I smell fuel.

[user 8898]

So I have my new-to-me 98 Vmax with Stage 7 jet kit, K&N filters and Kerker 4 into 1. Runs great but it's rich at idle and my buddy says when I blew by him he smelled fuel. Someone said the rich idle is because of the "constant V-boost". I don't understand how that works. The seller told me the Stage 7 was installed by the Yamaha dealer, but it didn't run right until he went through the carbs and installed the right jets and corrected needle clip settings. At this time he also removed the V-boost controller and butterfly assembly. As I get it, the V-boost opens the butterflies between front and rear carb air intakes at a certain amount of RPM/vacuum. How does removing V-boost make it run rich? Can I re-install the V-boost and correct this?

Thanks!!

 

[gamorg02]

its kind of a well known 'thing' that opening the vboost butterflies makes the bike run rich. tuning for off idle and low rpms may make your idle rich, and as you whack the throttle WOT.

that being said i'm not sure why it does. if you're pulling through one carb or two, the air should get split up at some proportion and then pull fuel via venturi effect for the same volume and speed of air coming through.... but hey i've seen it on a dyno so i don't let it keep me up at night.

 

[user 8898]

its kind of a well known 'thing' that opening the vboost butterflies makes the bike run rich. tuning for off idle and low rpms may make your idle rich, and as you whack the throttle WOT.

that being said i'm not sure why it does. if you're pulling through one carb or two, the air should get split up at some proportion and then pull fuel via venturi effect for the same volume and speed of air coming through.... but hey i've seen it on a dyno so i don't let it keep me up at night.

OK, thanks for that. Obviously I'm just picking this up. I need to look at some diagrams maybe because I don't see how the butterflies sit physically or how I would install them with the K&N filters in place. Looks to me like there would have to be hoses to connect them between the carb intakes which are all straight up and the butterflies are straight through. There's something I'm not seeing here. :ummm:

 

[user 8898]

OK, I think I see where they sit now. Duh. I guess my question becomes this: If I re-intall the vboost system, should I expect it to run as well, but leaner, with not quite as much throttle response at the low end? It really snaps when I open the throttle.

 

[gamorg02]

yea probably slightly leaner. altho i like vboost always on for the smaller throttle opening response.

 

[user 8898]

There's a little switch on the left in front of the tank/cover, which must be V-boost on/off. Next time I pull the side cover I'll plug the servo in, and test the servo and on/off switch.

I like the idea of controlling the V-boost system. Not crazy about the richness and slight fuel smell of constant V-boost.

I noticed the right-side cover allows air to pass through it, while the left is blocked. Is that the way it's designed? If so, why?

Thanks!

 

[user 8898]

One other question... Will I have to pull two of the carbs to re-install the V-boost butterflies?

Thanks!

 

[naughtyG]

I noticed the right-side cover allows air to pass through it, while the left is blocked. Is that the way it's designed? If so, why?

Thanks!

Both air scoops on the Vmax Gen I are dummies. If you open up the left, you get wet electrics - not good. I think the right is slightly open because there are no electrics there - just the thermostat which can prolly do with a little air.

One other question... Will I have to pull two of the carbs to re-install the V-boost butterflies?

Thanks!

The vboost butterflies live in their own assembly which sits below the carbs. There is no way to get to them without removing all the carbs - they come off as a whole solid rack of 4.
Usually most people unplug the vboost while the valves are open to use full-time boost. I haven't heard of many actually removing the butterflies altogether.
If they have been removed, however, you will need to remove the air box (or all four air filter pods S7) and then remove the carbs rack. then below the rubber boots the carbs fit into, is the assembly holding the vboost butterfilies.

 

[Rhoy Carter]

I suspect that you will still have to do some rejetting to get rid of the fuel smell

 

[grimmie]

What kind of mileage are you getting?

 

[user 8898]

What kind of mileage are you getting?

I haven't actually measured it yet, since I've only rode 63 miles so far.

 

[user 8898]

Both air scoops on the Vmax Gen I are dummies. If you open up the left, you get wet electrics - not good. I think the right is slightly open because there are no electrics there - just the thermostat which can prolly do with a little air.



The vboost butterflies live in their own assembly which sits below the carbs. There is no way to get to them without removing all the carbs - they come off as a whole solid rack of 4.
Usually most people unplug the vboost while the valves are open to use full-time boost. I haven't heard of many actually removing the butterflies altogether.
If they have been removed, however, you will need to remove the air box (or all four air filter pods S7) and then remove the carbs rack. then below the rubber boots the carbs fit into, is the assembly holding the vboost butterfilies.

Yeah they've been removed alright, as well as the servo controller. Looks to me like there's a very short section of pipe in their place. I'll put them back in at some point down the road, and hopefully the switch on the front left of the tank/cover is wired to turn the V-boost on and off. If that doesn't clear up the rich issue, I may re-jet. But I doubt I'll find that necessary if the richness is due in any part to the constant V-boost. It's not *super* rich, just enough that I can tell it's definitely rich.

I'll post my mpg when I measure it. It'll probably suck because of my throttle habits and a good bit of idling. Went for a short ride and I'm just now getting to the point where I feel half-way comfortable with the handling and with controlling the bike under hard acceleration. :thumbs up:

 

[jmailley]

I've had a rich fuel smell since I got my Max last year. Can't walk behind it when it's warming up or I will smell like heavy exhaust and have to leave my cloths outside so my house doesn't stink.

I'm running all stock but when I did my carbs 2 weeks ago, I noticed I had 100's and 170's for my PAJ's and everything I've read says 90's and 170's. It is a Cal bike from what I gather. Elevation is about 1400 Ft. I've got the a/f screws out around 2 turns. Still very rich smell. I also hear some coughing in the airbox until it get's warmed up but even when I pull up to a light, the smell catches up and it's still strong. I'm getting just under 26 MPG. I gauge every tankful and it's pretty consistent. Sounds very low to all I've read here; 35-40 MPG. My fuel light always goes on at around 80 miles. I ride a bit into Boost but not enough to cut my MPG by that much, I wouldn't think.

Haven't got a sync set to fine tune but carbs are pretty close. He pulls hard and runs good except for these issues.

????

 

[naughtyG]

Have you checked all four of your spark plugs lately? Make sure they all fire - it sounds very much like they do not.

Also do take a good look into your tank with a flashlight - rust in there is often the culprit for issues of this kind.

The only mine ever got that bad I had a rusty tank and the rust dust wreaked havoc in my carbs, flooding the cylinders and all were firing randomly.

 

[user 8898]

I've had a rich fuel smell since I got my Max last year. Can't walk behind it when it's warming up or I will smell like heavy exhaust and have to leave my cloths outside so my house doesn't stink.

I'm running all stock but when I did my carbs 2 weeks ago, I noticed I had 100's and 170's for my PAJ's and everything I've read says 90's and 170's. It is a Cal bike from what I gather. Elevation is about 1400 Ft. I've got the a/f screws out around 2 turns. Still very rich smell. I also hear some coughing in the airbox until it get's warmed up but even when I pull up to a light, the smell catches up and it's still strong. I'm getting just under 26 MPG. I gauge every tankful and it's pretty consistent. Sounds very low to all I've read here; 35-40 MPG. My fuel light always goes on at around 80 miles. I ride a bit into Boost but not enough to cut my MPG by that much, I wouldn't think.

Haven't got a sync set to fine tune but carbs are pretty close. He pulls hard and runs good except for these issues.

????

You might start a new thread with the same text so it gets more exposure. I'm sure someone here can get you some valuable tips.

 

[Diablotin]

I'm getting the same rich condition. Guess what ... I just noticed than on butterfly remains open when all the other are closed... That could really be the source of the issue...

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[Diablotin]

And i just found a small canal preventing the butterfly from closing fully. Any idea how I can fix that?

Looks like this part of the assembly can not be bought separately...

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[naughtyG]

What do you mean by canal? Like a deep groove? If so, maybe JB Weld and then smoothing with a Dremel?

You can find complete vboost assemblies in the US - again Kyle or Sean may also be able to help you!

 

[Diablotin]

You can see the groove on the pic where the butterfly closes.
All the butterflies are having a nice copper color except the one not closing fully. It became brown where the gap is.

Would it explain gas smell and bad mileage?

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