Vmax low idle when engine is warm

[104460RSo]

My 2006 Yamaha v150tlr Vmax got a low and sometimes rough idle when motor is warm. At cold engine it starts great at 800rpm,goes down to 700rpm. It runs great at all rpm, but after a while running the idle gets down to 500rpm and sometimes stalls.
I have tried to turn the idle up a bit, but then it is to high next time I start the engine cold
Anybody know what could be the problem?

[rodbolt17]

could be the alternator, or possibly muffler bearings.
or you can actually do a tad o testing. check the plugs and caps.
test the fuel pumps.
test the compression.
test the spark.
this is actually how I have to do it.
my crystal ball is broke and my magic wand is missing.

[104460RSo]

Compression is equal on all six. Sparkplugs are New. Cables and caps look good and have the right ressistance. What do you recommend is the best way to test the fuel pumps? Is the fuelpumps a "wearpart " that should be replaced after X hours? My motor got 339 hours

[rodbolt17]

pump diaprams fail. no set time they just sometimes let go.
carbs get dirty, no set time sometimes they just do.
once the mechanics are known good go fix the fuel system.

[104460RSo]

Rodbolt17: have replaced both fuelpumps, just to be sure. The problem is still the same, idles gets rough and low when motor is warm, after some time running, sometimes stalls.
my next plan was to have a look at the carbs and ignition link/sync, to be sure it's where it is suppose to be.
Or do you think I should have the carbs cleaned?

[99yam40]

would not hurt to do the link and sync to see if it helps,
and then clean carbs if it does not help.
the link and sync will need to be done again after putting the carbs back on after cleaning

[104460RSo]

I performed a link/sync yesterday. Discovered that the full retard ignition was way of. Lower carburetor also har some opening while the two tops where closed.
Got everything adjusted according to the service manual. Adjusted idle to 725 rpm. on warm motor. It now had an incredibly smooth and nice idle, left it idling for 30 min.
The *****ing speed was 600rpm and sounded nice.
Was out driving for å while, but when i returned, the idle was low and rough.
I think I have to disassemble the carbs and have them cleaned....
If this does not help, I'm helpless.

[99yam40]

I would run thru the link and sync again just to see if something has changed.
it should not have tho.
did you use a timing light to see what the actual timing was?

I found my C40 idle timing was way off and setting it to where it should have been made the other setting way off.
had to replace the CDI some years ago to get it to do right.
hope you have a simple fix on yours

with yours being way off, it would make me question why

[104460RSo]

And that I did yesterday when I got back in, went over it again....sync/link looks good.
I did not use a timing light.
I saw right away it was way off before I started as the full retard adjusting screw was threaded all the way in, as far as possible....And tight. Also the trottle cam control link was to short and the threads was full og marks from some nippers or something. I did adjust all according to the service manual.
As said motor was running smooth after adjusting, never heard it that nice before.
For my own peace of mind I will do the carbs and do the sync/link again when the carbs are back on. Im sure I also heard a sneeze yesterday, never heard that from this motor before
Never know what the previous owners have done to this poor engine.....I might find more when I investigate further
Also I noticed some oil in the top carb and in the plastic inlet cover, is this normal?

[104460RSo]

Update!
Then I'm back from vacation and have taken off the carburettors. The engine only got worse so I had to dismantle. There was water inside the butterfly valves, zoom in and you will see it.
Then I guess I got water in my fuel , or can water come from elsewhere on the engine? Could not see water om the float cambers.
Somebody has been working on these carburettors before, ,it's easy to see ....Not used right size screwdriver, marks several places ...

[TownsendsFJR1300]

Is it fresh (rain water) or salt water (if used in salt water)? A touch on your finger to tongue will be very obvious..

Have you seen any water leaks, engine running with the cowl off?

Drain the fuel tank(s) and inspect for water...

I gather you don't have a water separator? Might be the time to invest in one...

Lastly, (if not already drained), drain the carbs into a CLEAN container and check for water / crap in the bowl.

ALL jets need to be removed, inspected and cleaned. A spritz of carb cleaner doesn't cut it...

[104460RSo]

The whole fuel system was new earlier this year, has got a fuel filter with water seperator , so I was a little suprised to find water in the carburettors. Anyway, I have drained everything . Will get a new fuel filter. Could not see any water when i drained the fuel tank.....little strange.

Have disassembled, inspected and cleaned all 3 carburettors and changed gaskets

I'll take a look at the vent for the tank tomorrow, might be something there.

[TownsendsFJR1300]

Yep, might have a vent line picking up water, obviously inspect all connections at the tank, gaskets, etc and any evidence of water running atop the tank...

[104460RSo]

Carbs are back on the motor, have done the link/sync. Gone over fuelsystem, tank, hoses, new filter. Started up right away, nice sound on idle. Started it at home, not with muffs, but I got a plastic tank that fits perfect....same hight as on the water.
Notised some water drops and a lot of white/grey smoke coming out of the two holes on the back of the motor, is this normal on idle? Left it running for 20 min, still smoke.

And, can anyone confirm correct settings for port and stb mix screws on these carburettors?
( 2006 V150TLR)

[99yam40]

Exhaust Idle relief ports, should be normal for exhaust and a little water to come out.

I have no idea about settings