81 Midnightmare!!!

[SLB1963]

I have an 81 Midnight that sat for years in my Brother in laws carport. 1,441 miles. I have the Carbs bench synked and clean. I have had them apart 4 times to make sure carbs are right. I have been through the air box, oil changed, brakes fixed, and now my petcocks are wanting to leak. My problem is when I start it #3 does not run right and is smoking from that side, It sputters and pops and the pipe is not hot like the 3 others. I am just about ready to sell the bike whole or part it out. I want to get this thing running but am tired of fooling with it. Could I have valve problems from sitting so long?? It has fire and gas.

[crazy steve]

Valve problems? Possible, but not likely if the miles are that low. Run a compression test, see what you find. Sometimes if a valve has set open for a long time you'll get corrosion on the valve or seat, but that will usually quickly wear off.

A much more likely scenario is carbs; you say you've had the carbs 'apart' four times, but did you really clean them? The carbs on these have a lot of really tiny passages and are notorious for clogging up. Unless you pull pretty much every removable part off the carbs and soak the bodies/jets/emulsion tubes, cleaning until everything will pass a white-glove inspection, you can chase your tail getting these running. These models carbs also have a o-ring seal on the float valves as well as a rubber tip on the valves themselves that will go bad with age/sitting, have you replaced those? If one of these leak, that carb will flood which is what it sounds like your getting. Look here for a rebuild guide: http://www.xs11.com/forum/showthread.php?t=36017

If the bike was running good when parked but has sat for more than a few years, it's at least a 95% chance that the carbs need to be rebuilt with new seals, not just 'taken apart'...

[SLB1963]

Steve,
Thanks for thr reply. I have been through every part of the carbs and used the reference you attached. I did have to replace some pilot jets that I purchased from mikesxs. floats have been adjusted and are correct as far as I can tell. I do have a compression tester and assume I would be checking for equal pressure. I will check it. also seals were replaced.

[SLB1963]

Compression test

I just checked the compression and have 160lbs across 4 cylinders. Is the carbs the only possible issue?? I know I have been through them but also see how hard these are to get correct looking at all the post about these carbs..

[crazy steve]

If you got 160 all across, it's a pretty safe bet it's carbs. It might be ignition, try swapping the 2/3 plug wires and see if the problem moves; if it does, then you probably have a poor connection in the plug boot on the end of the wire. Maybe a bad plug also so you could also try swapping that, but that's rare. If the problem doesn't move with the ignition, then it's carbs....

On any bike that has sat for an extended period, you really should clean the entire fuel system, starting at the tank, also cleaning the petcocks and octy (if it's still there). The slightest bit of 'stuff' in a carb can cause this.

[SLB1963]

I lined the tank with POR 15 tank liner and the fuel system is clean. Seems like I have read somewhere on here someone that will rework these carbs correctly. I would be willing to send them off if I thought it would solve my problem. It is getting old pulling them off with the same results.

[crazy steve]

Member 81XSproject offers rebuild service, look here: http://xs1100carbs.blogspot.com/

[DGXSER]

Did you remember to clean the enrichment jet in the float bowls on all four? If it is running poorly at start up, that could be the problem.

Otherwise, did you pull clean and replace the o-rings in the mixture screws? They can be overlooked sitting down inside that tower.

The on thing about a bike that sat that long is that all the rubber parts have not been exercised or lubricated with fuel or oil for all those years. Sitting for 20 years is harder on a bike than running it for 100,000 miles. So, be sure to look over ALL the rubber components.

[SLB1963]

Yes, I cleaned all jets and put new robber o-rings in the Carb. I have read about the jets in the bottom of the bowl and I know they are clean also. that is why it is so frustrating. I agree, Sitting is the worst thing you can do to a bike. I have gone thruogh most everthing, I just want to get it to run right.

[trbig]

The thing that stands out in neon letters is "Bench synched". This will most of the time get it to where you can start it, but many times it's not even close enough to get that done. Without ACTUALLY synching the carbs with a gauge with it running, you're pissin' in the wind.


Also, are the floats adjusted correctly? The neoprene floats on the later carbs are a fairly tight fit in the bowls, and I've had them catch on the sides of new gaskets. It sounds like #3 is just dumping raw fuel, hence all the smoke.

[SLB1963]

It would be imposible to try to put guages ob it now becuase it is running so bad. The # 3 floats seem to be moving ok. I can also turn the carbs ubside down and blow through the fuel line and 0 air passes through. I am not going to give up despite my aggrevation . I am missing something small but is is having a huge impact on my bike.

[DGXSER]

Drop the bottom of your air box, and set your petcocks to prime, and let the fuel flow to the carbs for a minute or two. See if any fuel starts flowing out of the air box. If so, you know if one of the carbs is flooding. The float valve in these things is about the most sensitive part of the entire system. As Tod suggested, I would definitely trim the float bowl gasket on the sides to be even with the float bowl or carb body. Also, make sure both sides of the float read evenly, same measurement from bowl gasket surface.

I had an issue with a flooding carb after my first set of these carbs. all new parts, no leaks on the bench, no leaks on a test stand prior to mounting on the bike. Put them on the bike, and one carb or another would leak every freaking time. I finally isolated it to the new fuel line I installed. I got the soft rubber inner wall stuff at my local auto parts store. that inner rubber was chafing off on the barbs of the Ts and getting to my float valves. changed fuel lines, no more leaking float valves.

If your certain the carbs are right, and it will not run any better than your describing, then for certain do the electrical checks Steve mentioned. If those do not change the poor running cylinder than it is carb issue.

[mack]

carbs

next time you take them off, set them up plumb and level and put the gas to them. If #3 is flooding you'll know. Levels for your carbs are to be set with clear hoses hooked to the bowls and adjusted individually. I found when I did mine that no two were the same. The crappy floats are not only different from one and other but from side to side as well. I have three sets of these carbs here that I have cleaned and adjusted and non of the float measurements are the same. As several have said, cut the gasket back so the floats can't bind on the sides. A couple members have actually sanded the mating ridge off the floats themselves. Something else to check is the bowl vents through the bells. Small insects like to nest in them. If you can get the bike started enough to idle, try to sync them for real. Also as steve stated, check your plug wires and caps, switching them around will be a good indicator, but try a fresh set of properly gapped plugs as well.

[mikubuilder]

from what you're saying it's probably enrichment passage in the bowl itself...I just had the same issue in my bike....ran fine, then all of the sudden quit running on 2 and 3...I thought it was coil related, but I was getting sparks on both wires. Needless to say, carbs came off once again(lost my count), but they all looked great...I took a guitar string and jammed it down the bowl passage, and it pulled out a bunch of black specks...sprayed some carb cleaner through a straw and more stuff came out, so I knew I was onto something

I have inline filters, but I guess that dirt was really embedded in there...soaked all bowl in carb dip overnight, ran guitar string in and out, sprayed some carb cleaner just to be sure, and voile, running like a rapped ape

[SLB1963]

Mack, Very nice Midnight. I will pulling the Carbs again.