Carb Slide Issue

[Clyde K.]

Good day Gentlemen, Ladies. I have a '78 xs 1100 that has been sitting for YEARS. I have totally stripped, soaked, cleaned and blown the carbs out half a dozen times. I have synched with vacuum gauges each time as well, and it seems to run well in the garage (we have 2.5 ft of snow), starts well, idles acceptably and has good throttle response. During synchronizing it looks like #4 carb is a little sluggish doing throttle blips so I removed the air box and the slide seems like half a beat behind the others and doesn't raise nearly as much. I read someplace here where it was suggested polishing the slide bore. Could that be the cure for my problem, and if so, how does one go about doing so?

[DGXSER]

Since you will be pulling the carbs out anyway, not that you HAVE to do this, first lift the slide with your finger, then place a finger or something over the fish mouth/ frown shaped opening in the inlet bell of the carb. That is the vacuum port that pulls the slide up. Seal that opening well, and remove your finger that lifted the slide. See if the slide drops slowly or quickly. Repeat on the other carbs as well so you have a reference to use. If it drops quickly, you have a hole in your diaphram or the lip is not in the groove properly or something similar.

As to polishing the slide, you could use some very very fine emery cloth or some 1500-2000 grit sanding paper with some light oil on it. Then clean it well with some oily fluids, or gas, and lube it well with WD-40 or similar during reassembly.

[natemoen]

Also, without a load on the engine with it just sitting in the garage the sides really won't move, just kinda looks like they twitch and jump a little.

[81xsproject]

Doubt it's related to your slide problem, but I did read some things in your post that set off bells and whistles. You said that you "stripped" and "soaked" the carbs. That sounds like you took all the removable parts out and soaked them in a carb cleaner like Chem-Dip. If you didn't disassemble, separate the carbs and remove the butterfly shafts and seals, you may have destroyed those seals in the dip. This can cause vacuum leaks around the seals and lean running conditions. If you end up with a bad slide diaphragm and need a replacement, let me know as I have several good ones stocked.

[LoHo]

Something else to look at is whether the diaphragm for that slide might have a pin-hole that causes it to react more slowly to vacuum. Hold it up to a bright light and look for tiny lights shining through. There is a thread in the Repairs section about fixing these with rubber compounds.

[skids]

I wouldn't use sand paper. Get some mother's milk polish and shine the bore. The slide cylinder may be coated with clearcoat or similar. Be gentle to that. Silicone might be a better lubricant than WD40.

[Clyde K.]

You guys are great. I have soaked only the jets and removable parts in carb cleaner. I used 2 cans of carb spray and shop air to blow the bodies out. I did the "hold the diaphragm up to the high intensity light" thing with negative results. All four slides return slowly, with a whoosh, when activated by hand. All that is left is polishing the slide. Maybe I am just over reacting to the no load situation natemoen mentioned. Thanks a bunch for doing all the brain work for this tired old mud Marine, guys. R/S, Clyde

[natemoen]

There is a video that was shot of the differences of the slides with load compared to without load. I will try and find it and post a link for you.

[TopCatGr58]

Also, without a load on the engine with it just sitting in the garage the sides really won't move, just kinda looks like they twitch and jump a little.

Hey Nate,

A little learning opportunity here!

http://www.youtube.com/watch?v=tR63vrfhwr8

This is my little Youtube site, this video shows the slides under load, actual riding condition, but the other video shows them on the center stand, and they do move depending on how much you tweek the throttle open and how quickly you do it.

Don't mind the small fuel squirts, my #2 carb float was maladjusted, and slightly flooding at the time, but the videos show the slide action fairly well under the different conditions of load.

Then, if you want some laughs, you can look at my other vids, my pathetic attempts at the drag strip a few years ago.!

Yes, I second that either he's got a vacuum leak from soaking the carb bodies, or the vacuum slide diaphragm has pinholes in it.

T.C.

[TopCatGr58]

Hey again Nate,

I took a while finding the link, and then posting it, didn't see your recent reply, so you apparently have seen the videos! My bad!

A few other places for vacuum leaks is the intake boot itself, the rubber cap that is over the synch port can harden, and allow a modest leak even though it seems to fit tightly over the brass nipple.

Also, see if the diaphragm will spin on the vacuum slide, if so, then it's gotten loose, and can also contribute to some vacuum leaking. Also, the intake boots where they are attached to the head, they can develop leaks there due to heat hardening the rubber contact surface of the boot against the head. Folks have found the bolts loose, rubber dried, cracking/peeling/flaking or crumbling off. They have removed the boot, cleaned up the surface, then either used a gasket or just fuel resistant gasket sealant material to seal the boot's connection to the head.

With it running before you take the carbs off, get a bic charcoal lighter, or some propane or butane, even starter fluid/spray that you can spritz UNLIT around the intake boot, synch port and listen for changes in idle revs, and if so, then you've found the vacuum leak.

T.C.

[natemoen]

Ahh I thought it was you that had the videos. was was not having any luck looking through your started threads list though. Glad you caught this had posted the link again!

[Clyde K.]

TC--Those youtube episodes were terrific. Both of the ones you posted plus several others on there put my mind at ease. Thanks. Hey, could I get you to come and ride in my air box to get pics of my slides? What a trip. LOL Now I can go look for something else to panic about, needlessly.