Topic: Help with petcock size

[uksparky]

Hi all
Need some help with my petcock...got a 78 CB550  with 74/77 tank, the petcock i have points down with two outlets...here is where i have my problem the petcock bung is 3/4 inch = 18mm x 1.5 mm. I need a petcock with a  90 degree turn so i don't have to loop the fuel line around the carbs...but all i see out there is 16 mm x 1.5 or 18 mm x 1 mm...or should i leave it the way it is reserve plugged...got another tank/emblems, same threads..

[db22]

Oh brother -- got the same issue with my '75s and their salvage tanks. The petcock bungs seem to measure around 18.5mm; not sure of the pitch. I accumulated six or seven old and aftermarket Honda petcocks before coming up with one intact one, and a functioning one with no standpipes. All the aftermarket petcocks I have tried are either too large or too small.

Have you thought of having a standard NPT bung welded to the tank? The alternative is to fit an aftermarket tank (neither of my bikes are stock), but the curved 550 top tube might cause a hinkey fit.

If anyone out there has a definitive guide to CB550 petcock sizes, please post it or point us to it!

[Duanob]

Big enough?

[wowbagger]

Is there room for a 90 degree filter or elbow?

http://www.bikebandit.com/visu-filter-large-capacity-90-degree-fuel-filter

[Dr. Noisewater]

I just ran into this problem as well. I've got a '75 with a trashed petcock and can't find the correct replacement. I see rebuild kits on eBay, would those work on the '75?

[wowbagger]

The 19mm petcocks from 75-76 have no rebuild kits. They used a plastic cone inside that was notorious for wearing out. If it is leaking out the face of the petcock around the valve knob then you can sometimes add a thicker washer to solve that problem. However, if it leaks out the spouts while in the off position then the internals are most likely worn out.

You can find NOS replacements on eBay for around $100 if it comes down to that.

[uksparky]

Thanks for the replys guys ..looks like i am going to leave it the way it is for now, just painted the tank...i can not hook up reserve so if anyone wants the tank filter kit i got brand new one 16952-341-671

[db22]

One of the experienced machinists on this forum could make a few bucks by making a run of adapters -- 19mm to some common generic petcock size. I'd buy two.

[new2bikes-again]

I think your supposed to run the lines through the two holes in front of the carbs. Between 1&2 & 3&4. I'm working on the same tank/petcock right now. I fixed the kinking problem last year, by running the lines where I read they were supposed to run (I had to run elbow filters because my screen was gone inside the tank).

TwoTired hooked me up with some part numbers and even the links to the parts. I ordered the proper 5.5mm fuel hose and the screen kit, last night. I'm taking the filters out and don't think I'll have to worry about kinking without their 90 bend.

[new2bikes-again]

http://forums.sohc4.net/index.php?topic=122697.msg1391292#msg1391292