fuel shutoff, replumbing, & individual filters

[ratbyk]

Exhaust Gas Analizers

Mike when you hook up to an EGA tomorrow remember that the only reading that it will give that is accurate is idle and just off idle. To get an accurate reading above those two requires you to be on a dyno. Either that or an EGA that is portable and small enough to set on the bikes fuel tank in your full view. If the engine is not under load at the higher RPM's the reading that it gives you is bogus. Sorry to rain on your parade but just like when you do a plug check, you put the engine to work hard-kill it- then coast over in neutral to get an accurate reading. Simply sitting stationary and reving the engine will give a rich reading if not under load. If it says the parts per mil are correct at higher RPM but the engine is not working under load it will be lean in the real world.
Something else to put in the equation
Ken/Sooke
78E Ratbyk

[Mike Hart]

still not there...

Put 125 mains in, ran it, it's got the teensiest bit of very light tan on half the insulator, so, I drove it back to the place that is swapping jets for me, traded 120's and 122.5's for some 127.5's and 130's. I'm going to put the 130's in first and hope they are too rich

The EGA said I was good at off-idle, but lean at idle. Didn't even bother to try revs above 2000.

[Mike Hart]

the XJ two-step

Okay, I started going two sizes at a time. Went to 130, still white, then three sizes - went to (of all things) 137.5's, which is the stock size in the 78-79 bikes, and guess what? Plug color, hooray!!!!!!! Only got 7 miles of freeway for a test ride, but there is some plug color now, and the bike does feel stronger.

It wasn't exactly classic lean 'lay down and die' before, it pulled to redline okay, just didn't feel like it had the snap that is of the 'almost scary' variety, the really fun kind of pull, but today it pulled real nice

I'm about to finalize (at last) this situation, will get back to this thread about it, and then post a new thread briefly summarizing where I wind up in the hopes it will help other XJ owners out should they go to individual filters and not want to buy a whole kit.

[xjguy]

Man, you are dedicated!!!! As much as I would love to venture with this bike, it's so close to original that I'm staying there as long as I can. However from a receipt I got with the bike I know the shop that owned it changed the main jets in hopes of fixing the carbs. They don't have any #'s stamped on them and the plugs run tan on the flame front and black the rest of the way around insulator. But other than wanting to cut off on decel after blipping throttle during 1st 30 secs. of cold running the bike runs super. But then I've never road another one. Do you think what i've described could be from larger main jets?
xjguy and the bike "gone with the wind"

course it's getting ready to get a lttle chilly here and all may be well. don't know the quirks of these bikes this well. I do have a little of the gyro effect on front wheel tho. wife says she can't feel it when she rides. I think her balls may be bigger.

[Ken Talbot]

Hoooray you say - I'll second that! Anything that will save another XSive from having to post a question, then endure through 123 replies spread across 9 pages of forum, all the while being viewed 2296 times, has got to be a good thing...

[Mike Hart]

Ken you are a riot Yes, I'll put it in a thread that we can hope will stay on one page. It might help if it had but a single subject

XJguy, I'm not clear what you are saying your bike is doing on decel when cold...does it tend to die? When its warm enough to idle, when you blip the throttle, do the revs go down below idle before coming back? If yes to these questions, sounds like you're a touch rich, but maybe not worth messing with.

[Mike Hart]

Got in a longer ride today with the 137.5 mains, and I was very disappointed to see my plugs are still mostly white. Sigh.

XJ doesn't have adjustable needles, either. I'll go up maybe to 145's and if I still don't get the right result, I'll have to convert my needles somehow over the winter.

It runs pretty darn good right now, I'll tell you that, and with winter coming, I suppose I don't have to worry much about running hot.

[tsears]

gas mileage

So Mike,

What kind of mileage are you getting now - with the 137.5 mains?

Tim

[woodstoc]

Originally posted by Mike Hart
Got in a longer ride today with the 137.5 mains, and I was very disappointed to see my plugs are still mostly white. Sigh.

XJ doesn't have adjustable needles, either. I'll go up maybe to 145's and if I still don't get the right result, I'll have to convert my needles somehow over the winter.

It runs pretty darn good right now, I'll tell you that, and with winter coming, I suppose I don't have to worry much about running hot.

You say the XJ doesn't have adjustable needles. Does it have the plastic doughnut spacer? I adjusted mine to fine tune by following one of the tech tips on this forum by sanding down the doughnut, measuring to get each one the same, then using washers to adjust. Worked like a charm for me. It does adjust the F/A mixture across a wide range though.

[Mike Hart]

I think it has the donut, yes, and may be going that route eventually.

In the meantime, finally, I went too far!!!! Ran some 142.5's today, and they are definitely too rich, while the 137.5 was too lean.

The 142.5 bogged a bit if given full throttle at 2500rpm, and had a very brief transition bog even at 4000rpm if I twisted it say 1/3 throttle. Full throttle, it ran great, it's probably the right 'full power' jet, but I'm sure the mileage would be crappy.

So if I have time tomorrow, I'm putting in 140's and going for a ride. If I'm lucky, I won't have to adjust anything else. And if I do, at least I know I have the right main jet in it at last. Getting closer....

EDIT: On second thought, I went to revisit http://www.factorypro.com/tech/carbtun.html, and I'm thinking their float height description matches what is happening with my bike right now. The 142.5 might be the right main after all, as my floats are presently set at maximum richness.

So, tomorrow's mission is the lower the float height 1mm and see if it makes the right difference.

[Mike Hart]

I sure am glad I re-read that cv carb tuning page.

I lowered the floats 1mm, and 90% of the rich symptoms went away - no more cruise rpm bog when throttle applied. As the bike got fully warm, it didn't quite bog when given full throttle at 2500rpm, but it wasn't quite not bogging either, so I think I have the right main jet (142.5), but still a tad rich on the floats.

I'll lower the floats another 1/2mm and go for a mileage run (not this weekend probably, hope the weather is as nice next week as it is right now - 60, clear, beautiful.

I'm still lean at cruise/idle though, but with the right main, I'll be able to tweak that with the idle screws and perhaps the pilots need to be bigger (than the one size bigger they are now - 50).

Needles, whew, I won't have to dig in, as the mid-range pulls really strong, cool or fully warm.

Getting much closer, will be glad to put this thread to bed, and post the final settings as a new thread.

[nashville_bill]

Mike,

Have you checked the true float level with tubing connected to the float bowls? Could you post a picture of that level after you get it the way you want it?

[Mike Hart]

Bill, on page 4 of this thread I describe why and how I'm doing the floats the way I am. I'm not at all set up for getting the carbs level, and without that, no good way to do it 'by the book'.

I am curious too though, and will look for an opportunity to check actual fuel level and take a pic.

[Mike Hart]

Hello, your friendly jet nerd chiming in...

Put the floats 1mm more lean, solved all throttle issues, but on a gorgeous ride today (not one cloud, fall leaves, could see Mt Rainier and Mt Baker, ooh ahhh) I got just shy of 34mpg, and when I was too lean w/ 125 mains, got 42 on the same ride. When it was stock, that was a 38mpg ride.

So, one size down on the jets, which is what I originally thought, and then I have to fatten up the cruise mix (small throttle opening, 4000rpm) and idle mix.

Hope the weather holds...

[TopCatGr58]

Fuel Mileage

Hey there Mike,
Well, after putting in my 117.5 mains, was unable to replace the pilot jets, ran to NC from Eastern Va.. Documented gas fillups and miles going and coming back home, didn't bother during the day there, too many ups and downs, mountain roads, and got some bad gas in the middle of the ride....lotsa fun riding the twisties with just full throttle or not, no inbetween available for 1.5 tanks of gas!!!!

Anyways, calculated, getting an average of 32mpg total up and back, not bad for a special !!!! Reminder for others reading; 4-1 pipes, Indy Filters, 1179Big Bore Kit, only small handlbar mounted fairing/shield and soft side saddlebags.