First, I'd like to thank everyone on this board for it's wealth of information. I have completely rebuilt my gs500 engine without consultation this far from the knowledge ive gained. This is my first post. Anyway, I just rebuilt the engine (spun rod bearing) using a gs450 crank and rods. The bike ran beautifully for the first 50 miles. Upon starting yesterday (no choke, cold) I noticed excessive amounts of smoke when revving. (valve seals?) Also, after parking it coming back from a ride a revved it to see if it would spew any more, which it did, but very little and at high rpm. Just looking for some ideas. The engine was in beautiful shape other than the bearing. Only thing I can think of, if its smoking warm, is previous owner overheated engine and rings lost tension. And sitting overnight then smoking leads me to believe valve seals. Just hard to believe with such a clean engine. Thanks for your input! This site is great, I'll post up some pics of thr build soon.
Those GS450 rods and crank must be 3 decades old if your in the US but no mention of what year the GS500 is and how many miles on it. Old bikes with low milage can be a real bargain but they also can have dried out seals from years of sitting around with little or no usage.
I've put 80k miles on a 97 GS that I bought new and now have a 02 GS I bought a year old and have 92k miles on now and have had no hint af any valve seal problems. Everytime, about 20 or so, I check valves I shut them down hot and wait until next day to check valves cold and the pockets in top of the head that hold oil around the cam lobes for startup are always full of oil. This oil would drain down overnight into the cylinders if there was a valve seal problem I think. Pulling the valve cover next day after sitting overnight might be a good place to start to see if oil is draining down. I've seen a GS1100E shut down hot and restarted an hour later after dinner smoke like a chimney for a couple minutes but that clears up shortly when the excess oil in the cylinders burns off. THat's valve seals.
thanks fo your input, ive heard and read about your expertise with the high mileage gs's you have owned through the years. the 500 motor is a 94, the gs450 crank was from an 83 or 84, rods same. they looked great though. i'm not sure how long the bike sat, i purchased it as a basket case. the odometer says 8k but i have no way to verify that. based on how the cylinders and pistons looked when i pulled it down, it looks like very low mileage. no signs of compression escaping past the rings, could even make out some cross hatch on it. im going to assume that it is old valve seals from sitting, just wanted to confirm, and you are to go to guy when it comes to these bikes.
mines been doing that for a while. except only when starting choked.
see if you can replicate it later, and if its not water vap/unburned fuel rather than oil.
Its definitely oil, my bike starts right up without choke, which also makes me wonder if the stock jetting has been altered considering the general consensus is that these bikes are cold blooded. It clears up after riding it for a few, but will blow light smoke after a spirited high rpm ride. I imagine snapping the throttle shut at high rpm allows some oil to enter the combustion chamber. I'm not overly concerned, it runs strong and smooth so when I have time I'll replace the valve seals and see what happens.
most likely the seals from what you describe. you should be able to change them easy peasy. If you are good, you'll be able to change them using the rope trick. If you really want to get into it you can pull the head.
Good luck, brotha!
How would you compress the valve spring with the head still on? Not much room to get a compressor in there. Ive done valve seals on cars with the head still on using compressed air. But I was able to get a valve spring compressor on easily.