Exhaust Smoke, High Idling, and General Annoyances (1981 GS850G)

[Guest]

Hi all,

I just got my 1981 GS850G all put back together after cleaning the carbs, replacing the air box hoses, intake boots and o-rings, and changing the oil. When it finally fired up, it sounded great, and was idling steady for the first time (around 1250rpm's). After about 45 seconds, the exhausts began to smoke (white/whiteish-blue smoke), and then after about four minutes, the idle went from nice and calm to 3000-3500rpm's! I couldn't get it to come down from there (I was only idling the bike in neutral, I didn't put it in gear), although when i gave it a bit of throttle, it calmed for a few seconds before going back up. What could be causing this? I am also seeing that I have smoke coming from the engine itself (the same color smoke as is coming from the exhaust). It seems to be coming from below the engine (but it's focused around parts of the exhaust). I was thinking it could be excess oil on the metal, but I can't say for sure.

A few things to note: I replaced the stock air filter with a K&N High Flow filter, but I didn't rejet the carbs. Could this be causing any idling/smoking issues? If so, I still have the old filter, and I can clean it and put it back in. Also, I noticed that I put too much oil in the bike, so I am waiting for it to cool down before I drain some and get it to a good level. Could overfilling the oil cause any damage to the bike? I've only let it run for a total of about five minutes before deciding the smoke was too excessive. Also, I have not adjusted the idle screws or anything (I've been avoiding that part--this is my first mechanical project, and I'm trying to take things one step at a time). The last thing to note is that I believe the previous owner of the bike tightened the oil drain plug to the point where the threads came out with the plug when I took it out. Needless to say, I have about 4 drops a day leaking from the plug (probably more when the motor runs and the oil thins). Is there any way to bore a slightly bigger hole to fix this? And could this be causing any of my problems?

Any help would be extremely appreciated. I've been waiting so long to get the bike back together, and I'm itching to get back on the road! I'm hoping the problem is something on the simpler side (fingers crossed I just have to drain some oil, but I don't think that'd solve the idling issue).

Thank you so much,

Brian

[terrylee]

Idle problems could be caused by not rejetting, which you'll have to do since you went to pods, even more if you have aftermarket exhaust. Lots of threads on here about rejetting, do a search on here. Be sure not to overfill oil or could cause leaks, oil has to go somewhere. Smoke in the exhaust could be overfill or you may want to do compression test to make sure no problems with rings in engine. Check out Basscliff's site from here and will have manual you can download.

[81GS850]

I don't think jetting will cause idle issues.. I ran mine without the airbox and it would idle fine. Did you remember to take the choke off? I think I remember high idle is a lean mixture. What did you set your idle mixture screws at? They should be around 2 turns out from lightly seated. Did you check valve clearance? Do that first before trying to diagnose carb issues. How about did you bench sync the carbs or sync them after they were installed? I wouldn't worry too much about the smoke out of the exhaust.. Yet. What oil are you using? The plugs will tell the tale. If they're wet and oily then you're leaking oil. If they're black and sooty then you're rich. If they're tan you're perfect. Also the smoke from under the engine is probably the seals in the crossover. Did you tighten up the clamps? Also is there any exhaust leak at the head?


On the oil plug, was there a metal seal under the plug? If not that's why you'd be leaking. You should be able to pick one up at the parts store.

[tom203]

"....Also, I have not adjusted the idle screws or anything (I've been avoiding that part-...."
you did take the idle mixture screws out for cleaning,right?? Make sure you get oil level correct- bike on center stand .