Stumped, frustrated, and missing riding season!

Hey all, as some are aware, I've got a VF500F that I've been working on for a while. Problem is, I've hit a bit of a roadblock. I can't get the damn thing to run.
It'll run on carb clean or gas sprayed right into the carbs, but not run on it's own. It'll stumble, seem like it's going to start, but not quite start. I've taken the carbs apart twice, looking for any sort of issue. Nothin'.
There's fuel in the float bowls, everything moves freely and is clean, mixture screws are 2.5 turns out.
My ex-mechanic father and I agree that it's some sort of fuel delivery problem, but can't figure out exactly what the problem is. We're stumped.

Any help would be tremendously appreciated.

If it runs off of direct fuel to the carb then I'd wager you have a fuel problem. Checking the Fuel System from the easiest part to the hardest part would be my start.

Fuel in the tank?
Fuel line from the tank not clogged?
Fuel filter servicable?
Fuel pump fuses and fuel pump relays working? (if your bike has em, not too familiar with your particular model bike)
Fuel pump working?
Check wiring and connectors?

Just throwing suggestions out there.

[image: View Post]Infidel, on 30 June 2010 - 01:19 PM, said:

If it runs off of direct fuel to the carb then I'd wager you have a fuel problem. Checking the Fuel System from the easiest part to the hardest part would be my start.

Fuel in the tank?
Fuel line from the tank not clogged?
Fuel filter servicable?
Fuel pump fuses and fuel pump relays working? (if your bike has em, not too familiar with your particular model bike)
Fuel pump working?
Check wiring and connectors?

Just throwing suggestions out there.


Thanks for trying, but I know the fuel is getting to the carbs, as loosening the drain screw on the bottom of the carbs causes a fuel to leak out (as it should).
It's the thought that counts. hahaha

Spark plug age/condition? They might be good enough to light the ether & not the gas... Choke on?

[image: View Post]SEBSPEED, on 30 June 2010 - 01:28 PM, said:

Spark plug age/condition? They might be good enough to light the ether & not the gas... Choke on?

Plugs are brand new, NGK's.
I've tried it with the choke on, off, and everywhere in between.

Did it sit for a while?? Did you actually pull the pilot jets and clean them?? Can you see through the hole on them?? How about the mixture screws? Did you actually pull them all the way out and clean the ports?? There is a spring behind them, so be care not to lose it.

[image: View Post]Turbocharged314159, on 30 June 2010 - 01:38 PM, said:

[image: View Post]SEBSPEED, on 30 June 2010 - 01:28 PM, said:

Spark plug age/condition? They might be good enough to light the ether & not the gas... Choke on?

Plugs are brand new, NGK's.
I've tried it with the choke on, off, and everywhere in between.


Well then, if it runs on starter fluid and gas spray, and it has spark, and your air filter is not clogged, AND you have fuel in your bowls, then the problem is in your carbs.

[image: View Post]wera803, on 30 June 2010 - 01:53 PM, said:

Did it sit for a while?? Did you actually pull the pilot jets and clean them?? Can you see through the hole on them?? How about the mixture screws? Did you actually pull them all the way out and clean the ports?? There is a spring behind them, so be care not to lose it.

I completely rebuilt the carbs a month ago, but didn't start it. It didn't sit with gas in in it. I completely went through them again yesterday.

At this point I'm trying to scrape together enough money to buy a running bike so I don't miss the entire season. :angry:

There are 2 motorcycle shops near me, one only works on Harleys, and the other guy doesn't know these bikes well enough to feel comfortable working on it. :dry:

[image: View Post]SEBSPEED, on 30 June 2010 - 01:54 PM, said:

[image: View Post]Turbocharged314159, on 30 June 2010 - 01:38 PM, said:

[image: View Post]SEBSPEED, on 30 June 2010 - 01:28 PM, said:

Spark plug age/condition? They might be good enough to light the ether & not the gas... Choke on?

Plugs are brand new, NGK's.
I've tried it with the choke on, off, and everywhere in between.


Well then, if it runs on starter fluid and gas spray, and it has spark, and your air filter is not clogged, AND you have fuel in your bowls, then the problem is in your carbs.

That's my conclusion too, but I can't figure it out. I've had them apart twice in the past month, and nothing looked amiss.
I'm beyond stumped. This bike is defying everything I thought I knew about motors.

float bowl vent line clear?

What did your cleaning job consist of? Did you completely disassemble the entire carb rack, float bowls and jets only, soak the carb bodies at all? Etc...?

Test your fuel pump too.

[image: View Post]SEBSPEED, on 30 June 2010 - 02:06 PM, said:

What did your cleaning job consist of? Did you completely disassemble the entire carb rack, float bowls and jets only, soak the carb bodies at all? Etc...?

Float bowls, jets, mixture screws, slides, choke valves. All were removed and cleaned.

No fuel pump on this bike.

[image: View Post]Turbocharged314159, on 30 June 2010 - 02:16 PM, said:

[image: View Post]SEBSPEED, on 30 June 2010 - 02:06 PM, said:

What did your cleaning job consist of? Did you completely disassemble the entire carb rack, float bowls and jets only, soak the carb bodies at all? Etc...?

Float bowls, jets, mixture screws, slides, choke valves. All were removed and cleaned.

No fuel pump on this bike.


Please don't take this as an insult, that isn't my intention, I just don't know your mechanical background.

How did you clean the pilot jets?? There are the small holes in the bottom, but there is another one right up through the center. The center one is the one that usually gets plugged. Did you blow compressed air through it?? If you look through the center, can you see light through it??

I just did my VF500F carbs too and had to soak all of the pilot jets longer then anything else and then blow them out with compressed air to get them clean. Also ran a torch tip cleaner through them to clean them.

What about float level adjustment. If you get fuel to the bowl when you pull the bottom plug out, is it possible there's only 1/4" of fuel in there, which gets replenished when you take the plug out, due to incorrect float level so not enough for the tubes to draw from?

[image: View Post]wera803, on 30 June 2010 - 02:45 PM, said:

[image: View Post]Turbocharged314159, on 30 June 2010 - 02:16 PM, said:

[image: View Post]SEBSPEED, on 30 June 2010 - 02:06 PM, said:

What did your cleaning job consist of? Did you completely disassemble the entire carb rack, float bowls and jets only, soak the carb bodies at all? Etc...?

Float bowls, jets, mixture screws, slides, choke valves. All were removed and cleaned.

No fuel pump on this bike.


Please don't take this as an insult, that isn't my intention, I just don't know your mechanical background.

How did you clean the pilot jets?? There are the small holes in the bottom, but there is another one right up through the center. The center one is the one that usually gets plugged. Did you blow compressed air through it?? If you look through the center, can you see light through it??

I just did my VF500F carbs too and had to soak all of the pilot jets longer then anything else and then blow them out with compressed air to get them clean. Also ran a torch tip cleaner through them to clean them.


No offense taken. I did clean the jets well, soaked them for 3 days (the first time I rebuilt them). The second time I cleaned them the center holes were still clear.

[image: View Post]BCmcrider, on 30 June 2010 - 02:46 PM, said:

What about float level adjustment. If you get fuel to the bowl when you pull the bottom plug out, is it possible there's only 1/4" of fuel in there, which gets replenished when you take the plug out, due to incorrect float level so not enough for the tubes to draw from?


Good point!

Just throwing something out there: How's the compression on your cylinders? Maybe there isn't the vacuum that you need to get the fuel mixture in there.

Maybe read this to make sure you've covered everything.
My link

I think you have missed an orifice in the carbs somewhere. Probably the circuit for the pilot jets. You must blow compressed air through every hole when the carbs are completely disassembled (but don't remove them from the top plenum! Only do that if you have to replace the fuel tube o-rings.) Spray some carb cleaner or contact cleaner in first and then look for the mist going out somewhere.
After working at a Honda dealer for over 12 years, I learned that I trust about 1% of the population to do a proper carb clean.

I know it's frustrating and I'm not trying to insult you. I've just seen it too many times that I have to do a carb clean on carbs that have just been "cleaned".

Go through them one more time. I know it sucks. They are not fun to remove and install. I worked on a buddy's VFR700 and we "de-Californized" it. I could have the carbs apart on the bench in about 10 minutes from a fully assembled bike. Lots of trial and error making one change at a time.

Good luck!
Mike.

[image: View Post]Captain 80s, on 01 July 2010 - 01:16 PM, said:

I think you have missed an orifice in the carbs somewhere. Probably the circuit for the pilot jets. You must blow compressed air through every hole when the carbs are completely disassembled (but don't remove them from the top plenum! Only do that if you have to replace the fuel tube o-rings.) Spray some carb cleaner or contact cleaner in first and then look for the mist going out somewhere.
After working at a Honda dealer for over 12 years, I learned that I trust about 1% of the population to do a proper carb clean.

I know it's frustrating and I'm not trying to insult you. I've just seen it too many times that I have to do a carb clean on carbs that have just been "cleaned".

Go through them one more time. I know it sucks. They are not fun to remove and install. I worked on a buddy's VFR700 and we "de-Californized" it. I could have the carbs apart on the bench in about 10 minutes from a fully assembled bike. Lots of trial and error making one change at a time.

Good luck!
Mike.

That's the plan. Tear it all apart again.
It sucks, but so does not having a working bike. :mellow:


And it takes you 10 minutes to pull the carbs and take the bowls off?? I can do it in 5 at this point. :laughing6-hehe:

I am thinking the vacuum operated fuel petcock...

Try this:
Remove the tank
Turn the fuel to on (no fuel should drip from the tank)
Apply a slight vacuum (by mouth)
Fuel should start to flow and you should not need a constant flow of vacuum.
If you do need constant vacuum, you have a torn diaphragm on the vacuum side of the petcock.

Good luck!

While reading this I kept thinking the same thing as others - the float level. Just because there is some fuel in the bowls doesn't mean there is enough. Hopefully the next carb inspection will turn up something for you!

I'm assuming it actually ran for a few seconds on a prime, not just popped a little - yes? if so it can run with proper fuel delivery.
if not, starter clutch / igniter pickup timing, compression, bulk vacuum leak, incorrectly installed cams.
I'll assume no one touched the starter clutch or cams for now.

If so, make sure the gas in the carbs (and tank) is fresh. bad gas will frustrate anyone and isn't always as obvious as you think.
make sure the carb boots aren't ripped and clamps are tight.
looking in the carb bowl there is 3 brass tubes, main jet, low speed and starter.
the starter jet doesn't appear to have hole in it, but it does, requires a very small wire to ensure it is open.
Most carbureted V4s will not run w/out the air cleaner, it leans them a lot.

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[image: View Post]PLCGuy, on 12 July 2010 - 08:37 PM, said:

Most carbureted V4s will not run w/out the air cleaner, it leans them a lot.


I've not had any problem getting a VF to run without the airbox in place, but the certainly don't run very well!

If you want, you can swing by and grab my set of carbs. Jets are probably going to be different, but at least I know they're good and you'll be able to tell if it's a carb issue or not. If you do, just get the gas out of em, and don't let any spiders gum em up with their damn stickin thread.

Ok, just an update, I got it running. :biggrin:
It was a combination of a few things, including the petcock.
I'll be disassembling the petcock today, and I'll either figure out why it's not working, and fix it; or disable the vacuum valve.

[image: View Post]Turbocharged314159, on 13 July 2010 - 09:56 AM, said:

Ok, just an update, I got it running. :biggrin:
It was a combination of a few things, including the petcock.
I'll be disassembling the petcock today, and I'll either figure out why it's not working, and fix it; or disable the vacuum valve.


Nice! What were the few other things?

[image: View Post]Turbocharged314159, on 13 July 2010 - 09:56 AM, said:

Ok, just an update, I got it running. :biggrin:
It was a combination of a few things, including the petcock.
I'll be disassembling the petcock today, and I'll either figure out why it's not working, and fix it; or disable the vacuum valve.

Hmmm... did you try:

Quote

Disconnect the line from the petcock to the carbs. Put the line into a mason jar. Turn the petcock from off to PRI. The fuel should just run right out.

IF it does, turn it to off. Then take the vacuum line from the carbs to the petcock off. With the delivery line still in the mason jar, turn the petcock to run. Then suck on the vacuum line. Fuel should flow from the delivery line.

from the PM I sent last week? Could just be crud on the filter on the petcock...

[image: View Post]Turbocharged314159, on 13 July 2010 - 09:56 AM, said:

Ok, just an update, I got it running. :biggrin:
It was a combination of a few things, including the petcock.
I'll be disassembling the petcock today, and I'll either figure out why it's not working, and fix it; or disable the vacuum valve.


You'll need to turn the petcock to OFF whenever the bike's not being ridden if you disable the vaccum operated part of the petcock..

[image: View Post]squirrelman, on 18 July 2010 - 01:11 PM, said:

[image: View Post]Turbocharged314159, on 13 July 2010 - 09:56 AM, said:

Ok, just an update, I got it running. :biggrin:
It was a combination of a few things, including the petcock.
I'll be disassembling the petcock today, and I'll either figure out why it's not working, and fix it; or disable the vacuum valve.


You'll need to turn the petcock to OFF whenever the bike's not being ridden if you disable the vaccum operated part of the petcock..

Yup, gotta remember that. I read Jamie Daugherty's guide, good stuff.

I coated the gas tank with Red Kote (after the degreaser and Metal Ready), which will fix my rust issue, which I suspect was the problem all along. The starter jets got clogged quickly, probably because the gas was brown from the tank. Though I have a fuel filter, maybe it's no good/not good enough.
We shall see.