Assistance Requested: Startup Issue & White Smoke From Exhaust (Not Vapor)

[roxxer69]

My apologies for posting a new thread instead of continuing this one. The new thread started out as a different topic but ended up evolving into a continuation of this one after modifying.

Updated Thread: http://gstwins.com/gsboard/index.php?topic=72935.0

Before I winterized the bike it ran great. No issues, starts up on a dime, had some smoke out of the exhaust but it dissipated quickly so i assumed it was just vapor. First time I ran her this spring the following issues came out of nowhere.

1. The first thing I noticed was that when I uncovered the bike I noticed a small amount of fuel residue on the left side of the starter cover. I brushed it off and started her up with the choke all the way down. The idle RPMs were barely touching 3,000 with the choke enabled. Playing with the choke hardly caused any movement in RPMs. Prior to this, the choke would rev the engine up to around 5-6,000 RPMs. I first thought this was a carb issue, so I tore it down, cleaned and checked the carbs as well as the choke lever. Oddly enough the choke & RPM issue seemed to fixed after I started her up again but a couple days later the same low RPM choke issue came back. I am not sure what is going on here. I tried new gas, cleaned the carbs again, and still the same issue occurs with the startup process.

2. Furthermore, and I'm not sure if this is related, I noticed a substantial amount of white smoke coming from the exhaust. After reading some other forum posts, I am able to deduce that it is not vapor and is most likely burning oil or something other than vapor. The smoke seems to increase when I rev the engine to higher RPM's and then seems to back off when idle, but it was still very noticeable. I do not visible see any oil residue and I just recently got the engine gaskets replaced. After about 5-10 minutes the smoke seemed to dissipate and I road the bike around. I noticed the smoke essentially stopped, or was not as pronounced as before.

She idles great (after warmed up), runs good, but these issues are on my mind.

Before I attempt to fix the issues, I am wondering if anyone had any advice. Here are a list of issues that I am thinking could be the problem based on some Google searches:

1. Valve seal issues
2. Piston ring issues
3. Compression issues

Thanks in advance.

[Armandorf]

Following your thinking line:

1. Valve seal issues -
-symptoms: oil consumption, smoke
-test: none that i imagine now


2. Piston ring issues
-symptoms: oil consumption, smoke

3. Compression issues
-symptoms: low power, bad rings , oil consumption, smoke
test: compression , cold, hot , and with oil added to seal rings more and look for increase, no incresase:good rings


could also be valve cleareances but i doubt it changed from winterizing only.

[prmas]

If the smoke was only apparent one time I suspect that you have had a carby that flooded and leaked externally but also internally. Theoretically, if the side that flooded happened to have the piston at TDC with both valves open, fuel could have gone straight through the chamber into the header pipe and sat there in the cold weather. By the time you came to start it the chamber would have dried out enough that it would not cause a miss-fire but the fuel in the pipe would vapourise as the pipe warmed up, more-so with higher revs (hotter gas), thus causing the smoke/vapour.
If it does not happen again, I believe that is the answer. It is the only logical thing as valve stem seals do not "go bad" if the bike is parked for a few months.
The other thing to check, if my theory is correct, there will probably be some fuel in the oil. It should be changed ASAP. Remove the dip stick and sniff at the hole. If you can smell fuel it is almost 100% as I suspected as some will have leaked down past the rings over time.

Macka

[Kilted1]

All of the above.  It could also be bad fuel. 

[roxxer69]

Been out of town, thanks for the advice. Have not see oil consumption but I will change oil, test compression, and use new gas and see what happens. If that does not do anything I'll try compression test. Otherwise it'll be the valve seals or piston rings. Great ideas for testing though.

[Suzukirider74]

White smoke indicates that it burns antifreeze,since this are only air-cooled that's not a problem.
If it burns oil it will be blue smoke, are you sure its not vapor?
If the bike runs normally I would just change oil and filter and use it, check oil level regularly.

[roxxer69]

If the smoke was only apparent one time I suspect that you have had a carby that flooded and leaked externally but also internally. Theoretically, if the side that flooded happened to have the piston at TDC with both valves open, fuel could have gone straight through the chamber into the header pipe and sat there in the cold weather. By the time you came to start it the chamber would have dried out enough that it would not cause a miss-fire but the fuel in the pipe would vapourise as the pipe warmed up, more-so with higher revs (hotter gas), thus causing the smoke/vapour.
If it does not happen again, I believe that is the answer. It is the only logical thing as valve stem seals do not "go bad" if the bike is parked for a few months.
The other thing to check, if my theory is correct, there will probably be some fuel in the oil. It should be changed ASAP. Remove the dip stick and sniff at the hole. If you can smell fuel it is almost 100% as I suspected as some will have leaked down past the rings over time.

Macka

Macka, Took her for a quick ride, saw the smoke but it stopped after I came back from the 25 minute ride. Changed the oil and the old stuff definitely smelt like gas. Started her up again and the smoke/vapor/whatever the hell it was seems to have stopped. I will start her up again after it sits to see if it was in fact the issue.

Another thing. if you have the time. I finally located the gas leak from the Carb (I think), and it does not leak all the time, maybe after it sits for a couple of days. See the picture below. I haven't taken the carbs apart again but from what I remember it's leaking from a spot that is blocked with some kind of metal plug that can't be screwed in or out.   Thanks for the time.



https://imgur.com/a/7VBY5bz

[prmas]

It sounds like my theory about the flooding might have been correct. I have to confess that I do not know what is up that tube on the carby as I have never had to touch mine from new (K9) except to adjust the idling speed a couple of times. I have never had a fuel problem of any sort and have not even adjusted the idling mixtures from factory original.
My philosophy is "if it ain't broke, don't fix it".
If the leak only shows up after a few days it would seem that you might have two problems.
Firstly, the float level on that particular carby MUST be rising slowly over time when parked. That can only be due to a leaking needle and seat which needs to be replaced. If left, you may have the same problem next time the bike is parked for a long period.
Secondly, the vacuum operated fuel tap is supposed to prevent this sort of thing from happening. It seems that your fuel tap is also faulty. Either that or you are leaving it on "PRIME" all of the time.
I am sure that many Forum members here can tell you what is up that tube where the fuel is leaking from but unfortunately I cannot. As a temporary fix you could put a firm-fitting rubber cap over the end of the tube.   
I hope that this is of some help to you.

Macka

[roxxer69]

Macka,

After some online research, it seems to be that the tube is in fact the fuel mixture screw, so maybe this needs to be replaced? But I do not want to touch it until I try fixing the other issues first because I also believe in your philosophy. The last thing I want to do is create a new headache messing with the fuel mixture when it may not be necessary. I will try to detect a faulty float needle in the left carb, this may be causing the whole issue huh?

Lastly, I am not sure if it was parked in prime, but after doing some more troubleshooting, with the fuel petcock assembly in particular, I noticed that the vacuum operated diaphragm was faulty, so a new one is on the way.  Thanks again for the help.

[roxxer69]

My apologies for posting a new thread instead of continuing it on this one. Thought it would be a different topic but ended up evolving into a continuation of this thread. Anyway, see the updated thread here if you are interested.

http://gstwins.com/gsboard/index.php?topic=72935.0

[prmas]

I am happy that I could help.
If that is the idle mixture screw it will have a small "O" ring around it.
It may be perished.
Without mucking up anything you could firstly gently screw it in (clockwise) until it seats lightly and count the turns, then remove it and replace the "O" ring. Then refit it until is seats gently again and back it out the same number of turns that you firstly turned it in. That will leave the mixture unaltered.
The "O" ring is very small so make sure that you have the correct replacement part before you remove it.

Macka

[mr72]

After some online research, it seems to be that the tube is in fact the fuel mixture screw, so maybe this needs to be replaced?

The pilot needle o-ring is leaking. You will not be able to get the bike running right or control the pilot mixture at all until you fix this.

Again, go check out my infamous blog post on the topic of fixing up your carbs. If that plug is still there then you have an 18 year old motorcycle that's never had the carbs freshened. I guarantee it needs it. Every single o-ring in there is shot, even more so if you put carburetor cleaner in it without first stripping the carbs all the way to bare metal.

https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html