white smoke coming from 02 sensor area on exhaust pipe

[sf_guy]

hi. I just changed the head gasket on my downtown 300. Engine starts fine but after reaching working temperature, wisp of white smoke start coming out of 02 sensor area in exhaust pipe (if you take off the seat bucket). First in small amounts then getting greater. Also noticed that the radiator fan does not turn on. My bike has 18k mi. Also, my valve cover gasket has a small oil leak. Can this be the culprit?

[sf_guy]

Btw, it's a 2012 I bought used last August. I was trying to fix a small leak on valve cover gasket but upon returning the cover, I overtorqued one of the bolts and it broke into two and got stuck on the cylinder head. I had to get the cylinder head out to extract the bolt so that's why I changed the head gasket. Also, what is the cube thing about 3in x 3in x 3in that's connected to the radiator fan? Help will be appreciated

[scooterfan]

I don’t have a Downtown 300, but white smoke coming from any given water cooled engine usually means cooling liquid is leaking into the combustion chamber.

If the white smoke is coming from the outlet of the Exhaust pipe, you might be sitting with a warped or cracked cylinder head.

If the cylinder head has enough “meat”, you should be able to install a bigger bolt by re-tappping the hole , or installing a Helicoil, and using the original bolt.

[sf_guy]

thanks. Do u think those gasket sealers that you pour on the radiator will work for a warped cylinder head?

[scooterfan]

thanks. Do u think those gasket sealers that you pour on the radiator will work for a warped cylinder head?

I know about sealer products for cracked cylinder heads on the market, but I do not know whether it really works.
Maybe somebody else would have better knowledge about these sealers.

[CROSSBOLT]

The cube thing on the fan is an EMI filter (Electro Magnetic Interference filter). These things fail open circuit and the fan will never turn on. The connector scheme on my side by side allowed disconnecting the filter and the plugs mated inti each other, bypassing the filter. My sxs has been runnig well without the filter for over a year.

[scooterfan]

The cube thing on the fan is an EMI filter (Electro Magnetic Interference filter). These things fail open circuit and the fan will never turn on.

Is this a common problem on these models ?

Sorry about asking this question. I am hoping to buy one of these models in future and it sounds like in this case the EMI filter probably got faulty, caused engine overheating problems - and therefore the blown head gasket ?

[sf_guy]

thanks. I tested the radiator fan by connecting it directly to a battery and it was working. Then I tested it with the cube thing, even though not knowing what it was then, and the fan wasn't turning. I was afraid I broke something.

In my case, my coolant leak I guess was the result of maybe me not doing the head gasket reaplacement correctly or also maybe that I did the coolant replacement wrong (as a friend told me).
I should've joined this forum way earlier 

[CROSSBOLT]

Is this a common problem on these models ?

Sorry about asking this question. I am hoping to buy one of these models in future and it sounds like in this case the EMI filter probably got faulty, caused engine overheating problems - and therefore the blown head gasket ?

Not in my limited experience. Not had any fan problem in two DT300i, one Yager 200i and one People GTi300. Just one failure in an UXV500i.

[sf_guy]

Thanks guys for the replies. Here are more details about my situation:

At first, I didn't replace the head gasket after successfully extracting the bolt and returning the cylinder head (newbie diy mechanic here). I also didn't torque to specs the cylinder head nuts. Then I took it out for a test ride. It was running fine and I was monitoring the temp gauge and it was fine. A few feet from our garage door on my return (after about 10 min test run), the rpm suddenly went up a little bit without me twisting the throttle (idle is 1.8, it went to about 2.5-3). Then I took a look at the dashboard and the temp was full and flashing. And some white smoke came from engine area.
   So, after some research, I decided to replace the head gasket and took out the cylinder head again. I checked the flatness of the head before putting it back (though I didnt use a feeler gauge, just a steel ruler). I also torqued the head nuts this time to specs. Then I tested it but this time I didn't go out (just stationary at garage). And now, back to present time. I wonder if I cracked the engine that first time I test rode it.

[scooterfan]

Thanks guys for the replies. Here are more details about my situation:

At first, I didn't replace the head gasket after successfully extracting the bolt and returning the cylinder head (newbie diy mechanic here). I also didn't torque to specs the cylinder head nuts. Then I took it out for a test ride. It was running fine and I was monitoring the temp gauge and it was fine. A few feet from our garage door on my return (after about 10 min test run), the rpm suddenly went up a little bit without me twisting the throttle (idle is 1.8, it went to about 2.5-3). Then I took a look at the dashboard and the temp was full and flashing. And some white smoke came from engine area.
   So, after some research, I decided to replace the head gasket and took out the cylinder head again. I checked the flatness of the head before putting it back (though I didnt use a feeler gauge, just a steel ruler). I also torqued the head nuts this time to specs. Then I tested it but this time I didn't go out (just stationary at garage). And now, back to present time. I wonder if I cracked the engine that first time I test rode it.

The only way to know whether you really have a cylinder head crack is to do a proper inspection on the cylinder head.
If the crack is quite big, you should be able to see a crack with the bare eye. Or you can use a magnifying glass to look for cracks. Just turn the cylinder head upside down, remove the Valves, clean the surface properly, and concentrate on looking at :
 - The areas between the water channels and the outer edges of the valve seats.
 - The area between the two valve seats.

That's normally the areas where cracks occur.

The best way to look for cylinder head cracks is actually to use a marking spray or "dye". You just need to clean the cylinder head properly, spray the dye on the complete surface, and wipe the dye off with a clean cloth. If there is any cracks, even the smallest of cracks will be visible.
In our country these dye's come in kits - which include a pre-cleaning product, as well as instructions how to use the kit.

Again, you will never know whether the cylinder head indeed has a crack - unless it's been checked properly.

[sf_guy]

Sorry I should've said , 'I wonder if I damaged the engine during that test drive when I first took out the cylinder head'. But that sounds like a good diagnostic procedure for a cracked engine, mr. scooterfan.  Anyway, that was the first time the temp went full bars and flashing since I bought it last August (though I've only put maybe just around 60 mi since that time). I wonder if that instance that the idle went up suddenly by itself (to around 3k rpm) at the same time the temp gauge went flashing after my test ride meant that maybe I warped/ damaged/etc. the engine. It must've been like 2-3 secs. that the rpm went slightly up before I realized that  the temp gauge was full/ flashing.