Carb rebuilding time?

[a1bummer]

If I was to rebuild my carbs, is there anything I should be on the lookout for? A while back I was having troubles with it not running on all four. The issue came on all of the sudden. I ran some Seafoam through it, and after a while it came back. Everything appeared to be fine for quite some time. But then I noticed my mileage dropping. I was getting 38-40 mpg, but now I'm getting down to 32-35 mpg. I tried Seafoam again and it makes no difference. I've also changed the fuel filter, spark pllugs, plug wires, plug caps, synched the carbs, checked the diaphrams for holes and nothing has seemed to make a diff. I was having trouble with a bad stator about the same time and thought maybe a week charge (or lack of), may cause a week spark that might lead to a lack of a good fuel burn and have someting to do with poor mileage. I replaced the stator this fall. I didn't run more than two tanks or so through it since then. But it still seems to be getting the same crappy mileage as earlier. Anybody have any other ideas? Time for a rebuild? Won't be riding for a few more months up here in WI. so I have plenty of time to do it.

 

Thanks, Bill

[Snaggletooth]

Hey Bill.

 

You having any flooding problems or overflow from the vent tubes? Gas puddles under the bike? Engine revs running up suddenly and staying there?

 

These are the problems I was having before I rebuilt the carbs on my '84. Turned out the biggest issue I had was a couple of the floats were sinking on me and the needles were badly worn. I had lousy mpg and trouble starting.

 

I treated the floats with airplane dope, (a cheap patch but it worked with some side effects), and replaced the needles. And some intensive cleaning of every part I took apart. My mileage came up to about 41 mpg after the rebuild so I figure I had the fuel going to all the right places after I was done.

 

The needles are easy to replace but if you plan on replacing the net filters in the top of the carb body get back to me and we will talk about that. LOL! PITA!!!!

 

But first things first. Check the diaphragms and slides for sure. Check the the bowl fuel level before you remove them from the bike so you have a reference point after the rebuild. Pull the plugs and look for wetness from fuel fouling after sitting for a while. Do a sync on the carbs to make sure they are a properly set.

 

The best test I have found for checking to see if the floats are bad or needles are sticking open is this.

 

Warm the bike up to operating temp. If possible a 20 minute ride or a long idle time to warm her up. Keep her running and remove the airbox so you get a good view down the carb throats. Shut the bike down and turn off the lights and watch each throat with a flash light to see if you are getting and excessive amount of vapor from any of them. Do this on the center stand and again on the side stand. The heavy vapor would indicate the fuel is getting past the needles and running into the hot cylinders.

 

Mine was so bad on two cylinders it looked like a Vicks vaporizor! This was causing the plugs to foul so badly they had to be removed and dried off to get the bike to start.

 

Replacing the needles and resetting the floats to get the right fuel level in the bowls solved that problem. The plugs stayed dry and the bike starts like a champ after the rebuild.

 

Hope that helps a little bit.

 

Mike

[Dragonslayer]

Hey Bill.

 

You having any flooding problems or overflow from the vent tubes? Gas puddles under the bike? Engine revs running up suddenly and staying there?

 

These are the problems I was having before I rebuilt the carbs on my '84. Turned out the biggest issue I had was a couple of the floats were sinking on me and the needles were badly worn. I had lousy mpg and trouble starting.

 

I treated the floats with airplane dope, (a cheap patch but it worked with some side effects), and replaced the needles. And some intensive cleaning of every part I took apart. My mileage came up to about 41 mpg after the rebuild so I figure I had the fuel going to all the right places after I was done.

 

The needles are easy to replace but if you plan on replacing the net filters in the top of the carb body get back to me and we will talk about that. LOL! PITA!!!!

 

But first things first. Check the diaphragms and slides for sure. Check the the bowl fuel level before you remove them from the bike so you have a reference point after the rebuild. Pull the plugs and look for wetness from fuel fouling after sitting for a while. Do a sync on the carbs to make sure they are a properly set.

 

The best test I have found for checking to see if the floats are bad or needles are sticking open is this.

 

Warm the bike up to operating temp. If possible a 20 minute ride or a long idle time to warm her up. Keep her running and remove the airbox so you get a good view down the carb throats. Shut the bike down and turn off the lights and watch each throat with a flash light to see if you are getting and excessive amount of vapor from any of them. Do this on the center stand and again on the side stand. The heavy vapor would indicate the fuel is getting past the needles and running into the hot cylinders.

 

Mine was so bad on two cylinders it looked like a Vicks vaporizor! This was causing the plugs to foul so badly they had to be removed and dried off to get the bike to start.

 

Replacing the needles and resetting the floats to get the right fuel level in the bowls solved that problem. The plugs stayed dry and the bike starts like a champ after the rebuild.

 

Hope that helps a little bit.

 

Mike

I've got a similar problem with #4 flooding. I'm curios about float sinking and checking float level, How do you do that?

[a1bummer]

Hey Bill.

 

You having any flooding problems or overflow from the vent tubes? Gas puddles under the bike? Engine revs running up suddenly and staying there?

 

These are the problems I was having before I rebuilt the carbs on my '84. Turned out the biggest issue I had was a couple of the floats were sinking on me and the needles were badly worn. I had lousy mpg and trouble starting.

 

I treated the floats with airplane dope, (a cheap patch but it worked with some side effects), and replaced the needles. And some intensive cleaning of every part I took apart. My mileage came up to about 41 mpg after the rebuild so I figure I had the fuel going to all the right places after I was done.

 

The needles are easy to replace but if you plan on replacing the net filters in the top of the carb body get back to me and we will talk about that. LOL! PITA!!!!

 

But first things first. Check the diaphragms and slides for sure. Check the the bowl fuel level before you remove them from the bike so you have a reference point after the rebuild. Pull the plugs and look for wetness from fuel fouling after sitting for a while. Do a sync on the carbs to make sure they are a properly set.

 

The best test I have found for checking to see if the floats are bad or needles are sticking open is this.

 

Warm the bike up to operating temp. If possible a 20 minute ride or a long idle time to warm her up. Keep her running and remove the airbox so you get a good view down the carb throats. Shut the bike down and turn off the lights and watch each throat with a flash light to see if you are getting and excessive amount of vapor from any of them. Do this on the center stand and again on the side stand. The heavy vapor would indicate the fuel is getting past the needles and running into the hot cylinders.

 

Mine was so bad on two cylinders it looked like a Vicks vaporizor! This was causing the plugs to foul so badly they had to be removed and dried off to get the bike to start.

 

Replacing the needles and resetting the floats to get the right fuel level in the bowls solved that problem. The plugs stayed dry and the bike starts like a champ after the rebuild.

 

Hope that helps a little bit.

 

Mike

 

No flooding, puddles or irratic idle. I've synced the carbs already. Ran much better but still got sucky mileage. I'll check the rest that you mention when I'm able to put the brass monkey back out on the porch without freezing his ba**s off . What are the floats made of? Brass or composite? I don't think I've heard of ariplane dope before, what kind of side effects were there?

 

Thanks, Bill

[GeorgeS]

Have they ever been Replaced ???

 

If not, they need to be replaced !! 24 year old rubber, is Rotten !!!

 

Check the " Tamper Proof " screws, one on each Diaphram cover, If they are still there, you need new diaphrams !!

 

In addition, to new float valves.

[a1bummer]

I checked the diaphragms this summer to see if they might have anything to do with it. There weren't any tamper proof screws. They appeared to be in good condition. I held them up to a 100 watt bulb to check for holes and cracks, and didn't see any.

[Snaggletooth]

The floats are composite. They do hold up well for their age but they do get to a point where they absord gas over time. What I did was take out the old floats and hung them in the sun for about a week to let them dry out real well. I then gave them a coat of airplane dope to reseal them so they would no longer soak up the gas. That was about 5,000 miles ago. That did work, BUT, you have to apply ONLY one thin coat. Too much dope does add weight to the float and I had overdone mine a bit. I ended up having to bend the tang on the float that rides against the needle to the point where the float almost hits the inside of the carb body when I'm adjusting the float level to adjust the fuel level in the bowls. With mine adjusted as far is they will go without hitting the body I'm still a bit low on fuel level. I will be replacing the floats with new ones this spring just to make things right.

 

As far as checking the fuel bowl level it's really very simple. The already have the start of it built into the bike. The 4 bowl black drain lines that stick out of the carb rack brackets.....2 on each side of the bike...go to them. Pick up a male to male splicer at an auto part store. I got a pack of 6 different sizes for like $5.00. You will need a short piece of clear fuel line the same size as the drain lines also. About 4 or five inches.

 

Insert the splicer into the clear line and stick the other end of the splicer into one of the drain lines. Start the bike and let her idle for a minute or two. Shut it down and while holding the clear line up along side of the carb body open that drain screw and let the line fill with gas. You will notice there is a scribe line cast into the body of the carb that indicates the center line of the slider needles. Use that center line as your reference as to the fuel level. Make a note of the level on each carb as you do this on each one.

 

If they are all the same or damn close you are probably ok. If one is way lower than the others the float may be stuck, sunk or a have a bad needle.

 

Oh yeah. Make sure the bike is on the center stand and the carbs are as level as possible.

 

If you have a low one, or two, you can pull the carbs and and adjust the tang on the float to raise the fuel level. Or you may see the problem when you open it.

 

I packed my manual away for the winter but maybe somebody has one handy with the correct measurement for the level reading. It's a bit below the center line on the carbs but off hand I can't remember the numbers.

 

Fuel flow it always critical. If the fuel filter is good, the pump is working properly and the fuel lines are open there is only one more place that can be a problem. Where the fuel enters the carb bodies there is a plug in the body that is inline with the needle seat. Under that plug is what is called net filter. It is the last filter before the gas enters the needle seat and into the bowl. Make real sure that filter is clear. Blow through the needle seat or through the feed line nipple and make sure it is open. You can apply a little Sea Foam or carb cleaner to help clean it out. If it is not allowing gas through it is a PITA to change. You would need to order the net filters, new plugs for the body, an o-ring I believe and then you have to drill into the plug, not all the way through it, then blind tap the hole and install a screw into the newly tapped hole. Pull out the plug and old filter and change the needle seat while you are at that point.

 

Not a fun job. So with that said, at best, new needles can be installed in the old seat with no problems. The needle is what wears out not the seat. The problem is that the needles and seats are sold as a set at about $37.00 each if I remember right.

 

If the floats are damaged there are floats out of the Vmaxs that will work just fine. Other wise I'd try the reseal with the airplane dope. Go lightly.

 

As I said, when I did mine I changed the needles, treated the floats and cleaned everything and it made a world of difference. The only hitch is in setting the fuel level. There is no way to do it once and be right. You install the carbs, start the bike, check all four bowls and then remove the carbs, open them up again and adjust the low one, or high, then reinstall and try again. My take few trys.

 

I need to rest. My fingers hurt. LOL!

 

Mike

[Snaggletooth]

I mentioned the way to test for the gas leakage past the needles in the other post. All of mine had some vapor but the #3 cylinder was the most obvious.

 

Here is a short video of what you might see if a needle is bad.

[a1bummer]

WOW! Great info. I read through the manual last night a bit. Crappy pictures and vague instructions. Now that I've read through your post, I think I understand better.

 

Thanks, Bill