More Carb Stuff!

[rickt]

My carb stories continue. I started restoring a '78 GS750 this fall and have spent the majority of my time dealing with carbs in the basement. I brought some trouble on myself when I attempted to free a stuck slide with a screwdriver. Dumb move - I eventually got the slide out but deformed it in the process. Found a set of carbs from a '77 GS750 on Ebay. I'm not a huge Ebay buyer, maybe 30 or so purchases, but this was the first time that I felt like I was taken. I won the carbs for $100, but when they arrived, I wished that some other bidder had won. Two of the four have frozen slides - one has a sunken pilot air screw with no slot left in the screw - and the entire assembly looks like it sat under a tree behind the barn for the past 20 years. In any case I was hopeful that I could salvage enough parts to give me four serviceable carbs.

This brings me to what I hope others might find to be a useful technique for removing stuck slides. This is a much better method that than the screwdriver. I cut a ~21 mm circle out of heavy sheet metal with a hole saw. You can probably find a thick washer that will serve the same purpose. The hole saw provided a 1/4" hole in the middle of the circle. I then drilled two small holes on either side of the 1/4" hole for the two small screws that mount the slide arm to the slide. I then took a 3" one-quarter inch bolt and ran a die down it to give more threads. The bolt was placed thru the hole in the 21 mm circle and with the threaded end pointed to the top of the carb the two small screws were inserted into the slide. This provided a secure handle coming out of the top of the carb body. I then placed a couple of 2" fender washers and a nut on the 1/4" bolt. Now for the real secret that was taken from experience in removing and installing cycle wheel bearings. I poured a pot of boiling water over the carb body, mounted the carb gently in a vise, and tightened the nut. The slide came out easily and smoothly. I was successful with two carbs, both of which had been soaked in a tank of carb cleaner and sprayed for many many days.

So after all of this, I discovered another unpleasant fact. The slides from the '77 750 are slightly different. The thickness of the slide wall from my '78 is ~2.3 mm. The slide from the Ebay carb is ~3.8 mm. The length and diameter of the two slides are the same. So, if anyone has a good slide from a '78 GS750 that they would like to trade or sell, I would be most interested.

Even though it is unlikely that I will use the carb body with the messed up pilot air screw, I thought that I would try to remove it just for practice. My thought was to drill a small hole in the center and use a tiny Easy Out. Does this sound like a workable plan?

Please send a PM if you would care to part with a slide from a '78.

Thanks,
rickt

[49er]

Sounds like you had an unfortunate experience on Ebay. If you do your homework, they are rare. I trust that you left the appropriate feedback for the vendor.
You will need to replace your slide with one with the same wall thickness.
I think your bike is fitted with VM26SS carbs. I have the same carbs on my 850, but not sure of the slide wall thickness.
Before you attempt to drill the damaged air screw, screw one of the others out and check how deep you can drill before damaging the seat area and threaded part of the carb body. You need to drill as large a hole as possible without damaging the thread in the carb body. That way you're less likely to break your easy out. Also,use a little heat on the body to assist its removal.
Good luck.

[REDDY]

Another old machinist's trick for removing screwed up screws; Drill a hole half the size of the available screw material. Depth depends on available screw material. Using a rod of similar material and a close fit to the hole and a fast drill motor, put the rod into the hole, bottom it out, and turn the rod in the direction needed to back the screw out. Use enough pressure and speed to create heat. The rod will weld itself to the screw and usually bring it out so quickly you will be suprised. An air drill works best but electric will work.

It is best to not tighten the chuck more than hand tight on the rod. In this instance it helps to heat the carb body as sugested before. if the screw dosn't come out readily, let the carb body cool ( soaking in water ) and start all over.

[ta473]

parts

do you need any parts for that bike i have some fuse box, air box with chrome ends. i bought the whole box off e-bay for one part if you want any of it let me know. there free i was just cleaning my garage and almost tossed the just pay the postage and there yours or whoever needs them