Crankcase Venting

[90GTVert]

If you are still using a stock airbox, this should be unnecessary. Once you switch to an open filter, you are left with a hose coming from the vavle cover's vent that has nowhere to go. Plugging the vent off is not an option, because the pressures inside the crankcase need a way to escape. If left open you may end up with oil coming out of it and ending up coating everything around it. That makes for a mess and can be dangerous if near the rear tire. An oil catch can or other form of ventilation system can easily cure this problem though.

When I first isntalled a hose 14-16 inches long and small air filter to my valve cover vent, I didn't get too much oil leaking out. Then the hose ripped and I just cut it shorter (8-9") and put the filter back on. After that, I got a lot of leakage. I decided to try a longer hose. I ran a hose 2 1/2' or so and then put the filter on the end. I think 2 1/2' is a bit overkill, but hose is fairly cheap and it's not in the way. It's very simple and it is working well for me.

Choose a tubing or hose that is safe for use with hot oil and appropriately sized to fit your filter and vent barb. Local autoparts stores should have plenty of choices. When running the hose, make sure to keep it away from anything that can pinch, burn, or cut it. Secure the hose with plenty of zip ties, clamps, or whatever works best for your needs, but be sure not to pinch it off. I feel it works best heading uphill. That way if oil is sent up into the line, gravity should return it to the engine.







The filter I used can be found at lots of auto parts stores at a reasonable price. I beleive it was made by Spectre. I used a short length of aluminum brake line tubing to securely attach the filter to the hose. I zip tied the filter into place on a support. Always test fit panels and the seat to be sure there is no contact or pinching.





Another option is to buy or make an oil catch can. The catch can allows ventilation as well as catching oil overflow from the valve cover's crankcase vent. It may need to be drained periodically. Here's a diagram of all that's involved in a simple crankcase breather/oil catch can. You can search google and find ready made catch cans to use or to give you more ideas to build your own. Again, be sure that you use a material suitable for hot engine oil.



Some people choose to handle this task very simply and just route the PCV hose into a soda can or pill bottle to catch the oil.

[usmcdoc]

Easy..cheap..and effective oil catch can...
Cheapest fix..AND works the best.. Cost is 2 bux! This what I did until I fixed the blow by issue. Take a $2.00 8 oz.Hamster water bottle from wal mart..bore a hole in the bottle bottom to allow gases to vent.. Fill bottle with steel wool..but DO NOT pack it in tight or the air will not flow. Pop out the check ball in the tube at the bottom or saw the tip off to remove it. Use NO CHECK VALVE or it will prevent oil back flow into engine. The steel wool acts to catch the oil..cool it and hold it in the bottle..so at idle..low speeds or when shut off..the pressure being lower..the oil will drain back into engine. The vent hole on the bottles bottom allows built up gases to pass through. Run just a hose from the valve cover vent to the nipple on the bottle and attach it up on the frame above engine level..about seat height.with Zip Ties. Now your blow gas escapes the hole in the bottle and the oil is trapped in the bottle then recycled.. Looks too easy huh? Well on the old scootdawg site I posted this...many many tried it..it worked and they ridded themselves of the problem without some expensive oil catch can and check valve.. Here is a pick below.

Mar 2, 2014 13:52:00 GMT -5 FrankenMech said:

From my own experience I would suggest using copper scrub pads that have been well cleaned with solvent and blown out to fill the bottle. The steel wool will crumble and release steel particles into the oil.

Mar 2, 2014 14:08:43 GMT -5 thephranc said:

You can use stainless wool and a layer of coarse on the bottom with a layer of fine on top works best.

[90GTVert]

When swapping to a pod filter, I considered cutting the front section of my 150's airbox off. That's the section of the airbox where crankcase gases are vented in stock form. Then nothing would really have to change from stock. The 150s usually need an adapter of some sort to fit a pod filter, so it could be tapped for a hose fitting and connected to the airbox. I didn't want to cut up the airbox and didn't necessarily want to route crankcase gases back through the engine, so I took another route.



Here's an example of a simple adapter for a 125-150cc GY6 using a pod filter. It's a piece of a radiator hose (actually a couple in this case) with PVC pipe to give the filter something to clamp to. It wouldn't be difficult to tap the PVC pipe and install a hose barb if you wanted to route crankcase gases back through the engine.






I made a little sort of catch can out of PVC pipe and caps, a couple of NPT hose barbs, and a small automotive breather filter. You can usually find these little filters in auto parts store or they sell cheap on eBay and amazon.



The canister itself is just a short section of PVC with pipe caps glued on. I wasn't looking for any specific volume, just something that may ake it more difficult for oil to escape from one side through the other. PVC should be durable for this purpose and it's pretty cheap and easy to find. You could get creative and build something similar in many ways though. If you want more info on building little PVC canisters, there's some HERE.

I started out by drilling a hole near the edge on one end. Using pipe caps, you can't go right to the edge you you will end up cutting into the PVC pipe. Then I tapped the hole to accept the NPT hose barb and installed the barb with a bit of teflon tape.







I repeated the process on the opposite end. I positioned the second hole across from where the first hole was. This way it would be the least direct path through the canister that I could easily make.



Then I clamped the breather filter on one end.



The opposite end was connected to the valve cover vent and the canister was secured to the frame.




So far, so good. I haven't seen any oil residue at all around the filter.

[90GTVert]

Dec 31, 2015 13:53:09 GMT -5 Fox said:

Crankcase vent.



Better to buy some fuel line and route that hose up the frame and into the atmosphere. The crank vent allows aq pathway for the pressure that builds up inside the engine to escape. It spews out hot, oily, dirty, watery crap that will make your air filter dirty as hell in no time. Rerouting that hose with an uphill slope will keep the oil in the engine where it belongs. The pressure and fumes can still escape.



The yellow line represents hose routing.



Some guys will put a little filter on the end. I don't think it's necessary but that's your call. Here are a few examples: