jrhendryx Posted September 7, 2007 Share Posted September 7, 2007 I am looking into purchasing a set of vacuum gauges to sync my carburetors up. i was specifically looking at this set on ebay. how can i tell if these will work on my bike? will i need a special adapter to make them screw into the vacuum synchronizing screw hole? how will i know when they are set properly? neither the haynes nor the yamaha manual really explain how to make sure that they are set correctly. i want to learn to do this myself, but its difficult when i cant get any good (idiotproof) information. thanks. jeff Link to comment Share on other sites More sharing options...
mcspecial650 Posted September 7, 2007 Share Posted September 7, 2007 I am looking into purchasing a set of vacuum gauges to sync my carburetors up. i was specifically looking at this set on ebay. how can i tell if these will work on my bike? will i need a special adapter to make them screw into the vacuum synchronizing screw hole? how will i know when they are set properly? neither the haynes nor the yamaha manual really explain how to make sure that they are set correctly. i want to learn to do this myself, but its difficult when i cant get any good (idiotproof) information. thanks. jeff For the past few weeks, I've been working on a 1975 XS 650, and it seems to me that the bike(motor and carbs) really seem to scream out what they need. I can obviously tell when one side is running rich, and loaded up(by sound) and if I really want to get into it, I go to the exhaust, and you can tell who's running faster, hotter, or not at all. I guess what I'm trying to say is that these bikes have a way of telling you what you need to look at. If you've gotten to the point that you're considering buying these guages, then you already know that 30 year old carburaturs don't work like brand new ones, and that the guage will only tell you what you already know. For example, I know that one of my floats(in carb) falls a little slower than the other side. So when I've been cruising at 45 or 50 mph and let off for a while, I get a slight backfire. OK, I can live with that! My grandfather gave me this bike when I was 16, and I'm not going to "fix something that isn't broken". I will completely restore(piece by piece) this bike in the winter, but for now, I'm going to enjoy riding around in the clean mountain air. Good Luck, No disrespect intended. Jeff Link to comment Share on other sites More sharing options...
jrhendryx Posted September 7, 2007 Author Share Posted September 7, 2007 For the past few weeks, I've been working on a 1975 XS 650, and it seems to me that the bike(motor and carbs) really seem to scream out what they need. I can obviously tell when one side is running rich, and loaded up(by sound) and if I really want to get into it, I go to the exhaust, and you can tell who's running faster, hotter, or not at all. I guess what I'm trying to say is that these bikes have a way of telling you what you need to look at. If you've gotten to the point that you're considering buying these guages, then you already know that 30 year old carburaturs don't work like brand new ones, and that the guage will only tell you what you already know. For example, I know that one of my floats(in carb) falls a little slower than the other side. So when I've been cruising at 45 or 50 mph and let off for a while, I get a slight backfire. OK, I can live with that! My grandfather gave me this bike when I was 16, and I'm not going to "fix something that isn't broken". I will completely restore(piece by piece) this bike in the winter, but for now, I'm going to enjoy riding around in the clean mountain air. Good Luck, No disrespect intended. Jeff none taken the reason i am considering this is because i get a slight backfire out of the left side when i roll off the throttle, or downshift. also, when pulling hard (5500-6000rpm) uphill, or if i really jump on it to pass someone, it tends to miss every now and then. how do i adjust it without the gauges? once i get the tank restored (rusty) i am going to tear the carbs apart and clean them out, so i need to know how to adjust them once i put them back together, and if i can do it without the gauges, that would be pretty good. Link to comment Share on other sites More sharing options...
mcspecial650 Posted September 7, 2007 Share Posted September 7, 2007 I'm just a rider----, but it's hard for me to say, because, I'm a cruiser---never hit 5000 rpm's but anyway, if you're running that hard---I hope you have some hot burning plugs(NGK) don't buy the Autolite or whatever(of course this is purely my opinion, but if you're anything like me, you'd by the $4 plugs just to see) also, there is only one screw on the Carb that is adjustable without taking it off. If you know which side is backfiring, turn it in 1/8 of a turn, and ride it. See what happens. I'm definately no expert-- but please let me know what you figure out! Good Luck Jeff Link to comment Share on other sites More sharing options...
mcspecial650 Posted September 7, 2007 Share Posted September 7, 2007 I think that you could probably get your bike to run at 6000 rpms and not backfire. But I also think that unless you weigh 400 lbs, it's not necessary. If you want your bike to run a little faster, change a sprocket. If you want your bike to run a little smoother, clean the carbs, tank, and buy premium gas(it does make a difference in the dinosaurs that we ride) I really don't know why, but my bike(and probably yours too) runs much more comfortably on the high octane gas--and since we're getting 50-75 mpg---give it to her, it might be the best 60 cents you ever spent. jeff Link to comment Share on other sites More sharing options...
mcspecial650 Posted September 7, 2007 Share Posted September 7, 2007 Right on---ride her like you love her We all know that you get better results from an old bike that a woman anyway! Link to comment Share on other sites More sharing options...
jrhendryx Posted September 7, 2007 Author Share Posted September 7, 2007 i wouldnt hit 5k rpm either, except on this bike, thats 50mph. i actually am running the ngk plugs in this bike, and have been filling it with high octane since i bought it (1 month ago.) cleaning the tank is the next project, followed by the carbs, though i will have to adjust them when im done, and thats what worries me. the sprocket thing was already suggested by yamahead (i think, maybe it was yoda... strong with the yamaha he is).... and im going to try it out as soon as i get the chance, though i have quite a bit more reading to try out. im going to fiddle with the carbs tomorrow after work, and will update you on my progress, though i think it may just be a symptom of a rusty gas tank. any idea which way to turn the screw to make it stop backfiring? does a backfire generally mean too rich of a mixture (detonates twice?)? Link to comment Share on other sites More sharing options...
Cy Welch Posted September 9, 2007 Share Posted September 9, 2007 i wouldnt hit 5k rpm either, except on this bike, thats 50mph. i actually am running the ngk plugs in this bike, and have been filling it with high octane since i bought it (1 month ago.) cleaning the tank is the next project, followed by the carbs, though i will have to adjust them when im done, and thats what worries me. the sprocket thing was already suggested by yamahead (i think, maybe it was yoda... strong with the yamaha he is).... and im going to try it out as soon as i get the chance, though i have quite a bit more reading to try out. im going to fiddle with the carbs tomorrow after work, and will update you on my progress, though i think it may just be a symptom of a rusty gas tank. any idea which way to turn the screw to make it stop backfiring? does a backfire generally mean too rich of a mixture (detonates twice?)? If it's a sharp popping sound it likely lean, if it's more muffled it's likely rich. First off look at your plugs, if their white it's definetely lean, if really dark that would tend towards rich but on an older bike that is not quite certain. Especially with higher rpm backfire it's more likely lean than rich though, and while you don't need the guages to adjust the mixture (they won't help with that at all) you do need some sort of gauge to syncronize the carbs. Do a search as their is an article on a homemade syncronizer using clear plastic tubing that is supposed to actually work better than the gauges and you can put one together for just a few $$. That said, if they carbs are in sync now, don't seperate them when you work on them, and as long they use a single throttle cable and you don't touch the screw on the shaft between them they should stay in sync although the manuals for my bike at least recommend checking/adjusting the carb sync every few 1000 miles. That said, if you don't want to make the homemade one, I have seen decent sets for around $35 on ebay. As for the plug advice, my experience has been that you use hotter plugs if you do a lot of low speed short trip stuff, and a lot of long trips or high speed/rpm driving usually requires a lower temp plug. The standard plug for your bike is generally the right temp for average mixed driving. Link to comment Share on other sites More sharing options...
Renfield Posted September 13, 2007 Share Posted September 13, 2007 FWIW, $35 seems like a steal for that gauge package. I paid about $55 for an electronic version that I've used for several years. Hookup is simple, calibration is quick and precise. Worked with my carburated Vstar 650, and still works with throttle bodies on the fuel injected 1300. I'm no mechanical genius, so listening to the pipes or reading the tea leaves is not an option for me. Props to those of you with such skills. I consider the sync tool an excellent investment that eliminates guesswork beyond my capabilities, and keeps my ride running smoothly. I can tune my guitar and bass by ear, but I use a $50 stage tuner for that task as well. Hey, it's fast, simple and very precise. So shoot me. Good luck! Renfield Link to comment Share on other sites More sharing options...
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