OK...ready to blow these carbs up!!!!

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

I think I am past my ability to get this bike running good again. I have had these carbs off 4 times, twice without doing much except for a good cleaning. The last two times to install all new needles & seats, o-rings, and other parts. Put it back together, and after some long cranking, it fires up and runs really good-EXCEPT it backfires through the exhaust on DECEL only. Thought I could live with that, but after parking it for a week for lousy weather, took it back out of the garage and pretty near killed the new battery trying to start it. Finally got it to fire and warm up. Still pops through the exhaust on decel. Shut it off went inside for a sandwich, came back out- GAS LEAKING ALL OVER THE GROUND FROM right SIDE CARB, where the filter attaches. This happened to me BEFORE the rebuild, so I bought new pins for the floats to ride on, and the floats are not filled with fuel and tip easily when I had the carbs up. Adjusted the floats per spec.
I think I've had it with this bike...how much are new carbs????

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

What year bike and size carbs? If it is a vacume petcock you don't want it on prime or they will leak gas out carbs.

xsjohn

How many MM from the gasket did you set the floats..........80 carbs which I have are not noted for flooding.....and are thebrass covers off the mix screws....Think I know more about 80 carbs than I do about my own life.......... and politics......some say......

xsjohn

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

Joseph wrote:

What year bike and size carbs? If it is a vacume petcock you don't want it on prime or they will leak gas out carbs.

This is a 1980 XS 650 Special.....I have no idea what a "vacumm petcock" is, but maybe you have something there-----
I have not ridden this bike in years, and I actually do not know what I am doing when it comes to positioning the gas valve (I assume this is the petcock?) when starting the bike. I turn that damn thing every different way trying to start the bike, along with the choke in and out, half way etc. I did have (I think) the valve on prime for a few minutes, but moved it over to reserve since there is only a little gas in the tank. Again, I assume the lever part of the valve is NOT where it should point, in other words, the opposite side of the handle is where it should be pointing? Should this thing be on "ON" position? When should it point to prime? Is it leaking because I had it on "prime" too long????

Xumi

Your gas problem may be either a stuck float or bad valve seat - because it's intermittent, I'd suspect stuck float.

Try tapping the carb bowl several times with the handle of a screw driver (pretty hard). If it fixes it, it's a stuck float.

Your hard starting could be due to several other issues... Battery voltage at the coil being my first suspect.

Bottom line - you may be dealing with multiple issues. I think someone wrote a howto guide / checklist of things to go through to get these things running right (was it Jayel?) - someone will post the link soon enough... I'd go through it and check your bike out top to bottom at least once. If you're not running right, and hard starting, and you've cleaned the carbs and replaced all your jets... well, time to take a look at other stuff. Not saying it couldn't be the carbs, but I'd want to rule out everything else before taking the carbs apart again, or replacing them.

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

xsjohn wrote:

How many MM from the gasket did you set the floats..........80 carbs which I have are not noted for flooding.....and are thebrass covers off the mix screws....Think I know more about 80 carbs than I do about my own life.......... and politics......some say......

xsjohn

The book I have says to set it at 27 MM.
Also, obviously, the gas ran out of the filter only when bike turned off. After leaking for about 2 minutes, it stops on its own?
PS: I have installed new stock jets also.

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

Xumi wrote:

Your gas problem may be either a stuck float or bad valve seat - because it's intermittent, I'd suspect stuck float.

Try tapping the carb bowl several times with the handle of a screw driver (pretty hard). If it fixes it, it's a stuck float.

Your hard starting could be due to several other issues... Battery voltage at the coil being my first suspect.

Bottom line - you may be dealing with multiple issues. I think someone wrote a howto guide / checklist of things to go through to get these things running right (was it Jayel?) - someone will post the link soon enough... I'd go through it and check your bike out top to bottom at least once. If you're not running right, and hard starting, and you've cleaned the carbs and replaced all your jets... well, time to take a look at other stuff. Not saying it couldn't be the carbs, but I'd want to rule out everything else before taking the carbs apart again, or replacing them.

I have checked the floats repeatedly, they do not hang up, and no holes in them, and installed new seats.....

xsjohn

Often times taking a bit of "fine" steel wool on the end of a q-tip and inserting it in the seat and turning it a few times will polish the seat hole for a good seal......and cleaning all connections on the bike and using dielectric grease is a must......kill switch ....multi connectors and the 2 wires at the coil.......if this isn't done problems will be never ending.......

And a lot pf people say replace the fuse holder but a good cleaning and replace the fuses with new ones is all I did........the old fuses like to fall apart and give you trouble after they are removed I found.........

there is "much" better jetting for these but we can discuss this later.........

xsjohn

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

So you are saying setting the floats at 27 MM is OK?
I think now I've been messing up trying to start it with the gas valve (petcock?) on all different positions, so I am taking it for a ride down the street to fill the tank...wish me luck.
PS: I have already changed the fuse block, and all new fuses.

jayel

first off those vacuum petcocks suck and they are 30+ years old, three posistions On is normal operation, yes you do have to have enough gas in the tank, Prime is for starting when you haven't run the bike in a long time and the carbs don't have any fuel in them, runs fuel in without the engine vacuum, Res is reserve, you say it leaks after shut off when you park the bike, on the side stand? that says high fuel level in the carbs and when you tilt them to the side they leak, mikes sells a manual replacment valve, if you have a old bottom bowl drain screw can can drill a hole in it to run a piece of tubing to check fuel level it a lot easier to set proper float level

Sledhooligan · Full Member Joined: May 04, 2009 Posts: 12

I would also try adjusting the valves, points etc.

yamaman

The vacuum petcock has 3 positions, on, reserve & prime. On & reserve should only work when the engine is running, the vacuum created by the motor allows the taps to open. Prime is a manual operated tap that allows fuel to flow from the reserve outlet!
With a full tank, remove the fuel line from the carbs, start the engine (it will run for a fair while on whats in the carbs) and collect what fuel comes out in a jar, testing each position!

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

jayel wrote:

first off those vacuum petcocks suck and they are 30+ years old, three posistions On is normal operation, yes you do have to have enough gas in the tank, Prime is for starting when you haven't run the bike in a long time and the carbs don't have any fuel in them, runs fuel in without the engine vacuum, Res is reserve, you say it leaks after shut off when you park the bike, on the side stand? that says high fuel level in the carbs and when you tilt them to the side they leak, mikes sells a manual replacment valve, if you have a old bottom bowl drain screw can can drill a hole in it to run a piece of tubing to check fuel level it a lot easier to set proper float level

Jayel--some good info. However, yes When I parked the bike on the side stand, BUT fuel ran oput the RIGHT carb!
Took it down the street for fuel, fill the tank. No issues whatsoever. Parked the bike and no fuel leaks..I am now wondering if iot was because I had the valve on PRIME for a couple minutes when trying to start it cold?
It starts now with a HALF RPM at most, starts right up and runs great. I guess the next time its cold will tell, just not sure how to start it cold!!!

xsjohn

Have you got a fuel filter on it.......27mm ok.....xsjohn

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

xsjohn wrote:

Have you got a fuel filter on it.......27mm ok.....xsjohn

I think there is a filter in the tank where the petcock is?

xsjohn

Won't stop the small flakes that will hold the needle off the seat.....need one in line.....have you cleaned out the tank.......flakes....

And the q-tip and fine wool trick will take the sharp edges off the seat hole for a better seal and maintain the viton tip on the needle..........

xsjohn

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

xsjohn wrote:

Won't stop the small flakes that will hold the needle off the seat.....need one in line.....have you cleaned out the tank.......flakes....

And the q-tip and fine wool trick will take the sharp edges off the seat hole for a better seal and maintain the viton tip on the needle..........

xsjohn

I did flush the tank....but did not touch the filter...where should the in-line filter go, and where/what should I buy?

xsjohn

You are probably getting crap from the tank screen and petcock.....should remove them and clean.....vise grips to get the screws loose from the tank......I use a mikes filter because it was somewhat flat and fit decently under there.......I added some more gas line to put the filter in a good place.........wouldn't cut the original gas line........

xsjohn

ramvett · Full Member Joined: Sep 12, 2006 Posts: 20

thanks for everyone's help!

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