Problem with carbs getting gas?

[rc8774]

I have an issue, I think with gas but could be the carbs. It seems that time to time, when I fill up after a day of riding (100+ miles), after the fill up and going at high speed (50-60mph), once I slow down the bike will hardly run. If I keep it at 4k rpm or more, the engine appears smooth but get to less and it runs horrible. From a dead stop, I about can't even get it to go.

I know gas is coming out of the tank as I removed the screws from the gas cutoffs and it flowed good on both sides. But when I did the same with each carb (screw at the bottom), both right sides flowed good but the left 2 (from riding position) barely had a flow. If I was rating on 1-5, right side was a 5, left side 1.

I can park the bike for a while, start it up later and take off. I'm good for about 2miles and then it starts running badly again.

Things I have done:
1. Since gas flows good from the tank, appears the tank in-flow of air is fine. I even loosed the cap and had no effect.
2. While draining the tank, I checked for particles/water. Find very minute sparkly particles. Not sure how much is considered something to really worry about.
3. Draining the carbs, found minute particles. Again, very small and very few.
4. I have added gas treatment to some gas, with no positive effect.

Is the slow flow of gas to the left side the problem? Recommendations on what to check/fix this? Any other suggestions would be appreciated.

Thanks,
RC
1980 XS11

[JWSanders]

Hey, good to see another Tennessean on the boards. Welcome to the site!!

There are a lot of tips and tricks for these bikes here. The tech tips to your left are a good pace to start. The maintenence and repair forums are great places for info as well. Regardless, searching the forums in general will yield the answer to just about any question you may have.

For your particular problem, I'd say the octopus is a good place to start. Makes sure it is feeding both sides. It has a vacuum tube that goes the the #2 intake which allows gas to flow thru it when the engine is running. You may want to see if you still have the problem while the petcocks are both on prime, which bypasses the octopus.

If the octopus is flowing, the your next target should be the carbs. A deep cleaning can work wonders on them, especally if they've sat for any length of time. They are the source of the bulk of frustrations with these bikes. Once again, there are many posts and tips about carb cleaning.

Good luck!!

[GNEPIG]

.. i think i would start by pulling the hose from the fuel valve that leads to the left side carbs and see if fuel runs freely straight from the valve. if not, then you have to remove the valve and clean the crap off of the filter screen. if you have a special then OFF means fuel off, if you have a standard then ON means off with the engine not running. i would try this first, if you still have a problem, then we will talk more
good luck

[GNEPIG]

.. ok, i see you have a Special, so your fuel valve will say ON, OFF, RES and PRI.. PRI is suposed to send fuel straight to the carbs[bypasses the octopuss]. make sure you pay attention to where the hoses plug to the fuel valve, or this will be a problem.
good luck again

[prometheus578]

"What GNEPIG said"

Could be octopi related. (vacuum, etc) Petcock on left could be plugged, as well.
Recently had two bikes in the shop were the "screen towers" came out of the petcocks, allowing all the rust and grit in the bottom of the tank into the petcock orifices. One wouldn't allow fuel to flow, and the other wouldn't shut off.

after the fill up... once I slow down the bike will hardly run.

Filling up stirs the sediment in the tank.
Sounds like Fawlty Towers, as the Brits say.

[fxrer]

Check for a kink in the fuel line which supplies left carbs #1 & #2. The way the petcock outlet tubes are angled, it can be tough to find a route for the left side fuel lines, down to the float bowls, without them kinking.

[rc8774]

Problem with carbs getting gas? (Update)

Sorry for long delay on reporting my progress. I did manage to get the seat & tank off, then remove the carbs. Checking the tubes, I didn't find any blockage, nor were there any build ups in the carbs. But while taking them loose, I found what looks like dry-rot on the gaskets connecting the carbs to the engine. I used some automotive cement to help seal them.
After that, 200 miles later and no hickups as of yet.

I know the cement is just a temp fix. But is that the probably reason for the bike acting up and not wanting to run with power unless hitting 4.5k rpm or more?

Also, if/when I re-do the gaskets. Any suggestions on good sealant for these or website to purchase them?

Thanks for all the suggestions/information,

RTC98

[prometheus578]

, I found what looks like dry-rot on the gaskets connecting the carbs to the engine

Gaskets? Are you referring to the Carb Holders/Boots/Manifolds? (The black rubber tube thingies that hold the carbs to the engine) They can be cracked, etc, but as they are double walled, the cracks don't go all the way through, but I have seen some that did. Most people, including your's truly, smear black silicone on them for cosmetic purposes.
As for actual gaskets, these things are designed to be gasket free. Screw to the engine, as is. (But they may get dry and brittle and might not seal, so a sealant there "might" be called for)

[audijunky]

Hey rc8774 if your looking for new "carb. holders" try here

Not sure what bike you have but these might fit

https://www.partsnmore.com/cat_index...&category=carb [/URL]

[TopCatGr58]

Hey RC8774,

For the OUTSIDE of the manifolds, the black RTV makes a nice sealant, but it's been recommended NOT to use straight RTV where gas is involved. I can't remember which version of Yamabond which is not hardening, that can be used on the mating surface of the intakes to seal them. Other's have used Permatex Black #2 IIRC. Also, there is a higher grade of high temp Copper/silicone gasket maker type RTV sealant that works well in gas/oil environments!

[sxigh]

hmm.. is this permatex copper rtv sealant? I used the black rtv to fix some float bowl gaskets, thought this was impervious to gas..

[TopCatGr58]

Silicone and GASLOLINE don't MIX!

Yes, that is Permatex,

But I just read the label, and it, TOO, states NOT for use in applications that will expose it to GASOLINE but oil is apparently okay!! I used it to seal my Spin On Oil FIlter Adapter to the engine, no leaks in 2+ years!
T.C.

[sxigh]

I use a bit of anti-seize to re-use the copper crush gasket to the xs2 I also own, works great.