Fuel starvation problem?

Hi,
I have a low mileage Triumph Speed Triple, 1996 (ie, with
carburettors).
Since I took it out of storage for the winter, I have had a persistant
problem: The bike starts fine and runs smoothly, but after about 1
mile, it starts sputtering and quickly dies -even at high speed. With a
bit of persuasion, and using the choke and prime, I can then start it
again. Once I have done this, it then works OK until the next time I
cold start it.
I assumed this was a fuel contamination/filter problem, so I emptied
the tank, cleaned the tap and filter and put it back together with new
fuel. However, the problem is still there!
Any ideas?
Thanks,
Ray

 

It sounds like the float bowls are running dry. Gum and varnish will
build up on the edges of the three or four-side float valve. It sticks
and fresh fuel doesn't get into the bowls.

Rather than do a lot of disassembly, you might try running 3 ounces of
Berryman's B-12 Chemtool Chole and Carburetor Cleaner through a tank of
gasoline. You can get the B-12 in non-aerosol form at Wal-Mart for less
than $3. Repeat the fuel treatment until the can of B-12 is used up and
your carbs will be as clean as they will ever get without actuall
disassembly.

Does your Triumph have a vacuum-operated petcock, like most Japanese
machines have? You might have a vacuum leak problem or a clogged up
vacuum valve on the petcock in that case.

Further down the fuel system, some carburetors have little filters
right above the brass float valve seat. If you have to pull the carbs
off to clean the gum and varnish off float valves you can probably
unscrew the float valve seat and clean above it and see if there's a
filter there.

 

The cleaner that yamaha sells around here says that you dilute it 3:1 with
gasoline, not water.

rj

 

Does the label say what is in Yamaha's carb cleaner? So far as I know,
most aerosol carb cleaners contain petroleum distillate, zylene,
acetone, and maybe some methyl alcohol.

 

What is interesting is that the xylene concentration is low enough that you
can leave the cleaner in overnight without worries and yet it does a pretty
good job. I highly recommend that one try it first. Be patient and see if
it doesn't fix your issues. I had to go through two bottles by the time i
was done, but then again I had 6 carbs that needed to be cleaned.

r

 

and here I thought I was the only one stuff like that happens to. >)
Thanks, you made my day!

r

 

Doh! You are right- I just looked at the bottle. Good thing I didn't try mixing it with water. I have absolutely no idea where I got the water and 50/50 mixture from.

Maybe radiator fluid/coolant? That's 50/50 with water.

Careful with B-12. I left some parts in there for a couple of hours
(didn't know how long I was supposed to), it melted a few brass screws.
After the long soak, I could twist them apart with my fingers. But if
you dissassemble, you'll see which parts have the small holes and need
cleaning... you can do most of it with aerosol carb cleaner and a small
brush.

Gas tank vapor lock, maybe? Would that apply in this case?

 

Bzzzzt! B-12 won't hurt brass parts. If stuff like xylene and acetone
would harm brass, your idle jets and main jets would get eaten up by
the additives in gasoline.

B-9 Carburetor Dip might harm metal after long exposure, it contains
cresylic acid for dissolving incredible crud on really funky car parts.

 

Could it be that the vent hole in your filler cap is partially blocked?

If this happens, fuel may drip through to the carbs when left standing
awhile, but will not gravitate to the carbs quickly enough when
running.

Try running with the filler cap open.

 

Hi Guys,
Thanks for all your advice. I will certainly try the carb cleaner this
weekend - I will get whatever they sell here in Switzerland.

The other suggestion you have made is that there is a problem with the
vacuum operated petcock. Can you give me any ideas how I can
troubleshoot this one? If I understand from a bit of 'Googling', the
'prime' setting on the switch by-passes the vacuum switch. Can I just
try running the bike on 'prime' to see if the problem goes away, or is
not possible? The only risk I seem to have seen is petrol overflowing
from the float bowls if the inlet valve is not closing properly.

 

I'm jumping into the conversation a bit late....

I ride a 1996 Triumph Daytona which is very similar to your Speed Triple.

These things are NOTORIOUS for having a kink in the vacuum line to/from the
petcock. I had one a few weeks ago and experienced the exact same symtoms
that the original poster has.

Running carb cleaner through the system can't hurt. However, he should
carefully inspect where the vacuum line connects to the petcock. Triumph
made this an incredibly tight fit and almost a 90 degree bend. It is very
easy to get a kink in the line at that junction. If you can find one, put a
90 degree elbow on your petcock to avoid this infamous kink.

Otis
96 Triumph Daytona

 

No really! My B-12 ate my screws! Ahh nevermind, never works as well
as dogs eating homework...

I guess it wasn't the B12 then. But why would the brass screws do that
then? Just old? They all easily separated in exactly the same place,
exactly halfway down the threads as if you looked at them with the
heads upwards, and then cut them in half with a horizontal cut.
Weird... fatigue?

Anyway, yeah... unhook the fuel line from the filter (or whatever is
after the petcock) and drain it into a plastic cup. Also a good way to
get rid of water if it's collected in the bottom of your tank.