QuestionI have a 2005 Yamaha V-star 1100 that I bought used with custom pipes (no idea what brand, I have looked all over them). I bought it with 6500 miles and there are now 9500. I always thought that the previous owner just put on new pipes and didn't bother to rejet the carbs. I have not been able to ride it recently because of being in flight school. I went to start it yesterday because it hadn't been started in about two months. I always start it with the choke full blast. It started fine but started backfiring a lot at high RPM (sometimes spitting flames) and only from the exhaust pipe leading to the rear cylinder. When I tried to reduce the choke, it died. Started again. When I tried to roll on the throttle, it died. I let it run for about 45 minutes total while trying different things, but to no avail.
Then I took the following actions, in order:
Put SeaFoam in the gas tank and let sit overnight.
Changed spark plugs and oil.
Allowed it to run with no air filter, because the current one needs replaced.
I was finally able to roll on the throttle quickly and rev the engine to very high RPM, but I still had no results at low RPM and with no choke. So, I went further:
Removed carbs to find that they have already been rejetted. This is what they looks like:
Front carb:
Main Jet: 118
Pilot jet: 42.5
PMS screw: Seem like 8 turns to me. I've never seen anyone talk about setting the PMS that high.
Rear carb:
Main Jet: 115
Pilot jet: 42.5
PMS screw: Didn't check it yet.
I cleaned out the carbs with carb cleaner. This is where I stopped. I have a K&N on order to be here tomorrow. But I have no idea what my PMS screw setting is supposed to be, or how to determine it. I read a similar post and was clued in that it may be a pilot circuit failure? How do I check that as well? Please help.
Lane
AnswerHi Lane,
This problem is almost always that the fuel has gelled
and plugged up either the pilot jets or the
carb idle circuits themselves.
The carbs should be soaked in some good Yamaha carb
cleaner and blown out with carb cleaner spray or
compressed air.
the Yamaha carb cleaner will not hurt the various o-rings
and gaskets like auto carb cleaner will.
It sounds like your main jets have been changed
but the other jet you mentioned (42.5) is the starter
jet which is rarely replaced.
The pilot or idle jet will be about #17.5 if it
is the stock one.
If the bike runs at high rpm it means the low
speed jets or passageways are plugged.
The pilot jet is very small and can plug easily.
Also clear the main jets out physically.
Sometimes you have to use some small smooth
wire like guitar string to make sure the jets
are clear. Even compressed air cannot remove
hardened fuel deposits.
The PMS screw is usually about 2.5 turns out.
It should be adjusted to where the bike
idles the smoothest. There is no perfect
setting as it varies from bike to bike.
If the PMS screw was turned out so far it means
either the pilot jet was plugged or it
is too small.
If you have to turn it out past 3.5 turns
it may pay to increase the pilot jets by one size.
The pilot jet is right next to the main jet in the center
of the carbs. The other jet farther over is the starter jet.
Make sure your fuel is fresh and no moisture in it.
The seafoam was a good idea but the jets may need
to be physically cleaned after sitting two months.
The fuel these days is very short lived.
If you have any more problems check your
fuel supply from the tank is sufficient.
(Pump, filter and petcock valve)
Luck to you!
Wayne S.
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