Topic: Smoke out of air filters

[yellowjacket]

Just got my bike running today.  I did a top end on it, rebuilt carbs ect... Finally stepped on it today and it fired right and I got it to idle, sounds great.  Noticed what appears to be smoke coming out of the air filters on the carbs.  Has anyone heard of this or dealt with it?

[Terry in Australia]

Did it backfire at all mate? That'd be my first thought, followed by an inlet valve not sealing. Cheers, Terry.

[Don R]

Uh oh, he said filters, here comes the pod police.

 What did the top end include, valve seals, Guides, valve job, lapping in valves, rings, etc?

[rotortiller]

Uh oh, he said filters, here comes the pod police.

 

[Terry in Australia]

"The Pod Police, they live inside of my head,
The Pod Police, then can drop dead.............." (with apologies to Cheap Trick)

[yellowjacket]

Thanks for the input.  I have had a lot of success with smaller single cylinder engines.  I did a small rebuild on a KZ650 that runs great and then I saw this 550 for sale for $200 and I thought it would be a fun project and it has been.  The top end included new gaskets and seals, lapping the valves, a honing, i did not use new rings but the measured out fine, and many other upgrades.  All of this was done by me except the honing.  I had a blast and I know the bike.  Started right up, that is exciting stuff.  2 questions, 1. Could the smoke be from the engine just settling and it just needs to be ran for a while(no smoke from the exhaust). 2. How do I tell if the top end is getting oil?
Thanks,
Curt

[Terry in Australia]

It could be Curt, I replaced the crappy Keihin carb on my Harley with a new Mikuni on the weekend and I got a "burp" through the carb when I first fired it up that caused a whisp of blue smoke to mist out through my air filter.

If this continued for any more than a minute or so though, you have to assume that combusted fuel is working it's way back from the combustion chamber/s. For this to occur, an inlet valve might not be sealing, so a good place to start would be to check your valve clearances, they may be too tight.

I'm not a 500 guy, but I imagine checking if your top end is getting oil is similar to the mighty 750, just unscrew your valve clearance inspection caps and take a peek with the engine running, you should be able to see oil splashing about in there.

One other thing to think about, is smoke coming out of your carbs, or out of your cylinder head or crankcase breather? Cheers, Terry.

[yellowjacket]

Thanks Terry,
I appreciate your response.  I will check my tappet adjustments and my breather. I did not get any backfire at all.  Once I messed with the idle a bit it settled right down and idled nicely.  I hope it is just a few adjustments.
Curt

[mystic_1]

Say, are you sure the smoke is actually coming OUT of the filters, and not just coming from oil sitting on the motor NEAR the filters?

If the bike is running, then the carb inlets are under vacuum and any smoke should get pulled INTO the motor. 

You just did a top-end rebuild, oily fingerprints on the cooling fins or valve cover would totally cause some smoke on the first startup.



Also, please describe the smoke, is just some thin wisps, or is it belching clouds?  Is the smoke white or blue?  Is it drifting up slowly or being blown out under pressure?

mystic_1

[yellowjacket]

Thanks for the reply.  That's why I think it is strange as well too, because I can't understand how it would be coming out of the carbs when they draw air the other way. I need to investigate it a bit more I think.  To describe the smoke, it appears white, in thin wisps, and it does drift up slowly but when I rev the engine a bit it does seem to create more.  I did clean the engine well and there could be some chemical burn off going on.  I am going to check the clearance on the valves start it and watch it closely.  I will report back when I do that.  I am still pretty pumped it started.
Curt