2001 YZ 125 bogs at half throttle

szokeL 247
Edited Date/Time 10/9/2019 6:54pm
Hi my bike runs and idles well with good throttle response and no problems when snapping the throttle, revs just fine in neutral but when In gear and about to go into powerband around half throttle, it makes a bwaaaaaahh sound like your typical bog. Is this a problem with jets, reed valves or PV? (Or all three?)
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early
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early 10/9/2019 5:22am
10/9/2019 5:22am
Check the reeds
Boomslang
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Boomslang 10/9/2019 5:34am
10/9/2019 5:34am
What position is the clip on the needle? Possible that you are lean.
kb228
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kb228 10/9/2019 5:38am
10/9/2019 5:38am
Prob try lowering your needle clip 1 slot
SKIDLID
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SKIDLID 10/9/2019 5:38am
10/9/2019 5:38am
I will go with the reeds are chipped or not shutting all the way.

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Boomslang
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Boomslang 10/9/2019 5:42am
10/9/2019 5:42am
SKIDLID wrote:
I will go with the reeds are chipped or not shutting all the way.
Will be good to inspect the reeds but if they are chipped or not shutting as they should the problem will not only be in the mid.

I reckon his clip is slotted at the top of the needle - to lean.
FortyHat
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FortyHat 10/9/2019 10:16am
10/9/2019 10:16am
Could be so many things, and no information about whether it used to work well for you until now, if anything was changed/added recently, etc.

Sounds like a lean bog, in the area that normally indicates the needle needs adjusting, but before you even start messing with that, be sure that your float level is set properly, and that you don't have any air leak at the intake. If you try to compensate for those issues with jetting, you'll be chasing your tail forever.
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SKIDLID
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SKIDLID 10/9/2019 10:27am
10/9/2019 10:27am
If you start it and extra fuel mist is coming out into airbox it is a reed problem.I have had many reeds that go bad yet the bike will still run on the topend just hiccup of the bottom to the top.
ctbale
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ctbale 10/9/2019 2:20pm
10/9/2019 2:20pm
FortyHat wrote:
Could be so many things, and no information about whether it used to work well for you until now, if anything was changed/added recently, etc. Sounds...
Could be so many things, and no information about whether it used to work well for you until now, if anything was changed/added recently, etc.

Sounds like a lean bog, in the area that normally indicates the needle needs adjusting, but before you even start messing with that, be sure that your float level is set properly, and that you don't have any air leak at the intake. If you try to compensate for those issues with jetting, you'll be chasing your tail forever.
Yup, when did it start doing this? Put some 100LL in it. (Joking)
szokeL 247 10/9/2019 3:26pm
10/9/2019 3:26pm
Thanks for all the info, I’m not sure what position the needle is in I plan on tearing down the carb today and I’ll take a look at the reeds too to see what they are like. As for more info, nothing was changed in the carb recently by me as I bought this bike a few months ago but have been doing minor things (changing sprockets, fork seals etc) but I’ll ask the previous owner to see if he changed anything.
szokeL 247 10/9/2019 5:17pm
10/9/2019 5:17pm
Update, I was taking out the slide and immediately noticed that the slide was cracked and there was part of it missing. Could this be the reason for bogging?
FortyHat
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FortyHat 10/9/2019 5:39pm
10/9/2019 5:39pm Edited Date/Time 10/9/2019 5:40pm
szokeL 247 wrote:
Update, I was taking out the slide and immediately noticed that the slide was cracked and there was part of it missing. Could this be the...
Update, I was taking out the slide and immediately noticed that the slide was cracked and there was part of it missing. Could this be the reason for bogging?
100% that's your cause.

Edit to add: time to tear down the top end too to inspect any damage from the slide's shrapnel. The old owner is probably high-fiving himself about now.
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szokeL 247 10/9/2019 6:02pm
10/9/2019 6:02pm
Will do that, I doubt the top end will be damaged as there was a top end rebuild done with only 2 hours before I bought it so fingers crossed the slide was damaged before the rebuild
ctbale
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ctbale 10/9/2019 6:07pm
10/9/2019 6:07pm
Never seen that in 40 years of tearing apart carbs, wow! Maybe it got dropped?
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FortyHat
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FortyHat 10/9/2019 6:52pm
10/9/2019 6:52pm
ctbale wrote:
Never seen that in 40 years of tearing apart carbs, wow! Maybe it got dropped?
Yeah same here, that's extreme. I've heard of simple cracks in slides causing a lean condition at mid throttle, but that slide looks like it's been shot!
FortyHat
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FortyHat 10/9/2019 6:54pm
10/9/2019 6:54pm
szokeL 247 wrote:
Will do that, I doubt the top end will be damaged as there was a top end rebuild done with only 2 hours before I bought...
Will do that, I doubt the top end will be damaged as there was a top end rebuild done with only 2 hours before I bought it so fingers crossed the slide was damaged before the rebuild
If the previous owner did a top end and didn't notice a grenaded slide, I wouldn't assume anything. Even the fact that he even did the top end. Unless he's a friend of yours anyway. Good luck with it.
SLOWTIME
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SLOWTIME 10/9/2019 6:59pm
10/9/2019 6:59pm
that slide is probably the reason for the new top end.
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gsxr6
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gsxr6 10/9/2019 7:02pm
10/9/2019 7:02pm
Seen the stop on the top of the slide break on a pwk buddy's kx500 . Stuck throttle wide. Happened right when he started it up at the truck thank God . But that is just wow. Crazy
gnarwhip
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gnarwhip 10/9/2019 7:58pm
10/9/2019 7:58pm
After you’re done with that, throw a Bill’s pipe on that murfurrer. I had one on my 01 and it was so sweet

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