carb diaphrams

[kevxs]

hey guys if my carb diaphrams were cracked or not sealing what symptoms would the bike get? i had my carbs apart for a month or so and a couple of the diaphrams didn't seem to fit back in as good as before, its like they shrunk or something

could this possibly screw up the vacuum advance on the ignition?

[fredintoon]

hey guys if my carb diaphrams were cracked or not sealing what symptoms would the bike get? i had my carbs apart for a month or so and a couple of the diaphrams didn't seem to fit back in as good as before, its like they shrunk or something

could this possibly screw up the vacuum advance on the ignition?

Hi Kev,
there's enough vacuum in the intake to work the advance but it'll sure screw up the carburation.
Hold the diaphragms up to the light to look for pinholes.
I've never done it but the search button should point you to several pinhole home-fixes.
The diaphragms are also a right swine to get back in properly.
Note that there's a small D-shaped lobe on the diaphragm edge and a matching cut-out in the carb body to match it.
Align those.
I use a light smear of vacuum grease on the diaphragm's edge to hold it in place then carefully put the cap down with light hand pressure and a small circular motion that lets you feel that the diaphragm is in position. Hold the cap in place with one hand and put the screws in with the other.

[kevxs]

yeah i think theres a good bet they didn't seal when i was putting them back in, the lined up the notch but the rubber just was not big enough to fit al the way around on a couple of them, could they have warped from sitting near a sunny window?

[DGXSER]

As that rubber dries out form not being in the carb and the fuel vapor on them, they tend to shrink a bit. It can be tough to get them to go in. I typically run my finger around the edge being sure the lip on the diaphram sets in nicely in the groove in the carb. Then its like putting one of those psring snakes back in the can, you gotta work quick.

[thewiz]

I have fought with ...

a couple of these shrunken diaphragms in the past too. I finally ended up taking a toothpick with a tiny amount of 3M trim adhesive and putting a bit in the groove to hold the diaphragm in place while I assembled it... worked great

[kevxs]

thanks i will give that a try, and other tricks? is there a way to expand them back out a bit?

BTW thanks for all the help, the push pin tricked saved my butt recently and the broken coil wires fix helped alot among with tons of other info, this site is the best

[cywelchjr]

thanks i will give that a try, and other tricks? is there a way to expand them back out a bit?

BTW thanks for all the help, the push pin tricked saved my butt recently and the broken coil wires fix helped alot among with tons of other info, this site is the best

I'm pretty sure that once shrunk it's for good, but the good news is you can get brand new ones from siriusconinc, they can be a PITA to get off and on, but they work good. I hear it can even be done without cutting the plastic pieces that hold them on the slides as well, but I couldn't figure that out. A hint if you do replace them, make sure the new ones go on EXACTLY like the old ones or the carbs will NOT work right DAMHIK, you will get bogging etc. The good news is that it can be figured out, as the relief hole goes exactly on the engine side when everything is put together.

[CaptonZap]

HI, CY,
I looked at the Cirusonic site, and could not find carb diaphrams listed in the parts for an XS 1100. Have you actually purchased some from them? Is it something that they don't list, but can supply if you call them?
I would like to rat hole a set, since the ones I have show deterioration creases.
One thing I learned was that brake fuild would swell neoprene parts, (put a couple of teaspoons in an automatic transmission that has leaking seals),
and rubbing the rims of the diaphrams might swell them enough to fit. Try it on something that is junk if it doesn't work. CZ

[cywelchjr]

I just looked and they are not listed on siriusconinc anymore, and I just looked at them a few months ago. However, a quick search on ebay turned up these for the budget minded and complete assemblies from georgefix.

[CaptonZap]

Thanks Cy, I will keep my eye on that sale.
Appreciate the help, CZ

[kevxs]

thanks for the link, is says for 80-81 xs11, would they work on my 79sf?

[tadtl1]

diaphragm

Hi,

Mine seemed to have shrunk also while the carbs were apart. It took a little time, but patiently working them into the grooves seemed to warm them enuff for them to stick in the grooves eventually. I am thinking that the body heat from my hands may have made them more pliable. I did use a little tiny bit of vaseline in the grooves also.

[latexeses]

Mine did the same thing.

My solution was to get a second set of hands (wife or girl friend or boy friendand) and have them hold a couple sets of feeler gages on each side of the diaphram down (.012 worked well) while you get them in place into the groove for the diaphram. Put the tops on the carb and start a couple screws and snug them down to the feeler gage and carefully pull the feeler gages out and finish tightening the tops down.
Just repeat for each carb.

Works like a champ

[cywelchjr]

thanks for the link, is says for 80-81 xs11, would they work on my 79sf?

I don't believe so. I think the 78-79 carb diaphragms are different from the 80-81, and I think that the 82's use the same ones as the 80-81.

[DGXSER]

Woww...for as much as those diaphrams cost, if there is not holes in them, I'd be danged if I would go buying new ones.

Really, no need. Like others have stated, this is just normal for them to get a little tight to install. Just stretch it out a little and run the tab nto the groove of the carb using your fav method to get it to stay in place. Lots of good ideas here for that.