89 yz 125 boggs down at wide open throttle

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#1
The bike I just rebuilt has alot of mid range power and it seems to be hitting the power band but then when you try to go full throttle and really get the revs high it boggs down. Almost like fuel is completly shut off. Is this a jetting problem?
 
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#3
I had the same problem with my dr200...I cleaned out my carb and it was better...but its back again so I have to figure out what else to do.
 
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#4
cdorsey50stang said:
Almost like fuel is completly shut off. Is this a jetting problem?
Ya i think your on to it. Have you adjusted your float level before on your bike? While you have the carb out check the reeds for and cracks.
 
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#5
I should note that the carb is dumping fuel out the bowl overflow constantly. This makes me think maybe the float needs adjusted. How do I go about that? How do I know where to adjust it to? Thanks
 

IndyMX

Crash Test Dummy
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#6
cdorsey50stang said:
I should note that the carb is dumping fuel out the bowl overflow constantly. This makes me think maybe the float needs adjusted. How do I go about that? How do I know where to adjust it to? Thanks

Get a service manual for your bike.
 
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#7
cdorsey50stang said:
I should note that the carb is dumping fuel out the bowl overflow constantly. This makes me think maybe the float needs adjusted. How do I go about that? How do I know where to adjust it to? Thanks

then for sure its your float level, get yourself a manual and it will show you exactly how to do things, its a liitle difficult to explain but a manual with diagrams will help you out.
 
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#8
No matter how many times you try to set the float level, it will continue to overflow if the needle valve doesn't seat properly. On a bike that old, the needle valve and seat could be worn and may need to be replaced.
 
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#9
With the bowl overflowing would this be the cause of the bogging problem though? Say the needle does need replaced, would it be a good chance that the bogging would stop?
 
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#10
Yes an overflowing float bowl can cause carburetion issues which lead to bogging. I don't know that you need to replace the float needle valve yet. If you try to set the float but it keeps creeping higher, then you do. But, you need to try setting the float level first.
 
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#11
Ok, I set the float level and there is no longer any fuel coming out of the bowl which is good. The reeds look good......everything looks good.....I just thought of something else, I'm running 89 octane fuel, I know you are suppose to run 93 octane... would the octane level make that big a difference? By the way, thank you for all your help so far!
 
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#12
No, the octane wont make the engine bog down but it will burn a hole in your piston. Run 93!
 
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#13
unless your compression ratio hasnt been changed, by say adding a doomed piston or shaving the head i wouldnt worry about running 89 octane. But i would run higher octane to be on the safe side, better safe than sorry.
 
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#14
Hi, i also have a 1989 yz125.
Maybe your main jet is too lean, maybe water in gas, clogged carb/jets, dirty air filter, or i guess it could be an air leak. Make sure it is in fact a 89 model if you are gonna order parts, if it has gold rims or drum brakes, then its not an 89, its older. Make sure the tubes that hang out the carb isnt stopped up also.

tip, if your stator ever goes out,, but the stator and the wiring harness all in one.