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Replacement carb diaphragm for GS450 (Mikuni BS34)

  • Thread starter Thread starter HestonsRightNut
  • Start date Start date
H

HestonsRightNut

Guest
Hey everyone,

I'm in the process of fixing-up a 1980 GS450E and have been working to get the carburetors (Mikuni BS34) back into shape. The diaphragms were in pretty poor shape and I purchased a set of replacements from JBM Industries (M-73).

Unfortunately, I did not measure before ordering and come to find that the slides in my carburetors measure 24mm in diameter. The JBM diaphragms have a 25mm inner diameter (the JBM diaphragm's outer diameter is perfect). The slide's groove is also wider than the diaphragm (see pic).

Before ruining them by gluing in place, I was hoping to hear from others who may have used these on their bike.

Thanks in advance for the feedback

Jay
 

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Hi Jay, sorry to say mate but none of the JBM diaphragms will fit. I measured and did everything I could but the closest I could get on their list still won't fit. The 80 - 82 450 carbs are the red headed stepchild of the GS twin family along with the ignition setup.

My solution was to put some 2001 GS500 carbs on and they are so much better. Just make sure to use the correct GS500 intake boots rather than the 450 boots though, they don't sit quite right with the stock ones and you will get an intake leak. The catch is obviously you can't use the stock airbox, I use velocity stacks with a foam filter over the top.
 
Yep you can still buy them brand new, but unlike more modern versions they come with the slides, so for me it was going to be around $AU400. I picked the 500 carbs up for $AU150 and they were recently in use so no need for a rebuild... my 450 is not a stock bike nor is it a restoration, so for me that was a no-brainer.
 
Hey guys,

Thanks for the feedback.

The good news is that the folks at JBM Industries will accept returns from bone-heads like me who don't measure accurately.

In the meantime, I'll hunt around for a good used set...$140US for new is a bit heavy for a "free" bike I got off Craigslist!

:p

Jay sends...
 
HestonsRightNut said:
Hey guys,

Thanks for the feedback.

The good news is that the folks at JBM Industries will accept returns from bone-heads like me who don't measure accurately.

In the meantime, I'll hunt around for a good used set...$140US for new is a bit heavy for a "free" bike I got off Craigslist!

:p

Jay sends...
Click to expand...

You might find a set. Fleabay is your best shot. I found two new old stock for my Euro model 400 in Germany. Took 14 months to find. CML has them but at 177 Euro each. Only place that stocks them that I could find.

My diaphrams were in excellent condition so they now sit on the shelf inside the house.
 
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