YZ80 not running right

[Nick_R_23]

Well I got bored today and put my new throttle cable on my 1977 YZ80 today. It runs but doesnt idle or rev right. It needs to be started in 3/4-full choke, and dies when you try to take it off. It wont let me go past 1/2 throttle in any gear or it will die then too. And when im moving it will go then act like it dies for a second then go fine again over and over. It will start right back up after it dies though. Any ideas on what to check?

-Nick :TrikesOwn

[oldskool83]

any air leaks?

[barto411]

sounds to me like the reeds are bad.

[Nick_R_23]

I can guarantee that there is no air leaks on the motor itself, the only possible place is between the reeds and intake boot. Wouldnt the motor just run away with an air leak though? :wondering

Im not sure the reeds are bad, this was running just fine before it sat for the winter. They were clean. Im gonna take it all apart and clean out everything when I get home though, just to be safe.

Someone also suggested it might not be getting enough gas?

-Nick :TrikesOwn

[oldskool83]

my wifes cr80 kinda ran like that. i replaced reeds 2 times, rebuilt the entire motor and then finaly after i spend to much onit i took it to a honda dealer and they spend 30 hours working on it also to find out i had a hairline crack in the right crank case. we fixed it and it didnt help one bit.

1st i say check your carb float hight, if not clean and rebuild the carb. is your jetting off, the needle could be at the wrong position causing it to wanna run the best.

[barto411]

i couldnt se it starting if it wasnt getting enough gas.. but then again u have to start it in 3/4 choke... but i know i had a kx 80 and i had to jumpstart it to get it to start and couldnt get it up on the pipe when i rode it.. and it ended up to be the reeds.... id try just cleaning the carb out very well and try flipping the reeds over...

Mike

[Nick_R_23]

I forgot to mention we rebuilt the motor last year...new gaskets, piston and rings, NOS clutch assy., and we ended up getting a new right crankcase cover too.

Im gonna go over the carb very carefully, as I seem to remember messing with the idle a bit because it idled too high (ended up being the throttle cable was too short) ill reset all the screws on it. All the jets are stock, and the clip on the needle is in the middle slot. Plug looks fine, so its jetted right just got a little too much oil in the gas lol.

Ill try flipping the reeds also. It will start at 3/4 choke but it likes full choke better.

-Nick :TrikesOwn

[Nick_R_23]

Alright, I got an update. It had about 1/2" of slop in the throttle cable, idk how it got like that. I took the carb apart and cleaned it out, and reset all the screws. I cleaned out the reeds and they look real good. Ever since I tightened the throttle cable it didnt want to start anymore. It will pop and catch for a second every once in a while when you push start it, but thats all it did.

So I got bored tonight and went out to screw with it some more. I found out that it doesnt get very good spark, if any at all. Everything tests good though. I tried 3 coils (known good) and it still doesnt wanna spark. I tested the kill switch, also. I know the stator is good, because if you touch the wire from the stator to the frame it gives off a bright spark. The electrical is a 1 wire, points deal. The points are new, btw.

I played with the points a bit, it looked like they werent opening very much. I cleaned them off also. It now will give off a weak yellow spark sometimes. This bike is really pissing me off, we completely rebuilt the engine 3-4 years ago and it STILL isnt running!!! Its got like the simplest ignition ever too!! 1 wire!!! :wondering

The only thing I can find that might possibly be wrong is the condensor? The wire from the stator coil and the wire from the points both run down to the condensor, and then a wire runs up to the coil. The problem is, last year the wire came unsoldered from the condensor. I resoldered it on, but is there a chance that the condensor melted or something internally, allowing the solder to come off? I say this because, one, it melted the wire off, and two, if you take a continuity tester and touch one end to the ground and the other to the wire on the condensor, it grounds out. This also affects the points, because it allows the wire from the points to ground thus making them either 'open' or 'closed' all the time.

Anyone got any more suggestions?

-Nick :TrikesOwn

[Greiver430x]

you did check the spark with aew spark plug right? Sometimes a plug wont look bad but its shot. I hope its something simple I know things like this drive me crazy, I had probkem with my rm. I tested everything couldnt find nything wrong ended up bein that my friend mixed the gas wrong. hope you get it figured out.

[oldskool83]

i know all about blown plugs that dont look blown....

[RedRider_AK]

I lol'ed when I read "played with the POINTS" about a YZ80...

[Nick_R_23]

"I lol'ed when I read "played with the POINTS" about a YZ80..."

Yeah, so does everyone else that sees this thing, its ancient. :lol:

It has a brand new plug in it, but Ill check it with another one when I get home. It doesnt look brown (still looks new because its only been on one run.) but the plug IS wet so its getting gas, just not firing.

Just curious did anyone understand what I said about the condensor? I'm starting to think that its the problem, because it grounds out the wire coming from the points, which isnt supposed to be grounded.

-Nick :TrikesOwn

[RedRider_AK]

Just curious did anyone understand what I said about the condensor? I'm starting to think that its the problem, because it grounds out the wire coming from the points, which isnt supposed to be grounded.

Well, I have an ATC90 engine a buddy gave me a long time ago, and it would only spark if you grounded the condenser (at least I think that's what it was) against the engine case. It had a single green wire going from the points, and two more from the magneto I believe, up into a big tan coil-looking thing (looked almost like a CDI), which was normally bolted to the frame with 2 contact points. Maybe you have a bad contact point somewhere in your wiring system or ground, maybe some corrosion.

[Nick_R_23]

Well the stator is real clean, everything has good ground. The condensor is actually part of the stator assembly, so it has good ground. But what Im getting at, is that the wire from the stator coil (which provides energy for spark), the wire from the points (which tells it when to spark), and the coil lead wire and the kill switch ALL go to this condensor wire. The condensor I think is bad, because it allows ALL of those things to be grounded to the engine/frame.

-Nick :TrikesOwn