Worn butterfly valves

Hi,
I was merrily rebuilding a rack of carburettors that I bought of ebay last night and after polishing the butterfly valve shaft, putting in new shaft seals and beginning to tighten the butterfly valve plates I could see light around the edges when the valve was closed shut.
I loosened and jiggled and opened and closed and tapped but still couldn't get the light to block out on the sides.
I took the plate out and compared all 4 to the plates in my other set of carbies and this is what I found.

Here are the 4 'worn' plates with one of the 'non worn' plates below.


and a closeup of one of the worn plates.



and finally a closeup of the not worn plate.


To me these look worn but in saying that I'm no expert and they could be special super performance butterfly plates... but just in case they aren't I thought I'd ask the questions.

I have fitted one of the 'non-worn' plates into the carb to see if it was some sort of irregularity in the throat of the valves and with the 'non-worn' plate the valve closes completely with a hard clack after alignment.

Now the questions,
1. Is this a normal type of wear? and if not what do you think has caused it?
2. Can you get replacement butterfly valve plates? or Make them maybe?

Thanks ahead of time for your input!

 

Can you post-up the miles/k's on each rack for comparison??
I'd say that's just as much of an idle air leak as bad shaft seals or cracked boots and would never idle right.

 

If that throttle plate is worn that bad then the carb body it came from is toast also.

 

Sorry I have no idea of the k's on either of the racks.

One of the racks is off my parts bike (non-worn plates) and the other is the rack I bought off ebay which looks like it has been worked on before (SS mix screws and floats set so far out they would never actually shut the fuel off)

 

Looks like someone took a file to those. Like you said float levels off no way it ran right. As far as making a set, if you look at the good one you have you can see the edge is not square to the face its cut on an opposite angle top and bottom. As far as buying that part by itself I have never seen it listed separately. Good luck

 

Looking at the carb throat it doesn't have any crazy wear and now looking again at the 'worn-plate' I'm inclined to agree... me thinks some PO got confused and thought they grew maybe when getting them jammed pulling them out or putting them in and decided to do some ingenius engineering.

Damn shame. Thanks for pointing that out Waldo.

I guess I'm only going to end up with 1 good set of carbs from the 2 still so all is not lost... hopefully!

 

I was thinking the same thing. They don't look worn so much as modified.

 

Hi mate.

Will be returning your color tune plug shortly. Would you like a spare throttle plate? I have some from the old set of carbs I cut up/sectioned.

 

That'd be great darkfibre. I'd love to take them off your hands so I can stop looking sideways at the re-engineered plates trying to work out how to make some out of old computer cases

You sectioned the carbs! Sounds like a good photo op and did I mention you shouldn't drive milling machinery angry?

Thanks again. Give me a call when you want to take a trip down.

 

How many do you actually need?

And for the record I needed to know the internal structure of the carbs before rejecting option 3 of setting up the injectors. :wink:

 

All 4 of them have been filed back to varying degrees.
Must've been a rainy day and the PO couldn't find any decent wood to whittle away on.

I'll take whatever you have spare though... looks like you have one spare at least hehe.

 

Make new butterflies out of an old computer case???
I sure hope it is an appropriate type of aluminum, steel would be a bad idea. Is the thickness the same? I sure hope Darkfibre can fix you up, a much simpler fix.

 

There is the possibility that they are not worn.

That the Elliptical Holes in the Throttle Plates are used for Precise Centering of the Plate within the Venturi.

Much the same way as the "Butterfly" Plate on the Bosch K-Jetronic Air Flow Meter needed to be "Centered" after cleaning the Metering Assembly.

We'd use Scotch Tape or Newspaper to keep the Plate from touching the Sides while tightening the Sensor Plate.

When the Plate was tightened in place. The Tape or Newspaper got removed
and you were assured that the Plate was "Centered" and wouldn't bind.

 

The madman with the file probably had no idea that the edges were supposed to be at an angle, and decided they needed to be squared up because they were binding.

I wouldn't recommend trying to make any yourself. They're actually a pretty precision part.

 

Substitute hardware.

Delete the Slotted Head Screw that Fastens the Butterfly Plate to the Throttle Shaft.

Add Cap or TORX Screw with an Internal Star Locking Washer under a Flat Washer and "SHIM" the O-D's of the Butterfly's within the Space ... using Plastic Shims cut from Ultra-thin, Plastic Packaging, ... held with tape.

 

If darkfibre doesn't have all the butterflies you need I have some if you wanted to pay the shipping for them.

 

Xyxj thanks a lot for the offer I'll let you know how many I scrounge off darkfibre!

Rick your saying to use the filed back plates and make shims the right size/shape of the non-worn plate out of thin plastic material and mount them on the shaft on the front of the filed down plate as a cover? stick them on with tape too? for testing?

On the back would be better from a flow perspective but that would move the plate away from the original position.
On the other hand if the plastic shim is on the front and we start sucking like mad and the shim starts vibrating perhaps we could produce an atomisation... yes I'm thinking about the reed valves out of my old RD250...
I guess a two stroke burns the fuel on that stroke though where as the 4 stroke compresses it before it burns it? so... turbo must be the answer for that idea.

I'm not sure what the tape part does though although I can see what it does in the procedure with the Bosch K-Jetronic Air Flow Meter you described before.

Being at that end of the carb I would need to find some plastic which would be fuel resistant... the plastic from a bottle that had metho in it maybe (i have an empty square one of those in the garage).

Is that the idea you mean? Sounds like a nifty substitute too... shouldn't wear or melt since it shouldn't be too hot in there and once the carbs are setup the butterfly is cracked open all the time anyway and I suppose the only portion of the shim that is exposed away from the plate will be the small filed areas too... hmm hmm

 

No. I didn't realize that they had been altered.

I thought you were dealing with just the "Elipiticals"

This place in Nashua, NH might have what you need.
I have been up there "Fishing-around" in the Mountain of Carbs they have.

If you get behind the 8-Ball, ... stuck without an option.
I could take a ride up there for you, ... if you call them and they say:

"You are going to have to come-up and look".

http://www.drumhillcycle.com/