77 gs750 white smoke

[saindon420]

Ive been helping a friend of mine get his 77 gs750 running good. We changed the fluids and plugs and it runs and idols really well but its blowing alot of white smoke when you give it gas. The bike dosent smoke while idleing. It doesnt look or smell like its burning oil. Could it be because the previous owner put a crotch rocket exhaust on it?

[Nessism]

You need to figure out what the smoke is from. White smoke it typically from burning oil (some people call this BLUE smoke). An exhaust will also give off some steam, which looks like white smoke, while it's warming up so keep this in mind.

Assuming the smoke is from burning oil, the next step is a compression test. Do the test with the engine warm and throttle wide open. If the compression numbers are lower than 120psi, add one tablespoon of oil to each cylinder and test again.

An exhaust pipe will not cause smoke to occur...at least not for a while. Free flow exhaust pipes, along with free flow air filters, will cause the engine to run lean which means hot. It's normal to rejet the carbs when the pipe is installed to keep the engine from damaging itself. Unfortunatley, many people do not rejet properly and thus damage can occur over time. Hopefully this did not occur on your bike.

Report back with the findings after the compression test.

[Dogma]

The last time I saw WHITE smoke from an exhaust was a pickup truck with a warped head, causing coolant to leak into the oil and combustion chambers through the head gasket. Coolant or water shouldn't be a problem here... Can water standing in the header become steam just from the heat of exhaust going by?

[TheCafeKid]

The last time I saw WHITE smoke from an exhaust was a pickup truck with a warped head, causing coolant to leak into the oil and combustion chambers through the head gasket. Coolant or water shouldn't be a problem here... Can water standing in the header become steam just from the heat of exhaust going by?

Yes, and dont forget the motor will develop condensation as well. But usually this is burnt off pretty quickly. I would do as said, with the compression test. Sounds like some valve seals and perhaps the piston rings could be faulty, allowing oil to pass into the cylinders. With the age of the bike, mileage or not, it would be MY guess.

[doctorgonzo]

Bumping a white smoke thread

So happy to get my charging system problems resolved I didn't REALLY start to worry about this until this morning. After I got my charging system fixed and ran the bike last night it blew quite a bit of white smoke at first. It settled down after a few minutes, but was still a bit smokey. It had never really done this before. I checked the level and don't think I overfilled (I had to dump the oil and refill when changing the stator). During the course of trouble shooting the charging system there was much cranking without starting, use of carb cleaner and later starting fluid, and running on only three cyliders (a wipe of a wet plug after charging system fixed resolved the dead cylinder). Is it possible these lead to the smoke? I'm going to run a compression test when I get back to the garage and just confirm good compression, but now I'm worried....

[TheCafeKid]

The fouled plug black and shiney? If so, its definately oil. I would have to say thats what it sounds like to me. BUT, dont freak out TOO much, these 8v motors REALLY are cake to work on (Im sure the 16v is little different, but i havent had the pleasure of cracking one of those open yet) If you are mechanicly inclined enough to read, and you have a manual, you can likely do this job QUICK. I'd say a solid day on it, and you can have it done once you have the parts.

[doctorgonzo]

It's running on all cylinders now after drying a clean but wet plug. I've just never seen white smoke from the bike before, and it smoked like crazy for several minutes then settled down to just a bit of white smoke when the engine was revved. I guess my question was, could all the running on three cylinders while I was testing the charging system, carb cleaner sprayed in the carbs to make it start, etc... have gotten crap in the engine that it had to burn off? I'm bringing it home sunday. Hopefully a good 20 mile high speed drive will resolve it.

[TheCafeKid]

Its entirely possible. I know this motor i just put back into my 77 750 cafe project did a bit of smoking when i first fired it up, but now its pretty calm. Smokes a lil but its gas cos shes a hair rich, but not blowing WHITE smoke. If a motor has been sitting for a while with oil in it, generally it doesnt matter HOW good those seals are, oil is going to find its way down thru them. The questions are, how much? and how long will it take to rid it from the cylinders? and will it STOP? If not, like i said, its not difficult. If *I* can do it, so can you.

[doctorgonzo]

Good point. It sat for a week without starting, and it did calm down after it ran for a bit. A complete rebuild is next winter's project. Trying to get all the problems resolved to ride this year, then when fall gets here, it probably gets torn down to the frame.