Yikes.....white smoke from breather....

[blackbetty]

Strangely enough I wasn't able to find much on this problem using search function...

So I've been getting my bike tuned and working on ironing out a few wrinkles.

I got it running decently and have been cruising around; the other day I rode about 5 miles, stopped, then rode another 2-3. When I parked I noticed the breather was puffing white smoke/ as the bike was idling....it was almost vapor like

I have another thread regarding my carb tuning woes. I'm fairly certain I have a few leaky valve seals. But when I stopped I noticed the white smoke puffin out the breather at a steady rate. Killed the motor and checked the oil and it wasn't smoking like it was at the breather. The motor wasn't very hot. I let it cool down and then got it back home. It started and drove fine.

I drained the oil and there wasn't fuel in it and it was at capacity, pulled the plugs and they're black, so indicating lean or preignition, and I peered into the cylinders to see healthy piston tops, albeit a bit of oil. I've only out about 30 miles on the bike since I finished the rebuild.

When I got the sidescreen off there was an accumulation of grit that felt like clutch material (bike has new new clutch discs). I haven't pulled the sump yet. I've been advised that my culprit is most likely the headgasket pulling oil from the cam chain tunnel, but what other reason could there be for smoke to be coming out of the breather at temp? Blow by?

I should mention that it seems more like vapor than smoke.....after I got it home I looked at the breather and it's almost like it was misting raw fuel....smelled like exhaust. But it's definitly not putting out any oil.


EDIT: I've read on a few Honda forums that this could simply be water vapor.....any thoughts? Was hoping to ride out the season before I do any head/piston work.

 

[littlebill31]

What's it smell like?

 

[blackbetty]

It's weird, it doesn't smell like burning.....

When I got home it kinda smelled like exhaust, very gassy smelling, but by that point it wasn't really smoking, it was more of a mist, but not oil.

I was planning on clearing the sump and then putting oil back in, new plugs, and just running it to see if that does anything. Everything else is adjusted and in spec.

 

[littlebill31]

Hmmm. Mine does that every so often. Like a little white smoke. Similar to breathing in cold weather. But just a little.
I wonder if it's just some exhaust blow by. Just not getting all of it out.

 

[Gordon]

On your rebuild, did you do new piston's, ring's, and a valve job? If yes, what your seeing is probably blow-by because the ring's haven't seated yet. And yes, water will accumulate from moisture in the air (humidity?) . That would be considered normal for about 500 miles, with it getting less and less, as the ring's seat.

 

[blackbetty]

Well I haven't pulled the head or jugs yet since there was evidence of a prior rebuild on the bike, with the exception of a bad left cylinder exhaust valve seal. I just wanted to get it running in decent order to ride until winter comes before I yank the engine to rebuild.

I kept trying to conceive a possible explanation, but pulling the dipstick it didn't seem like temperatures were out of range....so I was initially thinking, maybe too hard on a new clutch? Bike was running and driving strong, I simply noticed it when I bent down to kill the motor.

It was hot out, must have been 85* that day I noticed it, and I was hammering on her pretty good, put certainly not driving the bike too hard.

 

[XSLeo]

Any moisture in the oil, engine blow by, condensation, starts to boil out of the oil at about 200 degrees, This is probably what you saw. It takes about 20 miles to get the engine fully warmed up and boil out this moisture.
If your burning oil, you will see it in the exhaust. Any one riding behind you will see and smell it.
The raw fuel smell may mean your float level is high or the float valves are leaking.
Black on the plugs does not mean lean or preignition. Lean is very white insulator and preignition is metal specs on the insulator.
Black, dry fluffy is rich, black wet and oily feeling is oil burning.
I would pull the carbs, pull the float bowls and remove the floats. Take a q-tip, pull off the cotton and wrap with 4-0 steel wool and use this steel wool q-tip to clean the valve seat in the carb body. Look very closly at the valve needle, even a tiny groove can cause a leak. replace any bad parts.
With good float valves, reinstall the floats and set to spec. Be precise, both sides of the floats must be to spec.
Bech test the float valves by hooking up a test tank to supply fuel to the carbs. I have a gas tank off a riding lawn mower with a shut off and filter inline. Hook the test tank to your carbs, With the float bowls off turn on the gas while gently holding the float up. Lower them till fuel flows, lift them up, does the fuel stop flowing? Check both carbs. Do both floats stop the fuel flow?
Now if the float setting is right and you know they stop the fuel flow put the bowls on and put them back on the bike.
Now with the mix screws set to spec for your carbs the plugs should be a very light tan or off white.
Good luck.
Leo

 

[aussiejohno]

Hi guys I am having the same problem but it is only coming out the left breather hole. I have had a rebuild too with brand new vm34mm minuki carbs. it is running really well, but I haven't had it on a dyno yet I as this a tuning problem?

 

[XSLeo]

The same applies. They tried several thing with the breather. One was it had two outlets with one plugged off. If yours is one of these then it can only blow out one side.
Running a hose from the breather to down below and to one side of the engine is a good idea. with the breather open out side air and any crap In the air can get sucked back in. A long hose will stop this.
Adding a Dorman #80190 power brake check valve in the hose close to the engine with a 3/8 hose on it's outlet that goes down below the engine is a good idea. this check valve lets the air inside the engine get pushed out but won't let out side air return. This creates a small vacuum inside the engine. This can help slow or prevent oil leaks. It also lets the rings seal to the cylinder walls better.
Leo

 

[aussiejohno]

Thanks Leo once again a wealth of information. I will do that.

 

[Gordon]

Hi Leo,
As leo stated, the only white smoke can be condensation. The check valve along with a small cone filter on the end is the best remidy for this situation. The filter is not really a nessisity, but it is a kind of added insure that nothing will get back up into the engine. Road dust can get a long way up that hose, and the filter does prevent that from happening. Just my 2cent's worth.

 

[chopit25]

My 73 has two outlets with long hoses on them. Would I need two check valves and two filters to set mine up right?

 

[Gordon]

You could do that, or get a vacuum 'T' and put the 2 hoses' together. Then run one hose down with the check valve at the top and filter at the other end.