John, You should have asked me for a spare strainer one as I have a repacement pump assy and gas gauge sender sitting in my garage. Contact me at [EMAIL PROTECTED] if you are interested.
David >From: John Laurenson <[EMAIL PROTECTED]> >Reply-To: GTS-1000 Owners List <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: Quiz Answer >Date: Sat, 22 Jun 2002 08:58:36 -0400 > >The technical term is NPSH (net positive suction head) > >The definition of NPSHA is simple: Static head + surface pressure head - >the >vapor pressure of gasoline - the friction losses in the inlet strainer. > >But to really understand it, you first have to understand a couple of other >concepts: > >* Cavitation is what net positive suction head (NPSH) is all about. The >gasoline boils in the pump inlet. > >* Vapor Pressure of gasoline varies with the fluid's temperature and >elevation. > > >As I was leaving southern British Columbia, it was about 2pm in the >afternoon and the temperature was reaching the low nineties. The >elevations >were in the 5 to 7 thousand foot range and the bike started stalling out >again. It was like some one would turn a switch off and on to the fuel >supply every 10 seconds. Also the problem became worse if I would sit >still >and allow the bike to idle while doing something or stuck in traffic. The >gasoline was heated up by the engine heat and it would start to idle rough >and kill. > >Off to my right was an old farm house surrounded my trees. I pulled the >bike in and knocked on the door. Explained I was having mechanical >problems >and asked if they had a daughter......sorry that is another story...:>) > >The gentleman coming to the door said I was welcome to work on the bike in >his front yard and asked if I would like a cold glass of water. Nice >people. What I found throughout the trip. Actually the farm house was >being rented by a railroad engineer and his family. It was a 200 year old >log cabin that was once a stage coach stop. Interesting history. > >I started pulling off luggage and removing the plastic panels around the >gas >tank. Not a minor job. I felt the problem had to be inside the fuel tank. >Why would it start happening on the way back from the ride and not be a >problem on the way in? Something had to have changed since I wasn't >having >the problem on the way up. > >I removed the fuel pump plate and assembly from the gas tank. > >Let me add, my problem may be slightly unique in that I have a modified gas >tank with an additional nearly 2 gallon capacity. I hold 7.4 gallons. The >tank has been bumped out in all areas and voids under the plastic cover for >long distance riding. I may be picking up some additional engine heat >because of these mods. Some of the problem may have been caused by this >fact, but everything regarding the problem still applies to a stock set up. > >One thing I soon found was that my modified pump assembly was extended down >a few more inches into the deepest section of the tank. The rubber gas >hose >used to extend it was the wrong type of hose. It was gas line hose but its >outside cover was not made to be submerged in gasoline. It had virtually >peeled off and lay at the bottom of the tank under the suction strainer. >The people living at the farm house took me into town to get a new piece of >fuel line. I removed the pieces of hose from the bottom of the tank. > >I pulled off the pump suction strainer, which is a very fine nylon mesh >material covering a plastic frame. I noticed it was visibly showing signs >of being pulled, by the pump suction, in against the plastic support frame. >When I put the strainer to my mouth and tried to blow air through it, it >appeared to be nearly totally blinded. Even though it didn't visually look >dirty. The nylon weave material probably absorbed water and expanded. >Nylon absorbs water. The pump was working against a nearly closed off >suction. I imagine all GTS owners will find this is the same condition of >their gas line strainer on 7 and 8 year old bikes. > >With the pump submerged in the gas tank, NPSH, doesn't become a problem >until the pumps NPSH required is exceeded. This was being caused by the >elevations I was riding at and the high ambient temperatures, casing the >gasoline to become much hotter than normal. Both of which were now allow >the gasoline to boil off between the strainer and pump....vapor lock. > >What had probably happened was the poor quality gasoline I was using in BC >and AK, caused further blinding of the strainer. It is also possible the >fuel water absorbing additive caused the nylon mess to tighten up its >weave. >It got just to that point were the slightest elevation and temperature >change during the ride was now exceeding the minimum NPSH required by the >pump. > >I tried a temporary fix, not having a replacement strainer. I used a >needle >and punched a bunch of holes in the strainer in hopes of allowing more >gasoline to flow to the pump. It only helped marginally. The pump pumps a >rather high flow rate to the injectors and most of the gasoline returns to >the tank unused. I still found I had to stop and top off the tank to over >come the vapor locking while at higher elevations. When it cooled off in >the evening and as I got back down to lower elevations the problem went >away. > >I have a new suction strainer on order. I recommended all GTS owners >replace theirs if they have any plans to ride at higher elevations in the >summer. The gas tank on the GTS is completely covered with plastic and >doesn't cool down as effectively as an exposed metal tank would. Just put >your hand on the gas cap after you have sat in traffic to see what I mean. > >hawke _________________________________________________________________ Join the world�s largest e-mail service with MSN Hotmail. http://www.hotmail.com
