Crankcase vent question.

Thomasa said:

Where does one get an XS650 reed valve? From Yamaha? Aftermarket? Do you have a part number? I've been using a VW Rabbit power brake booster check valve for 20 yrs or so on several bikes. Recently I sent a friend to the NAPA store for one for his Ducati single and he came back empty handed. Perhaps he didn't know how to coax the counterman to look under vintage volkswagen, I don't know. The XS650 valve looks like a better solution anyhow.

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L.A.B. said:

PCV Reed Valve - Crankcase Breather

Color/Finish: Silver Material: Metal Dimensions: Overall Length: 86.50mm Width (at widest point): 28.85mm Engine Inlet OD: 14.15mm Engine Inlet 11.85mm Filter (Air) Outlet OD: 12.00mm Filter (Air) Outlet ID: 9.45mm Fits: Universal Note: Easy Installation (Linked Below)

www.mikesxs.net

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That's where I got mine, but the prices seem to have doubled since I bought mine.

I understand the reed valves connected at or near the bottom of the crankcase and I use them. They do an excellent job of helping to quickly clear a wet sump'ed crankcase and of course keep the pressure out of the crankcase. I can see how those connected near the top of the timing chest or in the breather hose can keep the pressure out of the crankcase, but do they help clear a wet sump? Also, is there any trouble with hoses being blown off them?

The XS650 is a repurposed EGR valve, so look on eBay for motorcycle EGR valve for cheaper ones. I use a Yamaha 125 version.

marshg246 said:

I understand the reed valves connected at or near the bottom of the crankcase and I use them. They do an excellent job of helping to quickly clear a wet sump'ed crankcase and of course keep the pressure out of the crankcase. I can see how those connected near the top of the timing chest or in the breather hose can keep the pressure out of the crankcase, but do they help clear a wet sump? Also, is there any trouble with hoses being blown off them?

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I don't look for mine to empty the sump out. If I leave the bike for more than a couple of weeks, or so, I empty the sump and refill the oil tank. Takes 2 minutes. No problem with hoses. I do flush it through with brake cleaner and blow dry each oil change, in case I get any emulsion blocking the valve, but it's been clear and I may do it every other change in future. Don't really see a downside to it as a simple, cost effective benefit?

Mart UK said:

I don't look for mine to empty the sump out. If I leave the bike for more than a couple of weeks, or so, I empty the sump and refill the oil tank. Takes 2 minutes. No problem with hoses. I do flush it through with brake cleaner and blow dry each oil change, in case I get any emulsion blocking the valve, but it's been clear and I may do it every other change in future. Don't really see a downside to it as a simple, cost effective benefit?

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Ten years ago, I did as you say without a thought. Now, it's out of the question - cannot get down to do it and if I did might not be able to get up.

When I start the bikes with the cNw (Comstock) breather, the sump clears very fast and there's very little likely hood of the main seal blowing out.

I run my Yammy reed valve and breather hose into a catch bottle and vent the catch bottle the reed valve is connected on the outlet from the top of the timing case and the hose straight into the large catch bottle, I don't run it up to the oil tank at all, if my bike wet sumps I just drain the crank case, I been running this set up for 13 years and have had no problem, I have run my breather hose into a catch bottle for 40 years now and have never had much oil in the bottom of the bottle in all those years, my Norton has only wet sump 3 times in all the 46 years of ownership when it was a everyday rider (most of its life) it didn't wet sump but now its semi retired and not ridden every day, but only wet sumps if I leave it for 4 months or more.

Ashley

Motown1 said:

You will receive many more educated answers than mine as for oil level in the crank case. My bike sumps pretty good and still has great oil pressure and return. The oil will just sit in the case and keep your bottom end and cam properly lubricated. If you have to much down there and start it, you have a good chance of oil coming out the crank seal and filling your primary case up. If it’s sits for a long time and your level is low you can drain the case some and put back into your tank.

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Others will chime in soon.

marshg246 said:

I understand the reed valves connected at or near the bottom of the crankcase and I use them. They do an excellent job of helping to quickly clear a wet sump'ed crankcase and of course keep the pressure out of the crankcase. I can see how those connected near the top of the timing chest or in the breather hose can keep the pressure out of the crankcase, but do they help clear a wet sump? Also, is there any trouble with hoses being blown off them?

Click to expand...

marshg246 said:

I understand the reed valves connected at or near the bottom of the crankcase and I use them. They do an excellent job of helping to quickly clear a wet sump'ed crankcase and of course keep the pressure out of the crankcase. I can see how those connected near the top of the timing chest or in the breather hose can keep the pressure out of the crankcase, but do they help clear a wet sump? Also, is there any trouble with hoses being blown off them?

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With a reed valve breather exhausting from the top of the timing case, the only way excess pressure can momentarily build up in a wet sump situation is if the piston skirts contact the excess oil in the case. That can cause blown seals. Under most conditions a negative pressure will ensue after a few revolutions of the crank.

My bike doesn't wet sump drastically but after a week or more of sitting idle, several ounces of oil will have drained into the sump. The reed valve breather keeps crankcase pressure negative until the scavenge pump returns the excess oil to the tank.

No blown hoses or any signs of engine oil leakage.