kbregler
XS650 Member
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
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