Good catch!! When I block the 34's, they barely move. As soon as I pull the choke, they drop like a rock (well... maybe not that fast....
), about as fast as Bob's here....
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Mailman’s XS2 a full on restoration
- Thread starter Mailman
- Start date
), about as fast as Bob's here....
That’s what I thought, when I perform that test on the BS38s on my other bike, the slides fall very slowly.
I’ll have a closer look tomorrow. Thanks for the suggestions.
I’ll have a closer look tomorrow. Thanks for the suggestions.
+2 on choke valve leak Bob. Maybe housing is leaking. Needs a new gasket? Get out your Felpro and exacto.
Maybe the diaphragm isn't fully seated Bob? An air leak in that top groove would do that. BTDT.
I know you love your plumbers silicone. Did you grease them up?
Do your thing as you did on your 77. Every piece, every part, every bit and you'll solve it.
Maybe the diaphragm isn't fully seated Bob? An air leak in that top groove would do that. BTDT.
I know you love your plumbers silicone. Did you grease them up?
Do your thing as you did on your 77. Every piece, every part, every bit and you'll solve it.
I just went out and tried it again.
Choke housing is in place, it’s got a new gasket. I tried it a few times with the choke on and off, and with me pushing down on the choke plunger. No change. It’s weird.
Robin, you know me so well, yes I did put silicone on the top edge of the diaphragm. Haha!
I know I’ll figure it out eventually, it’s just puzzling, I was very careful on assembly.
Huh. Figured you did all that Bob. With the rate it's dropping it looks like a leaking/poor diaphragm seal.
Maybe the diaphragm slipped on reassembly? I had that happen once, didn't hold the cover on tight enough and the spring pushed the diaphragm out of the groove in a spot. Easy to pop the cover and check I guess. I know I'm reaching here, just trying to look for a cheaper answer than new diaphragms!
Walk away, start fresh my friend. You'll figure it out.
Maybe the diaphragm slipped on reassembly? I had that happen once, didn't hold the cover on tight enough and the spring pushed the diaphragm out of the groove in a spot. Easy to pop the cover and check I guess. I know I'm reaching here, just trying to look for a cheaper answer than new diaphragms!
Walk away, start fresh my friend. You'll figure it out.
Haha, thanks Robin, I’ve got time. I’ll figure it out.
DIAPHRAGM TEST PART 2
Ok I was thinking about this all night, it had to be something wrong with the choke leaking air.
So today I pulled the choke assembly off and tried the test again, this time covering the vent as usual, and also covering the opening for the choke, and guess what? ......the slide came down nice and slow, just like it’s supposed to.
I then checked the gasket, it was homemade and I double checked I cut all the openings correctly, still no problem. Then I disassembled the choke plunger and it hit me!
Remember when I was bitching about the fact that I bought a new choke plunger and they sent me one that was completely the wrong size?
I said how it was way bigger than the one that came out if my carburetor, and I put it aside and decided to just reuse my original.
The original is on the left.
When I pulled my choke apart I realized that the one that came in the carburetor was the one that was wrong! Look at the two next to my choke housing.
The new one fits like a glove. The old one was rattling loose in there.
And Viola! The end result.
Ok I was thinking about this all night, it had to be something wrong with the choke leaking air.
So today I pulled the choke assembly off and tried the test again, this time covering the vent as usual, and also covering the opening for the choke, and guess what? ......the slide came down nice and slow, just like it’s supposed to.
I then checked the gasket, it was homemade and I double checked I cut all the openings correctly, still no problem. Then I disassembled the choke plunger and it hit me!
Remember when I was bitching about the fact that I bought a new choke plunger and they sent me one that was completely the wrong size?
I said how it was way bigger than the one that came out if my carburetor, and I put it aside and decided to just reuse my original.
The original is on the left.
When I pulled my choke apart I realized that the one that came in the carburetor was the one that was wrong! Look at the two next to my choke housing.
The new one fits like a glove. The old one was rattling loose in there.
And Viola! The end result.
I don’t suppose anyone has a drawer full of these lying around? I just need one. I keep finding things that were missing or wrong on these carburetors.
Haha!
Haha!
Believe it or not, Yamaha still sells that little part, lol. It's not cheap though, part #15 .....
http://www.boats.net/parts/search/Yamaha/Motorcycle/1972/XS2/CARBURETOR (XS2) (TX650)/parts.html
http://www.boats.net/parts/search/Yamaha/Motorcycle/1972/XS2/CARBURETOR (XS2) (TX650)/parts.html
cn prolly spare one to a good home.
Ha! I had already ordered a replacement and it is now installed. I still can’t figure out how that skinny little choke plunger wound up in there!
Way to go Bob! Knew you'd figure it out.
Another win for the Mailman!
Another win for the Mailman!
Indeed. As you’ve pointed out before, given all the defects you have found in those carbs, it is amazing that the bike actually ran! I don’t recall - did the electric starter work?
It works, but sounds about like the rest of them! Haha! 
Sorry Bob but I had to chuckle a bit when you started to tell the story about the choke plunger. Right a way I knew where the story was heading. I know my eyes are getting bad also as I age.
Well today, I finished assembling my right side carburetor, so now both carbs are completed and boxed up and waiting to go on the bike. I have a question about bench syncing these early model carbs without the joined linkages.
Each butterfly is set independently using the idle screw on each carburetor. What’s a good initial setting on these carbs? I’ve used the slip of paper under the butterfly and open it just enough that the paper slips out. But I’ve been looking at the tiny passage holes in the top of the bore of the carburetor.
You don’t have to put much pressure on the idle screw at all for the first of the passageways to show. Would that be a good visual benchmark? Turn the screw until that first hole is just hidden by the butterfly? Opinions?
I’m also a little concerned about synchronizing these carbs once the bike is running, since there are no vacuum ports anywhere. I’ve already bought new intake manifolds that don’t have vacuum attachments. I looked at them but somewhere I read that the early boots were somehow angled differently?
I spent the rest of my day going through the ignition switch and the front brake switch ( that little oddbal switch that hangs down below the front brake lever.)
I broke them down and cleaned them, spray painted the ignition switch housing, cleaned up all the contacts, checked the wires for continuity, and replaced all the brittle PVC wiring loom.
All of my switchgear have now been gone through. That feels like a pretty big milestone. I deliberately tackled the more detail oriented fine work first.
So , jobs completed to date;
Instruments rebuilt
Switchgear rebuilt or replaced
Ignition switch refurbished
Front brake switch refurbished
Frame mount hardware cleaned in ultrasonic cleaner
Rubber bushings and mounts softened ( time will tell how well that lasts)
Swingarm bronze bushings installed
Battery box stripped and painted
Center stand stripped and painted
Swingarm stripped and painted
Carburetors rebuilt with CORRECT jets and choke plunger, and missing parts replaced!
I’m beginning to feel like I’m gaining some momentum on this build! And I just got a call today from Marbles Motors
He called to tell me how much I owed him!
I should have my painted parts by the end of next week, right after I sell one of my kidneys!
Until next time,
Bob
Each butterfly is set independently using the idle screw on each carburetor. What’s a good initial setting on these carbs? I’ve used the slip of paper under the butterfly and open it just enough that the paper slips out. But I’ve been looking at the tiny passage holes in the top of the bore of the carburetor.
You don’t have to put much pressure on the idle screw at all for the first of the passageways to show. Would that be a good visual benchmark? Turn the screw until that first hole is just hidden by the butterfly? Opinions?
I’m also a little concerned about synchronizing these carbs once the bike is running, since there are no vacuum ports anywhere. I’ve already bought new intake manifolds that don’t have vacuum attachments. I looked at them but somewhere I read that the early boots were somehow angled differently?
I spent the rest of my day going through the ignition switch and the front brake switch ( that little oddbal switch that hangs down below the front brake lever.)
I broke them down and cleaned them, spray painted the ignition switch housing, cleaned up all the contacts, checked the wires for continuity, and replaced all the brittle PVC wiring loom.
All of my switchgear have now been gone through. That feels like a pretty big milestone. I deliberately tackled the more detail oriented fine work first.
So , jobs completed to date;
Instruments rebuilt
Switchgear rebuilt or replaced
Ignition switch refurbished
Front brake switch refurbished
Frame mount hardware cleaned in ultrasonic cleaner
Rubber bushings and mounts softened ( time will tell how well that lasts)
Swingarm bronze bushings installed
Battery box stripped and painted
Center stand stripped and painted
Swingarm stripped and painted
Carburetors rebuilt with CORRECT jets and choke plunger, and missing parts replaced!
I’m beginning to feel like I’m gaining some momentum on this build! And I just got a call today from Marbles Motors
He called to tell me how much I owed him!
I should have my painted parts by the end of next week, right after I sell one of my kidneys!
Until next time,
Bob
Bob, your carbs' starting point should be similar to mine.
Set mix screws to 3/4 turn from bottomed.
Set throttle stop screws 1/2 - 3/4 turn from fully closed.
This should just begin to expose the first transition port.
The mix screw controls flow from the idle port, upper/left hole in this pic. The transition ports are unregulated. As the throttle is opened, more of the transition ports get exposed, and start delivering. The adjustment influence of the idle/mix screw is reduced as more of the transition ports get exposed. If adjusting the mix screw give little, or no change, the throttle plate may be too open, meaning that there are serious problems.
Synchronizing these is an old-school skill, by ear and feel. For starters, have a look into DogBunny's thread:
http://www.xs650.com/threads/simple-carb-mixture-screw-and-sync-adjustments.33791/
Then, do a forum search on: "dead cylinder", click "titles only"...
Set mix screws to 3/4 turn from bottomed.
Set throttle stop screws 1/2 - 3/4 turn from fully closed.
This should just begin to expose the first transition port.
The mix screw controls flow from the idle port, upper/left hole in this pic. The transition ports are unregulated. As the throttle is opened, more of the transition ports get exposed, and start delivering. The adjustment influence of the idle/mix screw is reduced as more of the transition ports get exposed. If adjusting the mix screw give little, or no change, the throttle plate may be too open, meaning that there are serious problems.
Synchronizing these is an old-school skill, by ear and feel. For starters, have a look into DogBunny's thread:
http://www.xs650.com/threads/simple-carb-mixture-screw-and-sync-adjustments.33791/
Then, do a forum search on: "dead cylinder", click "titles only"...
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