First bike help

[Guest]

Hello, I just bought my first bike, an 81 gs450t. I bought it not running and finally got it going yesterday and rode it for the first time. It runs well enough to ride but not perfect. I have no idea how to diagnose the issue so I need your help. The first problem it had before it rode was when I finally got it to fire up, it would start, rev up hight to 6-7000 rpm and then slowly die, Sometimes it would rev high, then go back down to 1000, then way back up totally randomly, without my hand on the throttle. Sometimes I was able to get it to idle around 4000 rpm but tons of white smoke out of the exhausts, and from the pipe where the exhausts join, I assumed that was just oil dripped on the pipe burning off. I read something about the oil getting gas In it and overflowing, so I changed the oil with 10w-30 synthetic motor oil. After cleaning the carbs, I could get it to idle but still lots of white smoke coming from somewhere that I couldn't point out, almost like the entire engine was smoking. And the engine would rev on it's own randomly. I thought that the white smoke was coming from burning oil, possibly there was too much oil? So I took some out, so it was about 1/2 to 3/4 full on the dip stick. The smoke stopped. But when I fill the oil back up so the dip stick says it's full it smokes again. Maybe a leaky seal in the engine or something. Am I using good oil? When I start the bike on choke, it doesn't idle at a constant rpm, and sometimes just dies, after a few mins, if I use the throttle or take the choke off slightly, it dies. When I finally got it warm and took it for a spin, at a constant speed, it seems to give itself random bursts of speed, it's barely noticeable above 40mph but you can feel and hear it. What could be the issue?

[Crankthat]

Welcome to the forum.

Your symptoms are likely a combination of a few different things.

With the knowledge I have gained from the more experienced members of this forum I would start doing some likely much needed maintenance.

A real carb cleaning would be at the top of the list.
When I say carb cleaning I am talking about a full tear down and dip in chemicals made for carb cleaning with replacement o-rings all around.

Another thing I would do while the carbs are off is check for possible ways for air to leak by from your filter housing back to the motor.
A common problem from the GS line and the symptoms range from high idle, idle that takes a while to drop, and sometimes a racing idle that jumps around alot.
I am not familiar with your model but if your bike has rubber flanges that bolt onto the motor and then clamp onto the carbs there is a large o-ring that deteriorates over time causing a air leak.
It is located pressed against the motor between the flange.
If you model has the rubber boot with clamps on both ends then you do not have A o-ring there.
Sometimes a air leak is found with deteriorated boots that are located on the other end of the carbs.
They get hard usually and will not connect correctly.
The airbox may not be connected to the filter housing correctly.
The lid on the filter housing may have lost its seal.
The air filter may have deteriorated beyond usefulness.

The carbs are delicate when it comes to there settings and to much air can cause problems as you are experiencing.
When you have the boots off on the motor side to clean your carbs examine everything real closely and insure things are hooked up right.
There may be a screen on your filter housing lid and sometimes critters nest in there so be sure to check that out also.

When it comes to the white smoke the first thing that comes to mind is your valves.
You will need to ensure they are adjusted correctly or serious damage may occur.
I am pretty sure worn or old valve seals will cause the white smoke you are seeing.
I have read here that sometimes they will seal correctly with just running the bike for a few hundred miles so you may not need to replace them.
You should check your adjustments though.

Another cause of the white smoke could be worn out rings or cylinder damage.
Lets hope that is not the case though.
Running it with damage like that can cause more damage.

Below is a link to a members site.
You will find much info on the things I listed above and many other things related to your bike.
I would suggest you start reading and become familiar with his site as it will help you very much on your GS.
These old bikes require care and patience.
Many of us are willing to help where we can so this is not a ok I am done helping you post.
This is just to help you get started.
And yes we expect to be asked more questions as you learn and work on your bike.

And once again welcome to the forum!

Basscliff's site

[Crankthat]

Here is BassCliff's mega welcome link.

It is post # 1 in the thread.
Great links located in the welcome that you should open and read.

[78550GS]

When you get a chance, Put your location in your profile. There may be a veteran GS guru here close by to lend a hand.

And put your bike in your signature.....you will not have to keep repeating what you have if it's there.