Petcock blues - '78 KZ400 B1 - single or double? swap the CVs for slides?

[RobK]

OK, second post in as many hours., but just received an email of dismay.

I have a leaking petcock diaphragm. This is an issue as I have the stock Keihin CV carbs and no diaphragm means no vacuum. I've been riding on Prime and turning the petcock to On when parked. Works, but none too elegant. When I ride in the On position, the bike will stall soon after as a result of lack of vacuum, (this is my best hypothesis, anyway- pls let me know if I'm off here).

So after figuring out that the diaphragm was shot I set about finding another. I had some trouble finding the part (gotta love Kawa's for this), but thought I lucked out when I found it on bikebandit.com. $30 + $7 for shipping - gulp, but OK. Well, just got an email saying that the part is discontinued - argh!

So here's the question: does anyone know an economical way to replace the whole petcock? I've seen some good prices on single outlet units (eg. at Dime City Cycles), but I assume short of swapping the carbs for flat slide units, I need a vacuum out as well, no? And can I even swap the carbs? If so, is there a difference b/w a Mikuni for a 2 stroke and a 4?

Thanks, all.

 

[HerrDeacon]

Re: Petcock issues - '78 KZ400 B!

My vacuum petcock died on my KZ650 a year or two ago, rebuild kits were too expensive and from what I hear, not always successful. I went with the regular non-vacuum type from Z1 Enterprises. Works great, just have to remember to turn it off.

They sell vacuum repair kits: http://www.z1enterprises.com/detail.aspx?ID=306

Here is the one I picked up (need to buy adapter plate as well):
http://www.z1enterprises.com/detail.aspx?ID=1744
http://www.z1enterprises.com/detail.aspx?ID=1740

They also sell vacuum petcocks for Suzuki's but I've heard they bolt right up (can't confirm).

Any questions, fire them off an email or call them, great bunch of guys, know their KZ's.

 

[RobK]

I like the idea of a single output petcock from a simlicity perspective. I've been digging around and I did find a blog where an owner mentioned that the reason the vacuum petcocks were introduced was to prevent the floats from sticking.

Anyone know if this is a valid concern?

BTW - thanks for the info and headsup on Z1.

 

[Big R]

Rob, if you look in the last couple of pages in my build thread, Jay Kent posted a link of an Ebay store that has a lot of different petcocks. The great thing about the store is that they give precise measurements of all the mounts.

Don't know if it's any help, but there ya go.