Getting an old bike to run

[mxmatthew]

well mine has a switch that you can either slide to on or off and it also has a key that you can switch it off with. They both work fine.

I dont really know much about the electronics on bikes, sorry. But just check out all the cables and make sure everything looks ok and connected right. The cable could just be shot, who knows.

 

[R E A L]

hm.. I wonder if I could just order the whole wiring setup for the kill switch. It shouldn't be to much, there is only like 3 wires routed around the bike.

Does anybody know another effective way to quikly shut off the bike if it does get stuck wide open?

 

[mxmatthew]

you can just lay the bike over and it will run out of fuel pretty quickly.

 

[reelrazor]

All you need to do is ground the coil lead to stop spark. You can check the original kill switch with an ohmmeter. You should have continuity in one position of the switch and not in the other.

If it is bad, you can pick up a generic kill switch just about anywhere for a few bucks and wire it in.

I wouldn't ride it until I had a guaranteed way to shut it off.

 

[R E A L]

ok well I have a good feeling I fixed the throttle cable getting stuck but first, can someone give me an overview of what the mixture screw does. because when I turn it all the way to the right it feels like it hits somthing inside the carb, im guessing that might be the little cylinder that holds the needle, when I pull the throttle cable and it gets stuck im thinking thats from the other side of the screw getting caught on the cylinder thing that holds the needle and thats why it gets stuck. Im thinking this because when I turn the screw to the left and start it, it doesn't do it at all.
any opinions?

Jeff

 

[gwcrim]

Sounds like the "Idle Speed" screw. That adjusts the idle speed. The round thing is the "slide". The idle speed screw should be beneath the slide to catch it as the throttle is closed. Get it to where it's a full turn out after contacting the slide. Obviously, you'll have to adjust it as needed when the bike is running.

There is another adjuster screw called the "Idle Mixture" screw. This controls the air/fuel ratio at idle. Gently screw this one all the way in and bring it out 2 full turns. It ought to run at that setting. But it will need fine tuned once the bike is running.

 

[R E A L]

I dont see any mixture screw on the carb, I will take a picture of it tomorrow in the light. If the idle speed screw is beneath the slide then would I want to pull the throttle and then tighten the screw so it will stop the slide before it goes down to far to make my bike die?

Jeff

 

[gwcrim]

If the idle speed screw is beneath the slide then would I want to pull the throttle and then tighten the screw so it will stop the slide before it goes down to far to make my bike die?

Dat's right!

 

[R E A L]

I did that and it still dies, but I dont mind at all just having to restart it once in awhile, at least I have a dirtbike!! I got the parts today and installed them and they ordered me the wrong airfilter, so I need to figure out somthing for that. I got it started and checked to make sure gas was getting through the new line and through the fuel filter and at first it wasn't then after I let it die some went in there, so that is fine.When I was kickstarting it, it started to leak what smells like gas from the base of the exhaust pipe, it drips about 3-4 drops about every 15-20 seconds and its REALLY dark, maybe its old from when the bike was sitting. Then it wouldn't start back up, my dad says its probably flooded but I don't know how if I got it started.
Any help?

Jeff

 

[R E A L]

HOLE-E-CRAP!, I can tell you guys now I am gonna be a dirtbiker till the day I die! My dad took me out with it in the desert behind my house and I rode it around on some hilly trails, but since this was my first time on a dirtbike, I figured that the speed I was going was normal for the bike, then my dad gives it a try and really worked the throttle and then after a minute it started running "normal" which was CRAZY, it would rev way higher and go REALLY fast. Then after a few minutes of it running normal is would either die while we were going, or just slow down a lot and sputter. My dad said it probably the carb that needs cleaned, so im going to do that tomorrow. When I clean it, do I just take it off and spray it with carb cleaner and then put it back on, do I need to oil it or anything? Once I get it to run "normal" all the time, the bike should be fine to ride a lot. I just need to pick up a few bolts and tighten everything down.

Thanks,
Jeff

I don't have to worry about the idle screw thing anymore becuase it fell out when we were riding it today. Would that hurt anything?

 

[mxmatthew]

that sounds more like a jetting problem than a dirty carb problem to me, but dont hold me to that.

Its never a bad idea to give it a clean though. Just go at it with compressed air and carb cleaner. Make sure you dont put too much pressure on the plug ball things tho, they can pop out and ull have fun with that problem. Dont need to oil it or anything that i know of.

 

[R E A L]

Ok, I will clean the carb tomorrow and see if thats it. Could you explain to me how I would fix a jetting problem?

Jeff

 

[mxmatthew]

well i'm no expert at it by any stretch of the imagination so hopefully you can get the idea from THIS website.

 

[gwcrim]

There shouldn't be a jetting problem. That bike isn't that finicky. The stock jets should be OK.

Spray the carb with carb cleaner, dry it with compressed air (if possible), making sure to blow out all the tiny passages. Be sure that you use a new bowl gasket when you reassemble. Oh, and get an idle screw (probably a spring too) while you're at it. Nothing worse than a bike that doesn't idle.

 

[R E A L]

ok, It starts perfect, on 1st kick when it is cold. Then after I ride it around for awhile it get harder and harder to start. After about 30 minutes of riding it wont kick start but it will push start. Maybe its overheating? But still, I couldn't get it to run "normal" at all during my ride. I got it up to about 15-20mph in 4th gear. Yesterday it would go at least 30-35 when my 220lbs dad was on it. (I weigh 130lbs) also, today it was kinda sputtering when I was going anywhere from 2nd-4th gear.
Any ideas?

Thanks,
Jeff

 

[gwcrim]

Any chance you could run a compression test on it?

 

[R E A L]

I do not have the gauge for that and im currently out of cash. Also, the bike smokes a lot, its like a blue smoke and it smokes a little more when im at slower speeds. would this mean that its burning to much oil?

Jeff

 

[mxmatthew]

that would be my guess, that's why i think it might be jetting.

 

[R E A L]

I just got back from another ride, I have ridden the bike for a total of about 45-60 minutes today. Towards the end of the last ride it really started to sputter and die on me when I was in motion. It seems like the sputtering starts in the higher RPM's of each gear. The dieing happens mostly in 1st and 2nd gear. Do you guys think that the dieing could have been from me jumping it? Because it only sputtered before I jumped it and then it started to die after I jumped it. I didn't get very high at all, just about a couple of inches.

Jeff

 

[mxmatthew]

ahh yes..... jumping the '79 GT80. hahah feels like your ridin a totally rigid bike dont it?

i dunno, I've never had a problem with it when I jumped it.

 

[R E A L]

ohhh yeahhh, I will clean the carb tomorrow after I get home from school and post back to see if it helped any.

I thank every person that posted on this thread for helping me get my first bike running, I will definatly be a dirtbiker as long as I can. Hopefully I will get a new bike soon so I can lay the ol' yamaha to rest.

Thanks,
Jeff

 

[R E A L]

Ok, I cleaned out the carb with carb cleaner then blew some compressed air through all the holes and stuff and put it back on. I rode it around in the desert for about 10-15 minutes and it ran as crapy as usual, then I was on the street heading back to my house and that thing just took off! So I turned around and kept riding it in the desert with it running "normal". Then after about another 10 minutes it started screwing up again, it would sputter and slow down then take off again. After about another minute of it sputtering it would just die on me. Then it wouldn't start at all so I had to walk it home.
Before it started running normal, it started to just suck the gas through the line and then out of the overflow lines, I think thats what they are called. Would that be the float getting stuck? Then after a little bit it just stoped driping the gas through the overflow lines, but it still sucked down the gas, even while it wasn't running.
If there is gas in the line and the gas is turned off, the gas will saty in the line, but the sencond I turn the gas on, it sucks it straight into the carb.

12 MINUTES LATER
I went back out and it started up 2nd kick and when it was in neutral, it reved just like it should. But when I let off the throttle it very slowly lowered the rev until it died.

20 MINUTES LATER
It started up 3rd kick and had good throttle response but it wasn't running "normal", it was just like it was earlier. I also noticed that the gas wasn't getting sucked through the carb anymore.

Jeff

 

[mxmatthew]

hmmmm, yeah the pouring out of the overflow line sounds like it could be a stuck float.

If there is gas comming out of the overflow when it it shut off but not when running I believe it would most likely be a stuck float.

 

[gwcrim]

Is there crap in the gas tank?

 

[R E A L]

There is some rust, but I flushed out all of the loose stuff with new gas.