Wacky Carb

[Donnie]

This was a horrid season for riding for my family. We finally had a weekend to get out and ride and only made it 4 miles before an issue arose.

My brother's '86 Vmax started to lose power in the left cylinder. The EGT's went from 800 to nothing. It soaked the spark plug with gas and wasn't burning.

I unhooked the gas line and we resarted the sled. After a few seconds you could hear the left cylinder kick back in. I hurriedly hooked the fuel line on and we started back for the trailer.

If I kept the sled running at 30 mph, which was about 5300 rpm, the sled ran fine. If I gave it more gas, it would start to bog down and lose power. If I went below 15 mph, then the carb would fill up with gas and flood the left side of the motor. It's almost as if the needle was stuck in only one spot and fuel flow was at just one setting.

I took the carb apart and found no dirt. The thing was spotless.

The same thing happened last year. I took the carb apart, put in new floats and we road on a trail ride for 40 miles with no issues.

What's going on???

Donnie

[tyler440]

maybe you slide or needle is hanging up? the are suppossed to have 2 plastic washers above and below the clip, i guess the intent of these washers is to keep the needle straight... other than that im lost

[Donnie]

I had thought about the stuck slide too, but was moving. I snapped the carb a few times and you could hear it bottom out against the idle screw. The needle wouldn't be able to hang up because his slides have the piece with the screw that goes through and holds it all together.

With regard to the washers... mine only have a plastic washer under the E-clip before it goes into the slide. Nothing above other than the metal tab that the spring then compresses against. Both my Vmax's are like that. I think it only shows one in the service manual too, but I don't have mine close to me right now.

Keep the ideas coming. I only have 9 months before it might snow again... I hope!!!

Donnie

[ThePipe]

I had the same issues for a bit myself in January
I replaced the needle and seat and it was fine for maybe week and then the left cylinder started loading up again.
This time I bent the little tab that opens and shuts the needle and seat.
I bent it 1/2 a mm up and problem was solved.

[srxvmax50]

Donnie the one nylon washer was originally placed above the e-clip. Yamahs reasoning was to hope to minimize needle vibration and wearout in the needle groove area. I've seen needle grooves wear so thin then snap apart. Thats not good, thats not good at all. a person would unscrew the needle retainer plate to get at changing the needle's e-clip position and not realize that there was a plastic washer beneath the plate, held in place by dampness (hydraulics.) And that washer, if eventually detected, was supposed to go--where? So one poly washer was norm, although in a calibration pinch the washer was placed beneath the circlip in order to richen up the mixture. That worked, sometimes. Your problem sounds like float-needle-seat hangup. If the floats or needle/seat hang up you got instant floodout. Check your needle/seat assembly. Turn your carbs off at night or while trailering, they just love to flood out thru vacuum siphoning gas thru the idle circuit venturi (little demons). Oh, don't trust on dash fuel shut-offs. There is a plastic part in the cableing that fails. Go to '83-84 underdash shutoff valves. More reliable. MJD

[tyler440]

awe yes in '86 you would have the nice plates that screw into the slide... i always snapped the throttle a few times when i put slides back in also... i agree with these guys your needle and seat could also be bad... look for any imperfections on the needle to indicate leakage... sometimes they dont even show wear and they fail...

[tyler440]

awe yes in '86 you would have the nice plates that screw into the slide... i always snapped the throttle a few times when i put slides back in also... i agree with these guys your needle and seat could also be bad... look for any imperfections on the needle to indicate leakage... sometimes they dont even show wear and they fail...