No power to orange coil wire

[nomad007]

Since you got them both turning, I don't see the need for that extractor, and like you said, there's more of a chance of damaging (and maybe even ruining) the carb body with that. Just keep at it with the penetrating oil and heat. What penetrating oil are you using? PB Blaster is pretty good but Kroil is even better. I'd say they need to come out so you can replace the o-ring at the bottom. That's what seals the screw in the hole and if it's bad, the mix screw won't function correctly.

Yes, when screwed in all the way and lightly "seated", the tip of the mix screw will hang out into the main bore a little bit, like so .....

View attachment 349543

But, a stock bike with stock size pilots runs best with the screws set between 3 and 3.5 turns out, so you wouldn't see the screw's tip then. Even a modded bike with larger pilots still likes 2 to 2.5 turns out.

Hi Everyone,
well I got the Kroil. and took my time soaking the mixture screw for days removed the one with the choke knob side. those rennsteig extractors are nice. I am afraid the right side is probably buggered. It is a shame because these carbs are very clean. Neither of the screws had springs btw. Is that how they came from the factory. Does anyone by chance have a right side 1980 xs650 special carb they would be willing to sell? I have seen some on eBay but a lot are crusty. Am I wrong in assuming I can just plug in a new right side carb body of the same model? At least I am learning a lot and again thanks for all the great advice. On a brighter note I was given a titled 1976 cb 750 with a powder coated frame and running engine with 14000 miles. It needs a tank and a front end tho but it was free. Now I have 3 non running projects . Thanks Damon

 

[nomad007]

Hi Everyone,
well I got the Kroil. and took my time soaking the mixture screw for days removed the one with the choke knob side. those rennsteig extractors are nice. I am afraid the right side is probably buggered. It is a shame because these carbs are very clean. Neither of the screws had springs btw. Is that how they came from the factory. Does anyone by chance have a right side 1980 xs650 special carb they would be willing to sell? I have seen some on eBay but a lot are crusty. Am I wrong in assuming I can just plug in a new right side carb body of the same model? At least I am learning a lot and again thanks for all the great advice. On a brighter note I was given a titled 1976 cb 750 with a powder coated frame and running engine with 14000 miles. It needs a tank and a front end tho but it was free. Now I have 3 non running projects . Thanks Damon

Also what are thoughts on the Mikuni vm34 s ? sorry if that is a can of worms but since - the used carbs on eBay cost half of what that new kit costs just wondering if anyone likes them and how they would work with stock airbag or if they are better with pods - also read the come for 2 strokes and you need different emulsion tubes ?

 

[5twins]

Yes, there should be a spring, small washer, and tiny o-ring on each mix screw. The washer and o-ring often remain stuck down in the hole (the spring may be in there too) and must be "fished" out with a little "special tool" (safety wire w/ a little hook bent on the end) .....

Yes, the generic off-the-shelf VM carb is set up for a 2 stroke dirt bike so you would need to change ALL the jetting and the needle and needle jet. But if you bought a set set up for 650 use already, that stuff should be changed for you already. You'd still need to fine tune them (main and pilot jet sizes) but they should come jetted pretty close. But I don't recommend going that route. Contact forum member gggGary, he can probably set you up with a right carb body. He's got lots of parts, lol.

 

[nomad007]

Yes, there should be a spring, small washer, and tiny o-ring on each mix screw. The washer and o-ring often remain stuck down in the hole and must be "fished" out with a little "special tool" (safety wire w/ a little hook bent on the end) .....

View attachment 350010

Yes, the generic off-the-shelf VM carb is set up for a 2 stroke dirt bike so you would need to change ALL the jetting and the needle and needle jet. But if you bought a set setup for 650 use already, that stuff should be dhanged for you already. You'd still need to fine tune them (main and pilot jet sizes) but they should come jetted pretty close. But I don't recommend going that route. Contact forum member gggGary, he can probably set you up with a right carb body. He's got lots of parts, lol.

thanks 5 twins - i like the idea of sticking with the bs34s- i have a few questions tho- first my float bowls have brass nuts on them with no apparent drain and look different then anything i have seen online. I have seperated pd46c carbs on a 76 cb750 f supersport and it was not my favorite experience. FOr these I suppose i just take the screws off the right side butterflies ( are these screws pinged like the honda) when replacing i assume I should use blue loctite on them. Are there any felts? You already sent me the orings to get for the bottom part - are there any other tips for sucessfully seperating and reassembling. I looked in the carb guide , which is awesome - but did not see that info. Thanks as always damon

 

[5twins]

The brass bolts are the drains on the 1980 bowls, remove them and the gas drains out. In '81, they changed to drain screws on the side, loosen them and the fuel runs out that little "nipple" on the bottom .....

They are the same shape and size inside, and can be interchanged.

If you want to replace the butterfly shaft seals then yes, the carbs will need to be separated, or at least one removed from that bottom angle bracket. The butterfly shafts pull out towards the inside, hence the need to separate the carbs. The screws in the angle bracket have Loctite on them so you'll need heat and penetrating oil to remove them. Even after all that, I had the head of one break off on me, lol. Here's some threads on seal install ....

https://www.xs650.com/threads/bs-series-throttle-seals-whos-done-em-who-needs-to.11980/

https://www.xs650.com/threads/direction-of-throttle-shaft-seal.63799/#post-785573

And yes, the butterfly plate screws are "peened" on the end so it's best you grind that off first before removing them. The shafts are just brass so that "peened" end can bugger up the threads on the way through .....

And you will need 6mm long screws for replacements, 8mm are too long. And yes, use blue loctite on them .......

 

[Its been a long time]

thanks 5 twins - i like the idea of sticking with the bs34s- i have a few questions tho- first my float bowls have brass nuts on them with no apparent drain and look different then anything i have seen online. I have seperated pd46c carbs on a 76 cb750 f supersport and it was not my favorite experience. FOr these I suppose i just take the screws off the right side butterflies ( are these screws pinged like the honda) when replacing i assume I should use blue loctite on them. Are there any felts? You already sent me the orings to get for the bottom part - are there any other tips for sucessfully seperating and reassembling. I looked in the carb guide , which is awesome - but did not see that info. Thanks as always damon

Maybe I missed one crucial piece if information. But anyway, just in case.

Don't attempt any work on the carburettors without buying a set of JIS screwdrivers. They're absolutely essential for removing the screws on the carburettors. Don't try to make do with standard Phillips and posidrive screw drivers. Hope that helps.

 

[arcticXS]

Maybe I missed one crucial piece if information. But anyway, just in case.

Don't attempt any work on the carburettors without buying a set of JIS screwdrivers. They're absolutely essential for removing the screws on the carburettors. Don't try to make do with standard Phillips and posidrive screw drivers. Hope that helps.

I believe I read somewhere that if you grind or file a little bit off the tip of a Phillips screwdriver, it effectively becomes a JIS screwdriver. Or at least will be much better than an unmodified Phillips.
Pozidrive is a "different animal" altogether, as Pozidrive bits and screwdrivers only work on Pozidrive screws. I guess one can use Phillips on a Pozidrive screw, if in a bind, but not the other way around.

 

[nomad007]

I believe I read somewhere that if you grind or file a little bit off the tip of a Phillips screwdriver, it effectively becomes a JIS screwdriver. Or at least will be much better than an unmodified Phillips.
Pozidrive is a "different animal" altogether, as Pozidrive bits and screwdrivers only work on Pozidrive screws. I guess one can use Phillips on a Pozidrive screw, if in a bind, but not the other way around.

Hi 5twins. - sorry I inadvertently replied to you while having a conversation with ggggary- he was able to get me the right side bs34 carb body which i am going to attempt to replace the carb body that i had buggered the mixture screw getting out. I was asking him about vm34 carbs. I have a really nice set of Jis screwdrivers- any advice on seperating the carbs-can I just remove right side( side without choke knob ) and slide replacement in. Gary put new seals on the throttle shaft of replacement. Thanks for recommending GGGgary -and thanls for the advice

 

[gggGary]

 

[5twins]

Yes, you can just remove the right carb from the angle bracket and replace it, not disturbing the left carb. Take care when removing the choke rod. There are small detent balls and springs installed in the carb body. The parts diagram calls for two sets, one in each carb, but many times you only find one .....

 

[nomad007]

Yes, you can just remove the right carb from the angle bracket and replace it, not disturbing the left carb. Take care when removing the choke rod. There are small detent balls and springs installed in the carb body. The parts diagram calls for two sets, one in each carb, but many times you only find one .....

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Thanks 5twins - this is very helpful!