Electrical Components

[myac455]

Hey Mark,

First of all, if you used Photobucket, you photos are still there, just PB changed their service and don't provide off-site linking for free anymore. There is a PB plug in you can get with the Chrome browser that will still show the photos instead of just LINKS to PB, but if you use IE or FF, you only get the links.

Next, didn't reread this whole thread, so let's recap. I saw reference to the screws over the pilot jet towers, so we know you do have 79 carbs, not the bastardized 80 ones that sometimes uses the rubber pilot tower caps.

I saw your question about where to get genuine Mikuni jets, but no later comment on whether you DID or didn't get Mikuni for the PILOTS. IF you got any other brand, that will be the most common reason why you are getting black plugs. If your headers were scavenging too well, then you would be getting WHITE plugs due to too lean, but black plugs are too rich. You've got the 3 ohm coils....BTW did you BYPASS the Ballast resistor under the left side of the gas tank? If not, then your 3 ohm coils are only getting ~9 volts instead of the 12 they need and could also cause poor spark. Did you put on new plug caps or use the OEM ones?? IF oem, did you check them with Ohmeter to ensure they are within specs ~5 kohm, If much higher, they can also cause problems.

Aside from the Genuine Mikuni Pilot jets, did you check the choke/fuel enrichener plungers to make sure they were sealing while you had the carb rack apart?

You said you were using some Velocity stacks, how are they mounted to the carbs, is there any restriction of the inlet bell ports from a mounting lip?? The cheap EMGO cone filters were known to cause this and excessively rich as well, unable to get enough air flow to get past ~6k rpm.

Also, with the carbs, are the UPPER T's connected to OPEN AIR VENT TUBES, not capped or plugged, they need to be open to properly vent the carbs to maintain fuel height and float function. Also make sure you don't have FUEL going to those upper T's. The LOWER T fittings are the fuel inlets.

Just throwing these things out there to check.
T.C.

Hey, TC
First of all, I haven't used PB in years. Long before the SHTF. I used Post image recently, which just creates a url for the pic...No idea other than that.

Yes, ballast removed. The NGK caps appear to have no resistance to then. I had asked if this is correct in 79.
Went to BP-5ES from 6 , but didn't do much with the original jets back in place.

I got the jets from Mike's XS, and I seem to be on the right track..It IS getting leaner..just not enough.

Have to disagree on the headers. TRI Y's have been known to suck so hard that they pull additional fuel that say a 4-1 wouldn't . We've seen this phenomenon on race engines..either 4 cyl. or V8 (one head, per header, of course). Only remedy is to keep going leaner..often times several steps leaner than stock jetting. Kinda explains why it runs a bit cleaner with the baffle in place. I know this is contrary to the norm. Apparently ,it keeps the header from working so good.

I tried to pull the choke tubes out with pliers but they wouldn't come..just as an experiment. I thought about soldering them up, temporarily. Then was afraid it might not start at all, cold. Then what?
Right now, it starts with no choke at all.
If (a) choke passage was bad or clogged, then they all must be. Bear in mind all cylinders act exactly the same. The header is the common component here. What else?
Yes, I get your point about the stacks. I did try it with none in place and it doesn't seem to make a difference, but I will re-visit it .
Upper vents go to a common hose with a notch out of it, way above the carbs.
Thanks for reply.. Not an engineer, but always willing to listen to some, as long as they don't get too deep and arcane. LOL

[myac455]

Hey, TC
First of all, I haven't used PB in years. Long before the SHTF. I used Post image recently, which just creates a url for the pic...No idea other than that.

Yes, ballast removed. The NGK caps appear to have no resistance to then. I had asked if this is correct in 79.
Went to BP-5ES from 6 , but didn't do much with the original jets back in place.

I got the jets from Mike's XS, and I seem to be on the right track..It IS getting leaner..just not enough.

Have to disagree on the headers. TRI Y's have been known to suck so hard that they pull additional fuel that say a 4-1 wouldn't . We've seen this phenomenon on race engines..either 4 cyl. or V8 (one head, per header, of course). Only remedy is to keep going leaner..often times several steps leaner than stock jetting. Kinda explains why it runs a bit cleaner with the baffle in place. I know this is contrary to the norm. Apparently ,it keeps the header from working so good.

I tried to pull the choke tubes out with pliers but they wouldn't come..just as an experiment. I thought about soldering them up, temporarily. Then was afraid it might not start at all, cold. Then what?
Right now, it starts with no choke at all.
If (a) choke passage was bad or clogged, then they all must be. Bear in mind all cylinders act exactly the same. The header is the common component here. What else?
Yes, I get your point about the stacks. I did try it with none in place and it doesn't seem to make a difference, but I will re-visit it .
Upper vents go to a common hose with a notch out of it, way above the carbs.
Thanks for reply.. Not an engineer, but always willing to listen to some, as long as they don't get too deep and arcane. LOL

BTW, the current pilot jets right now, are the original ones that came in the carbs.

[myac455]

Pictures?

Still wondering what happened to them. I can post them again, but not on a regular basis. LOL


Got # 127.5 jet and #40 pilots on the way. Plugs are just starting to color, but it still craps them up around town. The bike is getting faster too, while the plugs are still clean but that doesn't last long.
Speaking of..Anybody make a speedo that goes over 85 mph? Probably hit that in third gear.
I'm not going to race this thing on a drag strip but would be nice to run it through a quarter and see what the mph is.

[myac455]

Pictures?

Still wondering what happened to them. I can post them again, but not on a regular basis. LOL


Got # 127.5 jet and #40 pilots on the way. Plugs are just starting to color, but it still craps them up around town. The bike is getting faster too, while the plugs are still clean but that doesn't last long.
Speaking of..Anybody make a speedo that goes over 85 mph? Probably hit that in third gear.
I'm not going to race this thing on a drag strip but would be nice to run it through a quarter and see what the mph is.

[myac455]

Pictures?

Still wondering what happened to them. I can post them again, but not on a regular basis. LOL


Got # 127.5 jet and #40 pilots on the way. Plugs are just starting to color, but it still craps them up around town. The bike is getting faster too, while the plugs are still clean but that doesn't last long.
Speaking of..Anybody make a speedo that goes over 85 mph? Probably hit that in third gear.
I'm not going to race this thing on a drag strip but would be nice to run it through a quarter and see what the mph is.

[TopCatGr58]

Thanks, but I'm no engineer either!

Even though it has the same pilot jets you got with it, there's no guarantee that someone else/police mech might have put in something else?? Mikuni has a unique double diamond logo that they stamp into all of their jets, you may need strong magnifier to be able to see it, but would be a good idea to check just to make sure they are truly Genuine Mikuni, otherwise you could be chasing your tail with tuning steps that would not be fruitful. Many a member on here has had similar black plugs with the aftermarket pilot jets, and once went to genuine Mikuni, and were then able to get them to tune/idle/throttle respond and good plug color. YMMV

The "choke" plunger UNSCREWS from the side of the carb body, it's fitted into that piece, you can't just pull them out with pliers.

Running stronger/better WITH the muffler baffles is also a common experience with members that have tried to run just straight pipes/open headers. Folks have reported loss of low rpm power/torque with the open straight pipes, again possibly due to excessive lean condition. The engineers put a lot of work into these engines/intakes/exhaust to get the best OVERALL performance across a wide rpm band. Making drastic changes to intake/exhaust can lead to a lot of experimenting to try to get it tuned well, but often end up with a compromise, ie. more power at upper rpm ranges but with loss of low rpm torque/response.

Okay, if the plug caps had NO resistance measured as ZERO (0) ohms on the meter, not the (---) symbols or "OPEN" or "Infinity" message which would be NO continuity/excessive resistance/open circuit, then zero would be okay. You can use regular resistor plugs, or even no resistor plugs if you don't mind a little RF noise in your radio/cell phone, the RF won't bother the TCI but may annoy some cars if they get too close. IIRC, the lower the plug number the HOTTER the plug which may explain why you tried the 5's instead of staying with the 6's, but that is possibly masking the problem, and these engines do run warm/hot and you could be heading for detonation/pre-ignition with too hot a plug!?

Good luck with the tuning.

T.C.

[DiverRay]

You can install a speedo from the late '70s 750/850 or 1100. They go up to at least 140, faster than you probably could go on the bike.

[myac455]

You can install a speedo from the late '70s 750/850 or 1100. They go up to at least 140, faster than you probably could go on the bike.

Oh okay . So I must have Special gauges that are just a bit new then.
Would the 750 /850 be the round type?

[myac455]

Oh okay . So I must have Special gauges that are just a bit new then.
Would the 750 /850 be the round type?

Okay, Google is your friend ;-)
So next question: Would the 850 tach use the same signal and work correctly?
I would guess that it would but would rather someone say they tried it.

[Radioguylogs]

No, the 850 tach works by rotating cable turned by the the exhaust cam.

The 1100's work by electrical pulses from one of the alternator windings.

They are not interchangable.

[myac455]

No, the 850 tach works by rotating cable turned by the the exhaust cam.

The 1100's work by electrical pulses from one of the alternator windings.

They are not interchangable.

Thanks for the info

[DiverRay]

The round Yamaha gauges ar all the same diameter on the big bikes. You can put the 850 speedo into the XS11 housing. I've done this with my Midnight Special to get a 120+ mph speedo in place of the 85 mph unit.

[myac455]

Went for a little 65 mile ride Sunday. Purrs like a kitten.
Ended up going 5 jet sizes leaner than stock, at 5000 '
It is what it is :-)
https://s5.postimg.cc/wovs9o16f/20180611_163328x.jpg






I see Postimage is getting goofy now too.They'll be charging $300 before long too.

[myac455]

Emulsion tubes/ needle jets, 1979

Hi guys,
I've been riding my bike quite a bit in the 6000-9000 ' areas of the Rockies.
Plugs were looking pretty good , except that after a lot of in- town idling, the # 4 plug would soot up, just like when I had too big of a jet in the carb.
After switching wires and boots around, and not getting anywhere, I switched all the removable components with carb # 1. Sure enough, # 1 became the black plug then.
Figuring I had replaced almost every other part already, I then switched the emulsion tubes, which were the originals, I believe, back again, and #4 again became the bad plug.
So, after examining them in a good light, I could see where the orifice where the needle passes through was all corroded and pitted. Honestly, the bad actor didn't look any different than the other three, put they all need to be replaced.
I'm not doing very well on a Sunday, finding the proper replacements for the 79 year carbs. Any ideas? Thanks in advance.
Also , does anyone know why the two middle carb tubes would have less holes drilled into the sides of them?

[bikerphil]

does anyone know why the two middle carb tubes would have less holes drilled into the sides of them?

The holes in the side of the emulsion tubes are air bleed holes, the less holes, the richer the mixture. Richer mixture runs a bit cooler in temperature so they were placed in the 2 inboard carbs. Those cylinders 2+3 run hotter because of less cooling fin area.