Butterfly Valve Removal Capers

[londonboards]

There is quite a debate on this forum about the necessity and difficulty of removing butterfly valves. I don't want to say you should or shouldn't do it but if you find yourself having a go this might help.

In the end I was glad I did do it as I discovered that one of the seals from the stainless throttle rod was missing completely. I wonder if my set of carbs was swapped out at some time as the damage inside them has been quite bad and we have owned this bike since new. It could only have been done at the shop where it was serviced.

See My GS1100G Blog Butterfly Capers for extra details.

Set up a wood throttle rod support





The burring (or preening) on the backs of the screws shouldn't pose a problem.





For carbs 1 and 4





For no. 3





and for no.2 remove this pin with a suitable punch



There is a more detailed explanation and further pictures on the blog

Greetings

[BassCliff]

Hi,

Good work with nice documentation. Thanks for sharing!

May I put a link to your blog on my little website?

Thank you for your indulgence,

BassCliff

[1980GS1000E]

Best pics I ever saw, man.

[londonboards]

Hi,

Good work with nice documentation. Thanks for sharing!

May I put a link to your blog on my little website?

Thank you for your indulgence,

BassCliff

Only if you think it is worthy. I am no expert. I am simply blogging what happens during the rebuild.

I would be honored.

Greetings

[Steve]

Very good documentation.

I would like to add one thing to this, though.

Especially with these small screws, be SURE to use JIS screwdrivers, NOT a regular Phillips screwdriver.

Those of you who have never experienced the difference will be saying "so what, it's just another driver", but you are WRONG.

Motorcycle Consumer News even thought it was worthy of an article, and put it on the back cover of the March, 2013 issue. Here is a scan of it.



.

[1980GS1000E]

I have found that for #2 and higher at least, good quality impact bits fit very well into the screw heads. I have used those bits in tip-interchangeable screwdrivers with success. The JIS screws seem to unscrew without any wear and can be reused several times. The impact bit tips look exactly like the photo in the article posted depicting the JIS tip.

[gsweakley]

I have a weird little hesitation in my 83' GS750ES as my engine speed hits around 2500-3000 rpms. The engine begins smoothly and then once it gets to those rpms it simply jumps a little and after that zone it runs smoothly all the way to redline. So in an effort to fix it I have completely disassembled my carbs and as I unscrewed the butterfly valve screws I learned that they were boogered on the end to prevent from being unscrewed. I powered through the first screw not realizing what I was doing and it "screwed" up the threads of the rod that goes through the venturi.

Is there any way to unscrew the butterfly valve screws without damaging the female side threads? If so how can I do this?

[greg78gs750]

nice to see someone can take a close up photo and hold the camera steady! nice pics!

[londonboards]

Now you say that I am hoping I have not screwed up mine!

Can't see why it would have damaged the thread on the rods. The screw material is only burred over slightly to stop it shaking out. In my case the burring got stripped off when it started to come through the rod when they were being unscrewed. I have bought new screws to rebuild this set of carbs and I am now hoping that they will go straight in. If they don't I will try to ream the thread with the appropriate tool.

I am not an engineer nor a metals expert but it seems to me that the rods are made of much sterner material (stainless steel ?) than the screws. It might have felt like you were mashing the threads but in actual fact if was simply the burred part being pulled off.

May be you should just try new screws and hope you can retrieve the threads.

Greetings

P.S. The new screws I have a hollowed out on their tips. This is (I am guessing) to help you burr them over when installed. I wouldn't reuse the old ones which would now necessarily be weakened.

[londonboards]

Here are some photos of the old and new screws. I would say they are self explanatory; new screws are essential. Try burring those old ones over again and bits are going to fall off:







Greetings

P.S. I will be showing the re-assembly process later on but the rebuild can't progress at the moment until I have all the small parts plated and cleaned.

[hampshirehog]

Well done for getting new screws Richard - it will be a lot easier to peen them over.

I'm too tight and have used the old ones many times before - especially on some Keihins where you have to take the choke plates out if you want to split the carb bank. I've never lost a screw in to the engine but I am extra careful putting those screws in.

You are correct that you won't have boogered the rods - the screws are softer.