GS450 Smokes when hot.

[chronoman]

Finally I got my new 87 GS450 running, new plugs, oil, tires, air filter, rebuilt the carbs, and tires.
The problem is when the motor gets hot , idling in traffic the left cylinder starts to smoke,light gray smoke, a lot. when rpm are above 2000 the smokes completly stops. I put 400 miles on it after it sat for a couple of years.
Yesterday I added some seafoam to the gas and today when I went out it cuts out, seems to loose all power and backfires when it reaches 7000 rpms, it drops to 6K and goes back up to 7K and so on.

Are rings shot? Maybe valve seal?
Ctutting out fuel or ignition problem?
any ideas? before I procced.

Claude

[Nessism]

Sounds like you have a carb problem. Did you replace all the O-rings and make sure everything is nice and clean?

To check the mechanical condition of the engine you are going to have to do a compression check. Oh, and check the valve clearances while you are at it although it's not likely to cause the type of problem you have noted.

good luck.

[txironhead]

Could it be a coil going out? Just asking....

I would recommend cleaning all of the plugs, reinstall and run the bike. Bring the RPM's up to where it starts cutting out, hold for a few seconds, then immediately hit the kill switch. Take out your plugs and check for differences. The color of your plugs will tell you a lot, as well as if the plug is wet or not. Post your findings here and some of the gurus will help you out.

[Road_Clam]

Finally I got my new 87 GS450 running, new plugs, oil, tires, air filter, rebuilt the carbs, and tires.
The problem is when the motor gets hot , idling in traffic the left cylinder starts to smoke,light gray smoke, a lot. when rpm are above 2000 the smokes completly stops. I put 400 miles on it after it sat for a couple of years.
Yesterday I added some seafoam to the gas and today when I went out it cuts out, seems to loose all power and backfires when it reaches 7000 rpms, it drops to 6K and goes back up to 7K and so on.

Are rings shot? Maybe valve seal?
Ctutting out fuel or ignition problem?
any ideas? before I procced.

Claude

Do a compression test. I am thinking you have a bad set of rings on the smoking cyl. A common issue for a bike that sat for years is rust buildup on the cylinder walls, then upon re-running the engine, the rust destroys the piston rings.

[feelergaugephil]

Mileage?????????????