1987 yz125 build

If it is having a hard time idling, it is most likely a plugged pilot jet. If you have not done it, take the carb completely apart and soak every brass piece in it in ammonia for around 15 minutes. Rinse them with water and blow them out with compressed air. Inspect all of the orifices closely for any blockages. As far as air fuel mixture guage, you only have the air screw on the side of the carb to adjust and that really only affects the mixture at idle when the slide is closed. You really cannot adjust much externally and will need to do it with different jets.

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Well, I had to make a air filter basket thingy cus the bike didn't have one and can't find one....dose the job. Lol
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Then started troubleshooting why the motor wouldn't run anymore..
After some testing I found I wasn't getting spark, then I would, then it would backfire, then no spark... checked the timing and it was WAY WAY off...this is what I found.... WTF!

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Nuts! Is the crank or flywheel damaged? Those press on pretty dang tight is there a chance it wasn't torqued down? Stator backing plate misaligned somehow?
 
Thankfully the crank is okay, magneto rotor is a little beat up but I think it's okay..
I actually don't remember torquing it down..I think I just hit it with the impact..witch probably spun the rotor/flywheel and broke the key..
When I went to take the nut off it was loose...so maybe I forgot to even tighten it altogether.. :o
 
Up and running again...still won't idle...longest it did was maybe a min...

I added locktite and a lock washer and torqued it down..if it brakes again I'm welding it to the crank! Lol
 
A lean pilot will have a hanging high idle Will it run if you twist the throttle a little? Some carbs you can adjust the idle on the carb, some you adjust on the actual throttle on the handlebar itself.
 
Yes, I can barely twist the throttle and it's at a low rpm..

My carb has a adjuster on the side for that,but I have it all the way in.

Last night I spent probably a hr trying to get it to idle on its own with very little luck.
 
Air, fuel, Spark are all you need to make it run. If you have determined that the spark is good now, then it has to be in the air/fuel mixture. Check to make sure you do not have a crack or break in your reeds and they are sitting flat against the reed block if you look through them from the carb side and can see light anywhere around the edges, you need new reeds. That could cause it to be getting to much fuel.
 
Reeds look good, I cinda got it to idle tho.
If I hold the throttle just a little for a few seconds it will idle on its own for a few minutes..

Got a few more parts in.. bike is 90% done..just waiting on my chain roller to show up..
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Also, idling and giving it a little throttle,it doesn't smoke..but the more throttle I give it past that, it smokes alot.
Running richer at higher rpms??


I was so focused on trying to get it to idle I forgot to open the door and I had the hole shop full of smoke lol
But surprisingly my eyes were not burning at all.
 
Bike looks great!!

The only way to tell the true jetting of the bike by the plug is to get the bike running wide open in 4th gear, pull the clutch in while giving it a quick rev and immediately hitting the kill switch. If you have just been cruising around, the plug is going to look rich regardless of jetting.
 
Guess I need to update this.

The idling problem was the reed's.
Runs pretty dang good now..Got a little throttle happy today and carryed a massive wheelie the langth of my back yard..not sure how I saved it but glad I did lol

Sadly tho I have the bike up forsale..the bronco needs tires really bad and my buddy Jeff is selling me his 42's..but need the money first...

I'm asking $1800 obo, think that's fare?
 
broncomitch said:
I'm asking $1800 obo, think that's fare?
Click to expand...

I don't know the market for vintage resto mod bikes so for the right audience they may have a much higher value but I have bought and sold a few different Yz250s including a newer aluminum frame model for less then that. I would imagine it'll take a while to find the right buyer that price.
 
The bike market is crazy.. I see one 07 yz250 sell for $2500 but a 06 sits for $1400?

And I saw a 1974 yz125 sell for $3k????

I'm hoping to get $1400 sense that's what I need and that's what I have in the bike...

I figured mine would sell pretty easily sense it's 90% rebuilt...but I just keep getting lame trade offers..
 
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