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.
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