Blue smoke out left exhaust only

I recently changed the engine in my VF500 and after finally getting it started I noticed a fairly thin but constant stream of blue smoke coming out the left hand exhaust (as you look forward). I haven't got round to doing a compression test yet or had a good look at the carburettor, but the valve clearances have been set and the spark plugs work fine but I'm hoping this doesn't look like a piston problem - the old plugs seemed a bit oily. Any thoughts would be appreciated before I get back to work on it. Cheers

 

Couple Questions:
1. Was the engine you just put in re-built or straght out of another bike?
1b. If it was out of antoher bike how did it run before swapping?
2. How long did you let it run/idle watching the smoke?
I ask this as mine did almost the same thing for about 45 minutes or so
after I got it running (sat in previous owners garagge for 3 years)

 

The engine was out of another bike - but not straight out. It came with my VF500 when I bought it and I don't have any history of the engine, other than a promise that it's sound - I don't even know the mileage. I let it idle for a few minutes - haven't let it run properly because of a fuel feed problem. Are you saying that your engine blows smoke out both exhausts or just one?

 

When I first fired it up, it smoked out of both pipes for the first few minutes. Then each time I started it afterwards it smoked out of one pipe only, until the engine had run for roughly 45 minutes (not all at once, over several short runs) then the smoking stopped. I'd let it run a bit before doing anything drastic, especially since you don't have a definate history of the engine. It may just have not been run in awhile and needs to clean itself out. Since you have a fuel feed problem, multiple short runs will work, its what I had to do (didn't have a gas tank at the time to run it very long)

 

Ok, that's encouraging. I've been running the engine off a remote fuel bottle straight to the carbs because for the life of me I can't get it running off the tank even though I know the fuel pump works - have you run into any problems like this?

 

No, sorry. I have the 86 model and it doesn't have a fuel pump at all. Is your fuel petcock working properly?? not sure if it has a vacuum connection or not. I used the direct method as well until I got my gas tank cleaned up and repainted. I'd check the fuel petcock and make sure everyhting flows though ok.

 

Vacuum connection? That's interesting - is it a thin polythene tube? Presumably it connects to some part of the carburettor? I do have one but I think I connected it to a conveniently located solid little nobble on the cylinder head, thereby not vacuuming much at all. '86 you say - is that in HRC colours? Nice if it is.

 

could be bad valve stem oil seal or maybe stuck (rusted) piston rings or scored cylinder or......

 

ahh, so you you're thinking it could be one of a dozen things, all internal and time comsuming?........

 

Leave the vacuum line attached to the cylinder.. that line is supposed to be there. As for the internal stuff, that might be a cause, but let it idle for awhile first to see if that gets rid of it. even a perfectly rebuilt engine will smoke after sitting for awhile without running. try th eeasy stuff furst then delve into the engine if necessary.