotless also

|

7/4/2017 4:03 PM

Blackjack31 wrote:

Are you 100% sure that it is jetted properly? Have you jetted it or did you take it somewhere? I know a guy who there CDI box was bad and they actually couldn't tell when they were riding it. He kept burning holes in the top of his piston and that's how he found out. idk much about the electrical parts of a bike but I don't know that you can tell when a CDI box is bad. I would buy one or two leaner main jets and see where that takes you. Like 6$ a piece

01buck1/4 wrote:

Positive. I have been running this jetting for about 2 years now with no problems at all and ive always made sure the carb was spotless also

Yeah but jetting will change within a month and that's usual. I've seen it change within the day. I would double check on jets. But as far as the CDI box, I would rule that out. I'm not mechanic but I have seen a lot of crazy stuff and the CDI problem I seen didn't have these symptoms. Usually a CDI box will make a bike run really hot. So if the piston is not in bad shape I would say no on the CDI box

|

7/4/2017 4:13 PM

Blackjack31 wrote:

Are you 100% sure that it is jetted properly? Have you jetted it or did you take it somewhere? I know a guy who there CDI box was bad and they actually couldn't tell when they were riding it. He kept burning holes in the top of his piston and that's how he found out. idk much about the electrical parts of a bike but I don't know that you can tell when a CDI box is bad. I would buy one or two leaner main jets and see where that takes you. Like 6$ a piece

01buck1/4 wrote:

Positive. I have been running this jetting for about 2 years now with no problems at all and ive always made sure the carb was spotless also

Blackjack31 wrote:

Yeah but jetting will change within a month and that's usual. I've seen it change within the day. I would double check on jets. But as far as the CDI box, I would rule that out. I'm not mechanic but I have seen a lot of crazy stuff and the CDI problem I seen didn't have these symptoms. Usually a CDI box will make a bike run really hot. So if the piston is not in bad shape I would say no on the CDI box

Awesome thanks man ill double check that needle too and then go from there

|

7/5/2017 7:01 AM

01buck1/4 wrote:

Awesome thanks man ill double check that needle too and then go from there

Good luck to you man!

|

7/5/2017 9:17 AM

Look for wear spots or flat spots on the needle and needle jet as they do wear.

Paw Paw

|

7/5/2017 1:42 PM

Also, I hate to follow up on the obvious since you seem to know as much as I do (or more,) but is the gasoline new?

|

Braaapin' aint easy.

7/5/2017 1:55 PM

Falcon wrote:

Also, I hate to follow up on the obvious since you seem to know as much as I do (or more,) but is the gasoline new?

I definately know alot but am just stumped on this haha and yeah brand new fuel and oil lol

|

7/5/2017 1:58 PM

Paw Paw wrote:

Look for wear spots or flat spots on the needle and needle jet as they do wear.

Paw Paw

By needle jet do you mean by main jet holder? Thats all i can find on the shop manual

|

7/5/2017 3:21 PM

The tube that holds the main jet is also the needle jet.

Paw Paw

|

7/5/2017 7:07 PM

Upon further inspectionidk how this got by me i found this on my reed cage after pulling off the reeds. Looks very deteriorated. Would this be a cause of it by chance?Photo

|

7/6/2017 11:28 AM
Edited Date/Time: 7/6/2017 11:29 AM

YES, that will keep the reeds from sealing. I have seen that when race fuel is in use.

Paw Paw

|

7/6/2017 12:22 PM

Okay im going to run the boyesen rad valve now but mybquestion is would the condition of the reed cage cause the mid range sputter/bog?

|