diaphragm

[LoHo]

As I am anxious to reveal my stupidity, let me throw this out:

The concave side of the diaphragms contact engine vacuum only and should encounter few fumes, right? The convex side is somewhat exposed to gas fumes, but not to any extreme. The repair should be made in the concave/vacuum side, right? I find it hard to believe that there'd be much exposure to repair-eating fumes.

[jetmechmarty]

LoHo,

I made one of these repairs to one of mine on a XS650. It was so long ago that I have no recollection what I used. I made the repair years ago. The bike runs great. I do remember the repair was minor. I think it was a little hole.

No worries

[motoman]

Wonder how many members have removed diaphrams, say one or two years later after using the Plasti-Dip on a couple pin-holes? If there carb issues were resolved with this being part of the equation, no reason to remove again......just making a point considering the flakey mess I found in places U don't want restricted/plugged a year later.........

[jetmechmarty]

I am positive that I DID NOT use Plasti-Dip. I haven't ever used it on anything.

[3Phase]

No, you're not stupid!

Loho, the enricheners are downstream of the diaphragms in the vacuum chambers and they can spit fuel when the enricheners are open, especially if the engine pops. They'll also spit fuel if the engine doesn't start and 'rolls back' when you let off the Start button.

Holes in the diaphragms... okay, assume that the P.O. didn't go mental trying to fix an electrical problem by tearing into the carburetors before giving up and grabbing an ice pick, then selling the bike. Take a look at the diaphragms and you'll see that they don't fit perfectly, they fold and wrinkle. The 'bottom' of the wrinkles rub and vibrate against the carburetor body.

Also, when the slide raises and lowers, the diaphragm has to roll through the length of the wrinkle but that's kind of hard to explain.

Look at a the vertical fold in a newspaper, the one that allows it to open like an unbound book. Open the paper and hold the upper edge of the paper against the bottom edge. Hold the bottom edge of the paper in one hand and with the other hand slide the top edge of the paper up and down as if it was attached to a carburetor slide.

The smooth part of the paper will roll just fine but the paper in the vertical fold won't, it'll try to bind and bunch up. If you do that long enough, the fold will start to wear out faster than the rest of the paper and eventually make a hole.

You can patch the hole and keep going but the patch won't roll at all and the paper around the edges of the patch bind. Because the rest of the fold is already worn where it was rolled there will eventually be another hole or it will just split open.

It's not exactly that simple with the original Mikuni diaphragms because they're a compound made of a fabric, possibly silk? and some kind of elastomer. When the elastomer starts to lose its elasticity it will crack and flake out of the fabric and leave a hole. Try the newspaper trick again but this time use a thirty-year-old newspaper that was splashed daily with gasoline and then wrapped around the furnace exhaust vent stack on the roof of the house to dry out.

[STEPPENWOLF]

Thoughts on this vendor...
http://www.ebay.com/itm/BRAND-NEW-4p...t_18837wt_1026

[jetmechmarty]

Thoughts on this vendor...
http://www.ebay.com/itm/BRAND-NEW-4p...t_18837wt_1026

I've heard chatter, but nothing negative. It looks to be the best option.

[STEPPENWOLF]

Thanks Jet...I will search around a bit more just to see who might have them. Two were just found to be ripped a bit so it is time to replace all four and be done with it.I plan on keeping the bike so might as well do it right.

[Rasputin]

I have bought 4 sets from him. Always on time delivery, good with returning emails etc, and seems to be a good quality product. Not quite the same materials, as the stock ones seem to have more of a fabric look to them. Installing them can be a trick depending on which method you use but the diaphragm itself is a good one. I have only had them in for about a year so I can not attest to their longevity.
A good seller with a good product is my asessment so far. I am a bit suprised at how low his rating was on the ebay item you posted. I will buy from him again unless I find a better price or product.

[STEPPENWOLF]

Thanks Ras...feel better now.