Yet more carb woes...

[rktmanfj]

I headed out to the MotoGP the other day, and of course the FJ started running on 3 cylinders, with the #3 carb flooding.

I tried riding off a couple of curbs, etc. to jar loose any debris, with no change at all.  A healthy dose of Berryman's didn't help either.

I finally got a free day to check things out, and I cannot find too much wrong with it.

I checked the usual suspects, and the carbs are clean as they can be.  No sediment in the bowls or any dirt at all.  I pulled the float valve, and the o-ring is fine, and everything is clean there too.

I did find a pinhole in the diaphragm, but I wouldn't think that this could cause the flooding issue.

These carbs were thoroughly (ultrasonically) cleaned last season, and they look just as good today.  At that time, they got the Factory Config 30 kit and Unipods (Cobra cans), and it has run well after the jetting was sorted until now.

Anyone care to take a guess?

Of course, this has to happen right before the Fall Rally...    

Randy T
Indy

[fjrpierre]

if bike runs on 3 cyl, maybe its a plug/spark issue, ie cyl getting gas but not firing at all, so cylinder eventually not taking gas properly anymore, gas backing up flooding carb, etc etc? This make any sense? Yes its true I only discovered where the carbs were last year but....

[Arnie]

Randy,

Did you check the float in #3 carb?  It could be cracked or the tang could be bent stopping it from closing the valve.  Also, when you checked the O-ring did you check that the needle and seat were clean?

Cheers,
Arnie

[rktmanfj]

if bike runs on 3 cyl, maybe its a plug/spark issue, ie cyl getting gas but not firing at all, so cylinder eventually not taking gas properly anymore, gas backing up flooding carb, etc etc? This make any sense? Yes its true I only discovered where the carbs were last year but....

Yeah, if I would open it up, it would clear out and run okay until I slow down again and the bowl overfilled.  But I know which carb it was by the wet plug and the slow drip from the overflow hose.  The other plugs look fine.

[rktmanfj]

Randy,

Did you check the float in #3 carb?  It could be cracked or the tang could be bent stopping it from closing the valve.  Also, when you checked the O-ring did you check that the needle and seat were clean?

Cheers,
Arnie

I did consider the float, and there didn't seem to be anything inside, and it looks brand new, with no flaws evident.  I then pulled the seat, and inspected the o-ring and seat and they were clean, with no problems.  I did give everything a shot of Berryman's just for good measure.  When I checked the slide and needle, I found the pinhole in the diaphragm, which I repaired with liquid electrical tape.

I left it for the night, so the diaphragm repair could cure, and I will reassemble it tomorrow.  I just wonder if I am missing something.

Did I mention how much I Iove working on carbs?       

[RichBaker]

If possible, weigh the floats.... the offender may have a crack or pinhole that isn't visible. If it does, it'll be heavier than the others.....

[rktmanfj]

If possible, weigh the floats.... the offender may have a crack or pinhole that isn't visible. If it does, it'll be heavier than the others.....

Hmmm...good idea.

I'll have to see if that nice set of triple beam scales is still around at work.

[Shaun]

Not sure if this works on FJ carb floats as I have not had mine apart yet. When I had a suspect float from a car I was working on I would just drop the float in the freezer for sometime (1 beer). When the float was good and frozen I would put it in a glass or glass bowl full of room temp or warmer water hold it on the bottom and watch for the bubbles. Theroy is when the air in the float gets cold it shrinks, when you put it in the water the air in the float expands and bubbles out the pin hole.

Shaun

[rktmanfj]

Not sure if this works on FJ carb floats as I have not had mine apart yet. When I had a suspect float from a car I was working on I would just drop the float in the freezer for sometime (1 beer). When the float was good and frozen I would put it in a glass or glass bowl full of room temp or warmer water hold it on the bottom and watch for the bubbles. Theroy is when the air in the float gets cold it shrinks, when you put it in the water the air in the float expands and bubbles out the pin hole.

Shaun

Guess I'll go buy some beer then...       

[rktmanfj]

Well, got the thing back together this am, and it wants to run at 5k rpm with or without the choke.

But, it was running on all four, with nothing from the overflows, though at idle it may be a different story.

I'll work on it some more tomorrow when I have more time and less frustration... did I mention how much I enjoy working on carbs??     

Randy T
Indy

[fj1289]

Randy,

sounds like the throttle cable didn't seat in the bracket a tthe carbs (running at 5K w/ or w/o the choke).

Maybe try swapping the offending float with another carb and see if the problem follows the float? 

Chris

[rktmanfj]

Randy,

sounds like the throttle cable didn't seat in the bracket a tthe carbs (running at 5K w/ or w/o the choke).

Maybe try swapping the offending float with another carb and see if the problem follows the float? 

Chris

Thanks Chris, that's exactly what I found it to be.  Better garage lighting (and perhaps bifocals) is in the works.

It's sitting on the trailer right now, ready to roll out to the Fall Rally in the am.

If it doesn't clear out, I'd rather be working on it there than here...   

If I can't sort it out, I'll take the XT and run some fire roads.

Randy T
Indy

[fj1289]

Cool - glad that part worked out easy -- NOT that I've ever been had by that issue...!


Enjoy the ECFR!