2006 HPDI 250 #1 cylinder problem

[jcclub47]

Thanks Chuck, it's very interesting.

[cpostis]

Thanks Chuck, it's very interesting.

Found a link that takes you to the bulletin I mention.

Yamaha Oxygen Sensor Information

[jcclub47]

Thanks Chuck, I checked my wiring diagram and could not find a O2 sensor. I have carbs. Would i have any issues if I attempted to rebuild my carbs because I have a rough idle, otherwise running great. 800 hours and never touched the carbs.

Joe

[jdavis1705]

cannot get to anything by dropping lower unit

That Figures

The exhaust plates are behind the CDI and are pretty easy to get to. I doubt you have any issues there if it's always been run in fresh water. The exhaust guide connects the powerhead to the lower unit and I burnt a hole in mine just before it dumps out the 2 rear exhaust holes, you should be able to see if it is corroded by looking at the flat area on the exhaust guide. Hope this helps.
Very good info, going to keep that in mind. If I pull off the plate on back think I could get a look at the exhaust stuff below and see any burns with a flashlight or small cable camera ?

Joe

BTW, I'm just guessing here. When I cooked my cylinder I fried my exhaust guide by spitting fire into it and rendering my exhaust guide to the extent that the cylinder did not have the proper flow characteristics it was designed to have and fouling the plug.

Did the motor run good after the rebuild or did you catch the damage at rebuild ?

Joe

Thanks Chuck, it's very interesting.

[QUOTE=cpostis;131222]Found a link that takes you to the bulletin I mention.

Yamaha Oxygen Sensor Information[/QUOTE

I dont seem to find any info in my manual about a O2 sensor, maybe you were refering to an OX66 engine ?

[boscoe99]

A Z250 or VZ250 does not use an O2 sensor.

It does not use a knock sensor either.

[jcclub47]

The motor did run good after the rebuild, however it did not idle properly until I replaced my exhaust guide. I questioned the rebuild guy about my exhaust stack and he said it was not an issue. Knowing what I know now I would have replaced the exhaust stack and cleaned up the water passages. Yamaha has had corrosion issues on the paint baking process on the exhaust guides on 4 strokes in this era, some say they should have had a recall on them. After paying 4K for a rebuild you look for answers why it happened and can only make educated guesses. I still think running in fresh water eliminates you. Shooting the head temp and cylinder wall should tell you if you are generating too much heat in that cylinder which should be your primary concern right now.

Joe

[99yam40]

Rodbolt or Boscoe,
any idea what would cause his motor to have,
" Number 1 plug always has a dry black carbon coating on it, all other cylinders the plugs look perfect"

[boscoe99]

Rodbolt or Boscoe,
any idea what would cause his motor to have,
" Number 1 plug always has a dry black carbon coating on it, all other cylinders the plugs look perfect"

I hesitate to proffer a guess. Waiting for the master to come along.

[jcclub47]

You don't have to take anything apart to get a look at the exhaust guide, just lift up the wire's and pig tail you will see the flat area on the exhaust guide. Do it at night so you can see better with a flashlight. If you see any paint missing on the flat area of the exhaust guide this will indicate corrosion on the inside passages making it way to the surface. I would wrap that plug in Teflon tape to see if your problem goes away, this would indicate a cracked thread and air leakage just for kicks and giggles.

Joe

[99yam40]

I am not sure but the only thing I can think of with my uneducated mind to get excess fuel would be for the injector to stick.

[rodbolt17]

gotta quit thread hopping.
gets to confusing.
the HPDI DID NOT have the ex corrosion issure.
now I have seen a few 3.3L HPDI that melted the muffler.

the only way to get that dry black carbon is a rich mix.
could be an injector leaking.
could be the wrong injector.
could have a faulty spray pattern.
could have a bad check valve in the recirc system or a recirc line installed wrong.

[jdavis1705]

gotta quit thread hopping.
gets to confusing.
the HPDI DID NOT have the ex corrosion issure.
now I have seen a few 3.3L HPDI that melted the muffler.

the only way to get that dry black carbon is a rich mix.
could be an injector leaking.
could be the wrong injector.
could have a faulty spray pattern.
could have a bad check valve in the recirc system or a recirc line installed wrong.

Thanks Rodbolt, Just sent injectors off and ordered new reed valves, I will check the check valve for #1 cylinder on the reedbox. Intake page #15 part # 650-11370-01-00, correct ?

[jdavis1705]

Hmmm, looking into the reed block mounted on motor
Top row: Right valve: can suck air, but not blow air Top left: Same
Second row Right: suck but not blow Left: suck or blow freely
Thrid row Right:suck but not blow Left: suck or blow freely
Fourth row Right: Suck but not blow Left: Suck but not blow
Fifth row Right: suck or blow freely Left: Suck but not Blow
Sixth Row Right: Suck but not blow Left: Suck or blow freely

Parts diagram shows 9 valves with the same part number 60v 11379-00-00
I have 5 that are open both ways and 4 that you can suck air but not blow through. I am assuming these five are bad ? none of these are on the #1 cylinder where I have had the dry carbon issue. Any thoughts ?

[rodbolt17]

wasted money on the reeds.
at low speeds or static they may stay open slightly.
and the reeds have noting to do with fuel delivery.
all the reeds do is seal off the crankcase for primary compression.

your money though.
for my money I would have bought a Kv tester instead.

[99yam40]

If all 9 are the same part # then yes you have some bad ones.
If that many are bad, might want to change them all.
Just my opinion, maybe lean sneeze took some out, who knows if the others are damaged or fixing to go bad too.

just make sure they are listed as the same part #.
My little C40 had 2 different part #s . Only some had the check valves in them