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'08 YZ 125 soft in midrange


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I have a bone stock 08 YZ125, sea level, Motul 800 2T @ 32:1. It feels a little soft in the midrange; almost a slight "bog" just as it comes on the pipe. Overall the bike rips, but I would like to know if somebody here can give suggestions as to what might get rid of the hesitation.

This is my wife's bike; I ride a YZ250. Been a long time for me on a 125, so it might just be the nature of the smaller bike's powerband. Like I said, overall the bike runs fantastic.

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Hard to tell from the description. On a 2T usually clean and crisp but lacking power is lean while rich will feel more torquey but a little less clean and sputtery. Low end lean will generally feel rather crisp but lacking punch as well as a bog or hesitation when snapping the throttle open from slightly off idle. Being too rich on the low end will tend to give you a sputter and feel slow to rev out but generally no hesitation or bog when snapping the throttle open.

Does your problem fit into one of those descriptions?

Assuming stock at 40p / 3rd clip / 410 main...I'd imagine your pilot would be rich in Florida with the temp and humidity you have right now. I'd probably try a 37.5 pilot and see how that feels with everything else stock.

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Hard to tell from the description. On a 2T usually clean and crisp but lacking power is lean while rich will feel more torquey but a little less clean and sputtery. Low end lean will generally feel rather crisp but lacking punch as well as a bog or hesitation when snapping the throttle open from slightly off idle. Being too rich on the low end will tend to give you a sputter and feel slow to rev out but generally no hesitation or bog when snapping the throttle open.

Does your problem fit into one of those descriptions?

Assuming stock at 40p / 3rd clip / 410 main...I'd imagine your pilot would be rich in Florida with the temp and humidity you have right now. I'd probably try a 37.5 pilot and see how that feels with everything else stock.

What is strange is that I notice the bog right before the bike really wakes up, but it is still crisp and smooth feeling throughout the rev range.

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Are you sure its not because you are use to the 250?

After riding a YZ250 for a while now I can jump onto a cleanly jetted 125 and it feels gutless right in the middle, compared to the 250 which has great useable power in the mid range.

Edited by noodle
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Are you sure its not because you are use to the 250?

After riding a YZ250 for a while now I can jump onto a cleanly jetted 125 and it feels gutless right in the middle, comapred to the 250 which has great useable power in the mid range.

Thats my thought also I hopped on an EC125 gas gas the other day and it just seemed so bad on the mid range and I could not allow the upshifts to be lazy or it fell off. I doubt it was the bike was me use to the YZ250

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The stock jetting is rich from the factory. Like kan3 said, try a 37.5 pilot. I'm currently running a 35 pilot in my 05 yz125 and it's right on the money at 800ft elevation and 80-90F. (pro circuit pipe with vforce reeds and UNI filter)

*When it's right on, I very rarely need to use the clutch granted I'm in the right gear. It has no hesitation whatsoever and pulls hard to the top without missing a beat.

Exhaust temps are also key to keeping the pipe and powervalve free of sludge. She's gotta keep the revs up.

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Are you sure its not because you are use to the 250?

After riding a YZ250 for a while now I can jump onto a cleanly jetted 125 and it feels gutless right in the middle, compared to the 250 which has great useable power in the mid range.

As good as the bike runs, I'm beginning to think this is the case. I really didn't get much seat time on her '06 before it was stolen, so I'm suspect of the new (to us) '08. I do know the history of the bike since new. Well cared for and not modified.

Thanks all for the replies so far, I might try a smaller pilot. I'm not even sure where the pilot screw is right now; I will play with it this weekend.

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