Diaphragm Replacements for '81 GS750

[hacka]

Hello,

I've cleaned and rebuilt the carbs for my '81 GS750 (not running when I got it, needs a lot of work), but the diaphragms still need addressing. They don't seal properly anymore and definitely feel perished.

I saw some videos showing that it should be possible to stretch and slide the old diaphragms off, then stretch some new ones on. So I ordered some from eBay (which I try to avoid...). I messed with them today but I don't think I ever got them in properly- they were always worryingly easy to pull back out and they didn't seem to sit right in the carb body groove.

So... Have folks had success replacing these rubber diaphragms? And if so, what parts did you use?

I've been to the JBM Industries website and I am leaning that direction, but clipping off the plastic rings makes me a bit nervous since you can't undo that! I measured the outer groove diameter at 70mm, but I don't think I can get any other measurements without clipping the rings. It seems quite clear that their parts fit BS34 carbs, but I believe I have BS32 carbs (BS32SS? not sure if those are different).

Thanks!

 

[Nessism]

I've replaced diaphragms before, but it's an advanced project. You have to bend up the crimped lip, remove the plastic ring, install the new diaphragm and plastic ring, then crimp down the lip again. Main problem: the lip is brittle, and it will likely break off in places. It's a sucky job, that may or may not work properly.

The china diaphragms are nothing like the originals. China = rubber. Suzuki/Mikuni = rubber coated fabric that don't stretch.

I'd get the JBM's. They work well enough from most accounts.

Also, do a full rebuild. check my signature for some helpful info. If you can't see my signature, go into your profile page and turn on the feature to allow visibility of signature blocks.

Good luck.

 

[hacka]

Seems like attempting to re-use the plastic rings may be easier on other carbs. Definitely agree that the cheap replacements are quite different. I'll go with the JBMs. Seems like BS32s should have the same measurements, hopefully that's true.

I'm very familiar with the rebuild pdf in your signature, thanks! I have a benchtop blasting cabinet for soda blasting and an ultrasonic cleaner, seemed to do the job well. Also glad to see that you're providing o-rings... I got mine from cycleorings.