Any idea what the problem is??

[sambodie]

Bike 81 XS1100SH

Here is the problem, starting cold I can go 10 or 15 miles engine runs fine no problem and then the engine starts loosing power like it’s hitting on three cylinders then slower and slower till it quits or will just barely idle. I can turn if off and restart it and it will run fine for a while and then the same drill all over again. It might go a mile or it might go another 10 or 15 or more before it quits.

This is what I have done / checked.

1. Pick Up Coil test – I can tug on the wires with the engine running no problem.
2. Replaced Plugs and Plug caps.
3. Changed all fuel and vacuum lines added inline filters cleaned carburetors.
4. Gas cap vent hole – all clear.
5. Checked battery and charging system
6. Replaced the fuse box with modern fuse system.
7. Coils ohm out to specs.
8. Checked and cleaned all connectors with electrical contact cleaner and put on dielectric grease from the headlight to the taillight.
9. Checked / cleaned the ground cable to frame and frame to engine.

Does anyone have any idea what I should try next?
Thanks in advance

Sam

[CMA1]

When the bike starts to 'stutter' and stumble, do you have enough time to stop and open the gas tank cap? I know, you'd need two keys.... if you have two keys, ride with one in the cap and open the filler while you are experiencing the problem. I know you said that the vent is cleaned out but???????
Are the OE filters in the tank clogging? If everything else checks out it sounds like a fuel starvation thing....or air (filter clean, LOL?)
Good luck.
<edit> oh yeah, check the crankcase vent hose too... if plugged (by bugs or whatever) or if the tubing is weak it may be collapsing, creating a pressure buildup in the crankcase (that hasn't blown a gasket yet????)

[sambodie]

I have two keys I'll try opening the cap, I have changed the air filter.

I have a small leak around the cam chane tensioner, just a drop or so nothing big, but I will check the case vent.

No clogs in the petcock tank screens for sure, they are gone.

I also removed the vacuum fuel shut off valve too.

[Ken Talbot]

Sounds like it could be a problem with float level in one or more carbs. They could be so low they're barely opening, and not allowing enough fuel to pass to keep the engine running. When the bike sits the bowls fill up over time. Then with what is in the bowl plus the minimal incoming flow, it is able to run for a while again. JAT......

[mitch]

Or

It could be the fuel lines air locking ! You said u run new lines and filters deleting the octupuss, Are the lines running low below the carbs . There is a couple threads about this . You might go to the modification pages or do a search on fuel lines or octupuss HTH................MITCH

[schpiff]

Just throwin this out there...Have ya tried ohming the coils after they are warm?

[sambodie]

2.7 and 2.6 ohms primary 12.5K Secondary after running for 15 min.

The pickup coils 760 and 870 ohms after 15 min.

[sambodie]

Update

I had a loop in my fuel lines below the carb bowls so I adjusted the line length so it would point up from the feeds on each pair of carbs. Checked the float level while the engine was running all are very even about 1/16" below the top edge of the bowls.

Next I went out on the road headed East on Hwy 90 ran ~ 25 miles at 65 to 90 MPH ( mostly about 75 ), made a u-turn and did the same all the way back.

No problem - no miss - the xs was streching my arms each time I cranked on the right hand grip


Thanks for all the good advise.