leaking gas tank - fixed

[Lee Dodge]

Some thoughts -miscellaneous ramblings-on PCVs.   The valve is merely a low pressure differential check valve.  As such the direction of "open" flow depends upon how it is installed, for example; spring end away from c'case and it will allow flow out of the c'case (relieving the c'case pressure of decreasing volume from a descending piston and carrying with it oil vapor at the least) in this mode there will be no allowance for any oil to drain back or -and maybe more import rant- it will not allow air to refill the c'case as the piston rises causing a significant vacuum in the c'case.  A vacuum in the c'case causes 2 things; !. a mechanism that would help oil to move past the oil ring into the c'case. 2. a pumping loss- loss of torque- due to the vacuum tending to want the piston to stay down.  (There's also a pumping loss when the piston comes down related to the inability of the c'case ventilation system to let air out quickly that also subtracts from torque.) Install the valve 'spring down i.e. on the c'case side and you reverse everything but with the significant difference in the fact that the c'case pressure cannot be kept from increasing since any ring blow by is trapped and can't get out the breather.  Big Bad-not a choice. So, is it worth while to install a PCV? Your choice.  I won't be Something else to note: Crankcase pressure is independent of RPM or throttle position the c'case atmosphere doesn't care what's happening on the other side of the piston save some blow by consideration The best answer from a design standpoint is to allow c'case air to move freely in and out of the c'case (low pumping losses= more torque) while keeping the velocity down (large pathways and/or/both large c'case volume) so oil is not so easily carried along.  Then the design would have a method of capturing the oil vapor, before it fouled the air cleaner, letting it gather into drops and flow back to the c'case.  The old thumper is in a class by itself - it tries to move it's displacement on every stroke.  Some motors have no change in c'case volume as in 180 deg twins(with common c'cases), boxers, and I think all 'V' motors. For what it's worth, Lee

--- On [b]Wed, 4/28/10, Jeff Saline [i][/i][/b] wrote: From: Jeff Saline Subject: [DSN_KLR650] PVC Mod To: DSN_klr650@yahoogroups.com Date: Wednesday, April 28, 2010, 6:19 PM   Listers, Here's a thread on another list about the PVC mod. http://www.klr650. net/forums/ showthread. php?t=41326 I haven't waded it through it and probably won't. I don't have personal experience with the PVC mod. I've heard reports saying it's the best thing going and also that it didn't work. Good luck making your own decision. Best, Jeff Saline ABC # 4412 South Dakota Airmarshal Airheads Beemer Club www.airheads. org The Beautiful Black Hills of South Dakota 75 R90/6, 03 KLR650, 79 R100RT . ____________ _________ _________ _________ _________ _________ _ Penny Stock Jumping 2000% Sign up to the #1 voted penny stock newsletter for free today! http://thirdpartyof fers.juno. com/TGL3141/ 4bd8deebef37e2fc fam07vuc

[mark ward]

[Darren Clark]

Attachments : First, thanks to all who replied with suggestions. I took the weld it route to fix the tank. Once the gas was drained, I wire wheeled the paint off the area where the gas was leaking, and once it was clean I was able to see where the tank shell was split. The seam that joins the top shell with the lower shell worked apart. After looking it over I took off the gas cap and valve and let the tank sit for a week (I had to go out of town for a week, so a week should be enough for the tank to dry out). Someone suggested that I put dry ice in the tank before welding or braising it, excellent idea, the CO2 coming off the dry ice displaces the oxygen in the tank, and without oxygen, gas won't ignite. Plus I didn't have a mess from putting water in the tank. I had to pick up some smaller wire for my MIG welder, I usually use 0.035" wire for my projects and repairs, but that would easily blow through this sheet metal. So I went with the smallest I could find, 0.023". After 20 seconds with the welder and a quick pressure test with some ATF in the tank, it was fixed. I still want to put a coating in the tank, and after looking at the procedures for the suggested treatments I think I'll use Red-Kote. But that will have to wait till the winter now. -- Darren Clark http://www.flickr.com/photos/84373829@N00/ 2004 KLR-650 Fowlerville, MI