Petcock for 1979 XS400F

[arfingdog]

Are there really no aftermarket petcocks out there for my bike? Every bloody one I see listed on Ebay that says it's for my model then shows that the space between the bolt holes is 34mm. My bolt holes are 46mm apart.

Meanwhile, I have the rebuild kit from Mike's but I don't see how one is supposed to get the phenolic spacer block in between the gaskets on the vacuum side. It doesn't look like that comes apart. I actually don't even want a vacuum petcock, but I might have to deal with it.

 

[xschris]

https://www.ebay.com/itm/Yamaha-Pet...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649 This is what I have used in the past. Mikes sell them also. 78-84 xs650 uses the same as the sohc xs400.

 

[arfingdog]

Thanks xschris. I've jumped on it. Glad to know that works (I see the bolt distance is correct!) and I'm happy to get out of the vacuum petcock business.
Tom

 

[xschris]

These are nice to use and not worry about them not shutting off and overflowing the carbs while they sit. I have them on all my bikes but the 79 that is all stock.

 

[arfingdog]

Just in case I can fix my original vacuum one, can you enlighten me on how I'm supposed to use the plastic spacer block from the original with the rebuild kit? The diaphragm part doesn't appear to be made to take apart.

 

[xschris]

It should pull through the spacer.

 

[arfingdog]

Ah ha. My spacer isn't like that...I would have to drill it out after cutting it off the original.

 

[xschris]

I have seen people with that type before. Not sure if it's an earlier type or off another type petcock or even a aftermarket one. Either way those are no good. All the ones I have ever had apart look like the one I posted. I know yamaha did have a recall on the 79 and prior years I think because or fuel leaks. Most where switched to a better less leak prone style in 1980.

 

[arfingdog]

So, I got that simple on/off/res petcocks..fits great. I'm using one of the right angle outlets off the right side. But I'm having trouble getting this thing not to leak! Seemingly from multiple spots. I really seated the plug on the left and tweaked the other screws and *maybe* got it down to the outlet base. Since that one isn't set up to use a wrench I hesitate to apply one, but should I? As it is, the outlet will be coming out the side instead of the bottom, which would have been ideal, but I'll really crank on it if I have to.

 

[xschris]

I use the straight fitting. Did you replace the tank seal washers for the screws? Those need to be replaced when you remove the petcock.
https://www.ebay.com/itm/Yamaha-Pet...EwAAOSwjYleGMMZ:sc:USPSFirstClass!14891!US!-1 Washers like these.

 

[arfingdog]

The straight fitting looked a little crowded to me (although it looks fine on yours). As it was I had to cut the end of the handle off a bit to clear the edge of the tank when turning to reserve. The petcock screws had no washers, only lock washers. I assume the tapped holes in the tank didn't go through to the tank contents since the previous petcock--and this one--don't have the kind of seal that attempts to isolate the screw.
At any rate, it wasn't leaking from the petcock to tank junction. Possibly was leaking from the joint where the two halves go together, though not now after tightening. After really cranking down on the outlet plug, it sealed, and the right angle connection which is now on the left is not leaking any.
So...all good. I need to get some larger diameter fuel line for my permanent setup and then deal with the slight difference now between the barb diameters on the petcock vs. carb.

 

[xschris]

There was no need to cut the lever as the fuel still flowed from the reserve at the point where it hits the tank. Although in the many years I have used these I have never needed to use this setting. I always fill the tank after every ride.

 

[arfingdog]

I noticed it seemed to flow at that position but I wasn't sure it was full flow. No worries...my slightly stubby handle looks fine. I might go the continual full tank route when I get the XS on the road, but I didn't want the tank full until I knew all was well.
I see you have multiple bikes, as do I. Fuel managment becomes a bit of an issue, as I don't like any of the fuel to get too stale. I recently drove 80 miles round trip to get 7 gallons of non-ethanol 93 octane gas for my vintage bikes. Since I don't plan to do long rides with the XS or my SRX600, that should hold me for a bit.
Thanks for your help on the petcock!

 

[xschris]

I use 93 octane fuel also but it has 10% ethanol in it. I use Yamahas fuel med Rx when I fill up my gas cans. It makes the fuel safe for older bikes and keeps it fresh for 6 months and more. I have been using it for many years now and the bike runs better/cleaner than when I used the non-ethanol stuff. It also saves me from having to pay for the much more pricey non-ethanol gas.

 

[arfingdog]

I had never heard of fuel med Rx. I'll give that a try.