Throttle Issues

[Welsh1100]

Greetings all. I own a 1979 XS1100F standard. Recently I have had trouble with the throttle sticking wide open. I have thoroughly lubed and checked the cable and found no binding. After completely cleaning the outside of the carbs I developed a new problem. After the bike gets to warm operating temps it will not idle. I have not messed with any of the idle screws, nor the mixture screws.

[TopCatGr58]

Hey Welsh,

Welcome. Okay, you own a 79F, but for how long, are you a newbie to owning it, or have had it for many years??

Cleaned the outside of the carbs, HOW, high pressure spray cleaner, brush??

You say the throttle is sticking wide open! When it happens, is there a lot of slack in the throttle control at that time vs. normal? IF there's no change in the slack, the throttle grip feels the same, same tension like when you are turning the grip, then the throttle plate is most likely NOT sticking and NOT holding the throttle plates open. However, folks have put the intake boot clamps on in a way where the throttle plate does get caughty by the clamp screw or such.

Sounds more like during the cleaning the synch screws got turned, along with the main throttle idle set screw, so that it runs up due to an imbalance, and then isn't set right when you bring it down to idle speed!?
T.C.

[Welsh1100]

Throttle issue

Hey TC...This 1100 I have owned for about 1 year. Previously I rode XS650's while living in Los Angeles. While living in Idaho I owned an 1100 special (1979). I cleaned the outer area using a spray on carb cleaner with a nozzle. I carefully wiped off the excess using a soft cloth. One thing about my XS is this. There is no main idle speed adjustment screw. There are, however, two such screws that control the idle speed only. These are unrelated to the idle mixture screws on each carb.
The mileage on this bike is 36788 and is original. The plugs I use are NGK BP8's. I run Castrol 20-50 in the crankcase. Oil changes are done at 5k increments. Oil filter at 10k. This may seem high to some. For example..I have a friend with a 1980 model "G". He changes oil and filter every 3k miles.
I run only the highest octane fuel I can buy (91+) Thanks for your reply.
Kevin

[CatatonicBug]

Have you cleaned the INSIDE of the carbs? The outside can be covered in crud without affecting performance much, as long as the throttle cable moves easily and freely when you turn the accelerator. The idle issue sounds like you have crud in the idle circuit inside the carbs. I would suggest taking the carbs out and using a couple cans of carb cleaner spray and some compressed air to get all the junk out. Be sure to take out all the jets and remove everything that can possibly be removed (except the butterfly, unless you really want to), and clean like crazy. There is a tech tip about performing this operation if you need details. It's very helpful.

[skids]

Make sure that the gooseneck at the handgrip area didn't come loose or break.

[rpgoerlich]

On the '79 there should be a main idle adjustment screw on the top rear of the rack between carb 2 & 3 unless the carbs have been changed out.
Which 2 Idle screws have you adjusted ? Is one between carbs 1 & 2 and the other between carbs 3 & 4 ? If so, this might be the source of your throttle problem as these screws are for syncing the carbs.

[DiverRay]

There is no main idle speed adjustment screw. There are, however, two such screws that control the idle speed only. These are unrelated to the idle mixture screws on each carb.
The mileage on this bike is 36788 and is original. The plugs I use are NGK BP8's. I run Castrol 20-50 in the crankcase. Oil changes are done at 5k increments. Oil filter at 10k. This may seem high to some. For example..I have a friend with a 1980 model "G". He changes oil and filter every 3k miles.
I run only the highest octane fuel I can buy (91+) Thanks for your reply.

Kevin,
If your bike is still "original", you DO have an idle adjustment screw. It is between carbs 2 & 3, and the top of the screw is about even with the base that the carb covers mount on. The "other" screws are for BALANCE, and getting them OUT OF ADJUSTMENT WILL make the idle go up!!
The spark plugs for this bike is NGK BP6ES, and ALL of the XS1100s were made to run on REGULAR gas. You will get a LOT of carbon buildup with premium.

[CatatonicBug]

ALL of the XS1100s were made to run on REGULAR gas. You will get a LOT of carbon buildup with premium.

I'm glad you said that. I had a harley guy try to convince me that I needed to use premium, and I could not convince him that a 30 year old engine runs better on regular. My first car was a '68 VW bug, and we noticed improvements when we used regular gas, and added a lead additive to it to fool the engine into thinking it was gas from the "old days".

[b.walker5]

Greetings all. I own a 1979 XS1100F standard. Recently I have had trouble with the throttle sticking wide open.

It looks like you've got plenty of good advice from the guru's on this one but i'm intrigued about one thing, How did you find out the thing was sticking at WOT? Hopefully not while leaving some boy racer in his souped up mazda behind at a set of lights That'd be scary with a nuclear missile like an XS11 between your legs. It'd sure make my rear end pucker up. Hopefully you discovered while tinkering in the garage without the engine running.

[Welsh1100]

Throttle issue revisited

Hey everyone,
Thank you for the great advise. To answer a few questions...yes I went down hard but managed to ride the machine home..albeit without my turn signals (which snapped and hung on the wiring). Secondly..I had the throttle stick wide open on a Saturday ride with two friends. In prepping for the ride I checked everything and fueled up. I rode 7 miles before they arrived at my house. Two miles out (on a stretch of highway) the throttle just stayed wide open. The grip felt normal and the linkage seemed to be returning to the normal rest spot. No noticable slack or tension in the cable. I managed to limp home in fourth gear while "featering" the clutch. Thirdly I have looked very carefully for the idle speed screw and I just can't find such a thing. It is possible I tweaked the balance screws while trying to adjust the idle (thinking I was adjusting the idle speed). A friend has the equipment to rebalance the carbs. My next stop will be to his shop.
Thanks to everyone for all the great advise. Ride safe...Keep two down and one up.
Kevin

[CatatonicBug]

It's definitely possible you tweaked the wrong screws, but I doubt that would have made it stick at WOT. Sorry to hear of your spill, but glad you managed to get home in the vertical position. This is a pic of my bike's Idle adjustment screw. It's kinda hard to miss. If you screw it in, that raises the idle speed, kinda like if you were turning the grip toward you just a little. It's a positive stop for the throttle linkage when it physically springs back down when you let off the throttle. Maybe it will help point you in the right direction?

[Dragon Tamer]

Hey Bug,
Nice work on the picture but on my 79 the idle adjustment knob is between #2 and #3 but is ABOVE the carbs and almost impossible to see. At best with the tank on it has to be adjusted with a LONG screwdriver by prying on the cogs. Not sure if it is the same on the standards as it is on my special. If his the same as mine it may explain why he thought there was not one there. It is easy to overlook the thing and the sync screws at first glance look as though they will change the idle, DAHIK!!!!

[DiverRay]

The '78 and '79 Standard Is the same as yours, Dragon Tamer. IF you know what you are looking for, you can find it looking from #4 carb, or the right side of the bike. You CANNOT see it from the left side!

[TopCatGr58]

Here are a couple of photos showing the main idle screw on the early model carbs, note it's knob is pointing up from the BACKside of the carbs!




T.C.

[Dragon Tamer]

TC,Ray,
Yup, dats what I have, and I assume that is why he thought he didn't have one. Like you said, you have to adjust it from over the top of the #4 carb, there just ain't no other way that I have found.