backfire

[revmaaatin]

List- I thought within the body of this thread, someone posted the type of material and the auto parts store they bought the rubber material to convert the petcock to 'manual'. Seems like it was $1.69 for a 1x12" strip. Did I read that here or some other forum? I thought I copied the data and archived it, apparently not. Any help/memory/link to that material? --thanks. revmaaatin.

--- In DSN_KLR650@yahoogroups.com, "John Biccum" wrote: > > When I was experiencing fuel starvation I was able to confirm the float bowl > was empty, as soon as it filled again the bike ran great until I ran the > bowl dry again. I didn't notice any correlation to altitude or > temperature. But all of my jetting work was performed at close to sea level > in Seattle when the weather was. typical Seattle weather, drizzling and not > so warm. > > > > The symptoms you describe *do* sound like vapor lock, a condition when the > gasoline is vaporized where it should still be in the liquid form. Ethanol > is more volatile than gasoline so 10% ethanol-90% gasoline is going to be > more likely to vapor lock than pure gasoline. > > > > But one of your comments is telling: "Sam's bike was running just fine on > the same conditions". What was different between your bike and his? Why > wouldn't Sam's bike be experiencing vapor lock as well? > > > > Perhaps the petcock diaphragm was marginal on your bike and no so marginal > on his. The high temps would exacerbate any pinholes in the thin rubber > material that makes up the diaphragm since rubber become more flexible at > elevated temperatures. If the diaphragm was just barely able to keep up > with the engine's demands for the fuel in the float bowl, you would see fuel > starvation symptoms that would mimic those of vapor lock in that in both > cases the engine would starved for fuel. > > > > Here is how I would test the diaphragm: > > > > I'd use a vacuum pump with a vacuum gage (e.g. a Mity Vac, used for bleeding > brakes) on the carb end of the vacuum hose serving the petcock. It should > hold vacuum and not leak down. If it does leak down the diaphragm is not > vacuum tight. > > > > After operating the bike for a while I'd stop the bike and pull the carb end > of the vacuum hose serving the petcock off the carb and see if it has liquid > gasoline or gas vapors in in. It should have neither, but if it does > gasoline is leaking down the hose into the carb meaning the diaphragm in not > vacuum tight. > > > > I am not fond of parts switching as a diagnostic measure. But vacuum > petcocks are a bit of automation that should not be necessary with a bit of > operator discipline (e.g. FINE-C), I always wondered if it was the > engineering department or the loss prevention department that invented them > J. I think that even those vacuum petcocks that have not failed are > destined to do so and mostly likely at the most inopportune time. So why > not just convert it to full manual operation with a rectangle of > nitrile-rubber (e.g. BUNA-N) and four Allen head cap screws? As I recall > someone (Krokko?) used to sell an inexpensive kit that was just that. Or > go for the Rhino petcock or similar? > > > > BTW I agree that your radiator sounds fine and is not likely to be the > problem. > > > > > > > > > > > > From: DSN_KLR650@yahoogroups.com [mailto:DSN_KLR650@yahoogroups.com] On > Behalf Of revmaaatin > Sent: Monday, March 28, 2011 7:32 PM > To: DSN_KLR650@yahoogroups.com > Subject: [DSN_KLR650] Re: Manual petcock for KLR? > > > > > > John, > Thanks for posting that information. > Is any of this 'vacuum-data' you have presented also, temperature and > altitude sensitive? > > The same bike that I rebuilt the pet cock on has developed a horrible > running problem at temps above 90/95F. Last summer, I could barely get the > bike to run...as the OAT increased. > > The problem initally presented RIGHT AFTER buying 10%ethenol fuel in > Yellowstone NP = no choice; I needed fuel. Very soon after that, I pulled > over and I drained the carb, flush/drain and continued. We limped into Cody, > WY; did the flush drain again. In the process of limping along: > I tried adding choke, > removing choke; > it would barely pull itself along/bucking/surging along at ~35 mph at the > high OAT. > > (I have had previous experiences here in the Dakota's with 10%ethenol and > temps above 90F. It would not go any faster than 60mphi.) Of course, I avoid > ethenol unless it is absolutely necessary. > > Leaving Cody at 10AM, it ran fine until noon, then while crossing the > Eastern WY from Worland, Eastward with increasing temps, it was a real pill. > I tried opening the gas tank while driving; no effect. > I stopped and drained the carb; a couple of times at Ten Sleep (only shade > for miles). In the course of time, > I had tried adding higher octane fuel, > draining the carb, > opening the fuel tank, > thinking hateful thoughts. > By now, we had completly used up/diluted most of that 10% enthenol. > Mind you, Sam's bike was running just fine on the same conditions. > > As I climbed out of Ten Sleep, WY the OAT slowly decreased as the altitude > increased and the bike ran better. (Seemed to me to be strictly temp > specific.) My son's KLR650 did not exhibit any of these problems. > > Next day, repeat of the previous two days. As temps got hotter, the bike > would barely pull itself along. > > Initally of a morning, ran like a very fine KLR, because, well, it is a very > fine KLR! But get a little temp increase. It gets naughty. > > Leaving Rapid City, it was running pretty good. Same story, 3rd verse. By > the time I got to Midland,SD it was hot outside and the bike beagan getting > naughty again. > I stopped in at the ACE hardware, Midland, SD and bought reflective bubble > wrap and wrapped the fuel line. It was a marginal fix; as the temp > stabilized below that 90/95F as the evening wore on we limped home. I have > put some miles on it since; no repeat/poor performance. > > A couple of other data points: > Thermo bob installed; temp was reaching above 220 during some of these > times. > > Fan is operating as advertised. > > Future: > I am going to throghly clean the radiator with soap and water--though I > don't think this is a problem. > I am going to look for a vacum leak in the petcock. > I don't think this is a problem. shrug. > > Saturday, I had the KLR out: OAT 30F; thermo bob took the bike to ~200F and > the fan cycled as advertised. It was only a short ride back to cold storage > for the bikes to await the spring thaw. again. > > Any ideas, suggestions? > > I am confident that it would present the same problems if the OAT was above > 90, and certainly above 95F. > revmaaatin. > > > > > > > [Non-text portions of this message have been removed] >