looking for some advice about carbs

[maxwell]

So I bought my first vmax a couple of months ago. Its a 92 that is completely stock with 16,000 mi on it. When I got it, it ran a little rough around the edges but when you twisted the throttle it would take off like a shot.unk: Now when I say a little rough around the edges it wasnt that bad. It would seem load up with fuel at an idle to the piont of dropping a cyl intermittently after about 20 seconds at idle, and a steady cruize wasnt so steady. But when you would roll on the throttle and it started beathing it would blow a bunch of black smoke ( no blue smoke only black fuel smoke) and your were gone baby gone.

Now I live in Colorado and the bike came from California, so it seemed to me like it needed a altitude adjustment so what I did was take it to my local Yamaha dealer.

I got the bike back a couple of days later and it deffinately runs alot smoother, and it idles fine at the stop light now. No more black clouds pouring out of the exhaust. The thing is, it has no power anymore:scooter 1:. I was out with a 600cc fazer and he was definatly passing me under wide open throttle, and he wasnt inching past he was passing. I hate to farm projects out but sometimes a guy just gets to much on his plate at one time and sh*% happens.

So here I am, I paid the dealer for a "co&balance" and lost a good 1/3 of my availible power. The bike runs smooth now and has a nice idle, but I want my power back. I dont know if I should take it back to the guy or tear into it my self.

I am an auto technition by trade and I am currently in the middle of ataining my airframe and powerplant liscence to work on aircraft so I do have a full cache of tools and a brain full of technical knowlege. My main hangup on it is I cant find any viable info on adjusting those carbs, or external adjustments( like on a car ). Also I dont really know what the hell the guy did to make it behave like a kitten:ummm: Any help or advise would be completely awsome

 

[RaWarrior]

You've got 3 main adjustments

a/f screw, may be hidden behind a plug. It's immediately under the diaphragm covers. This is for low end

Needle, inside slides, can be done with the carbs on the bike. These control the midrange. The stock needles are non-adjustable, but you can add shims to richen them up a touch.

Mains...these are from like 3/4 throttle to redline. You have to pull the rack and flip it upside down to get at the bowl screws, the mains can be changed through there.

there's also the two air jets, one in the throat(PAJ1) and one behind the diaphragm(PAJ2).

Though I'll have to leave it to someone else to recommend high-altitude carb settings for these bikes.

 

[maxwell]

Thanks for the quick reply, with that info I think I am going to go see if I can get in the back and talk to the tech. I think I used to work on the guys car at a shop I used to work in. Anyway I know where and what you are talkig about and that makes more sense to me that a float adjustment, and I dont really see or feel the need for a complete teardown. I will keep you posted

 

[TurcoLoco]

+1 to what Ra mentioned. My guess, he might have cleaned out your carbs (how thorough would depends on how much you paid and how long it kept the bike) and also sync'ed them.
Sync'ing the carbs make a world of difference, I have personally experienced that twice on a Vmax alone!
He might have also cleaned or replaced the spark plugs.

Curious, how much did this tune-up cost you?

 

[Rollie]

Does this California bike still have smog restriction parts ?

 

[bazwell]

Did he unplug your V-boost?

 

[Rally2]

^ agree with the VBoost comment, your "before" and "after" descriptions sound exactly like how my bike runs with VBoost forced on at low RPM versus coming on only at 6k+ rpm like stock configuration.

 

[maxwell]

The Bill was $350 and he had it for 2 days....where is the v-boost plug? Is it in that wiring harness part up under the faux ram air scoops that say yamaha?

 

[RaWarrior]

If you hear a whirr-whirr sound when you turn the key on, then the v-boost is working. Yes, the controller for it is behind the left scoop along with the blinker relay, I believe the v-boost controller is the front most box. The blinker relay is to the rear of it, and the diode block is third in line.

Cali bikes just vent the crankcase breather into the stupid charcoal canister rather than the airbox. makes zero difference to anything. and slightly leaner jetting.

 

[Rand-5107]

Calif. bikes have a charcoal canister for evaporative emissions from the gas tank. That's the only difference I can find.

 

[jfeagins]

I'd definitely get back with the guy that worked on it, and get a FULL, DETAILED description of exactly what all he did to the bike. That way, you know where to backtrack to find what it was he didn't do right.

If I remember correctly, that V-boost controller connector is the round one behind the left scoop. I'm thinking it's the only round connector back there.

 

[maxwell]

Vboost is plugged in gonna try messing with the air fuel mix a little bit, Been tied up with the "High Park fire" in Colorado