Centering butterflies

CalsXS2

CalsXS2

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I'm trying to center my butterflies after doing seals, and a cleaning.

I read where you're supposed to re-install the spring and let it slap shut a few time. Well I have it operating smoothly, but it's not 100% centered.

I shined a flashlight and can see light around the butterfly. I thought I really messed up, but I checked 3 other carb's that I have that has not been took apart as far as I can tell. They have the same light shinning around the butterfly.

Does this look acceptable, or should I keep trying. I think I might just be chasing my tail. Could this be as good as it gets. The light makes it look worse than it is. I think I might try setting it according to the light and see how it feels.

Input please.

tx750motor058_zpsbfaa12f5.jpg
 
You have to leave the butterfly screws a bit loose to let the butterflies center up.
Leo
 
Is that carb the left or right? The left side is the one with the idle speed adjust screw, this screw needs to be backed out so the butterflies can close completely.
Leo
 
XSLeo said:
Is that carb the left or right? The left side is the one with the idle speed adjust screw, this screw needs to be backed out so the butterflies can close completely.
Leo
Click to expand...


Thanks for the replies Leo.

This is the left carb. How ever. This is on my 72,,, so the carb's are not linked.

I tore the carb's completely apart,,, and put the butterfly in first. So there's no idle speed screw to deal with. :thumbsup:
 
Hey, CalsX2
Look closely at the bevel angle of the butterfly, top and bottom.
Your picture looks like the butterfly is in backwards.

Good luck...
 
If it was in upside down the number would be on the top or back, never seen that in the stock configuration.
I think it is a good as it gets Calvin. These weren't manufactured with the precision of todays products.
Nice choice with the allen heads. Did the spring punch work to stake them?
 
Well, it does appear correctly installed from the pic - numbers are usually right side up, below the shaft, and facing out like that. But that's not to say that some plates may have been stamped differently. Yes, check the bevels on the top and bottom edges. Are both carbs acting like this? And if you had both apart, could you have mixed the plates up between carbs? This is usually a pretty finely machined and fitting part, at least on the newer carbs anyway.
 
Just so happens I have a set of unmolested Solex's handy.
Never had the plates out. Witness the unboogered screws.
Both carbs have open gaps. On the sides and at the bottoms.
And the idle screws are out so they aren't closing any tighter.
 

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I've never heard much good about the early carb sets and this looks like just one more strike against them. It must be hell setting a good idle on those things.
 
TwoManyXS1Bs said:
Hey, CalsX2
Look closely at the bevel angle of the butterfly, top and bottom.
Your picture looks like the butterfly is in backwards.

Good luck...
Click to expand...

weekendrider said:
If it was in upside down the number would be on the top or back, never seen that in the stock configuration.
I think it is a good as it gets Calvin. These weren't manufactured with the precision of todays products.
Nice choice with the allen heads. Did the spring punch work to stake them?
Click to expand...

I initially tried the short screws and staking with the spring punch. It wasn't worth a crap.

So I ended up with some 8mm Dubro screw's from the hobby shop. I used blue loctite and buggered the thread's. Hmmm. I might have read to do that somewhere,,,, lol.
 
Yeah, just had to ask. There's a little dark shawdow ring showing at the bottom of the butterfly in the picture that looked familiar. I'm also becoming sensitized by the volume of posts of problems that were induced by some PO who did something goofy, then sold it, then prob shows up here. Also, since these things are so old, it's very likely we're diagnosing some aftermarket item installed 25 years ago, that looks stock, but isn't. Sorry if I mislead you, but my bs38s would close completely, and your butterfly just looked odd to me.
 
5twins said:
Well, it does appear correctly installed from the pic - numbers are usually right side up, below the shaft, and facing out like that. But that's not to say that some plates may have been stamped differently. Yes, check the bevels on the top and bottom edges. Are both carbs acting like this? And if you had both apart, could you have mixed the plates up between carbs? This is usually a pretty finely machined and fitting part, at least on the newer carbs anyway.
Click to expand...

I've never had the butterflies out before. And I only do one carb at a time when I do one. You know. Reference point to look at and all that for a newbie. :laugh:

Whats this bevel you guy's speak of. My 72 plate's are just flat. I just looked at my 73, and 76 carb's, and those plate's are flat too. And they all have they daylight around them.
 
weekendrider said:
Just so happens I have a set of unmolested Solex's handy.
Never had the plates out. Witness the unboogered screws.
Both carbs have open gaps. On the sides and at the bottoms.
And the idle screws are out so they aren't closing any tighter.
Click to expand...

I bet I know where there's a 750 motor those carb's came off off,,, lol. :D
 
Wish I could show you a picture, but if you visualize, from the side, an angled butterfly sitting in a pipe, the butterfly's top and bottom edges are beveled to match the resting angle of the butterfly in the pipe. Usually 3 - 5 degrees, so the butterfly makes a good seal, and more importantly, so the edge won't catch and jam when fully closed. Also, by ensuring this close fit, when opened to idle position, the proper vacuum signal goes to the top and bottom, where the idle port and transfer slots reside.
Now I'm wondering if faulty butterflys were sourced at manufacture, maybe cost-cutters...
 
CalsXS2 said:
I've never had the butterflies out before. And I only do one carb at a time when I do one. You know. Reference point to look at and all that for a newbie. :laugh:

Whats this bevel you guy's speak of. My 72 plate's are just flat. I just looked at my 73, and 76 carb's, and those plate's are flat too. And they all have they daylight around them.
Click to expand...

The edge is not perpendicular to the surface. If you cut slices off a sausage at an angle; two opposing edges would be beveled. All the butterflies are beveled like that.
 

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