Hey! I cleaned my carbs back in April, lined my tank with POR15 (found lots of rust sediment in carbs), and changed my fuel filter. My accelerator jets were completely clogged, and had been causing a bad stumble if I tried to punch the gas. It's awesome having those fixed.
Over the last couple months, I've been having a problem that has gotten gradually worse and worse. At first, I was noticing that my idle didn't want to stay steady- either the engine would race, or it would drop so low it wanted to die- I tried adjusting the idle speed, but this was the result each time, either it wanted to die, or was racing.
For a while, it was running well enough that I could let it go to a low idle and it would keep running, only threatening to die every once and a while.
Since then, it's gotten worse. It won't idle at all now. I have to rev the engine each time I get to a stop to keep the engine from dying. Now, when I go to accelerate, the bike wants to die off the start. The only way I could get it go is by revving it high and slipping the clutch slowly to ease it into riding speed. Once the engine gets above about 30% throttle, it feels like something "catches" and it just takes off like normal. It rides normally at about 35mph+.
Below about 25%-35% throttle is where I'm seeing the problem. If I'm at riding speed and let off the gas to about 25%, I can feel the engine stumbling as if it's short on power (Lean?).
I think its got to be a carb problem, right? But where to look? I just cleaned all the jets recently, and could this be just a problem with one carb jet? It seems like something that's wrong with both carbs. Feels like it's not getting fuel below 30% throttle. Where's that jet? Anyone experienced this before?
From your description it sounds like you still have some 'foreign matter' in some passages. A good cleaning and lots of compressed air to help clear the passages is in order. You do have a good fuel filter between the tank and the carburetors, do you not?
Could also be an air leak.
I'd go with what these guys said above. If you had bad rust in the tank, a piece the size of a grain of sand could have been hiding in a fuel line or in the fuel pump somewhere waiting to riun your day. The pilot jets are microscopic so it wouldn't take much to do. My bike had cracked rubber boots and a ruptured VICS membrane as well.
At least with the Vision, the carbs are quick and easy to remove. I did the carbs on my '84 Nighthawk last month and I had to take half the bike apart to pull the airbox back to get them out. And once out, there's four of them.
Thanks for such quick replies. I've started pulling the carbs outhe, I'plan do another thorough cleaning and see if that does it, it probably will.
I do have a fuel filter on there, just replaced it when I lined the tank and cleaned the carbs. I also have my carb boots coated in some RTV, so I hope those aren't leaking. The first thing I checked was my YICS, and both chambers are still holding vacuum (check out my other post for pics of my DIY YICS). Thanks for the help, and I'll let you know how she does after the carb cleaning! I do love how easy it is both to remove the carbs and to disassemble them. I did my friends Suzuki GS550 about a month ago and on every level it was more difficult.
Just a general FYI: silicone RTV is NOT fuel resistant. I have been sourcing some connector hose at automotive race shops and the silicone hose carries a warning that it is not to be used in a fuel environment.
I once made a "quick fill" funnel to hold about 4 gallons of fuel, and sealed and smoothed the interior with RTV silicone. The first time I tried to use it the silicone just peeled off in flaps and pieces. Best to find another sealant for use around gasoline (petrol). :police:
Thanks for the advice, Fret Nut. You're right, RTV probably isn't the best sealant for the carb boots. I will have to double check all my fuel lines to see that they are designed for fuel, also. I could see a deteriorating line being the cause for some annoying carb clogs.
Is anyone able to give pictures/describe a specific location where I should look on the carb for the troubles I've been having? I have them disassembled, and have been running carb cleaner through all the passageways I can find. The passages I was suspecting (those small holes on either side of the butterfly valve) seemed to all be very clear. I'll blow everything out with compressed air, too. Just want to make sure I'm not overlooking something while I have it torn apart. Hate to get it back together and have the same problem. Thanks a ton!
Someone above also mentioned this could be an air leak- could it be a leak at the carb gasket? Any ideas where I should look for that? YICS and carb boots should be good. I'll check hoses once I get it all back together.
Thanks so much for the help.
Make sure you can see through the pilot jet. It has to be removed from the carb body to make this check. Also be sure that the emulsion tube jet and the tube holes are clear.
Since you have the carbs apart, you should check the butterfly shaft seals. I have not experienced this but others say it is a fairly common problem. It is kind of a pain to get them out as you have to remove the throttle plate and the screws are staked. They are not too hard to get out but a JIS screwdriver makes it easier. It is recommended to replace the screws after use.
QBS- I checked both of those- all good. Thanks for the reply.
Walt_M- do you know what the symptoms of a bad butterfly shaft seal are? I'll take a search around the forums for that.
The carbs look in great condition, I assume they've been rebuilt with lots of new parts within the last 5 years (before I purchased)- since the bike has 40k miles on it and the Jets all look shiny and new. I probably won't touch the butterfly seals unless I can directly link it to the current problem.
The butterfly shaft seals would be an air leak. If you have it back together, with access to the carburetors, start it and warm it up squirt some WD40 or other flammable around the carb bodies. If the speed picks up, you have a butterfly shaft seal leak.
I changed those seals on a set of carbs. Some of the symptoms were typical of any air leak in general - erratically fluctuating idle was the most prominent. Running hot may be another. Just because the carbs look rebuilt I wouldn't assume the shaft seals were replaced. Walt's suggestion for checking for vacuum leaks there is a good test to apply to all areas of the carbs and manifold sealing surfaces.
" all areas of the carbs and manifold sealing surfaces." Including the manifolds themselves. They do have a tendency to crack with age, and leak.
Thank you guys. I'm sure I'll have to do those butterfly seals at some point. I like being able to build up a bank of knowledge about this bike. A thorough cleaning of the carbs solved the problem this time. I think something was clogging the idle circuit pretty badly- since I had to turn the idle adjustment WAAAAY down after putting everything back together. I also managed to shoot a stream of carb cleaner directly into my eye. I probably won't do that again... ha.
Next project is the oil leak. Seems to be leaking around the bottom of the casing on the left side of the bike. Would a new seal around that casing seal it? Or is the leak probably coming from somewhere else?
Leak might be the shifter shaft seal. My '83 leaks a little there. It's an annoyance, but not enough for me to go to the trouble to change the seal.
QuoteSeems to be leaking around the bottom of the casing
I'm not sure if you mean the engine cases or the left engine cover that houses the alternator and other troublesome bits and pieces.
There are few Visions that haven't had the alternator cover removed so that gasket (or AC wire exit point) may be leaking or perhaps the shift shaft seal as QBS noted. The best thing to do is clean the area thoroughly (engine degreaser, S-100, Simple Green) then keep your eye on things after each ride to see where the oil is leaking from.
Good job on the carbs BTW. I'm glad you got the idle issue sorted.
Clean the area real good as mentioned above and then put baby powder all over the area. This will show you right where the leak is occurring. My bet is on the grommet where the wires come out of the case.
Wanted to provide an update here as well. The carb idle fluctuation never fully went away. It got worse and worse until I finally gave in and replaced the throttle shaft seals. It actually was not too difficult of a job. I followed a video on Vimeo. I carefully filed the staked ends of the screws, then removed them. When replacing them, I used locktite. I did a quick visual sync on the carbs and WOW it runs WAY better! Hope that helps anyone who is facing a similar problem.