80 XS1100G runs rough full throttle only

[ernie elmore]

I have a 80 XS1100G I bought new over 30 yrs ago, with 95K mi
I have done all maintenance all these 30+ years. I follow all XS11 Forum threads, understand most problems.
PROBLEM:
I have a slight stumble or stutter at 3/4 to full throttle. Stutter like machine gun. This is felt more in top gear at lower rpm's, 3500 -4500. Higher rpm over 5000 stutter still there but rapid and hard to hear or feel. Runs smooth at less then 3/4 throttle

I just cleaned and synced carbs. Carbs were fairly clean and diaphragms are good, replacements.

I Sync with carb manometer with metal tubes inside. Tubes bounce at under 2000 rpm, even out and sync at 3000 rpm.

I checked Vac Advance unit, smooth action and advanced with increase rpm.

All ignition is stock with old Coils and wires, spark plug caps new. Cannot cut anymore off end of plug wires. MAYBE I need NEW coils and wires?

Any ideas?

I am 78 and still riding in So Calif where we ride 350 days year

Anyone want to buy 80 XS1100G with 95K mi? @ $1100 ?

[jetmechmarty]

I think you should go through the electrical and RIDE ON! For sure, you need to take apart and clean the kill switch, the ignition switch, and the connector behind the fuse panel with the wires off the alternator. That should fix you up.

[motoman]

+1 what jetmechmarty stated!

Sounds like you were using the MorganCarbTune? If so, make sure the small orfice pulse dampeners have been installed in each hose. If they're there, THAT end of each hose goes on the carb boot hose bibs, not on CarbTune end.
With hoses CORRECTLY attached, held level, those slides are steady with no fluxuation or bouncing......unless there's a low voltage to coils at the lower rpm's, and likely will be low voltage elsewhere if checked.

[Radioguylogs]

Another possibility:

Others have reported those symptoms associated with broken pick-up coil wires.

The advancing spark pulls on them.

[ernie elmore]

Yes, Using MorganCarbTune to Sync carbs for 20 years .. but never used damping orifices, do not think they were in original box 20 years ago?

I checked the pickup wires on vac advance, and with engine running, moved advance all the way both with throttle and manually, no change of effect.

This stumble at full throttle, felt in high gear at lower RPM, started when the bike tipped over while starting from a stop, making a sharp left turn. Got bike picked up OK but was flooded, would not start. Luckily on slope, so paddled down hill and finally bike coughed, sputtered, cleared and started.

From that time I have had this stumble at full throttle. I am going to Disconnect the "Tilt Emergency Shutoff Switch" under the gas tank and see if this has any effect. Also disconnect the Vac Advance hose to see effect. If this doesn't change the Stumble, then start cleaning electrical contacts and maybe change 30 year old Coils and Spark Plug Wires (maybe original spark plugs too)

[madmax-im]

Original owner 30+years...78 years young riding in california...ride on man Dont sell it...

[motoman]

Yes, Using MorganCarbTune to Sync carbs for 20 years .. but never used damping orifices, do not think they were in original box 20 years ago?

I checked the pickup wires on vac advance, and with engine running, moved advance all the way both with throttle and manually, no change of effect.

This stumble at full throttle, felt in high gear at lower RPM, started when the bike tipped over while starting from a stop, making a sharp left turn. Got bike picked up OK but was flooded, would not start. Luckily on slope, so paddled down hill and finally bike coughed, sputtered, cleared and started.

From that time I have had this stumble at full throttle. I am going to Disconnect the "Tilt Emergency Shutoff Switch" under the gas tank and see if this has any effect. Also disconnect the Vac Advance hose to see effect. If this doesn't change the Stumble, then start cleaning electrical contacts and maybe change 30 year old Coils and Spark Plug Wires (maybe original spark plugs too)

For your MorganCarbTune, on the four hose ends that hook to manifold barbs, spray silicone in them and push a SMALL Mikuni main jet in each one at least four inches up the hose.....wa-la, pulse dampeners.

Pick-up wire checking for internal breaking: remove cover, try to pull apart wire every inch. If a broken place exist, the wire insulation will stretch like rubber band. Rotating advance by hand won't find the broken wire.

The ballast resistor on the 80 and earlier bikes are a known problematic area also. Majority eliminate it.

[clarkcortez]

Are you sure you're getting good fuel flow through both petcocks when vacuum is applied? Maybe some gunk in the tank was dislodged on the tip-over and partially blocked the petcock screen?

[Bikes]

Replace the spark plugs......

[ernie elmore]

XS1100 Runs Rough:
Well I did some more checking as follows:
1. Checked the Vac Advance Wires again and they are all good, no sections stretch or seem broken inside insulation.
2. Disconnected and plugged the Vac Advance hose from #2 Carb. Went for a ride, same stutter. Reconnected Vac Advance, Same Stutter.
3. Disconnected "Tilt Shutdown Module" connector under front of gas tank behind steering head. Went for ride, Same stutter. Left disconnected
4. Petcocks have been rebuilt with good flow in 3 positions
5. Gas cap not problem

The bike runs good with lots of power under 3/4 throttle. Stutter is under full load, full throttle between 2000 - 4000 rpm. Over 4000 rpm full throttle, very slight stutter that goes away due to high rpm.

Problem could be old coils and wires.
Maybe a carb dia slide not lifting at lower rpm - full throttle
I have replaced the carb diaphrams with JBM Diaphrams which seem to fit ok.
Any way ... I need to get on Freeway again and check at higher RPM ... I think I had slight rumble there too, hard to tell

I just want to keep any problems to minimum on my old "Everlasting" XS1100

[motoman]

XS1100 Runs Rough:
Well I did some more checking as follows:
1. Checked the Vac Advance Wires again and they are all good, no sections stretch or seem broken inside insulation.
2. Disconnected and plugged the Vac Advance hose from #2 Carb. Went for a ride, same stutter. Reconnected Vac Advance, Same Stutter.
3. Disconnected "Tilt Shutdown Module" connector under front of gas tank behind steering head. Went for ride, Same stutter. Left disconnected
4. Petcocks have been rebuilt with good flow in 3 positions
5. Gas cap not problem

The bike runs good with lots of power under 3/4 throttle. Stutter is under full load, full throttle between 2000 - 4000 rpm. Over 4000 rpm full throttle, very slight stutter that goes away due to high rpm.

Problem could be old coils and wires.
Maybe a carb dia slide not lifting at lower rpm - full throttle
I have replaced the carb diaphrams with JBM Diaphrams which seem to fit ok.
Any way ... I need to get on Freeway again and check at higher RPM ... I think I had slight rumble there too, hard to tell

I just want to keep any problems to minimum on my old "Everlasting" XS1100

Even tho plug-wire ends may 'look' good, have you cut them back a quarter inch to 'new', clean wire and re-screwed plug caps back on, eliminating that as a higher rpm miss?

[ernie elmore]

Hi Motoman

Good idea to trim back the end of old spark plug wires
I have done this over the last 15 years until I have no slack left to trim
Time for new wires and coils .. thanks for the heads up

[rdmcguy]

ssstttuuuummbbbllllee

You mention JBM replacement diaphragms....I bought a set and don't know if they are the cause of my problem or not but very similar to your symptoms...I have rejetted repeatedly but still have issues..... running with no air filters reduces the problem significantly but still not quite right...the "fit"of the replacement diaphragms is questionable...I took their suggestion and put some super glue on them to tighten up the fit and to make sure the little hole in slide remains in the correct position ..(to intake side)The super glue melts and causes the slides to stick sometimes..I think there is a leak that is happening when I run wfo...I will try a different pair of slides soon to see if that solves the problem ...will inform then,....

[Radioguylogs]

The super glue melts ...

Really?

Perhaps it is hot melt glue instead?

[rdmcguy]

no

Zero chance of hot glue melting....never had it anywhere near anything on the entire bike.....