Need help with running issue….

[BikerMike]

Hey all, here’s the problem I am having. I bought my 1999 Vmax in May of last year. I bought it from an elderly gentleman. Drove two hours home from Orlando, Florida to where I live on true west coast. The bike ran perfect. It has 35,000 miles on it. It is an excellent condition other than needing just a little polishing. Molested the only mods that it has is a Kirker exhaust system. I drove the bike to work after that a few times and around the neighborhood. I always keep it on a battery tender. Started it up at least once a week when I wasn’t using it. Usually just push the choke all the way down and starts right up and then ease off the choke fairly quick and it would run fine. Last few times I went to start it after sitting for a little while it’s starting to get progressively worse and not want to run.
The bike has run perfect and all of a sudden this started happening. Trying to make a long story short, I bought brand new factory plugs (NGK) , gap them to the correct gap (0.35) I change the fuel filter so try a factory Yamaha filter. The old one looked like it had not been changed in a long time. I also changed the fuel pump with a brand new factory Yamaha fuel pump. It will idle a little bit better now with the choke on, and I can get the choke almost off with it barely running. It will not let me give it gas or it will stall. If I spray starting fluid in the carbs, I can give a throttle as I’m spraying it and it will rev all the way up and run fine as soon as I let off it, it will idle with the choke on a little bit, but I cannot give throttle or it will die. I just don’t understand how this has all of a sudden happened. I have a 2004 big dog with a 107 S&S motor on it. I am very familiar with that bike. But this bike is a whole different ball game for me with the four carbs. Any help would be greatly appreciated. Thank you all so much.

 

[Traumahawk]

2 things to check. One thing, do a shotgun. A shot gun is a way to clean the pilot jets, which is what the carbs run off of at idle and around town. Do you know when the last time that the carbs have have been synchronized? All 4 carbs need to open and close at the same time.

https://vmax.lvlhead.com/tips/shotgun.htm

 

[Rossco001]

Remove and clean and reset the carbs, there will be crap in the float needles and jets, also clean out the breather tubes that come up to the air box. Check no cracks in the rubber socks, check the diapragms all good, Shotgun can help but not 100 percent , .....99, that's 25 years of potential build up of crap. Same happened to me to my '93, rebuilt in 2011, so only 13 years since rebuild, but sat for a while and float needles jammed up...good clean and rebuild, starts, idles no choke runs like a scolded jaguar.. on just a stage 1 carb kit.

 

[Rossco001]

2 things to check. One thing, do a shotgun. A shot gun is a way to clean the pilot jets, which is what the carbs run off of at idle and around town. Do you know when the last time that the carbs have have been synchronized? All 4 carbs need to open and close at the same time.

https://vmax.lvlhead.com/tips/shotgun.htm

 

[Rossco001]

Meant to add, check the vboost operating correctly, and that the vboost is closed, reset them while you're in there

 

[BikerMike]

2 things to check. One thing, do a shotgun. A shot gun is a way to clean the pilot jets, which is what the carbs run off of at idle and around town. Do you know when the last time that the carbs have have been synchronized? All 4 carbs need to open and close at the same time.

https://vmax.lvlhead.com/tips/shotgun.htm

Thank you man. I have no idea when the last time they were synchronized. But blows my mind is it was running perfect, and then all of a sudden just started doing this.

 

[BikerMike]

Remove and clean and reset the carbs, there will be crap in the float needles and jets, also clean out the breather tubes that come up to the air box. Check no cracks in the rubber socks, check the diapragms all good, Shotgun can help but not 100 percent , .....99, that's 25 years of potential build up of crap. Same happened to me to my '93, rebuilt in 2011, so only 13 years since rebuild, but sat for a while and float needles jammed up...good clean and rebuild, starts, idles no choke runs like a scolded jaguar.. on just a stage 1 carb kit.

Thank you. I will check it out. True on being that old and **** being clogged, etc… but it was perfect and now this crap.

 

[Fire-medic]

I suspect that off-idle running issues are likely pilot jets being clogged. If the Shotgun under LVlhead's site doesn't do the trick, then do the starting fluid spray all-over the carb & VBoost boots & by the intake manifolds to the cyl heads, where the skinny O-rings are, A disassembly of the carbs and an ultrasonic soak is what I'd do, if the Shotgun is not resolving the issue. Pilot jets are the smallest passageways I know of, in the carbs. Removing them from the jet block, and ensuring they're not blocked, and then doing the ultrasonic cleaning is the best way to clear up obstructions in the pilot jet passageways and the removable jets.

Pictures and info on maintaining your carburetors:
https://www.vmaxforum.net/threads/vmax-newbe-longtime-biker.53821/#post-539262

 

[BikerMike]

I suspect that off-idle running issues are likely pilot jets being clogged. If the Shotgun under LVlhead's site doesn't do the trick, then do the starting fluid spray all-over the carb & VBoost boots & by the intake manifolds to the cyl heads, where the skinny O-rings are, A disassembly of the carbs and an ultrasonic soak is what I'd do, if the Shotgun is not resolving the issue. Pilot jets are the smallest passageways I know of, in the carbs. Removing them from the jet block, and ensuring they're not blocked, and then doing the ultrasonic cleaning is the best way to clear up obstructions in the pilot jet passageways and the removable jets.

Pictures and info on maintaining your carburetors:
https://www.vmaxforum.net/threads/vmax-newbe-longtime-biker.53821/#post-539262

Thank you so much!! I want to get this problem solved as soon as possible. As soon as I get a spare time, I’m going to do it. It’s just pisses me off knowing how sudden this happened. Thanks again