DISCLAIMER: This is currently a work-in-progress. I am no expert, and this has, as of this posting, not been tested under operating conditions. If you decide to attempt anything similar, just know that you have a fool for a teacher.
Like most people, I am aware of the infamous solenoid-operated fuel shutoff valve for the big 1300. How that the services it provides are of dubious value, and the unhealthy tendency to fail at the worst possible time. However, I ALSO love things being period-correct, and this includes (at the very least) a visual representation of every stock part, even if the functionality is different.
A while ago I managed to get my hands on an non-working solenoid. No big deal- it was easily bypassed by removing the plunger valve and spring, rendering it inert. I plumbed it in, and ran it for quite a while like that. But there was always this idea in the back of my head to make it, you know, USEFUL.
I always like to try to run some kind of fuel filter on all of my bikes- cheap insurance. Unfortunately, the routing for the fuel line on the KZ1300 (any way of routing) doesn't really lend itself to easily fitting a fuel filter. So, brainwave- why not repurpose my currently useless valve AS a fuel filter?
Only one problem- the inlet is 90 degrees to the outlet (not a problem) and they're RIGHT NEXT to each other (big problem). Even though the solenoid is two parts, I couldn't just sandwich a filter element in between the two pieces. Until, that is, I got lucky on eBay.
Apparently, fuel filters are not the only things that use sintered bronze filter elements. Pneumatic mufflers utilize the same element, and in identical micron sizes too. I found a pack of 25 likely-looking candidates, and bought them, hoping to get lucky. I figured I could use some kind of spring to keep the element pressed into the head of the valve, but as it turned out that was unnecessary.
The element fit into the head like a glove, and butted right up against that small stem on the valve body. I just needed to clean up the edges to get it to seat better, and voila. Screwing the valve together still "squished" the element a little, but I'd call it a feature. The bronze will flex a bit anyway, and now I know it's "locked" in, not going anywhere. So now I have an integrated, cleanable fuel filter while still looking bone stock.
Related to this, I've also decided to move the solenoid to it's possible pre-production location. It was always odd to me that it was placed next to the airbox like it was- it sat weird, and got in the way of the idle speed adjustment. But looking through some OLD images for the manual, combined with a strange knob on the access plate on the left side of the engine block (right behind the cylinders), I found that at one point the solenoid was supposed to be mounted like so:
(Old pic- pardon the "normal" fuel filter)
This location also solves a couple problems with the infamous less-that-stellar fuel line routing. Rather than the spaghetti roller-coaster, with this you have a light bend from the petcock into the side/top of the solenoid, then a second line straight out toward the rear, curving gently up into the carbs. Now, I'd be surprised if this ever made it to production- the closest I've seen is a '79 access plate that had a hole drilled into the mounting location (but not tapped). Later on in the A2 this hole didn't even exist, but the place where it would be is still there, probably as it wasn't worth casting another part.
Why did they change it? My guess would be engine heat. The solenoids already have a spotty track record when it comes to reliability, and placing them immediately downwind of a motor that gets VERY hot seems like a bad idea. It's possible it does nasty things to heating the fuel as well, but that's not anything I've run into yet.
Again, I still have to check for leaks, and this hasn't had a maiden voyage yet, but I'm hoping it works.
The following user(s) said Thank You: biltonjim, Kawboy
I'm surprised that you opted to re-purpose the solenoid valve if "period correctness" is important to you. That's your decision.
An interesting option for sure. My only comment is that there may not be enough surface area of sintered brass and the filter may plug up in a short period of time if you happen to pick up a bad batch of fuel. A pleated element filter if opened up and filter paper spread out flat may have a surface area of 100 cm2 and you have maybe 200 mm2 in your current setup? Would it be possible to gut the solenoid housing and insert a larger filtering media be it sintered brass or a paper element?
Maybe when you go for your initial road tests, take along an inline filter to swap out just in case.
I like the initiative and appreciate the effort you've demonstrated here. it takes a certain kind of talent to do these types of mods and work your way through to resolve and I appreciate the fact that you're sharing your ideas here.
Yeah, I'm curious how it's going to shake out. The amount of filter surface area could always be bigger, but is pretty identical to the "normal" filter I was running before (the one in my last picture), which worked just fine. It also helps that the head of the valve widens a bit past the inlet, so the element isn't jammed right up to it.
Hollowing out the body would definitely give more room for a better filter element, but the challenge is the two barbs being so close to each other. You'd need a way to pipe the fuel to the opposite end of the body, then all the way back through the element to the outlet. Still, if you could make it work and mount it in the normal position, you'd gain some properties of a sediment bowl as well.