Carbs overflow - probably heard it before

BT650 · Full Member Joined: Jun 09, 2009 Posts: 10

Newbie here. I have a 79 with stock jets (I think) but have pod filters and no mufflers just straight headers. The bike actually runs pretty good but will start overflowing fuel from either side out the drain tubes until I turn the gas off. If I take the filters off, they are drenched. The original tank had two petcocks with no vacuum lines. Now I have a single straight flowthru petcock going to a T-fitting to feed both carbs. I also noticed that the vacuum tube coming off the top of the engine has one going to the side cover and another that is blocked off. Carbs have been cleaned. Plugs are starting to get black and wet. Any suggestions? Jet size problem because of filters and no mufflers, float level adjustment, or vacuum problem?

xsjohn

If it were mine ..........I would drop the bowls and using a small amount of fine steel wool on the end of a q-tip I would push it in the seat and twist it like 20 times.........and see what happened..........polishes the hole for a better seal.........check the point on the needle for wear.....newer carbs had rubber tipped needles for that overflow reason........

xsjohn

BT650 · Full Member Joined: Jun 09, 2009 Posts: 10

Forgive my ignorance, but what is the seat you're referring to? The portion where the main jet is?

weekendrider

The float needle seat is what John is referring to. While there check the floats for leaks and the correct float level.
If it is leaking while running this needs immediate attention, if it only leaks when off then remembering to turn the petcock off is the answer?

newelly

mine leaks from the overflow/ drain plug area with the petcocks off... could that be a float issue or do I need to take it to the place that cleaned them and make them look at it for free???

TwistedLeather

I'm not sure if the '79 has brass floats or not, but if it does, check for fuel INSIDE the float...sometimes these things develop a pinhole in the brass..easy fix if that's the case...just find some good silver solder, flux, and a soldering iron. Your float level might be off a bit too. One little trick I've used for years is the Q-tip and auto polishing compound to polish my float needle seat...it will require a good spraying out with carb cleaner and compressed air, but it works wonders on those old tarnished brass seats making needle movement much smoother.

weekendrider

newelly, Try running the carbs dry before you shut it off.
Turn the petcock off, and run it for a bit. If it leaks after that the petcock is leaking, if not the bowls are too full?

BT650 · Full Member Joined: Jun 09, 2009 Posts: 10

The petcock is new and doesn't leak (I have clear fuel line and can see the fuel stop when I shut the petcock off). It does overflow when the bike is running until I turn the petcock to almost off. Am I just getting too much gas to the carbs or do you still think it's a float or clogged seat? When I had the carbs apart to clean a few days ago, it didn't appear to have any gas inside the floats (which are copper). I'll have to try the steel wool thing.

jayel

dirty needle/seat or float level is set wrong

weekendrider

Or maybe the float is binding/sticking.

Xumi

One way or another, it's a float/float needle/needle seat issue.

First:
Check floats to make sure no fuel in them. dry the outsides, shake and listen. Repair if necessary.

Second:
Pull the float needles out, and soak them in carb cleaner for a while (1 hour should be plenty). Make sure the spring pin works freely and the tip is not damaged. Clean float hinge pins and holes thoroughly. Make sure the float moves freely.

Third:
Clean the seat using steel wool. blow out with carb cleaner, chase with compressed air.

Fourth:
Re-assemble, and adjust float height. Search the forums for your exact float height. 27mm from gasket, I *think*.

Fifth: Check for float straight - measure height on both bulbs of the float and make sure they measure the same. If not, twist to flatten, and re-adjsut float height.

6Th: Re-assemble and enjoy.

If you still have an fuel overflowing issue, you only have a few possibilities left:

Incorrect measurement of float height
Damaged needle seat
Gremlins

Gtikyle · New Member Joined: Jul 08, 2009 Posts: 4

im having the same exact problem. i have no idea what to do

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

While we have this topic up , I have a question. When I put my petcock on prime (vacuum on an 80). With the bike not ruining fuel flowes out the air filters. Is that normal or does that mean my fuel in the bowls is to high. I usually don't use the prime but I would like to have proper fuel level. I would like to test it with clear line from the bowls but I see no way to attach it. I might see if I can rig something up next weekend.

xsjohn

BS34.....The o-rings on the seat shrink over time allowing fuel to seep past the seat and flood the bowl..........you can replace the o-rings or wrap some thread next to them to puff them out a bit for a permanent seal....then camphor the edge of seat hole in the carb slightly and push the seat in with oil for a snug fit......that's what I did............and a bit of "fine" steel wool on the end of a q-tip to polish the inside of the seat and the sharp edges of the seat hole is good.........mine just never floods any more after those 2 things.............

and the BS38's that have no viton tips on the seat needles ca be helped ..... the q-tip and steel wool can help stop flooding.................

xsjohn

Xumi

Gtikyle - this thread is a great place to start. Read it several times, then take your carbs out and remove the bowls.

Once there, you'll be staring at your floats. Re-read this post, and do a search for "floats" on the forum. Read every post, then go back and look at your carbs again. If you can identify everything, then go to work cleaning out your seats, inspecting your floats, and setting the correct float height.

Just keep reading and work slowly, you'll get it sorted out. If you run into problems, start a new topic with as thorough an explanation as you can give about the problem, and people will try to help you get it sorted out.

Good luck

Xumi

Wonderful trick on the seat rings, John!

(makes not to tear deeper into my seats next time in carbs.. left one is riding a bit high on the fuel level. Not leaking, but still high). Probably just need to adjust... but while I'm in there, might want to do some PM.

Gtikyle · New Member Joined: Jul 08, 2009 Posts: 4

i took apart my carbs and cleaned them, i set the float height , then i removed the needle and cleaned the needle and seat. i put the bike carbs and the bike back together. I thought it was fixed i was excited. that wasnt the case, so i removed the petcock and took it apart. It didnt look dirty or anything but i wiped down the internals. i put the bike back to tegether, added some gas not a alot but enough to start it. It ran fine no more leaking so i decided to take it for a ride to my friends house, I totally forgot i had no gas in it, i ran out on his street, then i put it on reserve and it started dumping all over the ground, i turned it back to on and it was fine. i sat on the bike and started it up and it was like i never ran out of gas. I decided to fill the tank and the entire 2 gallon i put in was lost in the gas station parking lot. I have decided the problem i have is with the petcock. It is like when i turn the bike on it is stuck in prime and dumps all the gas no matter what. to stop the gas i had to take a rubber plug and stick it over the fuel line of the petcock.

to make it even worse my driveway started on fire because of my smoking habbits and my leaking motorcycle.

jayel

Gtikyle wrote:

im having the same exact problem. i have no idea what to do

get the manual petcock from mikes and quit smoking

Gtikyle · New Member Joined: Jul 08, 2009 Posts: 4

Manual. Petcocks are backordered 5 to 6 weeks

cpt137 · Full Member Joined: Jan 10, 2009 Posts: 97

I hope i'm not missing something but if your floats are working properly you should never lose fuel out your carbs.

chopperhack · New Member Joined: Jun 27, 2008 Posts: 6

We're having the same problem on a 76 model.
Re'built the carbs with parts from Mike's...Leaks from float valve.
I noticed the needle valve/diameter of the seat fit is really sloppy and when filled from empty the needle jams as it rises into the seat.

If we tap the bowl as it is filling it will sometimes jar the needle loose and quit leaking.

y wife has an 82 and her needle valve/seat tolerance seems a bit closer.

I'm scavenging through some extra carbs to check for older parts to use.

Has anyone thought the problem may be cheap parts in rebuild kits?

xsjohn

Could try putting a bit of extra fine steelwool on the end of a q-tip and push in in the seat and turn it like 20 times to polish the seat and the hole...........

xsjohn

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