Right Carb Running Rich

kbregler

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Hi, been following this forum for years as I have been learning and working on my 79 Special 2. I have had the bike for about 3 or years now, cleaned it up a bunch and have been riding it with mostly no problems. The bike previously sat for about 15 years and only had 8000 miles on it, everything original works but the speedometer is slow. I have slowly been replacing the worn out rubber items, Including the original tires and just making general progress.

When I first got the bike, I did tons of research and cleaned and rebuilt the carbs (with some Mike’s parts), even though it did surprisingly ran after 15 years Without the rebuild. The one piece I did not replace when I rebuilt the carbs was the throttle shaft seals. The only performance mods on the bike are uni pods and some natural exhaust holes due to age. I jetted up the pilots to 30’s and the mains to 140’s (Real Mikuni) and dropped the needle down 1 notch. The bike ran well but a little lean for the little I rode it over the years due to the shaft seals. I did several hundred miles of local trips, an hour here and there. Year 2 of having it I did replace the points with the electronic ignition and coil from Mikes and put Iridium plugs in, which has worked great.

Fast forward to this year, I decided it was time to replace the shaft seals to help with the lean issue. I was a little scared, even bought the JIS screwdrivers. I ordered genuine Yamaha seals over the winter and a few weeks ago bit the bullet and went for it. I did make sure all was running good before, checked the valves, timing, and the cam chain tension. I was able to get 2 out of 4 of the butterfly screws out and drilled the other 2 out. The carbs were still clean, I did a full tank cleaning and coating 2 years ago and have had a filter on it, and I never run ethanol gas. All the gas lines were of course replaced too. While I had it apart I did pull the jets and cleaned them out with Carb cleaner, checked the diaphragms to make sure they still came down slow, etc. Put everything back together, did a bench synch, and back on the bike. The bike started up no problem. The left carb tunes great, started it at 2 turns out and it ended up a little more than that. If I turned it in too lean it would die out. Now the right carb, no matter how far it goes in it doesn’t matter, its running rich has hell.

I have had the carbs out at least 4 times now trying to figure out what is going on. I have checked the floats, both height and under hot water, took the aftermarket needle valves out and put the originals back in after polishing with a q-tip. Checked the slides multiple times, made sure the pilot air inlet was clean, swapped spark plugs from one side to the other (has the original type back in, cant find the iriindium plugs I took out), checked to make sure the right side choke was going back down all the way, and I got nothing. I knew it wasn’t going to matter but I even tried synching the carbs with my homemade manometer (I have a manual single petcock to a high flow filter then a Y to the carbs and the vacuum ports with caps on them).

I am almost at a loss, I have been searching and reading for nights now, many of the threads never have a final conclusion. I have read the carb manual over again and cant see anything I am missing. I do have a couple other things I am going to try that I haven’t yet, but I wanted to see if anyone had any suggestions. The bike starts right up, choke shut off after 5 to 10 seconds, and idles with a little fluff now and then from the right carb. I cant get it to stay stable down below 1000 RPM’s and before the shaft seal changes I could get it down to 700-800 stable to set everything, then I would put back up to between 1000 and 1100.

I have probably checked other things, just cant remember after a couple bourbons and reading the same posts over and over again. I always hate ask for help when I know a lot of info is already out there.

Next on my list:

-Check valves and timing yet again and make sure the advance is working correctly, who knows, when I lubricated it maybe some grease got on the weights and is slowing them down.
-Get new Iridium plugs, which should have nothing to do with it, but it ran great with them before so anything is worth a shot.
-Put pilot circuit back to stock, its not running rich anymore with new seals so maybe I dont need bigger, but one carb is good and I do plan on replacing the original exhaust so I will be right back where I was.
-Check the seals on the jets, some of the parts were from Mikes so I know low quality rubber, but I do have 2 big multi kits of the good o-rings, I just need to look up the sizes again
-Do the clear tube method to double check float height, need to go get some clear tubing that will fit into the drain hole.

Thanks,

Kevin
 

Jim

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Sounds pretty thorough. random thoughts.....
Possible the needle is hanging up and not dropping fully... letting some main jet fuel in... or the slide itself hanging up.
Air jet inlet in the bellmouth (inlet)... or it passageway partially clogged, not getting enough air to the pilot circuit.
Choke not fully closing.
One thing to consider is swapping all the brass and slides between sides and see if the problem swaps sides.
 

grizld1

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Kevin, congratulations for a very thorough and well written post.

+1 to everything Jim wrote. When the motor fails to respond to the mix screw, the most common source of trouble is the float system. If the fuel level in the line shows high, immerse the float in warm water and look for bubbles. If the float passes that test, consider replacing the needle and seat.
 

kbregler

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Thanks for the replies, I tried to remember to include as much as I could in my post, it gets tough when you try 15 different times.

After the first time of the right carb not operating correctly is when I checked the floats. I did submerge both sides in hot water held down by a 10mm wrench for a good hour. There were no bubbles and it floated right to the top when removed. I then checked to make sure they were set to 24mm on both sides of the float. I kept all of the original parts when I rebuilt the carbs a few years ago so I put the original mikuni needle and seat back in on both sides after polishing with a q-tip. Obviously they could be bad as well, which is why one of my next steps is the clear tube test on my bench to see where the level stops. I did also take the choke apart on the bad side and cleaned it out, but again, that does not necessarily mean the cheap replacement decided to stop working, I can clean one of the originals and put that back in as well and see if it changes anything, or swap with the other side.

Depending on the weather this weekend, my next plan is to check valves and timing again as well as the advance weights and springs since that is easy to do. If all of that checks out I will pull the carbs, which gets easier and easier every time, do the clear tube test. If that shows the floats and needle valves to be working correctly I will do as Jim suggested, swapping the brass to see if the problem follows.

Again, I appreciate the suggestions.
 

5twins

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You can buy a very nice "special tool" off eBay for checking the fuel levels via the clear tube method. It's a machined fitting that screws into the drain bolt hole .....

SightTube6.jpg


I have one and have used it numerous times. It works very well .....

https://www.ebay.com/itm/274881260720?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Recently, I replaced the needle jets in my '78 carbs. The plugs have been getting progressively darker over the last few years and I guess the needle jets finally wore out. Not an easy thing to measure but comparing old to new, it was pretty easy to see. The metering hole through the old jet was much larger .....

WornNeedleJet.jpg


WornNeedleJet2.jpg


Now, since your issue seems to have cropped up suddenly, it probably isn't worn jets, but do check their fit into the carb body, making sure they're tight and their sealing o-ring is good. Loose jets with a bad o-ring can suck fuel up around the outsides instead of just through the jet as they should.
 

grizld1

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gggGary came up with a cheap way to attach the sight tube. Get a M6x1.0 grease zerk from your local Big Box Auto Parts store, drill the hole until the spring pushes the ball bearing out, remove the ball and spring, thread the zerk into the float bowl, and the attach line.

Are both of your mixture screws OE? You might switch them from side to side and see if trouble follows.
 

5twins

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The drain bolt is an M8. That M6 grease fitting thing works for a vac nipple to attach sync gauges.
 

kbregler

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Thanks again for everyone's suggestions. We have been in a heat wave here in NJ and working in a 100 degree garage is not fun for an old slightly overweight guy like me. I am finally going to get back out there tonight and do some more tinkering.

The needles are not OEM, but I do have the originals I had removed, I keep everything.

Tonight I plan on checking the valves on the bad side just to make sure, even though I did it a couple months ago, its easy enough to do, the pull the carb out again and swap the brass from one side to the other and see what happens.
 

kbregler

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OK, making progress eliminating some things, and breaking others. I stripped a damn bowl screw, if I ever figure out my issue I guess ill be tapping for a larger screw…..I knew something was bound to happen taking it apart a million times.

So here is what I did tonight with no luck, but eliminated a lot of things.

-Started out easy, checked the valves on the right side, as suspected, they were perfect.
-Tried new spark plugs, didn’t think that would do anything, and well, it didnt
-Swapped spark plug wires, thinking maybe something happened to one of the sides of the coil, again, no change
-Swapped the mixture screw, again, easy try, and again, no difference
-Was going to swap the jets, ended up just swapping the whole bowl, no change
-Swapped the slides, cleaned them while out too……again, no change. They are original, but in good condition, no sign of holes, and pass the cover the hole and drop slow test.

Now its time to either build or buy( Edit…..I just bought the one on eBay) a contraption to do clear tube check to make sure float is set right / needle valve sealing. If that looks good, the one thing I didn’t swap was the choke/enricher. If all that doesn’t do anything, time to visit a friend that has an ultrasonic cleaner and start over again, I am running out of ideas.

I did take a video this time looking into the carb. I have been successful in tuning out the backfire, but I wasn’t killing myself for nothing, the video shows it. If I can figure out how to post it somewhere I will.
 
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kbregler

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I know a decent amount of bikers around here, not necessarily in Wenonah, but most are all Harley guys. Other than some of my older neighbors that see my bike and say wow, I had one of those in the 70’s, I know of no one else that has an XS650 around here.
 

kbregler

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OK, here is an update, I am an idiot, or as my wife says, the dumbest smart person. I am almost embarrassed to tell this, but if you can’t make fun of yourself, you cant make fun of anyone.

One piece I didn’t elaborate on was the ignition. I mentioned I had a Mikes (gen 1) in there for a couple years and no problem. Knowing I wanted to change the shaft seals this season, I wanted to make sure everything else was good so if there is an issue I only chase one issue at a time. Well, when I wen to start it for the first time, it started, ran a while, then shut off, nothing new for the first start of the season. Next start it backfired, then I got nothing. Long story short, a screw came lose from somewhere and jammed up the electronic ignition and tore off some components. No biggie, I’ll order a new one, the gen 2 looks better built anyway. Get it, and I have issues. Couldn’t get it to fire. Had a test light on the 2 terminals going to the coil and it wouldn’t light. Swapped the rotor around, and bam, i get light on, light off….well still wont start, its in backwards now so timing way off. I am an electrical engineer by degree (haven’t touched electronics for work in 25 years) so time to trouble shoot. When looking, the magnets on the rotor do not go in far enough when its in correct, they aren’t hitting the Hall effect switch. I reach out to Mike’s, they say oh, some people say they have to shim the other (advance) side a little. I didnt want to do that, its only aluminum, just need to move the magnets in a bit so I grind it down. Get it to work intermittently because there is a little play. I grind more, well, it stops working completely. I learned now that heat can cause magnets to lose their magnetism, so the high heat from grinding ruined it. Spoke to Mike’s, they were nice enough and sent me a new rotor. In the meantime I popped out the magnets, measured them, and ordered some replacements. I get the magnets, have fun pressing them in, and bam…..engine turns over, I get light on, light off. Start it up, it starts right up. Didn’t take it anywhere, but it ran……so now I can move to the shaft seals, and all the issues this thread was about.

Well, at 4AM this morning when the wife was going to work, I had an epiphany, is it firing once per rotation or twice? Well, my thought process was correct, it was only firing once, so I probably am not always flooding the right cylinder, its not always firing. I take the new rotor from Mike’s, put it in without the advance rod, and wow, light on, light off, light on, light off. Now I am back to the same problem as I originally was, it’s intermittent because the magnets aren’t in far enough to make constant connection to the Hall effect switch.

I have 2 options I guess, figure out how to shim from the other side and see if that little bit of play makes it so its constantly firing without making it too tight, or figure out the magnet thing on the one that does line up, but only once per rotation. I have extra magnets…..I am guessing I need to look at the Hall effect to understand how it really works, never touched one before. I am guessing just pressing in magnets aren’t enough, but I have to pay attention to the polarity and which way I put the magnets in, so its on off on off. That will be fun to do, little magnets, little holes, and anything to press them in is usually metal, so keeping it straight is a PITA…..maybe I will try using a metal blade on my jigsaw and just cut some off, not grind it.

Well now I will soon have a contraption to test the bowl height and a kit to do an M4 helicoil to fix the one bowl screw I stripped the hole out……new tools, and new learning experiences.

If anyone has any ideas on the rotor alignment / magnet issue, that would be great, I probably wont get to mess with it until the weekend again
 

kbregler

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OK, I a 98% there....now both me and the bike are firing on all cylinders. Did a little research last night.

Apparently the ignition has a Hall effect latch, uses + (south pole) to latch on, then - (north pole) to latch off. I actually had 2 of the magnets in right by luck. I decided to take my shot at swapping magnets again since I had like 20 of them left. Tested with a compass to figure out which end is which, marked each little one with a paint marker, used scotch tape to pick up the correct end and tape it in place so I could tap in with a hammer.

Runs so much better now. Tonight when it cools down a little I will adjust the carbs and synch them. The timing was still on point. The right mixture screw actually makes changes now, not quite as much as the left one, but I don't expect them to be perfect, it is nice to not have to have them out all the way due to the leaking shaft seals. I will have to take the carbs off one more time to fixt the one screw so it doesn't vibrate out and I lose it, its at least not leaking gas!

Now on to the next project, replacing the fuse box, then some sort of new exhaust.

Thanks all for your help.
 

jpdevol

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Awesome - well done sir!
 

kbregler

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I am still not out of the woods yet.....Finally got past my daughters wedding, so hopefully will have some more time to tinker. Its running better, but the right side is still rich. The left side I am sitting about 2.5 turns, and the right I can go all the way in. I had to get gas, going to take it for a ride tonight. I get no bogging, no hesitation on light throttle or full throttle, they don't sound way out of synch. I can idle with very little fluctuation down below 1000 RPM's.

Since finding this out, I swapped the brass back, did the clear tube check, which is actually a little low, and I changed the o-ring on the needle pilot on both sides, which I did 2 years ago, but figured what the hell, I had them, and no change at all. I had previously shot out all the air jets with carb cleaner and with my compressor. I even made sure my UNI filters weren't somehow blocking the inlets. Tonight I am going to swap the slides again since I did that back when I was still having ignition problems, and I can't remember if I swapped out the choke plungers, so I will do that too. It has to be running pretty damn rich because if i take off the boot on the intake vacuum barb it runs better, doesn't kill the right side.

I didn't actually swap the needle jets, just thought of that, I will add that to my list.

I looked at the butterflies again, and the right one lets a little more light through than the left but I have read that is normal and all gets equalized when tuned and sync'd if I ever make it that far. When I re-assembled I did snap the throttle a few times before fully tightening.

I am bound to figure this out one of these days.
 

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LikeyMeYommy

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You can buy a very nice "special tool" off eBay for checking the fuel levels via the clear tube method. It's a machined fitting that screws into the drain bolt hole .....

I have one and have used it numerous times. It works very well .....

https://www.ebay.com/itm/274881260720?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Recently, I replaced the needle jets in my '78 carbs. The plugs have been getting progressively darker over the last few years and I guess the needle jets finally wore out. Not an easy thing to measure but comparing old to new, it was pretty easy to see. The metering hole through the old jet was much larger .....
Thanks for the link to that "special tool." Been searching the forum for it! Just ordered one!

Regarding the needle jet replacement... do I just pull them out? Seems like a bit of brute force would be required. I have some replacements so was going to just grab some pliers and yank them out but was concerned about damaging the cast hole. What method did you use to press them back in? Mine didn't come with new o-rings. Guess I have to order them separate 🤷‍♂️
 

5twins

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I spray the needle jet with some sort of penetrating oil then tap it out from the top using a soft drift (wood or plastic dowel). You can't tap it completely out but once you get it started, that usually loosens it up enough to pull it by hand. Twisting it as you pull helps too. You may need to work it back and forth - tap it out as much as you can, then back in, out, in, etc. For install, you should be able to push it in most of the way by hand, then a few gently taps on a small block of wood (for protection) should seat it fully. There is sometimes an issue getting the '77 and earlier needle jets (Z-6 and Z-8) with their o-ring groove close to the flange to seat fully and stay in. You can just install the bowl and it will press the jet in fully and hold it there. Eventually, it's o-ring will work it's way up into the carb body.

NeedleJets.JPG


An o-ring size that works is the commonly available 1mm x 4mm.
 
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