Interceptor accelerator pump diaphragms on Ebay. Nov 2019

[Interceptor398]

Interceptor fuel pump diaphragms on Ebay.  Any bets on how much they go for???

https://www.ebay.com/itm/254401131882?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

This might be a good place to start the "How to convert the S&S carb diaphragms" for the 550 carbs??

[DougKauer]

I was bidding, got too high. What is the S & S carb diaphragms??

[Interceptor398]

Harley used a carb with a very similar style diaphragm but it needs to be modified to work in the Interceptor carb.  I have heard of the mods but have never seen or done it.  I have the S&S PN someplace??  Hmmm, where might that be???

[mswyka]

I wouldn't be opposed to spending $100 or $150 on a part if I was confident that it would solve a problem.  But I worry about buying flexible parts that are almost 40 years old.  For my day job I have done a considerable amount of study on the durability and ageing of flexible membranes.  I don't know what material was used for these diaphragms, but for many flexible membranes, the flexibility comes from the addition of plasticizers that will disappear over time.  Like the difference between a flexible PVC pool liner and a rigid PVC pipe.  The both use the same PVC monomer, but the pool liner is flexible - at least at the time of installation - because it has been compounded with plasticizing agents.  For anyone who has taken out a used pool liner after 20 years, at that time they can be as brittle as potato chips as a result of time, pool chemicals, and sun causing the plasticizers to migrate out.

When we had our Interceptor it came to us with no accelerator pumps.  I tried for a while to swap in LTD carb bowls but even then had trouble finding LTD carbs that didn't come with their own set of problems.  After a conversation with Keihin US, they directed me to a "sister" carb that they made at the time that was supposed to be a direct swap.  I think that information is in another thread here.  I will also look in my files to see if I can find that information again.

Today, if I could have done it all over, I would swap in the Mikuni carbs.  They may not be as sophisticated as the Keihin's, but they certainly are simpler to work with.  And on a side note, the heating control system in my Honda Accord is manufactured  by Keihin.

[mswyka]

Found the other post:

"A few years back we had an Interceptor whose accelerator diaphragms had been disconnected.  In our search to restore the carbs I contacted Keihin - 262-860-6000.  They told me that the carbs used on the Interceptor were no longer available but that they were from a family of carbs that were interchangeable and suggested that I replace theem with H/D 27001-88A.  We also found that the bowls from the LTD carbs would fit on the Interceptor.  The LTD carbs have the check valve in the bowl while the Interceptor had the check valve in the diaphragm.  With the LTD swap diaphrams can still be obtained.  I can't find my notes but had the part number for the diphragms.  These same carbs are used on Harleys and can be picked up at most Harley dealers.  Lastly it looks like 38mm Mikuni carbs can be swapped in. We have Mikunis on all the other sleds and generally don't have any problem with them."

[Interceptor398]

$325.00, someone is doing an original restoration??

[mswyka]

Wow