Ok, so my uncle has been giving me advice on building my streetbob, he is now suggesting a crank case breather kit...his theory is that oil should be differentiated from fuel and air mixture.

I hear that the v-twin is a internal breathing engine, you may need one if you're running on a flat head or possibly an evo engine, but on an '09 v-twin it's a waste of money.

Any thoughts or comments? and if it is a good idea to spring for one, what brand is good as well as the extra parts needed?

If I am wrong my feelings will not be hurt so be as blunt as possible!

 

The stock crankcase breathers sit at the air cleaner housing, most aftermarket air filters have bigger crankcase vents compare to stock. If you are getting an aftermarket air filter housing, I don't see the need of a crankcase breather.

 

Do you mean rather than feeding the head breathers into the air cleaner to take them off somewhere like to the road, a catchcan or a filter?

If so, then it depends on the age of the bike and how much you get out the breathers. If the bike is fairly old and slobbers a bit then you probably don't want that into the carb/throttle-body. If its a newer bike (<20K miles?) then I'd not worry about it.

 

Sorry about not giving spec's,
It's an 09 street bob, 4000 miles, and i have a screaming eagle (circle) air cleaner. the rubber breather hoses coming from the heads puts oil into the throttle body.

is crank case venting good for longevity? (not prone to crack under pressure)
And is the oil ok going into the throttle body?

 

On a new bike like yours its fine. There will be a tiny amount of oil and water vapour going into the throttle body. Not enough to do any harm at all.

The alternative is a breather kit. They do remove that bit of oil and water vapour from the intake but it has to go somewhere.

 

You bike will run fine how it is, however it will run better if you route the hot oily air from the heads to the atmosphere.

All internal combustion engines like cool dry air going into the intake, and the stock set up is EPA compliant by routing that hot oily air into the intake, which reduces performance and can lead to carbon build-up (reduced engine longevity).

 

Sounds like pretty solid information. Any suggestions of makes? i believe drag specialties makes a braided line set up with filter and everything included for $66 on dennis kirk

 

Here ya go- Breather Systems