fuel shutoff, replumbing, & individual filters

[Mike Hart]

Just gotta keep fussing with the bike, doubt if it will ever be perfect

For the third time in one year, I had another gas leak - okay, that's it, I've had it, time to replumb. I gathered the four petcock taps using two Y connectors, thru another Y (or T) to a fuel shutoff valve. I got the valve at a Yamaha dealer, it is a 1/4" inline shutoff valve w/ 90 deg outlets. WPS part nr 12-7118, $11.95. The handle also has positive stops, rotates 90 deg to definite On and Off positions.

From the shutoff, one could insert a single filter inline before the final T to the carbs.

I gave it a good hard run to see if there were any fuel starvation symptoms, none at all. I didn't expect any, I had flow tested the valve at over 20 oz/min flow. That means 32 minutes to empty the 5 gallon tank, that ought to be enough, I figured.

This arrangement minimizes the number of hoses and fittings, delivers gas to all carbs from whichever side of the tank.


I also was tired of the difficulty of carb removal on the XJ, the airbox barely moves out of the way, the heck with that too. Love the sound when I get on the throttle!

The airbox used to bolt to a tab on the frame behind the left side-cover, a nice place to mount a bracket to attach the shutoff valve (which is designed to be mounted that way, how convenient!) That's the little red handle in the Off position. Rotate the red handle 90 deg toward the carbs for On. I was thinking, gee that bracket kinda sticks out, maybe I should have painted it black, forgetting where it would be when the side cover was back on! Happy accident, that.


Now, if I can just remember to turn it on and off...

[oldnortonrider]

Looking at the side of the carburetor (?).......the float bowl bottom; you've got a slotted drain plug "adjustable" screw, on the side, on the bottom. None of my XSs have that type of bowl chamber. I think, yours, even look a little deeper than my type.
I think I can guess what you've done, and maybe why.
I'll let you tell me; and then I may have another question.

[Mike Hart]

float drain screw

Sorry, stock XJ carbs. Yes, a phillips head float drain screw, there is a nipple on the bottom of the float bowl, attach a clear hose, loosen screw, to find fuel level. So, what I did had nothing to do with that particular XJ-specific feature.

What I did was all octopus/petcock/overcomplicated Yam fuel hose system related. Plus, I was tired of the airbox!

So what is your guess about why? I'm curious....

[Bill]

Mike -

Everything looks real clean. But having the plumbing run below the level of the float bowls may cause problems under low fuel conditions. I had that problem on my Standard when I tried plumbing dual filters as shown in Gary LaPook's Inline Filters tech tip.

Keep us posted

[oldnortonrider]

I have the "MAZE" of lines, running below my carburetors, all over, and all around, also. "Fuel stuttering" problems solved by running on "Prime", when I'm low on fuel and/or in traffic.
Also, after making my above posting, it donned on me (duuhhhh..); that ain't an XS >> it's an XJ. These moderators trying to trick us old guys, all the time.
I'm working on a guy's Honda carburetors, right now, with that type of float chamber, drain line, float measurement. "Keihin" carburetors. That wuz whut my "so-called guess", wuz; that I was looking at an "XS", that had had, the "drainline measurement" type chamber put on our old type Mikuni carbs.
Has anybody ever put the entire XJ carburetor rack on an XS ?

Question.....; did you still leave the vacuum piston diaphragm on yer XJ ?
When they're working right, you can't beat 'em , IMO.
They do safeguard, from , all kinds of misery problems.

[nashville_bill]

I have an '81 XS and it has the same float bowls. Great way to see your true float level. I am also running the octopus with fuel filters. I just don't think I would remember to turn off the fuel after a ride and don't trust the needle/seats to do their job.

The only problem I have is that the petcock outlets are at a downward angle and that means that the fuel hose must come from below or risk kinking. My '81 XS650 has a vacuum petcock that has a rearward outlet that I think would work for this bike. As soon as I find a couple of them on ebay, I will try them. The bike would only have two fuel lines, with filters, and two vacuum lines - very simple.

[Mike Hart]

Makes sense that the 81's had the same drain screw - they had a few other features not on the earlier models too, like a clutch switch f'rinstance, smaller coils w/ no ballast resistor...

I already am used to turning two petcocks on/off, now I only have to turn one off

I always disliked the octopus for esthetic reasons, and for its lack of simplicity. My Bandit has one petcock, one vac hose, one fuel hose.

[Mike Hart]

Originally posted by Bill
Everything looks real clean. But having the plumbing run below the level of the float bowls may cause problems under low fuel conditions. I had that problem on my Standard when I tried plumbing dual filters as shown in Gary LaPook's Inline Filters tech tip.

Keep us posted

Well, you Standard guys have a simpler system (well maybe not - 2 diaphragms and vac lines) - the octo bikes already had the two final delivery lines coming in from underneath (the T's on the carbs pointing straight down!) with no probs. If I do have that prob, you will be the first to know!

btw, that tip is getting revamped to show some alternate methods.

[Mike Hart]

day two

I made a 6000rpm run today, pulled the plugs - white!

I putted around after, doing a couple errands, and they darkened a tad, but obviously lean.


Time for bigger mains. I have stainless M4 hex screws in the carbs, and use my cordless drill with a socket adaptor and a 4mm hex socket to make a fast job of it:


According to Denny's Jetting Recommendations, 3 sizes for individual filters; then subtract one (standard method); then subtract an additional 1 size for mismatch (stock exhaust), so I tried one size up for starters - nice new shiny Mikuni 115 mains: (replaced 112.5s)


Here's a shot of the carbs with all the plumbing prior to reinstall:


Before the plug-check run, I knew it was lean - when I blipped the throttle, the revs hung a bit before they came back down, a classic lean symptom. Haven't been out since doing this to check plug color, but blip test says it's close, I'll find out tomorrow.

Man do I like how fast it is to get the carbs out/in, how easy to get the linkage off/on, can't believe I put up with the airbox for so many years.

[TopCatGr58]

112.5 to 115 mains

So...Mike,
Whatcha going to do with your old 112.5 mains?? I'm running 110's now, and was wondering whether I should try a larger jet size since I also have Indy's and 4-1 pipes?? How much you want to mail them to me if you aren't going to save them??

[Mike Hart]

Dunno yet, T.C. Still have to test the 115's - who knows, maybe I'll have two sets available

What is your plug color like? I would think with your airflow they should look really white after a medium-to-high rpm run...

[Mike Hart]

plug color

Any plug color experts out there? This is how the plugs look now after installing 115 mains - they still look pretty lean to me...

[Bill]

Re: plug color

Mike Hart wrote:

Any plug color experts out there? This is how the plugs look now after installing 115 mains - they still look pretty lean to me...

WOW, that's one BIG SPARK PLUG!

In all seriosity, it looks about right to me, though it's definitely NOT too rich. For the price of one more set of jets you could do the "not too rich" check... i.e., if it still isn't too rich, then it must've been lean before.

FWIW, the Haynes manual describes it thus:

A brown, tan or grey firing end is indicative of correct engine running conditions and the selection of the appropriate heat rating plug.

AND

Black sooty deposits indicate an over-rich fuel/air mixture, or a malfunctioning ignition system... try one grade hotter plug


This is cool stuff. Please keep us posted on your progress.

[Mike Hart]

Okay, Okay I forget I run my monitor at 1600x1200, I cut it in half, and its only 42kb now.

I'll get some 117.5's and give them a run, I think it's too lean.

It sure runs good tho, I tweaked the idle screws and synched it today before the ride, smooooooth. Starts easier and with less choke than it ever has.

[Mike Hart]

Re: Re: plug color

Originally posted by Bill FWIW, the Haynes manual describes it thus:

A brown, tan or grey firing end is indicative of correct engine running conditions and the selection of the appropriate heat rating plug.

AND

Black sooty deposits indicate an over-rich fuel/air mixture, or a malfunctioning ignition system... try one grade hotter plug

Oh I like that last bit - try a hotter plug instead of getting the mixture right or fixing the ignition malfunction!