KZ650 Petcock Barb Missing

Hello fellow KZ Riders,

As I was restoring my 80 KZ650 LTD earlier this spring, I noticed that the fuel barb from the petcock was awkwardly pointing toward the back. The fuel hose had to be routed under the seat to avoid a kink. I chose not to worry about it as I had more pressing issues to address.
I have now the bike repainted in the non era-correct Kawasaki Golden Blazed Green (40R) - sorry for the purists out there - and I wanted to address (i.e. change) the petcock. Turns out that the PO installed one for a Suzuki GS550 (common alternative I reckon). I looked at a Pingel setup that many of you are touting, but this is above my budget and I'd like to keep the bike original if I can.

After several week of research and a few wrong buys, I finally found a petcock taken off a "80 KZ650 LTD". It's in pretty good shape after an ultrasonic bath, BUT I have 1 question and 1 issue:

1. Question: the fuel barb on that petcok is pointing forward. It can still work, but according to the diagrams i thought the barb for these models were pointing down. Which would be even better for a clean routing to the carbs. Do you know what was the original setup? Did the KZ650 had different petcocks?
2. Issue: as you can see in the picture below, the fuel outlet is missing the brass barb. How can is fix this? Can I easily find a properly size barb that I can press-fit with no leak? Should I thread the hole to screw in a 1/4" barb? What are your recommendations?

The first picture is the my current petcock from the GS550 with the brass barb.
 

The second picture is the KZ650 petcock I got with no barb.
 

Can you pluck the barb out of the Suzuki petcock and press it into the Kawasaki one?

Yes TexasKZ, I thought about that for a second but was afraid I would damage the barb by yanking it out. Maybe I could still one from another cheap used petcock ...

   Long time ago, we saw a barb pull out of a Z1 petcock when a stubborn hose was being removed.  We pressed it in with a very thin coat of epoxy on the barb & in the hole.  No leaks & it hasn't budged since.  We haven't really trusted barbs to stay put since.  We always apply a little silicone grease to barbs & hose ID's with a Q-tip prior to pushing hoses onto barbs now, and are very gentle when removing hoses.

Good Ridin'
slmjim & Z1BEBE 

slmjim+Z1BEBE wrote:

   Long time ago, we saw a barb pull out of a Z1 petcock when a stubborn hose was being removed.  We pressed it in with a very thin coat of epoxy on the barb & in the hole.  No leaks & it hasn't budged since.  We haven't really trusted barbs to stay put since.  We always apply a little silicone grease to barbs & hose ID's with a Q-tip prior to pushing hoses onto barbs now, and are very gentle when removing hoses.

Good Ridin'
slmjim & Z1BEBE 

 

+1 on using a thin film of epoxy. The press fit is a one time thing on those soft metals, and repeated presses will never be as tight as origional.

So I have decided not to mess with the GS550 petcock as a friend of mine will need it. 

finding a fuel inlet fitting is pretty hard but I came up with two options based on a 1/8” NPT brass barb.Option 1 is to file the threaded side smooth down to 9.1mm and press fit it into the petcock. 
Option 2 is to thread the petcock and simply screw the barb in with yellow teflon tape. 

I filed one barb tonight and it seems it could work but I’m not sure how long it would last before leaking…

I tested the second one on scrap aluminum and it seems like a great fit. But I know there is no going back from option 2. 

what do you guys think? Am I wrong to lean towards threading the petcock?

Only my opinion but given it's a fuel fitting if you are sourcing a replacement barb then threading would be a definite. Press fit would be ok if you had access to a lathe to modify the barbs rathe than filing

Do you have the selector/rubber disc(puck)/ wavy spring and cover plate for that newly purchased 650 petcock acquisition? Don't see it in the photo but would assume you do. If it were me i would verify operation first! Do you have vacuum pump? These old vacuum type petcocks can fail to completely shut off petrol because of a bad oring/pinhole in/on diaphragm. Don't need a barb to check operation. On that note, i have several of those Taiyo Giken petcocks. They aren't exclusive to just Kawasaki, Yamaha used a lot of them too.    

Rideallyear wrote:

... two options based on a 1/8” NPT brass barb.Option 1 is to file the threaded side smooth down to 9.1mm and press fit it into the petcock. 
Option 2 is to thread the petcock and simply screw the barb in with yellow teflon tape. ...

... what do you guys think? Am I wrong to lean towards threading the petcock?




 

You're likely on the right track with the NPT idea.  We've never probed a petcock's barb hole, but it's probably slightly tapered.

If you choose to do threads:
   Male NPT threads can exert enormous spreading force within a female hole due to the taper - scenario, the hole splits (unlikely).  Vice versa, the threaded hole can exert crushing force on the NPT-tapered brass tube - scenario, the tube crushes/wrinkles (more likely ? ).

   Although we're talking about soft-ish metals here with hollow brass and cast aluminum, be careful that the threaded barb and the petcock threads are as precise as possible.  Gut feeling is that engagement depth (more threads) be desirable vs shallow engagement.   If the bare barb can be screwed into the bare petcock hole by hand with moderate, smooth  effort, yellow teflon tape will likely prevent leaks for a lifetime.

   Threads on the tube can't be too deep, in order to maintain wall thickness at the thread root for strength.  The weakest flex point will be where the tube meets the petcock, acting as a fulcrum.  Bending forces there may create a failure point where the tube can break at the root of its thread where it meets the petcock hole.  Care be taken that the fuel hose exerts as little bending force as possible in the brass tube.  In other words, keep the external barb short as possible yet safe.

   Barbs have a swell at the end to assist with hose retention.  How to mimic that?

   slmjim's intuition be that coarse threads be preferable to fine threads.  No other supporting argument than his gut feeling.  Z1BEBE, not so much; her eyes glazed over a while ago.  Threads aren't her thing...

   Interesting project!  Please keep everyone posted.

Good Ridin'
slmjim & Z1BEBE

Petcock hole IS slightly tapered for a compression fit of barb. Actually finer threads would be preferred rather then course. But like Jim states you can easily crack the casting if cinched down too far. As mentioned though, don't waste your time till you can verify operation. TOTAL fuel shut-off when selector lever is in either RES or ON positions!! I do a lot of these various thingy's and have containers full of them. I do a lot of carb related stuff so what i do hinges on a proper related petrol valve functionality.   

Thank you guys for the boost in confidence.

Yes Wookie, I have sourced a threaded brass barb. Two actually. I tried the filing-the-thread method (i don't have a lathe yet), and wasn't convinced. The second one is pictured below. It's a 1/8" NPT thread. So it goes from 10.3 mm to 10.6 mm. I have the exact tapered thread cutter. The threaded end is 8mm long. So to slmjim's point, there is enough room in the petcock to fully thread the barb in. But to avoid too much bending pressure, I can shorten the barbed end. Although, the brass fitting won't be modified, so it will keep its full wall thickness.

 

Oh and yes, the petcock is otherwise fully functional. The cast aluminum is in good shape and I had a complete set of diaphragm/o-ring/washer/screws. Turning a valve is a bit hard so i may put some grease their. That why I wanted to keep these petcock. All the ones I came across where in pretty rough shape with oxidation.

I'll go ahead with the threaded barb and report back.

 

Carry forth with tapping but i could of given you a replacement ha.