does this need to be connected?

[xadmp]

dunno if this needs to be connected or if its ok

 

[Charles]

Are you referring to the Crankcase vent tube? If so, it doesn't have to be connected, but if you're running stock airboxes, it's supposed to be routed to them (can't remember which side). If you're running pods, just stick a Crankcase filter on there...or leave it venting to atmosphere.

 

[Scorpio1963]

Unless its plugged off your going to have a big vacume leak.By a 12mm filter for it and cap off the other end near the airbox tubes.Or even better yet get rid of those tubes alltogether and go with pod filters.

 

[Specdog]

I would replace the tube and reconnect the vent. If you do nothing, oil will mist and make a mess over time. Don't forget, the tube vents both ways and should have clean unimpeded air movement. On compression stroke there is positive pressure built up in your crankcase (exacerbated with bad rings) so you need the pressure relief via the vent tube. On intake stroke, a negative pressure will occur and air will move into your crankcase. In the old days these crankcase tubes vented into the air. Today we are more environmentally concerned, so this air is vented into the airbox to be used again. Yamaha claims there is actually a benefit in reintroducing this petrochemically charged air into the combustion chamber.

 

[MrStubb]

On older cars and trucks it was called a road draft tube. It vented the internal gasses from the crank case to the atmosphere. These applications usually involved a long tube running down the rear of the engine to a semi sheltered area under the vehicle. In the early 60's many manufacturers installed a filtered breather cap on one or both of the rocker arm covers. It is imperitive for engine life to at least put a filter on this line or route it some how to the air intake system. The possibility of grit being ingested into your crank case is too high to ignore. If you do nothing else at least wrap an old nylon around the end secured with a zip tie. There is also a benefit to re useing the crank case vapors since they contain a small amount of oil. It might help lube the upper cylinders. Long winded history of the road draft tube as I remember and my take on a reasonable alternative.