86 yz125 issues!

L

Larry Kennedy

Noob
86 YZ 125 bike ran fine first time it was rode by my father. Next day it would only run on choke.*


Replaced crank seals, plug, cleaned carb twice. With some carb adjusting I can get it to run off choke, but only if I'm whacking the throttle. Won't idle and bogs real bad off bottom. Starts first or second kick when warm with the choke on. So I don't think the top end is shot.*


I checked the reeds. A little gap in the corners. Like a 10 thousandth. Can that be enough to cause the issue? Don't feel like dumping $40 on reeds if it's not the issues.*
 
Could be the reeds. They should be closed. Maybe flip them to see if it makes a difference before replacing? All the jets and circuits open and working in that twice cleaned carb?

The '86 YZ 125 came from the factory with a nasty bog that liked to show it's bad self on the face of a jump. Mine was fixed was a Honda carb with a flywheel weight.

Here's how mine sounded back then...

 
Carbs totally clean. Did flip the reeds. All it does is change the place the gap is. This bog is with the bike on a stand. Can't get it to take off. Ran fine the first ride.
 
Well, it did make a change. If there is fuel in the boot behind the carb, bad reeds can let the fuel blow back. My last bad reed experience was with a bike that would idle or run wide open with a huge bog in the middle.
 
you said the carb was cleaned twice, did you make sure to get all the little passages? Did you soak it really good for a while and blow it out with an air compressor? Is fuel pouring out and floats be messed up? How clean is your airfilter? If you search around the net I'm sure you can find stock jetting for a 1986 YZ 125. If so there is an equation floating around on the net too into which you plug your current jetting, temp, and altitude and you can find which jets you should be using. This will get you in the ball park. Have you checked your sparkplug and made sure the sparkplug boot isnt failing either? Just a few ideas I came up with. :)
 
The reeds arent going to cause the bike to run better with the choke on, the only way that happens is:

#1 Air leak
#2 Clogged passage/jets in carb

Focus on causes for those two things. I would try cleaning the carb again, like mentioned above, paying close attention to all the passages and jets. Be sure to COMPLETELY disassemble it, soak it in a good carb cleaner and use compressed air to finish it off.
 
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