Newly rebuilt Carbs... Lots of WHITE smoke!

[Gumbo76]

Ok, So my Fiancée bought me a set of '78 GS750's for Christmas (). Lucky guy, I know! So I was parting out one (you've probably seen my thread) and I am trying to get the other one running. Well, I have NO idea how long it's been since the "Running" one was started and run last. I tried starting it right from the beginning of my reign with it, with no success. I decided I would start by rebuilding the carbs.

I got them all done today and reassembled and put on the bike. I was amazed that I got everything together with minimal complications, being that this is the very first time I attempted anything like this ever. Anyway, I let the fuel fill the Float Bowls, No leaking. I then put the petcock on run and hit the starter. IT STARTED RIGHT UP ON THE FIRST TRY! It didn't even take several tries to start! I am pretty proud of myself for pulling this off.

Ok, like I stated earlier, I have no idea how long it's been since this bike ran last. I had it running for about ten seconds and the exhaust was thick white smoke. I shut it down immediately because I wasn't sure what was going on. I let it sit for a few minutes while I contemplated what was going on. I was thinking that maybe it was running a bit rich since the idle was a bit high. I messed with the Idle screw so get the idle down some and then started it again. Still idling high (And yes I know I need to adjust the carbs more) so I turned the choke down to lower the idle closer to normal.

Well, there seems to be some black fluid spitting out of the end of the left tailpipe as well as a couple of pinholes near the connections of the exhaust. It looks like really thin oil...

Questions...
1. Is is possible that it's been sitting for so long that the rings are bad and the oils is getting into the combustion chamber? That would mean I would have to pull the engine apart I guess.

2. Is it possible that the bike "may" have spent some time on it's side and the oil got in that way, and that any residual oil will eventually burn off?

3. Are there any other things I can check to see what this could be aside from pulling the head off the motor?

4. Do any of you have any suggestions as to what else this could be?

I'd hate to run it for too long as the neighborhood was pretty foggy after just a few minutes of the bike running. But if you guys think a fan at the front of the engine (to keep it cool) and some time running will help, I'd be open to that.

I'm open to whatever you guys have to say. Like I said, I'm new to "Tuning" part of tinkering on bikes. Thanks in advance for the help!

-Gumbo

[Graham]

It sounds like you could have gas flooding out one of your cylinders and flowing out the exhaust. These are common problems.
Do you know what your float height is set at? If not set it to factory specs.
Have you done an oil change? If not do one. Your oil may be more gas then oil.
When was the last time the float needles were replaced? If you don’t know then replace them. Old Bike Barn has them cheap.
Have you checked the fire on all your plugs? If not check it.
Have you checked compression? If not check it with a gauge to factory specs.
Have you checked the petcock? If not pull the vacuum hose off the carb and suck on it (yea with your mouth). If you get any gas in you mouth spit it out and rinse with water then get a new petcock.

[SqDancerLynn1]

I would check the petcock, (mandatory) if that is Ok ? then check the oil for gas. IF all is Ok just run it. Don't worry about the engine condition until it has run for an Hour and had the valves adjusted.

[1948man]

Are you sure it was smoke and not just condensation? There are small drain holes near the front of the mufflers to let moisture drain and not collect. The exhaust system and the rest of the bike could be pretty moist if it has not been run for a long time. It might clear up in a few minutes. If it's not making terrible noises you might just want to run it a while but don't let it run a long time stationary. it is air-cooled and needs flow over the engine to keep from overheating so ride it if it is safe. Also, maybe the previous owner put a bunch of seafoam in the tank which will cause white smoke.

[Gumbo76]

OK, So today I will check the petcock to see if it's leaking. I had the tank off the bike for several days and it didn't leak at all, but I'll take a couple pulls off the vacuum line and see if anything comes out. As for the float bowls, I'll have to double check the heights. I never wrote them down, but I believe they were all set. I'll check them again just to be sure I measured the correctly. I'm supposed to measure from the gasket seat to the bottom of the float, right? That is of course while the float adjustment tab is JUST touching the needle.

I doubt the float needles have EVER been replaced, but the spring in them seemed fine when I cleaned the carbs. They moved freely, and I was sure to blow compressed air into them to get any residual crap out of it too.

Then I'll check the oil for Gas. I didn't even think that could be the problem.

As far as compression goes, I have not checked that yet. I don't have a gauge for that and I'll have to try to figure out how to MAKE one. I'll have to do some research on that one. Anyone have any ideas?

Now, when you say check the fire on all of the plugs, you mean, make sure they are all firing, correct? Well, when I started the bike it seemed to run fine, with the exception of the high idle. It appeared all cylinders were running. I'l pull the plugs and see if any have oil on them. Or just don't look right.

OK, That gives me something to do today. Thanks for all of the advice guys! I'll keep you posted on th results.

[Adler]

Sometimes the rings get stuck after sitting for a long time. It doesnt mean you need to rip it apart, it just means you have to ride it! The rings will let go eventually.

[Don-lo]

I would go with something along the lines of your guess #2: oil somehow got into a piston and just needs to burn off. Sitting on it's side would definitely do it, but also it could have been someone putting oil in the cylinder (checking for valve sealing, or thinking it was seized). Checking your plugs should tell you which cylinders are oil-soaked. It takes quite a while to burn out oil too. Stopping and starting it is the best way, not continuous running, like 3 minute trips, with 15 minutes off. Too much oil accumulation can glaze the cylinders and rings, in case it never stops smoking.

The boss of a speed shop where I was working had something like this happen to a GS1100. It was smoking, so the customer had us put in a big bore kit. Upon startup, it smoked a lot, and wouldn't quit after 10 mins. I told him to give it more time, but he was sure he had overlapped an oil control ring, so he tore right back into it (he had base and head gaskets on the shelf, which he would eat the cost, as well as labor). Upon inspection, everything was fine, no overlap, no damaged rings, and after reassembly the smoke cleared up on it's own (oil was also in the exhaust).

Gas in the oil is very common, especially with the CV carbs.

[Gumbo76]

#2 is the culprit

Thanks, Don! Funny you should mention #2. I didn't have much time to play with the bike yesterday but I did manage to get the plugs out to check them. Turns out that when I took the #2 plug out, I had smoke coming out of the plug hole. That was the ONLY one too. All of the plugs looked wet, but that might be because I'm running pretty rich. The #2 seemed to have more stuff on it. The Right side exhaust isn't smoking any more, so I am thinking I'll try running it intermittently for a few days while I get some of the other things worked out. When I ran it last night for a few minutes, the smoke seemed to be less intense, so maybe it's just burning off the residual crap. *crossing my fingers*.

I would go with something along the lines of your guess #2: oil somehow got into a piston and just needs to burn off.

Anyone have a Carb Sync tool I can borrow for a few days?

Thanks again, gentlemen! I'll keep you posted with the progress of this smoking issue.

-Gumbo

[Gumbo76]

OK, I checked the compression of the cylinders and this is what I have;
#1- 180
#2- 120
#3- 150
#4- 150

Numbers 1 and 2 seem off, but I checked them three times each and that's the numbers. number two was the one I found smoking yesterday. Any ideas? I believe I am well within spec as the Repair manual I got from BassClif said 8.7:1 was normal. Judging from my gauge, 120psi would put me somewhere around 8.7. Does that sound right? The manual also said that 100psi was the lowest tolerable measurement.

[Adler]

Those compression numbers are too far apart for the bike to run normally. I still think the rings in #2 are a little stuck and after you've ridden it for a bit those numbers will change. Then again, what do I know?!

[Gumbo76]

Well I was hoping the 180 and 120 average would compensate, but I guess not! LOL! Just kidding. Yeah, I'm hoping the #2 is just stuck, and that as I run it periodically, It'll turn out becoming UN-stuck! Crossing my fingers.

I was pretty psyched that the numbers were over the minimum Spec though. That is a relief! Plus I got a new tool! Only $27 for a compression test gauge at Advanced Auto Parts.

I'm currently RE-charging the battery as I drained it while running the compression test. Thank GAWD for a kick start! LOL!

Those compression numbers are too far apart for the bike to run normally. I still think the rings in #2 are a little stuck and after you've ridden it for a bit those numbers will change. Then again, what do I know?!

[Graham]

Make sure you have good oil in the bike and run it about 50 miles then recheck compression. I’m leaning more toward stuck piston rings and 50 miles should free them up. Could be some piston-scaring witch would leave some metal on the cylinder wall and cause the rings not to seat completely. If you begin to here some ticking noise take the bike back home, more than likely you have major piston scaring and the ticking is piston slap.

[Gumbo76]

It sounds like you could have gas flooding out one of your cylinders and flowing out the exhaust. These are common problems...

Have you checked the fire on all your plugs? If not check it.

I think the #2 is not firing properly. I pulled the cap off the plug while it was running and it didn't make any difference in how the bike idled. So, as far as Gas flooding out one of the cylinders, this could be the culprit. I'm thinking a non-firing plug would cause similar symptoms? There was some backfiring from the LEFT EXHAUST.

Next Step, New Plugs and caps so I can have them fresh for the Carb Sync.

Do you know what your float height is set at? If not set it to factory specs.

Still have to check these again.

Have you done an oil change? If not do one. Your oil may be more gas then oil.

I changed the oil yesterday. It smelled like there MIGHT have been some gas in the old oil. Anyway, It's fresh now.

When was the last time the float needles were replaced? If you don’t know then replace them. Old Bike Barn has them cheap.

I'm hoping I don't have to go this route. How would I know if it was bad? They all seemed to be OK when I did the rebuild.

Have you checked compression? If not check it with a gauge to factory specs.

#1- 180
#2- 120
#3- 150
#4- 150
All I can seem to find is what the minimum should be. Anyone have an idea what the standard should be? I'm guessing 150. Is it bad that one is at 180?

Have you checked the petcock? If not pull the vacuum hose off the carb and suck on it (yea with your mouth). If you get any gas in you mouth spit it out and rinse with water then get a new petcock.

Checked the Petcock by sucking on it. Yes with my mouth. And nothing came through. So the Petcock is good. No leaking at all either.

[Graham]

I think the #2 is not firing properly. I pulled the cap off the plug while it was running and it didn't make any difference in how the bike idled. So, as far as Gas flooding out one of the cylinders, this could be the culprit. I'm thinking a non-firing plug would cause similar symptoms? There was some backfiring from the LEFT EXHAUST.

This time pull the plug and lay it against the motor while attached to the plug cap. Unhook the other plug caps from the plugs to keep the engine from starting. Turn the motor over and check for spark.

Next Step, New Plugs and caps so I can have them fresh for the Carb Sync.

Good idea. Won't hurt.

Still have to check these again.

Float height 25-27mm per factory manual.

I changed the oil yesterday. It smelled like there MIGHT have been some gas in the old oil. Anyway, It's fresh now.

Well done.

I'm hoping I don't have to go this route. How would I know if it was bad? They all seemed to be OK when I did the rebuild.

Since your oil only may have been a little gassy then chances are your float needles are ok.

#1- 180
#2- 120
#3- 150
#4- 150
All I can seem to find is what the minimum should be. Anyone have an idea what the standard should be? I'm guessing 150. Is it bad that one is at 180?

128 to 171psi per factroy standard.
100psi service limit.

Checked the Petcock by sucking on it. Yes with my mouth. And nothing came through. So the Petcock is good. No leaking at all either.

Good your petcock diaphragm is not leaking. I’d target the plug issue next and see what you get.

[Don-lo]

Did you hold the throttle wide open when you checked compression?

Your compression numbers are above the minimum but they are supposed to be within 10% of each other, so they are not good. Also, your high compression number (180) is above the high service limit (171). That doesn't happen by accident, and 130s are generally the highest normal numbers, so there's a good chance you have a high compression piston kit. Unfortunately, I've seen a lot of them installed wrong, where the circlip or teflon puck are missing, resulting in a big nasty vertical scar on the cylinder wall. Just last summer, I helped fellow member Eric (Wingnut) replace gaskets on his GS1100E, and this was the case. It lowers compression and allows oil up into the combustion chamber.

Otherwise,

Your petcock may be good now, but it may have been fixed by the PO. It could be that cylinder is glazed. I like sea foam for trying to loosen rings. Try running it for a few short jaunts, see if any thing changes.

The low compression may be due to tight valves. Did you check them?