2000 Vulcan VN800A running rough after oil change

[mjkearns]

2000 VN800A, 12.7K miles
Just changed the oil, and cycle started missing, especially when first hitting the throttle. I pulled the plugs to check wear and gap. They looked pretty good so I regapped and replaced. The bike sat up a lot during our rainy season and don't know if that might have gunked up the carb. It cranks quick, and runs pretty good with the choke out, but once I shut off choke, it misses when I first hit the throttle and I can feel/hear it missing from time to time when I'm revving it. Any inexpensive quick fixes I can try before I have to break it down to get to carbs, etc.?

mjkearns
2000 VN800A

[MFolks]

Go to either Wal-Mart or any good auto parts store and for about $7 buy a can of fuel additive called "Seafoam" Follow the instructions on the can. It will help dissolve any crud in the fuel system.

[jeffs99vulcan]

+1 on the Seafoam... and +1 on starting with the simple cheap solutions first. The 800's are well known to be reliable, it's something simple and I'm going either bad gas, or gunked up carb.

Try to get new gas in there as soon as possible, siphon what you have if it's that bad, but stick with 87 octane...

Good luck, welcome to the forum, and update us as you go!

[Tendofreak]

Does it sit outside in the rain? You mentioned that it "sat-up" for awhile during rainy season. Just courious if it was IN the rain or OUT of the rain. Will make a big difference in the remedy for your problem. But first thing is to drain the old gas, get new gas and an additive in there to burn out any mositure trapped.

[mjkearns]

Tendofreak, it is garage kept.

[mjkearns]

OK, I rechecked the gap on the plugs, bought some seafoam and added to the tank. I ran it about 10 miles at what I thought was pretty high rpms. Today I pulled the aircleaner and noticed it smelled heavy of fuel. I ran it without the cleaner and even shot some carb cleaner into the carb. It runs OK with the choke pulled, but as soon as the choke is off, it start sputtering and when I pull the throttle, I can see gas blow out of the carb. Any additional thoughts?

[jeffs99vulcan]

Can't say for sure what the deal is with the gas blowing through the carb, I'm not a carb guy... but are you sure the sputtering when the choke is pushed in isn't the idle speed adjustment?

[mjkearns]

It also backfires frequently from the carb.

[mjkearns]

By the way, what is the best way to drain the tank? While I added Seafoam, I think I'd rather be sure that if it's bad gas, or water in the tank, that it's cleared out. I want to start with a fresh tank of gas.

[cosmicsclassic]

could be bad gas or water. to drain tank, remove fuel line from bottom of petcock, install a temp. peice of hose from petcock to a catch can, turn valve to prime. tank should drain. sounds like water in carb too. to drain , remove air cleaner cover-filter and back plate. watch out for hoses attached to back of plate. once removed, at the bottom of the carb there is a hose nipple, attach a peice of hose to the carb bowl, just above the hose nipple is the bowl drain valve. you will need a 3mm allenhead wrench, turn counter-clockwise and carb should drain. a little work but not hard.

[RichLockyer]

Ya... sounds like bad gas or water.
Running well with the choke on and having problems with it off is normally a sign that it is running too lean... probably due to a plugged jet.

Remove and drain the tank, dump in a pint of acetone and swish it around to take up any water that might remain in the tank (don't get it on the paint!), dump the acetone, and refill with fresh fuel and a half a can of Seafoam.

Take it for a good run with the Seafoam in the system, then park it for a few days to allow the Seafoam to work on cleaning the carbs.

If it doesn't gradually improve, then the carbs probably need to be worked on.

You didn't mention if the idle is high or the engine seems to be racing... a vacuum leak from a cracked carb boot can mimic a lean condition... but you're looking at pulling the carb(s) to replace that. Cleaning the tank and running Seafoam is cheaper and easier, and if it works, you're back on the road in a couple of days.

[mjkearns]

OK, thanks to MLK I had the day off. I emptied my tank and drained the carburetor. I got fresh gas and put approximately 1/2 can of seafoam in the tank. I started it up and as I said before, it runs great with the choke, but as soon as I shut it off, the motor bogs and sputters and backfires out of the carb. I noticed that if I impede the airflow into the carb with my fingers, the engine smooths out. I'm guessing this further points to the bike running too lean and possibly a plugged jet? I'm strapped right now, and can't afford to take it in for service, and I'm not a very strong mechanic either. Is it possible that the seafoam will unplug the jet? I'm having to sell it because my truck up and died on me and I need to have something that I can haul my kids around in. Obviously I'll have a better time selling it if it is running good. Thanks to all for the help so far.

[RichLockyer]

Give it a few days for the Seafoam to work.
Someone recently took their ATV out of storage and Seafoam "fixed" it almost immediately, but it can also take some time if it is badly blocked.

Another thing that might help if it's still acting up after sitting, is rev the engine to a moderately high RPM, chop the throttle, and immediately block the intake with your hand... anything that's loosened up but still partially blocking the idle jets may be drawn through by the high vacuum.

[jeffs99vulcan]

Can you ride it? Can you take it for a good run and get that half can of Seafoam through it? Don't be shy with it, you won't break anything, but don't get so far away from home that if you have trouble getting it started (which is doesn't sound like is the problem) that you end up walking...

But the Seafoam has a better chance of doing it's thing but you have to get it through the system...

[RichLockyer]

It's "in" the system... he drained the tank and the bowls, so as soon as he started it, it was pulled into the jets.

[jeffs99vulcan]

It's "in" the system... he drained the tank and the bowls, so as soon as he started it, it was pulled into the jets.

The stuff's not instant though, is it? I've used it, but only once... won't it have a better chance of cleaning out jets and small orifices if it's flowing, and flowing over a longer time than just a few minutes of idle? With all parts in full range of motion, opening, closing, different flow rates... I dunno, I'm only imagining how it must work, but I'm no Seafoam pro!

[RichLockyer]

The stuff's not instant though, is it? I've used it, but only once... won't it have a better chance of cleaning out jets and small orifices if it's flowing, and flowing over a longer time than just a few minutes of idle? With all parts in full range of motion, opening, closing, different flow rates... I dunno, I'm only imagining how it must work, but I'm no Seafoam pro!

The idle circuit would be best served by "soaking" with occasional running.
The needle is pretty much self-cleaning as it moves up and down in the orifice... and the main jet is too big to completely plug unless there's some serious debris in the bowl (which probably would have gotten stuck in the float valve).

Like I said... soak it a day or two, take it out and run it to high RPM, chopping the throttle, and see if it improves over time.
If not, then high RPM, chop the throttle, and block the intake to pull hard on the idle circuit... if that doesn't do it, the carb needs to come off and apart for cleaning.

Multi-carb racks are a pain, but a single carb can be torn down completely, cleaned in parts dip, and reassembled in an hour plus the soaking time.