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Discussion Starter #1
Hey all,

Recently picked up a 1976 CB500T. I'm learning a lot about these bikes. Finding out that they didn't make many of them and they're generally hated. None the less I am determined to get this thing running.

The problem I'm asking for help with today is the fuel petcock. I've researched in the inter webs and the consensus is that the fuel petcock should use a 16mm x 1.5 nut to attach the petcock to the tank. Problem I'm having is the threaded bit from the tank is way bigger than that. Using a micrometer it comes to 19.5 mm including the threads. So I'm thinking it would be closer to a 18mm x 1.5 for the fitting. I haven't found anything anywhere that would suggest this as a size for a CB500T.

Everything I can find suggests this is the proper tank for the motorcycle but the size of the fitting doesn't match any numbers i can find.

Any work arounds short of cutting and welding would be appreciated!
 

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My guess is 16mm is your ID measurement. You have measured the OD. Go measure your ID.

I COULD BE WRONG.

500T is a good bike, don't feel bad about what people said back in 1975.
 

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Your biggest problem will be finding a petcock for it. They are rare and expensive when you find one, in part because they are not the same as the 450 petcock as they have horizontal spigots to feed the carbs and the 450 has vertical tubes. I believe the diameter is larger than the 16mm size 450 petcock as well, it may be 18mm. I just know they are NLA and if you're lucky enough to find one at David Silver, cmsnl.com or elsewhere, it won't be cheap.

Since you're here now, please take a look at the link below and post an introduction for us

https://www.hondatwins.net/forums/23-member-introductions/121120-critical-read-before-posting.html
 

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Discussion Starter #5 (Edited)
I measured the ID and its 13.5. So I'm thinking the measurements are correct. But the petcocks I've gotten off Ebay have just been b450 ones that are incorrectly attributed to this bike.

I was hoping to find something that fits but wasn't the original style so it could be less expensive. This single part may be more expensive than the whole bike lol.
 

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most parts are interchangeable with the 450. Apart from a few specific pieces most can be found easily. You can use a different petcock, just do some searching.
 

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I measured the ID and its 13.5. So I'm thinking the measurements are correct. But the petcocks I've gotten off Ebay have just been b450 ones that are incorrectly attributed to this bike.

I was hoping to find something that fits but wasn't the original style so it could be less expensive. This single part may be more expensive than the whole bike lol.
I hear you on the price, but I'm afraid you're stuck with the situation based on the bike and gas tank - unless you go to a 450 tank, which likely wouldn't mate up to the seat properly.

Now, about this...

https://www.hondatwins.net/forums/2-non-model-specific-honda-twin-topics/123786-help-fuel-petcock-1976-cb500t.html#post1040234
 

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The 500 is not hated, in fact, it's thought of quite fondly by those who know it. Kinda like redheads.
 

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Hey all,

Recently picked up a 1976 CB500T. I'm learning a lot about these bikes. Finding out that they didn't make many of them and they're generally hated. None the less I am determined to get this thing running.

The problem I'm asking for help with today is the fuel petcock. I've researched in the inter webs and the consensus is that the fuel petcock should use a 16mm x 1.5 nut to attach the petcock to the tank. Problem I'm having is the threaded bit from the tank is way bigger than that. Using a micrometer it comes to 19.5 mm including the threads. So I'm thinking it would be closer to a 18mm x 1.5 for the fitting. I haven't found anything anywhere that would suggest this as a size for a CB500T.

Everything I can find suggests this is the proper tank for the motorcycle but the size of the fitting doesn't match any numbers i can find.

Any work arounds short of cutting and welding would be appreciated!
Ok - I just went around this whole issue with my '75 CB500T. Through trial and error (i.e., some experiments and some $$$), the issue is that none of the relatively new/repro petcocks made for the 350/360 and 450 work, and NOS petcocks are expensive and rare. I solved the issue with a Pingel petcok (6111-AH) & bung (A2000C). which together I got for $144, including shipping (directly from pingel). You basically have two options, one with reserve and another without, which was less expensive.

Indeed, the bung size is 20mm, and you can find a combo of bungs and cheaper petcock/bung combinations, but you'll find the following challenges by going that way:

> every dual output (which the original has) sends the fuel lines right into the carbs, so you while you can mount the petcock, you won't be able to get the fuel lines connected

> single outputs will require a "T", and now your challenge is finding enough space to route the fuel lines without having them collapse; additionally, the ID/OD of the petcock in combination with the "T" may restrict the flow of gas into the carbs

Hope this helps...

Greg
 

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and NOS petcocks are expensive and rare. I solved the issue with a Pingel petcok (6111-AH) & bung (A2000C). which together I got for $144, including shipping (directly from pingel).
So, the NOS petcock from cmsnl isn't a better choice at 102 euros plus shipping? I know Pingel makes a good product, but fitting the proper part for what would seem to be less or equal money...
 
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