carb surge, First Real Ride

[Cosmo]

After my 1979 xs1100f runs for ten or fifteen mins at idle the carbs seem to surge bringing the rpms to about 5gs. I turn the bike off...wait a while...start the bike again with the same results. I put a can of seafoam in it to try an easy fix but am not sure if it will help. I do not seem to have any leaks that I can see but fear that it is time to pull the carbs. I fear this because I have ZERO knowledge of rebuilding them and feel like a baby playing with a loaded gun. I have searched the forums for help but since I know so little about rebuilding I am afraid (very afraid). Is there better instruction available than my CLYMER manual or should I just seek a higher source ? Help me before I do something I will regret...Cosmo

[81xsproject]

I had an rmp rise problem for a while and it turned out to be high float bowl fuel levels/bad float vavles. Have you checked your float heights?

[webbcraft2150]

There is enough info here and plenty of people to help if you get in a bind. The carbs are not difficult to work on and you do not have to take them completley apart to do a good cleaning. Most of the gunk you will find will be in the lower part of the carb. The freakin air box is harder to get on and off than doing the triple clean to a set of carbs. Most of us started with zero carb knowledge and alot with zero motorcycle knowledge but now are riding well running rigs with information and tips from this site. Read the many posts on carb work, the tech tips on carb work, take a deep breath and go after them.

[Cosmo]

Pulled the carbs off and found a float stuck. There seems to be little trash in the first two bowls pulled but since I have them off will check all four. Everything seems to be very clean but I will also check the floats while I am at it. How much further must I go is the main question...Cosmo

[DiverRay]

If everything looks CLEAN, with no "mud" on the bottom of the float bowels, you should be good with checking the needles for wear, reset the float level on all 4 carbs, and put it back together.
If you find a needle that is worn, I would order a set of needle/seat gaskets and replace them all. You will then need to reset the float level, and be sure all EIGHT floats are at the same height. Once done, you will need to sync the carbs. It will cost you about the same money to have someone else do it, or buy a tool. Once you have a tool, you can check the carbs every 10K miles or so.

[Cosmo]

O.K. remounted the carbs, turned petcocks to prime, filled the carbs with gas and...no start. I did not remount the pod filters...would that make a difference? Also I am not sure I have the vacuum hoses hooked up correctly.

[AlanB]

Hi Cosmo,

Are you sure that the carbs filled? How did you check that they had fuel ?

AlanB

[Cosmo]

I opened the drain plugs. Also pulled a plug and poured a small amount of gas into the cylinder and got a sputter.

[TopCatGr58]

Okay,

You've got the 79F, uses vacuum petcocks. The vacuum lines from the carb mounts go to the petcocks, the line for the vacuum advance goes to the #2 carb body smaller port. The outlet from the petcocks goes to the carbs lower T's. The upper T's should be vented to air. Don't be offended, but the large part of the petcock handle covers the function, so make sure you have the large end covering/pointing to the prime function?

Having the pods OFF should not keep you from starting it, but are you using the choke/enrichener lever? Also, don't twist the throttle during start, that opens the butterflies, but drops the vacuum level preventing it from drawing the required fuel up thru the choke circuit into the carbs.

Hope you were able to check the small enrichener jet in the bottom of the float bowl to ensure it was open before you put them back on the carbs and the bike?
T.C.

[Cosmo]

Thanks T.C...I'm done for tonight but will try your suggestions tomorrow night. I am a novice so I take no offence at any suggestions because it might by painfully simple to you but equates to rocket science to me...Cosmo

[skids]

Originally posted by Cosmo
I am a novice so I take no offence at any suggestions because it might by painfully simple to you but equates to rocket science to me...Cosmo

With a handle like "cosmo" you should be one with rocket science. It does sound like fuel starvation. Do what TC sez, only I would probably twist the petcocks to prime prior to starting the bike, because it has not run in a while and the bowls probably need to be filled with gasoline.

[81xsproject]

Don't worry Cos, we all have to start some where.

[Cosmo]

Got off work this afternoon and started to examine my hoses. The vacuum hose had a huge crack in it. Replaced the gas and all the vacuum hoses just to eliminate any future questions. Ran fine without any surging issues so far. I am going to leave it alone tonight and start fresh tomorrow. Thanks to all...Cosmo

[HobbyMan]

to me, your original problem sounds like sync issure with idle being set to high. Once you get it running set the idle all the way out and snyc em

[Cosmo]

first real ride

Went over all the suggestions (thanks to all) and fired the bike up. Found the throttle cable was hanging up so I disassembled and lubed with graphite. Everything seemed good to go so I decided once around the block was in order. Thirty miles later I was back in my driveway. Checked various bolts for tightness and since its blue skies and 76 degrees here so another cruise was in order. Next step is the list of 101 little things that I promised to fix after I had my first ride. One small note...seemed to be a little hesitation between 1100-2500 rpms at first but seemed to get better after a while. I hope the can of seafoan in the gas will help matters. Once again thanks for the help...Cosmo