Getting an old bike to run

[R E A L]

ok, so I guess mine isn't an auto mixer, but how much oil is 30:1? how do I know when its mixed to 30:1? What kind of gear oil do you guys reccomend?

Do you think once I run it with proper gear oil and MIXED gas it might idle a little better?

 

[ivman]

R E A L

If a bike has been standing for a long time the following general checks apply.

1 Kick it over, to see that nothing has seized.
2 Remove the spark plug, check for fouling, and spark.
3 Make sure that you drain all petrol from the bike before trying to start it, and then put in some "new" petrol.
4 Make Sure the bike is in neutral, and that the petrol tap is open, and try start it.

After doing this ( whether it starts or not), you might want to start looking at the following:

Clean the carb.
Check the seals - Start with the ones that are fairly easy to get to.
Check the piston and ring.

A good word of advice though.. See if you can get your hands on a manual for the bike. Always a good place to start.

 

[Jon K.]

Another pic; this one under the seat. That is where the oil tank once lived.

Jeff; you might use Golden Spectro two-cycle. I have used it for years. Mix a 12 oz bottle with 4.5 gallons of gasoline. I don't remember what that ratio is, but it has worked for years.

In the engine, use some sort of 30 wt motor oil.

Yes, get a manual. Judging by your questions; you might not yet be ready to go digging into the carb. Perhaps you have a buddy that has been through a few carbs before?

 

[R E A L]

ya, me and my friend both tore the carb off last week and cleaned it up with carb cleaner. Im not sure if we would be able to go any further in working on the carb though. Today we are going to get a new throttle cable and airfilter and I will ask the guy there what he thinks.

 

[R E A L]

I couldn't get a ride there today but my dad said we will most likely go tomorrow.

 

[R E A L]

ok, we just got back from the yamaha place and the bike is indeed a 1979 GT80F. We have to go back tomorrow to order the parts. I will let you guys know how it runs once we get everything installed.

Jeff

 

[Jon K.]

If the throttle cable has the split to go to the oil pump, I'm thinkin' that you should install the cable on the pump regardless of whether or not the pump is working or even hooked up.

No loose ends.

 

[R E A L]

It has no pump, well at least mine doesnt. So I am just going to mix it at 32:1. I was emtying the gas out of the tank and there was some mud on the outside of the tank and it fell off and there was a hole under it, I have shoved a tooth pick in there for now but does anyone know anything I could do to patch that up? besides more mud

Thanks,
Jeff

 

[Jon K.]

It has no pump, well at least mine doesnt.
Jeff

The pump lives under the right side cover that is held on with two or three screws.

You can see the verticle split between the "A" and the "M" on the right side of the motor.

JB Weld will patch the hole pretty good, but that ain't the only hole! If you start rubbin' on it; there will be bunches of holes!

There is a product called "Creem" that you can use on steel tanks. I have had mixed results.

Tip: When you etch (step one of the Creem process) the tank with the (phosphoric?) acid; use hot water. Let it work. The etching is very important to get a good job.

Jeff; I have got to mention, and please don't get offended, but please don't spend a bunch of $$ and time on a GT80. The only value that bike has is as a teaching tool. If you stay the course, you WILL learn a lot about basics, and that is valuable in and of itself, but that time might be better spent on a machine with a brighter future than a GT80.

Maybe you can find an neat old XR200, or an air-cooled KDX200. Something that will treat you a bit better than the GT80 will.

 

[R E A L]

and please don't get offended

None taken, I wasn't planing on spending anymore then about $70 on the bike, the airfilter and throttle cable was about 45 so I am going to pick up some JB weld and most likely a fuel filter (this bike DEFINITELY needs one). Tomorrow when we go to order those parts I will have the guy take a look and maybe he could tell me if the pump is working or not.

Jeff

 

[mxmatthew]

but GT80s are wicked play bikes. their super small, still have 4 gears (i think, maybe 5), and a manual clutch!

 

[Jon K.]

Again; I have been proven wrong! :uh:

No pump under here!

 

[R E A L]

I am glad its not an auto mixer, one less thing that I have to worry about breaking.

 

[R E A L]

I went and ordered the parts today and picked up some gear oil. On the side right below the cap for the gear oil (on the motorcycle) it says "500cc", im guessing that means 500 cubic centimeters of oil I need to put in there. Please correct me if im wrong. How much oil is that? I bought a 32 FL. OZ bottle of oil and I need to know how much to put in.

Thanks,
Jeff

 

[Jon K.]

Half the bottle (16oz.) should be close.

 

[mxmatthew]

if it says 500cc then you put in 500 mL

 

[R E A L]

ok thanks. Since I am going to be owning my first RUNNING dirtbike soon is there anything I should check once in awhile on the bike or anything?

mxmathew, how fast is your GT80?

Thanks,
Jeff

 

[JasonWho]

500cc is 2/3 of a fifth. HICCUP

Any chance to buy a less rusted gas / fuel tank off e-Bay? Beyond that, you could check on the Kreem stuff mentioned by Jon K.

 

[R E A L]

I have looked a lot on **** and there was nothing. I think it should be fine as long as I get a good fuel filter for it, and a bottle of JB weld.

 

[gwcrim]

mxmathew, how fast is your GT80?

It won't be fast as compared to an 80cc MX bike even of the same vintage. It's a beginner off-road bike with a smooth, low key power band.

If you're looking for parts, the enduro version was probably all the same except for the lights.

 

[R E A L]

what is the name of the enduro version of the GT80F?

 

[mxmatthew]

the fastest ive had it up to is around 60 km/h (65 downhill :)). that was absolutely pinned, i mean ready to blow up pinned. Itll be an awesome bike to learn on tho man, i learned on mine!

The enduro version is the MX80. I knew someone who had one and im pretty sure its the exact same bike with a bit more suspension, maybe a little differnent gearing.

 

[R E A L]

ah. ok, thanks. Today I mixed up the gas and got everything ready for when the parts come in and I started it up and the throttle got stuck wide open, luckily I had it in neutral and had to mess around with the cable for a few seconds to get it to stop. Do you guys think that is just the cable messing up or is it somthing messed in the carb? Because that would REALLY suck to have that happen while im riding it.

PS. The kill switch doesn't work so the only way I can shut it off is when it is idleing, THATs why it would suck.

Jeff

 

[mxmatthew]

check how the cable's routed and make sure its not caught on anything or being pulled to much when you crank the bars either way.

i dont think this is the problem but sometimes when you run out of gas it will just rev like crazy and the kill switch wont stop it.

If it's not those, maybe try takin the carb apart and give it a good clean with carb cleaner and an air compressor.

 

[R E A L]

I am pretty sure its just somthing with the cable or the carb thats getting stuck, I will see if it does it when I get the new throttle cable installed. If it still does it I will take the carb off and clean it real good and see if it does it anymore. mxmathew, does your kill switch work ok? Does anyone have some information on the kill switch that might help me fix it?

Thanks,
Jeff