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Post by zummerp on Feb 25, 2018 19:20:28 GMT -5
I recently noticed that the valve on top of my valve cover is not actually connected to anything. I’m assuming it is supposed to have a rubber hose, but what should it connect to?  |
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Post by FrankenMech on Feb 26, 2018 2:55:51 GMT -5
The hose usually connects to a stock airbox. It is just a crankcase vent line, no valve. Put a hose on it and run it out the back of the scoot if you don't have a stock airbox. Some people run it to a fuel filter or a 'puke can' but neither of those are necessary.
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Post by dexameth on Mar 1, 2018 16:52:59 GMT -5
FrankenMech is correct. It's merely your positive crankcase pressure relief. If you don't put anything on it, hot "fumes" will come out after a long ride when everything gets all hot and bothered inside, and you will have oil residue all over then scoot. I did EXACTLY what he stated, ran a fuel line from the nipple on the head cover and up my frame all the way to the back with a tiny breather filter on the end. If I run WOT for a few miles and stop, the filter will be "steaming".
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Post by FrankenMech on Mar 2, 2018 13:19:08 GMT -5
Back in the early days, before the invention of PCV valves, they called the vent system a 'road draft tube' and it left oily dirt residue all over the underside of the vehicle.
When an engine operates there is some leakage, or 'blowby', past the rings which consists of hydrocarbons and steam. This must be vented or drawn back into the combustion chamber or pressure will build in the crankcase and blow out the seals.
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Post by jackrides on Mar 2, 2018 13:31:15 GMT -5
Into the airbox reduces pollution with a Very small power loss. Has anybody ever measured the difference on a dyno?
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Post by GrumpyUnk on Mar 4, 2018 0:58:51 GMT -5
Power loss? I dunno, you are adding some hydrocarbons. They should get burned and add some BTU to the fire.
My concern with crankcase vent would be vaporized or liquid oil getting pumped out the vent tube. A long hose of decent diameter would tend to catch any liquid and allow it to condense and flow back to the sump. A catch can would do a similar task. I dunno how much of a 'maze' or 'labyrinth' would be needed to condense any oil vapor or catch droplets and keep them attracted so they could flow back to the sump. Maybe nothing. If you note deposits of oily smear in the intake or where ever the crankcase is vented, a maze would help, otherwise, I would not bother.
tom
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Post by FrankenMech on Mar 4, 2018 3:13:20 GMT -5
Massive amounts of blowby usually mean the rings are shot, or the cylinder is scored, or there is a hole in the piston or head.
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