Logo
FULL SITE MENU

BF20 2 hp oil in exhaust

M

mr_neutron

New member
"I have a Honda BF20 (2hp&

"I have a Honda BF20 (2hp) that starts and runs well. At any speed much above idle, it blows oil out of the exhaust. This worsens as speed/compression increases.

I posted this problem here last year and someone reccommneded that I replace the fuel pump. I finally purchased a service manual to help with the job and discovered that this doesn't appear to have a fuel pump. I may be misreading this but certainly don't see a fuel pump anywhere in the manual.

I suspect that I simply have a bad gasket somewhere. Can anyone reccommend which are the most likely culprits? Thanks in advance."
 
I would start with a compressi

I would start with a compression check and a leak down test.

A 4 stroke blowing oil out the exhaust could be an indication that the oil is "blowing by" the piston rings...
 
I would expect to see a puff o

I would expect to see a puff of blue smoke when starting and running from the oil bypassing the rings into the combustion chamber and exiting through the exhaust?
 
"Thanks for the feedback. It d

"Thanks for the feedback. It does smoke a bit but not as much as I'd expect if there was a significant amount blowing by the rings.

As an aside, though old, this unit has less than 5hrs on it. Does this decrease the likelyhood of the rings being bad?

I'll start with the compression and leak down."
 
"Decrease the likelyhood? Mayb

"Decrease the likelyhood? Maybe.

Agree 5 hours is practically no time, but is the motor 5 months old or 5 years old.

Motors have a nasty habit of self destructing when they sit "unused" - they just don't like it - rust or other "cooties" can take hold...

Do the two tests - the leakdown in particular will quickly eliminate the rings as a cause (or alternately, prove they are the issue)..."
 
It's about 15 to 20 years

It's about 15 to 20 years old. Sat un-used in my inlaw's garage all that time. I'm amazed it runs as well as it does.

Thanks again for the advice. I feel like I'm on the right track at least.
 
"If it sat unused for 15 to 20

"If it sat unused for 15 to 20 years, it will most likely have rust on the cylinder wall preventing the rings from sealing. Run it, & it should improve. Monitor the oil consumption.
If OK, change the oil.
If not, overhaul it."
 
"Another possibility.
During

"Another possibility.
During the time in storage, if it has been on it's side, the sump oil can leak past the rings & through an open exhaust valve & into the exhaust manifold/silencer. Now being blown out by the exhaust. Keeping in mind that one drop of oil on water spreads & appears more like a spoonful.
This would explain the lack of excessive smoke."
 
"I've run two full tanks o

"I've run two full tanks of gas through the motor. The oil forms globs that end up on the ground. The amount of oil coming out doesn't appear to change over time. In this possible scenario, I'm assuming that the problem would improve as the engine runs, correct?"
 
"Neut, just a thought maybe th

"Neut, just a thought maybe the engine is running a little rich and the unburnt fuel is washing the carbon off the walls of the exhaust system and running out.

Check the spark plug if it is burning that much oil the plug will be foulled up with carbon. If it looks dry slight brown colour you are burning oil."
 
Back
Top