'05 yz125 sputter at high rpm

First off I've owned the bike since spring of 2006 and the beginning of this season is when the problem started. Jetting is stock and has never been an issue, that being said just rebuilt the entire carburetor with all brand new jets, needles, and seals, as I thought the main jet may be the culprit. I've researched the topic a bit and have a few ideas of what it may be, but I'd like input as I sure as heck don't know it all.

 

-Electrical? Brand new spark plug which I gaped to manual specs did not solve the problem. Maybe there is a loose connection somewhere where it attaches?

-Top end? My cylinder is in decent shape but the bike could probably use a new top end... However this isn't the first time "i could use a new top end" and I've never encountered this issue before.

-Air leak? Leak down test? Something I've yet to do but have heard it's worth checking into. I have never done that but I know my way around a bike well enough to do it I'm sure.

 

Very frustrated at this point, I don't ride motocross often, but when I do the issue is BAD. Only at wide open throttle does the bike start to spit and sputter. At all other throttle openings I couldn't be more pleased.

 

Thank y'all for your consideration regarding my post,

 

Dan

I would first do the top end and go from there

I had an aftermarket cdi do this once on my older yz125 (2000). Eventually went completely out when I was trying to figure out what it was. Luckily I kept my oe one and swapped out all was good...minus fact the aftermarket cdi made topend scream

I would say either the cdi like asnyder said or the silencer. Repack the silencer, it might solve the problem. Its like 8 bucks.

Check your coil as well for ground and connections at wires...inspect all wires for wear thru rubber coating...does it seem like its running out of gas like choked out up top rpm wise? Or just cut off for a sec ? Throttle manipulation change anything ?

Check your coil as well for ground and connections at wires...inspect all wires for wear thru rubber coating...does it seem like its running out of gas like choked out up top rpm wise? Or just cut off for a sec ? Throttle manipulation change anything ?

 

It feels like its choked up/cutting out.. I wish I could explain better. I have it wide open and it feels like its gasping for air. As soon as I let off the throttle things return to normal. When I ride woods i almost never even notice it. Checking all the wires sounds like a good idea, I was thinking of that myself. Its great to get input from all of you as they're are a few things mentioned I didn't think of like the CDI (mine is the original stock oem).

Have you been in you're carb at all?

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