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Jul 10, 2007
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I am doing a 71 rebuild more of a restomod. I split the cases and drilled holes for the late model breather.
I own a Yamaha Warrior 1700cc on which I am running a 'krankvent'. It works similar to a PCV but does not rely on engine vacuum to seal. I had a new MAP done for my PClll on the dyno and this valve made a 4hp differance. I was considering one of these for my Commando just to help cure oil leaks as this valve creats a slight vacuum on the upstroke. These krankvents are pricey but they work better than a pcv. I just don't want to create more problems than I solve. I know some have tried the pcv with mixed results.
What should I do with the old timed vent that comes off the end of camshaft? Plug it or connect it back up.
I run them. They allow good venting without a huge hose normally necessary with other systems. Put them in and forget them they always work.
Hi there , is there any difference with the 650 XS Yamaha, I had seen somewhere, and what is the best ? and if where could we get them , because I had allready tried a net search , but there is plenty krankvent proposed; at that time I had allready ordered 3 PCV from XS performance and waiting for them (one for me and two for friends); on a previous post we were talking about BMW boxer's one , but they seem less convenient to adapt than the XS ones. Any comments ?? Pierre
What's inside these? It sounds like a good permanent replacement for the $5 brake booster valve. Can you take these apart to clean them?
Are you using the 3/8" unit or the 1/2" unit.
Ron , the first pair I got through Vintage Rebuilds AKA Kenney Dreer these were 70 bucks a KVS crank vent year 2000. Made for HD's about 7/8 diameter 3/8 hose barbs both ends. Put it close to the motor run the line to the oil tank. Worked well for me. Later A friend bought one and read Krank vents directions routing was to the air cleaner still work kind of loud at idle. this type doesn't come apart. Can be washed using solvents. About a year ago I was doing a BSA and used this one : do a search on eBay about 80.00 case is a light press, fit 3/8 hose barbs, body is larger could go were the brake booster one goes up near the oil tank. Ron, I emailed a paint question to ya did you get it? Used you work address.
Thanks for the info. I did some searching on the 'net and found the ET performance (I think this is what you got from Dreer) has what appears to be a reed valve where the Hayden one uses an "umbrella" type. From what I know about these things, the big problem is them being able to respond to quickly and survive the oil mist. In this respect I believe the reed valve would have the advantage. Any input on any problems with function on either unit?

However, the ET unit appears to be a little pricey at $115 from the HD aftermarket suppliers.

Why would putting it close to the motor make a difference? If anything I would think putting it close to the tank might minimize the collection of oil in the valve and lessen cleaning cycles? The crankcase should see the same amount of vacuum regardless of where the valve is.

I didn't get your e-mail here at work. They have stepped up the spam and junk mail filters and often non-work related items get stripped. Try resending it to rleisner @ cinci. rr. com. (Remove the spaces I intentionally added).


I bought my krankvent at Hellriser Customs. I think it was $68. They are more reliable than a $3 PCV valve that requires engine vacuum to seal. I have never heard of a anyone on the RS Warrior site who has ever had one fail. Most people run a seperate line out the rear of the bike. I put a small K&N filter on mine and wrapped it with several layers of paper towels that stay in place with wire ties. I get very little oil blow back and have only changed the paper towel once.
Jim Wood, that looks right and it's a good price see it here.
Hey Ron L. Kenny Dreer told me close to the motor. I don't know why. If forced to guess I would say that the shortest line to maintain a vacuum in is best. Mine has never blown any oil at all. No question it works just open the oil tank while it idles. The take off is a 3/8 90degree fitting tapped into the back of the timing side case at the site of the future E-start. Not a lot of oil handy right there up that high.
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