BS34 Pilot Screw Question

Dave48

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I have an 80 XS650 with BE34 carburetors. I just purchased a used carburetor for a damaged one. The old carburetors have an adjustable pilot screw. The replacement carburetor has a brass plug where the others have the pilot screw. There's a small hole in the plug but it doesn't seem to go more than a ¼"into the plug. I've seen photos online of other BS34's with just this plug. Can anybody explain this?
Dave
 
Yup EPA made Yamaha install "keep your filthy little hands off the idle mixture setting" plugs. It's "best" to drill them out on a drill press, very carefully. Start with a small bit, STOP when you break through the bottom of the plug. Work your way up, when your drill bit size is near the plug OD the plug usually spins free and comes out.
 
It's best not to drill all the way through the plug. The mix screw is just below it and you run the risk of damaging the screw slot on top of it if you go through the plug. The mix screw is brass so it doesn't take much to damage it. How do you stop drilling in time? Note that small hole through the plug and its size. Drill a little and check the hole, noting the size of that small hole. Drill a little more and check, drill and check, drill and check. As soon as that small hole through the center begins to grow larger, stop your drilling, you're almost through the plug.

I use a 1/8" drill bit. Once the hole is drilled, I use a sheet metal screw that I've blunted the point on to extract the plug. I screw it down in tight, and usually the plug will start spinning when the screw bottoms out in the hole. I then grab the screw head with some vice grips and twist/pull the plug out .....

PlugRemoval2.jpg


PlugRemoval1.jpg


PlugRemoval3.jpg
 
hey there... Couple old threads, but I'll drop a note and maybe you can all tell me how screwed I am... Someone's tried to get my 82 running before me. The evidence has shown up in other places, but one of the carbs has been cleared of this plug and the screw comes out and goes back in without (too much) issue... fragile effing things.... But, the other, the cap wasn't completely removed leaving a rim around the hole and the screw head is buggered.... I'm guessing order new and VERY VERY carefully drill the screw to get a very small easy out into it?.... This can only get worse I expect....
 
No easy outs on brass jets
Most always I can cut the slot deeper with special tool I made and get the jet out with a screwdriver.
IF that fails a LH drill bit is your friend. Usually the drill bit catches and turns out the jet as you drill in.
 
Thanks for the quick reply! Special tool eh? LOL... I'm thinking a notched flat head screwdriver blade rubbed back and forth in the slot?... I ordered the new jet (SKU: 48-5011) from Mikes. Seems to be the only US source for this part and had two options. Couldn't find anything labeled "Canadian"... Hopefully I can get it replaced and get this beast running. It's the last of the carb work... till I get it to start and start tuning....

Thanks again!
 
The first time, it was a cleverly :wink2: ground pole barn nail, now the mark II is ground from the stainless steel strip found in windshield wipers (a favorite free tool, pick, scraper etc etc,) (windshield wiper strip connoisseurs know there are various thicknesses of strips from little japanese cars and big ass vans etc.) think a claw shape with a sharp edge that will readily scrape brass from the bottom of the slot. I like a bit of rust buster in the hole, allowed to soak in and a few loving hammer taps on the screwdriver to loosen the thread bond. Getting the carbs in a vice or well braced on the floor so I can be over them really controlling a custom fitted screw driver helps eliminate the dreaded stripped jet slot.
 
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