Smoke from carbs?

Hello Gentlemen,


I'm fairly new to the forum and just recently purchase a '71 Roadster. This is my first post and I was hoping to get your opinions on a little issue I ran across after doing my first modification.


I removed the stock cam breather setup and mounted the reed valve type crankcase breather from MikesXS to the crankcase blanking plate. I used clear 3/8 fuel line on the new breather setup and condensation was visible in the line shortly after startup. The ambient temperature was 57°F and the bike had been sitting for about three weeks. Not surprising this turned milky in the breather line as the oil mixed with the condensation. When the bike is idling gravity is keeping the milky oil from getting pushed into the oil tank but not sure if this is the case while riding down the road at higher RPM's. If I put my finger over the breather inlet inside the oil tank when I remove my finger it will spit a little bit of the milky oil into the tank. I'm assuming this condensation buildup is normal and if it makes its way into the oil tank it floats on the top until it evaporates?


After the new breather setup was installed I took the bike for a test ride for approximately six miles and stopped at a convenient store to inspect the bike. I noticed white smoke coming from what I initially thought was under the seat from possibly the oil tank assuming condensation was getting in the oil and maybe boiling in the oil tank. I didn't notice any smoke coming out of the oil tank vent line. When I turned the bike off there was still smoke coming out from under the seat. I forgot my seat key and couldn't inspect the oil tank at that time. I let the bike cool down for about 45 minutes while searching the forum for possible causes when I came across this post. https://www.accessnorton.com/Norton...lls-out-rom-the-carburetors-air-filter.20623/ . This led me to believe it may have been coming from the K&N air filter/Amal carburetors. I rode back home approximately four miles being very cautious. When I get home I turn the bike off immediately and inspect the oil tank. Nothing out of the ordinary. Started the bike and let it idle and could not get the bike to smoke again. If it was boiling condensation in the tank would I get that much smoke coming from the oil tank? Or if it was coming from the carburetors is this "stand-off" common on the Commando's?


Thanks,


Bruce

All are possibilities, you best go for a run and either get someone to follow and shout when they see smoke vapour or you leave the bike running and look to see where its coming from, only way to be definitive.

this can not properly vent the crank case unless you have removed the timing cover and cross drilled into the crank case. this is something that should only be done with the cases split.. go beck to the timed vent or a better option is to purchase the sump vent from jim comstock known as comnoz on here.

Moto Militant said:

Hello Gentlemen,


I'm fairly new to the forum and just recently purchase a '71 Roadster. This is my

I removed the stock cam breather setup and mounted the reed valve type crankcase breather from MikesXS to the crankcase blanking plate.


Thanks,


Bruce

Click to expand...

I venture to say that you have answered your own question. I don't use my motorcycles unless I know I'll be running them for at least 20 minutes after they reach operating temp, and this is when the ambient temp is between high 60s and high 80s.

I once accidentally set my ign timing very retarded, I got smoke out the carbs then...

Even flames I bet...

"smoke on the norrrton and fire in the sky"
Sorry! I'll get me coat