Another one about 'Pilot Jets'

[Doo-Daa]

Guess I've got myself confussed.

Got a '78E.

Doing a carb teardown and clean, clean, clean. Bike has sat for the summer, and once started ran rough. Time to do the carbs anyway.

During teardown, everything checks to Yamaha Specs as far as jet, needle, pilot jets, floats good, and fuel inlets valves good.

The only odd piece is the "Air Pilot Jet". The one that sits in the inlet side of the carb. Yamaha Service Manual doesn't give a spec, but everything else (Forum, Specs, Clymer, etc.) gives a spec size of 180. All four of the ones installed are clearly stamped 210.

So the question is: With everything else being stock, what should I expect with the 210s vice the 180s? Can it be compensated for with the Pilot Screw? Anyone else run into this?

Should I pick me up some 180s? I really don't want to complete an assemble and install, then have to pull the air box down to change them out.

Any advice would be appreciated.

OBTW: If it makes a difference, out here in Amarillo, Texas, the altitude is about 3,000' (a little less than 1000m)

Thanks,
Doo-Daa

[TopCatGr58]

Hey there Doo-Daa,

Don't have experience with your particular setup, but if it ran okay before, then.....it should still run okay after the cleaning!? That is a much larger sized pilot air jet, and that alone would make it run a bit leaner at idle and just off! However, you're at a slightly increased elevation, where a bit leaner would actually be beneficial! I would think you should be able to compensate for it a fair amount with pilot screws, letting in more fuel to mix with the increased air!?

I've got a big bore in my 81, Indy filters and 4-1 pipes, and went 3 sizes up on mains, but kept pilots stock, and with 3 turns out, they were too rich at altitude, bogging in the mountains, but great at sea level. Put them back in 1 turn, and they were fine for the mountains.

How do your plugs look? I can empathize about the hassles of remounting the carbs, but if it did run okay before, then put them back together, and play with the pilot screws!

Are your bowl vent tubes unobstructed? Are you sure it's carb related, not a new electrical gremlin, Pickup Coil wires for instance?!
T.C.

[skids]

Re: Another one about 'Pilot Jets'

Hey there DoDa. I have 2 sets of 78 carbs. All have 210 air jets in them. I am pretty sure the carbs were stock set-up. Maybe they were set that way for sell in the Denver area, I don't know. They do run good at 5000 feet elev.

Originally posted by Doo-Daa
Guess I've got myself confussed.

Got a '78E.


The only odd piece is the "Air Pilot Jet". The one that sits in the inlet side of the carb. Yamaha Service Manual doesn't give a spec, but everything else (Forum, Specs, Clymer, etc.) gives a spec size of 180. All four of the ones installed are clearly stamped 210.

Doo-Daa

[Doo-Daa]

Hey TC, thanks for the rapid response.

I guess this info tells me a couple of things. Since the bigger the Air Pilot Jet, the leaner you push it at idle, that means that someone has been inside the carbs before me. And they've got some knowledge about Mukinis with access to yamaha parts.

Also explains why in stop and go traffic my bike seems to load up so easy. She runs a bit rich at idle, ok on the open road after the plugs clean up.

So, it clean, clean, clean. Check the settings on the needles, check mains for wear, float level setting, (already checked for leaky floats), check float valves for leaks, and check for vacuum leaks.

My problem will be that whoever was in there first has probally done this before going to larger air pilots, especially ones 30 bigger.

Bowl vents are clear, and first thought of pick-up wires, no luck there.

It ran before, it will run again.


Till it runs!!!!!

Doo-Daa

[Doo-Daa]

Hey Skids,

Could be. We seem to get a lot of Denver influence down here. But then if you went south out of Denver, you gotta 50-50 chance of ending up here anyway.

Do you have them in use now, or get them as spares?
Not interested in extras, just curious. Ever come off that plateau to a lower elevation and have low speed fouling?

Doo-Daa

[skids]

Oh yes, I have been from 1000 ft elevation to 14,000 ft elevation. I think they tend to get richer at higher elevations rather than leaner. My bikes run well at lower elevations--better, I believe. The air jets feed the bleed holes in the sides of the pilot jets, so the more air you bleed, the less fuel is drawn from the bowls...at least that is what I think. This would indicate that bigger air jets cause leaner idle mixtures. I am pretty sure that the earlier model carbs had bigger air jets than the later models.

Originally posted by Doo-Daa
Hey Skids,

Do you have them in use now, or get them as spares?
Not interested in extras, just curious. Ever come off that plateau to a lower elevation and have low speed fouling?

Doo-Daa

[Do Lee]

Hey Doo-Daa,
The standard Air Pilot jet for the 78 carbs is the #210 jet along with #137.5 Mains and #45 Pilots.
The 79 model carbs is where the #180 Air Pilots jet was used along with #137.5 Mains and #42.5 Pilots.
Same part # for carbs. on both 1978 & 1979 XS1100E,F. (2H7-xxxxx-xx-xx)
The 1979 XS1100SF had a 3H3-xxxxx-xx-xx part # for its carbs.
In 1980 XS1100's carbs had a new design.

Do'Lee

[Doo-Daa]

Hey Skids, & DoLee,

Thanks again.

I guess with the info that the 210s appear to be factory, and if Skids is running such different altitudes, I'll stick with the 210s.

(Sure not like my Intruder- with that one, 5000' makes a difference)

So, I've just finished setting floats. Probally lower them a little into the bowl, and might move the needle clip to one notch longer.

Can anyone give me some info on how much clearance is involved with the needle and emulsion tube? I've got new needles, and have miked them to the old, they're identical out to .0002, but both sets have a little wiggle room when seated to the same stack height. It's not a machine fit, but may .001. I'm wondering if that is enough to allow fuel to be drawn up from the bowl and cause my rich idle condition?

[TopCatGr58]

Hey again Doo-Daa,

Do-Lee cleared up the size issue, thanks! I don't have or know about the snugness of the needle to emulsion tube, but I would think that they can't be too tight, otherwise they might tend to get caught or bind up, and then the vacuum wouldn't be able to pull them up easily!?

You stated that it seems to "load up" in stop and go traffic! In Texas, you're getting the engine quite hot, are you sure it's loading up....getting rich, vs. just overheating a bit?! I know my bike acts funky and sluggish when it gets too warm!!

If it's okay on the open road, then I wouldn't think you would want to adjust the slide needle position, since it's involved in the mid range and wider throttle openings, not much at all in idle/off idle! You're also talking about dropping the floats=leaning it out again all around, could mess up your overall performance.

Have you pulled the plugs during the stop and go setting to see if they are getting sooty/black? If you really think you need to lean it out for idle, then turn the pilot screws in more. You don't want to go too lean overall...not fun to burn holes in your pistons. Watch your plug color!!
T.C.

[Doo-Daa]

Good evening again TC,

I'm glad that Do-Lee cleared up the size issue. I have looked and looked, and all I came up with was the smaller air pilots. And having Skids respond with what he has found in other 78Es is the best way to validate equipment.

I'm sure it's loading up. I've pulled plugs, and after about 10 minutes, they are so black and sooty, they're almost wet. After about another 20 minutes of the same, (1/2 hour total), I'll start dropping cyclinders. This is confirmed by cold pipes. The odd part is, is that it could be any one cyclinder, but seems to hit #4 more often. I've swapped the wires for 1 & 4, but really doesn't follow the wires.

On this clean and rebuild, I set the floats at 25mm, they avaraged about 28mm before this cleaning. Put in new needles, jets, pilots, and air jets. (all Mukuni) My floats were good, and the fill needles and seats were nice bright shinny steel. Did the blow test and I'm getting a good seal. (I did get a good seal, but upon rotating the carbs back around to upright, it did take a good strong breath to open the float needles. But that might be because that gas acts as a lubricant also.)

So, with the float level set at 25mm, now you've got me thinking about returning the needles back to #3.

I'm just not sure where I could be drawing in the extra gas from if it's not the needles, emulsion tubes, and mains.

Any ideas or experience with that?

Yer Right about not wanting to burn a piston, so I'll keep a sharp eye out on plug color. A XSive friend down the road a bit has a Colortune, he's been wanting to try out, might have to do that. Of course I don't know how much more that will tell a person other than pug color and exhaust manifold temperatures.

Funny, on my Intruder, the first thing mentioned on the IntruderAlert site for any problems is to clean the battery terminals, and check for tightness. Maybe I'll try that too!!

Again, thanks for your help.

Doo-Daa

[TopCatGr58]

And back at ya!!!

Aha, the floats were set to ~28 before last rebuild. That's only ~1mm more than the stock range allowed of 25.7+ 1.0mm, and in your higher elevation a little more leaner in the float settings sounds like where you want to be! You will probably need to put it back up close to the 28mm, like ~26.7-27.0...the high end of the allowed range, and then using the colortune, you should be able to get your pilot screws set great for idle, which is where the colortune works!

I think it's a combo of pilot screws, and float height that's feeding it too much fuel, along with the thinner air of your altitude. You've already ruled out clogged bowl vent tubes!

Just my thoughts...have fun and good luck!
T.C.

[pgg]

Well, my manual seems different it says
78E - 137.5 42.5 180
79F SF - 137.5 42.5 180

I used 210 air pilot jets on a stock 78 with 142.5 pilot jets and in the zone between 40mph and 65mph in 5th it felt flat. (low elevation) After 65mph the main jet came on. Between 40 and 65 is 90% of the time on a road bike. 210's and 145's would have been better but I went back to 180's and 142.5's. Out of my 16 78' carbs only 4 had 210's, and still with only 142.5's. That set may even be 79' carbs.

[Doo-Daa]

Good Morning to All.

So the "Mukuni Plot" thickens.

PGG,
That's what my manual (Clymers) identifies for jet sizes also. My factory service manual does not identify a size. (for just the air pilot jet). The Yamaha Dealer (local) shows a part number that identifies the jet to be 210. (he needed the carb # to get to that information, the micro-fiche for the year just identified the piece as 'air pilot jet').

With Skids & DoLee identifying 210s, and your spares having a mix, I have to wonder what Yamaha had in mind. I've not heard anything about the stock mains ever being anything different than the 137.5s, and pilot jets being 42.5. So why "they" would change the pilot system, or have a need to have the same bike and two different carb jettings is an unknown.

This 78E is bone stock, and ran well before. Just had a problem of being way too rich while riding around town.

Thanx

Doo-Daa

[ratbyk]

Rich Around Town

Float level could have a lot to do with the richness around town. It was/is likely a little rich at speed as well but won't show on a plug check because the extra heat being created at high speed is burning off the evidence. Could lower the float level a mm to obtain a better air/fuel ratio.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[Do Lee]

I was going by my Yamaha tech bulletins and Service Data Sheets that I recieved when I was a mechanic for Yamaha Motors back in the 70's and 80's. Also the dealers recieved only 2 and if you were lucky an extra 1 (XS1100E). None of our XS1100E's made it to the Showroom Floor. As soon as they arrived we put them together and the shop employees took them home. These 3 bikes had the #210 jet along with #137.5 Mains and #45 Pilots.
"Now as it was well known don't have #45 pilots use something close to it, use what is available to meet deadlines." Data specs are only as good as the info given and inputted correctly into the system. So take the info with a grain of salt. We did get alot of Data Sheet updates. So I would not doubt that some 78 carbs could have #42.5 pilots as well as #130 or #140 mains. The microfiche even has discrepancies on them with it data around the carb jetting. So you can look at this info as guidelines of what might be actually in these carbs.
One other note the first year model XS1100E got the best gas mileage,(mid to upper 40's), the XS1100F (hi 30's low 40's), SF (mid 30's) the mileage was not as good. We did alot of rejetting the carb sets trying to match the XS1100E fuel mileage.
Do'Lee