fuel shutoff, replumbing, & individual filters

[Wayne]

Forget NASCAR, I'd call Nicky Hayden's Suberbike crew!

[Mike Hart]

XJ floats and pilots

Ken, I got really frustrated trying to do fuel levels a la the tip with your carb stand, as I am an apt. dweller with no carpentry tools, and so was not able to get a reliable level surface that was anywhere near convenient to deal with.

So...let's just do it some other way. Off with the float bowls, measure the float height existing. I found from base to high point on float to vary from 19mm to 22mm. (out of spec, in the sense that +/- 1mm is max variance). Also could see visually that things were not equal. That may or may not be a prob...

Next, off with the floats (marked them w/ indelible marker) to see if they have equal bouyancy - YES!!! Amazing! I spent some time at this to make sure I wasn't kidding myself.

Okay, now we can get to work, since the floats are equally bouyant, we can set them manually a la 78-80 carbs.

I don't know about you others with the black plastic floats, but they are a different shape from the brass ones, they actually can bottom out (when upside down) inside the float bowl if set too rich (low, when upside down). Turns out one of my floats was at maximum richness, the float needle maybe just barely closed as the float contacted the bowl body. So I backed it off 1mm, then set the other floats to equal that one. (Side note: that one float needle maybe closing or not could have been the problem I was having with gas getting into the airbox/crankcase!)

This shot shows they are aligned nicely - imagine you are in 3D, and can rotate this pic a bit, sight down on that red dot....


FYI, XJers, that is a float height of 20mm exactly (from the easy place to measure on the bowl surface, to the high point on the float - the green dots).

While I was in there, I thought, let's look at these XJ pilot jets that are supposed to be 47.5 stock (biggest of all XS/XJ models). Here's what I saw:



How about that - no holes! well, besides the one that really counts.

Have I re-installed and test run these yet? NO. Tomorrow, if I'm lucky. I'm sure you're hanging on the edge of your seats...

[Ken Talbot]

'fessing up...

Truth be known, Mike, when I did Tsunami's floats this spring, I didn't bother with the stand and the tubing to check the fuel levels. I had confirmed all the levels before, so this time I just adjusted each float by the 2mm the same way as called for for earlier carbs, just like you did. I picked a spot on each float and each carb body that I could replicate for each unit. IIRC, I found a combination that was 25mm before I started, and tweaked each to 27mm.

[nashville_bill]

I found that 25mm, or almost 1", for my floats gives me a level that is just right when checked with the tubing method. I too have the white spark plugs and have ordered bigger jets(110-115 mains and 42.5-45 pilots) to see if it will give them a little color. My mixture screws are all about 5 turns out and it seems a little lean up to about 3000. My mileage is low 30's to upper 30's depending on my speed.

[Mike Hart]

Ken, Bill, all, I can now report plug color - at last! I'm now at the richest float setting that I think is 'safe', that is, making certain the float needles close. Plugs have maybe 80% gray color on the porcelain, a spot of white here and there. Runs great!

XJ service manual gives no float height spec, only fuel level spec. I'm guessing that spec would be 20-22mm, and I'm at 20mm now.

IIRC, XS carb float height spec is 24.7mm-26.7mm (don't know about you, but I have trouble with fractions of a mm!), call it 25-27, so Bill is at rich end, Ken is at lean end.

It may well be that I need to go up one size on the pilots, since I have gone 3 sizes on the mains (according to Denny's Jetting Recommendations). That is what I will try next, in search of the perfect plug color. Right now though, there's enough color that I can ride without worrying about burning up valves/pistons!

Whew, I can leave the carbs alone for a while til I get some pilots, size 50, no holes.

[Mike Hart]

Re: lean running

Originally posted by tsears
FYI, on my '80 SG, I run 145 mains, 42.5 pilots, and my plugs are still grayish brown - definitely on the gray side. The bike has 4:1 exhaust, indy filters, and accell coils, and gets 30 mpg. I just got a set 45 pilots that I'll try soon.

Tim, are these recent mods? A few posts before this sounded like you were running kit jets, 128 mains? With brown/gray color and 30mpg, doesn't sound like you need to go any richer anywhere - do you get 30mpg if you cruise at 55? If so, that would say you are on the rich side (good for max power!)

[tsears]

bike confusion

Hi Mike,

I have 3 bikes. A '79 SF, '80 SG, and an '81 SH. The 79 is currently being cannibalized for stuff. The 80 is my daily rider and the 81 is the bike I'm working on right now.

The 81 had 128's before the carb rebuild. After the rebuild (during which the 42.5 pilots were all ruined) it runs way rich even with 110 mains. But I think you nailed it when you said to use stock (i.e. genuine Mikuni) 42.5 pilots. I've ordered them. The ones that came in the carb kit are unmarked, so who knows what they are?

BTW, you're posts and pictures set a standard for technical discussion I've not seen elsewhere. Good on ya!

Thanks,
Tim

[Mike Hart]

Ah 3 bikes, now I get it! Let us know what happens on the 81 when you get the stock pilots.

Thanks for the compliment, I appreciate it

[Wayne]

I agree with Tim. This forum is great, picts and info right there were you need it. And Mike is quite the master at using this forum to its fullest ability.

BTW, I gave this thread a rating of 5, everyone else vote for this one, its a great info thread. Just select the rating at the bottom right of this page.

[skids]

Re: the saga continues...

Mike, do you really think you are getting wide open throttle "equalibrium" conditions for a long enough time? I wondered how the midrange adjustments will be accomplished with those carbies. I suppose there is a way to raise the needles with washers if needed, but is there a way to lower them, or do you have to buy different needles? I have a couple of sets of 80/81 carbs.

Sid

Originally posted by Mike Hart
Tried 117.5 mains today - they are just as white as the 115's!!!

Hope to take a 'real' ride tomorrow, and look again. It runs real nice, feels strong, but I didn't really get a chance today to see if it feels 'thirsty' over 7000rpm...hmmm sounds like fun!

[Mike Hart]

No Sid, I'm not sure at all about WOT test validity. Just how long is long enough? Seems like a full minute should be plenty...if I can find a steep and long enough grade to keep it at WOT that long.

After getting color on the plugs by adjusting floats to max richness (with 120 mains), I'm now carrying my spark plug wrench in my pocket, and the next time I'm out and find a good steep grade I'll open er up a while, then hit the kill switch and check color again.

I'm thinking that on the XJ carbs, if I get the mains right, that Yamaha's needle design was appropriate and I won't have to mess with them. We'll see. I've still to try upping the pilots one size, will wait til I get a real good WOT plug color test.

Sounds like a good excuse to ride up Mt. Baker or Mt. Rainier!!!

[Dragonrider]

Hey Mike . . .

Seems to me that (with my XS at least) that if I found a good steep hill, and did a WOT test for a minute, that I would be launched into orbit!

[Chuck Olds]

Mike, I need more info on parts you used for fuel line routing.

I sure hope this post goes where it's supposed to go! Mike, I went to my local Yammie dealer yesterday and asked for that fuel shutoff switch by the number you gave and he couldn't find anything on it. No WPS in his computer, so he wanted to know what bike it was for or what the vendor's name was so he could look it up for me. Can you shed a little more light on it's heritage for me, please?

Looking at the Y's and T's you used, they appear to be a combination of brass and plastic vacuum line parts. Is this correct? Think the plastic ones will hold up okay?

At an auto parts store, I picked up two pieces of 3' long, 1/4" ID clear gas line that I assume they use for lawnmowers. I got it because it's a lot thinner walled than normal fuel line and, therefore, a lot easier to work with in tight places. Do you think it's okay to use it on the XS?

I really like the simpicity of your routing through one line. What I don't want to do is get involved in re-jetting or anything else to do with those imposing carbs until I move a lot closer to you or Squid or Tim or Bill or Ken or .......... !

TIA,
Chuck

[Mike Hart]

Hi Chuck,

The shutoff was just on the wall on the peg thingy at the dealer, no application data. The pkg has this blue WPS kinda logo like, so it's somebody's name I got the valve at http://www.lynnwoodmotoplex.com/ (in person), maybe the name and part nr can help you chase it down thru them online?

All T's and Y's are plastic. Two of them are from the stock octopus setup. The others are sold as fuel fittings, so should be no prob. Got them at Napa. Got my 1/4" black fuel hose at Lowe's, it was slightly smaller in diameter than the same stuff I saw elsewhere, and shinier too :P

If your clear line is polyurethane, it will be okay for a while. If it's polyethylene, it probably isn't going to last long.

Carbs are not that big a deal, if you have good screwdrivers. An electric drill (reversible) is real handy with a phillips bit to get screws out that have been in there a long time.

[Chuck Olds]

I just got back from a independent repair/parts shop I hadn't been to since I bought the bike and they have that same WPS valve on the wall, only it's a 180 instead of a 90. Their vendor for the valve is MotionPro and their price is also $11.95. I didn't get the valve today because I need to see if I can use the 180 instead. Need to see if I have a good mounting spot, since I still use the stock XS airbox.

The package on the clear fuel line doesn't specify what kind of rubber it is, but I used regular clear nylon hose on my dirt bike for years without any trouble. Still, I'll probably take another trip to Lowe's and get some shiny line like yours.

While I'm out, I guess I'll go to the only NAPA store that's left in the area and see if they carry anything at all. They'll probably have to order it, but might as well get the right stuff! There used to be several NAPA's in the area. Heck, the nearest Black & Decker repair center moved out of here too, and is now 180 miles away. Will the last one out please turn off the lights?

Sure appreciate you help, Mike!

Thanks,
Chuck