1982 XT125 - Electrical issues. Please help!

[S.O.A.N.Z]

1 hour ago, SirTwanz said:

Sorry I'm not sure what a 4t carb is?

4T refers to 4 stroke bikes

2T - 2 stroke

[SirTwanz]

Gotcha. Yeah it was a bit too dark and cold to do any testing tonight, but it fired up, got down the street, and then it died. I adjusted the screw out a bit and it started after a while and got it back. This weekend I am going to spend some quality time on it and mess with it with the new assumption that out=richer and in=leaner and maybe I'll make some better progress. I will keep everyone updated.

[SirTwanz]

Got it running really good yesterday, like amazing (didn't get past 40mph tho, not enough space). SO i decided the best thing to do was not touch anything, and try again after the bike had time to cool. Well, tried again and it didn't want to run nearly as well as it did. I would put it in first gear and it would try to die when i tried to move. Then I would get it going and it take very slow accelerating to get moving, otherwise die. The plug was white, but again, I just don't know if this adjustment screw is air or fuel (more on that in a second) Bigger issue I want to solve is about the carb leaking now!

I noticed ever since I put it back together the carb is leaking from the overflow tube. So my float height was too high right? I took it back apart and checked to make sure my valve was closing when the top of the float was 25mm away from the carb body. I am going to put it back on again in a bit, but wanted to hear what people thought as to why it is now overflowing since I put it all back together. Any other reason than float height?? I'd rather not put it back on if there is something else I can check. 

Side Note: the air flow has never been better on the bike, but I still don't know if this adjustment screw is an air or fuel screw. It screws into the hole CLOSEST to the engine. When looking through the carb (without the slide) from the side of the air box, the order goes, (Air Box) ; Main Jet hole, Pilot Jet hole, Adjustment screw hole (Engine). Feels like it controls how much mix gets delivered to the engine when the slide completely closed, but I have no idea at this point. If anyone has an idea let me know.

Compression tested just in case: 150psi (literally the very top end of the scale) & and a big fat blue spark from a brand new spark plug and brand new ignition coil.

I feel like this bike just has 23424 tiny problems, or this carb just sucks. My 250 has never been nearly this much of a pain. 

[Jens Eskildsen]

Its a fuelscrew, in is leaner, out is richer.
99% of 4 strokes are like this.

 

Overflowing carb is too high of a fuellevel, or a floatvalve thats worn or not seating properly due to wear/age.

[nobade]

If the screw is on the engine side of the carb slide, it normally is a fuel screw.

[SirTwanz]

Bought one of those paint cans of carb cleaner and gonna soak the carb (completely stripped down) for a few days, and then blow it out with carb cleaner and air, just to be dead certain. I have replaced pretty much everything in the carb besides the actual float itself. I have replaced all jets, screws, orings, fuel valve needle that connects to the float, everything, just not the float because I don't even know where to get one. Once I put it back on I am going to do a fuel level test. I will put the fuel adjustment screw to 2 1/4 turns out and hopefully this nightmare will be over. Anyone know where I can get a replacement float? I have searched and searched...

 

[SirTwanz]

Super late update, but hopefully it helps someone else.

After months/years of going through this thing, it was the CDI that was bad. I tuned and tweaked everything and was out of ideas. It ran, sometimes well, but never consistently. Slapped a new CDI in and it came to life immediately. No issues what so ever. Never stumbles, hits 60 no problem, completely reliable. Damn near as fast as my 81 xt250

 

If anyone ever finds this post and needs help with a early 80s XT125 or XT250, comment here and I'll help ya out. I have gone through both these models of bikes over and over again at this point. Anything to get more of them on the road.

 

Thanks everyone, especially the electrical diagram guy. Once I started looking at the diagram in a new way, it was the easiest way to understand it and I rewired the entire bike. 

 

Keep ridin!

[SirTwanz]

Reviving this thread. Does anyone know or could give me a step by step instructions on how to test the voltage regulator? Not sure if it could have an impact on the ignition system but the bike will run great one second and shitty the next. I believe it's related to some sort of issue with the wiring coming out of the stator/generator. 

 

Any advice is welcome. Thanks