125sx has a bog

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Apr 10, 2001
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#1
my 2001 125sx was running great last weekend. this weekend i couldnt get a bog out of it no matter what i did or anyone else at the track. just off the bottom it bogs. i`ve changed every jet up and down and it wouldnt matter. the bog was still there. couldnt come out of the corners unless i kept it revved out. could i have a electrical problem happenening? i changed the reeds the main and slow jet, dropped the needle and raised the needle and still it persists. it drove me nuts! does any one know something i dont? has this happened to anyone else?
 
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#2
seems you have checked all the right areas but Ignition timing check the cover and make sure your bolts have not losened.

Are you useing the same gas as last weekend?

You said Nothing about the Pilot ajustment

I would assume a clean air filter and good spark plug was used with the proper gap.

I have seen people pop the plug out of the box and screw it in. and comment they come pregapped ....lmao ...sure they come pre gapped ...lmao
 
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#3
seems you have checked all the right areas but Ignition timing check the cover and make sure your bolts have not losened.

Are you useing the same gas as last weekend?

You said Nothing about the Pilot ajustment

I would assume a clean air filter and good spark plug was used with the proper gap.

I have seen people pop the plug out of the box and screw it in. and comment they come pregapped ....lmao ...sure they come pre gapped ...lmao
 

Strick

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#4
Yamamoto has responded as I would have.

A bog is normally a lean condition. Air filter clean and not over oiled? Gas O.K.? I might go so far as to buy some gas from somewhere else and try it.

If your temps have increased recently you should be leaning the bike anyway, that is why the bog baffles me.

The only other thing I would check after the simple stuff is float height (too high).

Let us know what you find!
 
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#5
i was using fresh mixed gas. mixed as usual. pilot was 1.5 turns. checked the timing and was on the mark. i just cant figure this one out. plug was gapped right. it was the same plug as last weekend. didnt change anything from last weekend to this weekend.just washed the bike and the filter.changed the oil. and filled the tank and raced. ( with a bog ).it was flying on top end it just had nothing on bottom. since then i have completely cleaned the carb and blown out every hole on it. have replaced the carb and warmed it up and still a bog. checked for a vacumn leak and none found. i am really baffled.
 
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#8
I recently picked up a '98 125 SX in excellent shape, but it had a very similiar bog to the one you describe. I used it as a bargaining chip, but knew it was a lean condition just off the bottom. Once the revs were up, it ripped. I had to turn the air screw in from 1 1/2 turns to 1/2 turn, which cleaned it right up. If we weren't so close to warm temps here in Maine, I would have put a larger pilot in it, but I'll just back the air screw out as temps rise. Hope this helps.

Dave
 
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#9
I met a guy last Friday on my practice loop, same condition you speak of. He had a bog down low, but said it absolutely ripped on top once the revs got up. This was his third ride and doesn't know what happened between last weekend and Friday, cause he didn't have it the first time 2 rides. My advice was to gap a new plug and change out, as well as turn air screw in and if that did not help possibly go up a size on the main. It's starting to get warmier around here. From the previouse posts here I'm glad I was sending him in the right direction I'm a 4 strk guy. ;) Good luck, just thought I'd let you know your not the only one with this condition with the 125SX.
 
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#10
I am still with ya here buddy

well with all that done it now brings us to bigger things

On the ignition side, did you happen to notice and OIL spooge inside that cover? seeing that it ran great last weekend and not this weekend I am thinking that maybe when you shut the bike off it was hot and the crank seal may have gotten stuck to the shaft and when you started it, it maybe got a slight rip.

OR we have the big P ....Power valve ....I do not see any reason this would just fail but process of elimination would make me think of that as a possibility.