1977D BS38 ready for rebuild?

DanielBlack

XS650 Junkie
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Good morning friends,

I've been holding off on tearing into my carbs on the suggestions I've read and heard about leaving well enough alone until it isn't. Also, I've been dialing in the prerequisite stuff such timing, fuel delivery, etc.

1) I was all ready to sync them, but I've found the vacuum barb port on one side (L) is blocked by a screw as expected, but the R is plugged in a more permanent manner. In the famous pic (2nd below) showing the positions of the vacuum ports, the R barb is already installed and I can't quite find a mention anywhere of this particular blockage, nor its removal. Your advice would be appreciated.

2) My fuel lines are mismatched, aged, and seeping. I was all set to replace them, but when I went at it realized I'd have to remove the carbs to reach in there. No big deal, I could remove them and reinstall with new lines. But if I'm going to pull them, I fully expect the 6yo Mike's holders to be shot and need replacing. Also, the fuel running down the side of the float bowl in the pic below is fresh, as of the last 100miles. It seems to me the time is here to pull the carbs, tear them down, clean them, and reinstall with new holders, MMM's rebuild kits, fuel line, etc. Would you all agree?

While I'm in the region, I'd like a lighter throttle, any way to go about that?

And yes, the Carb Guide's text floats through my dreams.


Stella L carb new to me.JPG

carb barb ports.jpg
 
I'll bet your choke housings were inadvertently swapped at some time in the past. Take a look at the choke housing mounted on your left carb and I bet you'll see the block-off screw in that one.

As for the slight gas leak at the bowl/body seam, the gasket could be bad or the fuel level in the bowl could be a tad high. Ideally, the level should be about in line with the bottom of the lip on the carb body when checked with a sight tube, like so .....

SightTube6.jpg


The gasket and sealing surface on the carb body is actually a few MM higher than the bottom of this lip. Set as shown will put the fuel level below the gasket. It will splash it occasionally but not be constantly working against it and possibly soaking through. Slightly too high float levels won't be enough to belch fuel out the overflow tube but could come through the gasket as yours is doing.
 
I'll bet your choke housings were inadvertently swapped at some time in the past
+1. If you find the left carb has the same untapped choke housing someone replaced it.

5twins, neat trick and a better solution than my wiring the tubes up.
If your floats are sticking open occasionally though, the floats could be adjusted correctly and it would still happen?
5twins mentioned the overflow/vent. You aren't getting any fuel from the there?

For a lighter throttle, lube the cable till it drips? XSJohn did a trick for a quicker throttle but I don't know if it was lighter. nj1639 has done this mod, you might start a conversation with him..
 
You could clean and lube the twist grip too. I use white lithium grease between the plastic throttle tube and handlebar, and in the housing where it rotates too. White lithium grease is pretty light and really not suited for normal metal to metal applications, but it is ideal for plastic to plastic or plastic to metal applications. I also use it for some of the areas in my switches, as seen here .....

CleanSwitch.jpg
 
Excellent.
In searching about what you were referencing by 'choke housing' I found this thread in which you already answered this same question.

http://www.xs650.com/threads/only-one-removable-screw-on-bs38s.20746/

Thank you for the notes on fuel level. No, no overflow other than through the gasket seam. I'll be sure to pay attention that on the rebuild.

I think the call has been made to do an carb overhaul. The boots are likely shot, choke housings must be swapped, and I have no idea how things look inside. Ima gonna do it.

Great stuff about the throttle, too. Thanks. I'll check in with nj1639. Quick response isn't what I'm looking for, smoother and lighter would be great.

I'm going to lube up my switches too.
 
Usually, carb rebuild kits aren't recommended. Most are aftermarket and can contain incorrect parts. In the case of your '76-'77 carb set, the jet sizes contained in their kits are usually wrong. Stock, your carbs had a #25 pilot and a #122.5 main. The kits usually contain a #27.5 pilot and a #135 main. Those are the proper sizes for the next newer 650 carb set, the one used on the '78-'79 models. I don't know why the kits are like this. They've been made and sold this way for years.

So, all you may get to use out of the kit is the float bowl and choke housing gaskets. But, many times they don't need to be changed. The originals are very good and last pretty much forever as long as they're not damaged. Personally, I've never even removed a choke housing. There's no need to. The part that does need to be inspected and may need cleaning is the choke plunger, and that can be removed with the housing still installed.

There is only one o-ring in your carbs, on the needle jet, and it doesn't usually come in a rebuild kit. Many times it does need replacing though. You can just buy it separately if need be. The size is 1mm thick x 4mm I.D.
 
Hmm, ok. The choke housings need to be removed in order to swap them back to the proper side's carb, no? Also, I understood it's best to remove all rubber bits before cleaning.

I had planned to clean and reuse the jets that are in there already. If I can't get them clean, I'll buy replacements in the same size, but I don't know yet what they are. Could be stock, but who knows?
 
@ DanielBlack, when you go to remove the carbs you might find it easier if you remove the cam chain adjuster cap first.
@ 2M missed that thread. And I didn't get past the first page this time. That's a nifty cable cam.
 
Fyi, my 71 is still running great, touchy throttle is gone. A friend of mine rode it the other day, and had no problems with the throttle.
 
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