1986 Interceptor vf500f1 very serious running issue

Recently i set out to paint my tank (po painted it a gross black, i wanted to make it white to match the bike). Up until i pulled the tank the bike was running perfectly, accelerated smoothly all the way up to triple digits and would keep pace with my friends on their 00's 600's.

After i pulled the tank, painted it and put it back, the bike started running extremely rough. Low on power, very jerky, will only idle with the choke on alot of the time. Literally on the highway in 6th at 7k with the throttle 3/4 of the way open the bike cold barely do 60. If i pull the clutch and try to coast in neutral it shuts off.

At first i thought it was a fuel delivery issue. So i pulled the tank back off, checked the fuel lines and there was a kink in the line. I fixed that and the problem persisted. I pulled the airbox off and checked inside that, no obstructions or anything in there.

The only other thing i can think is did i maybe get paint in the gas tank? Would that cause a problem like this? I know these symptoms are usually associated with dirty carbs but i cant imagine that my carbs would get clogged from having the tank off for ~3 hours. I had it off for over 2 weeks in the summer and the bike started right up no problems.

If anyone has any idea what this could be i could really use the help. No suggestion is a bad one. I'll post a vid tomorrow when its light out of what the problem is.

Thanks in advance

 

Clogged pilot jets in the carburetors. They are a very tiny orifice (0.013") so any little bit of paint or crud in the fuel can shut them down. If the bike has set up with the alkyhol fuel it can clog up surprisingly quickly also. Only running with the choke and not being able to idle is a sure sign that this is the culprit.

 

Wouldnt the fuel filter keep anything big enough to clog a jet out of the carb?

 

Not always, no.

 

K looks like i have a project today. Can i clean the main jets without having to pull out the carb assembly? :wishful thinking:

 

Sure you can if you have a small pet with enough manual dexterity to remove the float bowls with carbs in place.

Pull and inspect the sparkplugs first, cuz if you find dark black, you may have some tank crud lodged in a float needle seat, flooding a cylinder and reducing power.

 

So i got the carbs pulled, wiped the jets clean on the outside, shot some air through them, couldnt seen anything blocking the outlets so i think they're good. Working on rebuilding the fuel lines and replacing the filter as well.

Squirrelman, i'm pretty sure its still firing on all cylinders, i checked the headers last time it was running and they were all hot. I'll pull the spark plugs next time i'm wrenching on it and check those as well.

I just wanna get it all put back together and ride damn it!

 

Using the search function i found this thread in the forums:

http://vfrworld.com/forums/mechanics-garage/22449-cleaning-carbs.html

Carbs don't care about dirt on the outside. Carbs don't talk, carbs just sits--and listens...

 

Sorry i meant wiped the jets clean on the outside. They had some small amounts of a brown, powdery residue on them, then i used canned air inside the jets.

 

You sure the Petcock is flowing fuel properly?

I cant see how you could have only taken the tank on/off and sudden'y have carb issues.

 

a #12 electric guitar strimg will be your best friemd here to cleam out the pilot jeys.

 

I got the bike back together yesterday, wouldn't start. I tried again this morning and it started right up, however the idle is really low (~500). At first it was driving fine, then after a couple minutes it started hesitating and bogging again. After maybe 10 it died all together on the side of the road. Thus far i've replaced the fuel lines, fuel filter, emptied the tank and cleaned the main jets. I'm getting really frustrated at this point :/

By petcock you mean the valve on the gas tank? How would i go about checking that?

I think i royally screwed something up with the fuel delivery when i pulled the tank so i replaced all the lines and filter; or possibly got paint in the tank, thats why i pulled the carbs and cleaned them.

Jets were nearly spotless, all the little pinprick size holes were completely clear. The only residue i found was on the bottom near the threads. They were cleaned by the po at the beginning of the summer.

 

When I switched my VF500F from the fuel pump to gravity earlier this season I just wanted to see for myself that it would flow enough fuel to run well. All I did was disconnect the fuel line from the carburetor, run it in to an empty gas can, and turn the petcock to the on position. I don't exactly remember what the flow was but I think that it was something like half a gallon in six minutes.

If it's not flowing at the carb, then try disconnecting above the fuel filter to see if the filter is the problem.

If it's not flowing before the filter, then possibly you have a pinched fuel line or problem with the fuel line routing, or a problem in the petcock.

 

Yup! That's the guy. The one at the bottom of the tank and has the Fuel Selector Knob attached.

Looks like this when removed:



Did you remove it before painting the tank?

Did you re-install the small rubber vaccum line into the nipple, and then the other side is going to the side of the motor?

 

The '86 VF500 petcock runs off the motor vacuum. If the engine isn't running the Petcock won't be letting fuel by.

The way to test if fuel flows from the Petcock is to have the Gas tank sitting flat (with enough gas in it)

Then you connect a rubber vacuum hose to the nipple on the Petcock.

Ensure the petcock is set to ON (or RESERVE)

...and then Suck on the rubber hose. Fuel should come out of the Larger Petcock Outlet. When you stop sucking...it should stop flowing.

 

also ... and i know this sounds stupid but did you clean your fuel tank cap. you us a a lot of carb cleaner . flip it over spray than spray some more. also spray out the little hole that you see. if your tank is not venting right, no fuel is flowing.

 

Also, i couldnt find an exact match to the oem fuel filter so i got extra lines and had to kinda snake them around to make them reach. So now the line going to the left carbs is a little less than twice as long as the one going to the right, would that make the bike run like i described? I'm thinking maybe the fuel cant get through those lines as readily, so the left 2 cylinders are leaning out.

 

I didnt think of that, will throttle body cleaner work too? Or does it have to be carb cleaner?

 

carb cleaner works best