apathetic Posted March 31, 2007 Share Posted March 31, 2007 hello im a noob and i need help any help would be much appreciated i recently bought a 1977 xs360 i rode it home and it gave me no problems the next day it started having hesitation and choking issues while it was in gear and at speed this problem continued to get worse until the bike no longer ran the previous owner told me to replace the spark plug wires and points i spliced in new wires and boots i installed new spark plugs i installed a nos condenser i removed the carbs and cleaned them (although i had no idea what i was doing, i reassembled them correctly, i at least know this for sure) one thing that should be noted is that the one of the needle valve assemblies (the little needle with the spring inside that touches the float) is more springy (stiff) than the other i am not sure if this causes problems or not but i thought it was an important item to mention also when i cleaned the carbs i did not have a manual i just took apart what looked easy to take apart and cleaned it with carb cleaner i am 100% sure i reassembled the carb correctly as i read the manual afterwards and had luckily done all the right steps the bike now runs there are still a number of problems at idle, the motor would rev to 4000 and stick i eventually got it down to 1200 by adjusting the idle screw if i revved the bike, the revs would stick to however high i opened the throttle i somewhat fixed this problem (once again with the idle screw); it still persists although not as bad the real problem is after getting it into gear, i get the same hesitation and choking problem i had before after reading a haynes shop manual, i believe that i have to sync the carbs, but i am not sure the manual has instructions on how to sync the carbs, but they are hard to follow apparently i have to get a pair of vacuum gauges hook one to the hose that goes from the carb to the backside of the petcock and the other to the same corresponding hose on the other carb (this hose is connected to nothing and plugged with a bolt) and then adjust some screw i cant find until both gauges read 5 hg cm while the motor revs at 1200 is what i have talked about a common problem? have i diagnosed the problem correctly? is a carb sync the next step? is there an issue with how i described the needle valve assembly? did i describe the carb sync process correctly? i still need to do the points the previous owner gave me 2 points but they are 2 lefts i need to order a right thank you for your time thank you for your help your time is much appreciated Link to comment Share on other sites More sharing options...
Moderator drewpy Posted March 31, 2007 Moderator Share Posted March 31, 2007 WOW some text 1) Sounds like air is getting into the inlet side of the bike. Spray some wd40 around inlets and listen for any engine revs which would iindicate a leak there 2) you need to get a keyster carb kit and replace everything with the kit 3) tune the bike by setting the valves, points gap, timing and finally balance the carbs. If you get the vaccum guages there will be instructions in there. you need to find a way of supplying fuel with the tank off the bike and you use the stubs on the inlet rubbers as vaccum take-off. hope this helps Link to comment Share on other sites More sharing options...
apathetic Posted March 31, 2007 Author Share Posted March 31, 2007 1) Sounds like air is getting into the inlet side of the bike. Spray some wd40 around inlets and listen for any engine revs which would iindicate a leak there i will try to do this today and i will let you know how it turn out. i actually bought some high temp rtv and made a seal in between the block and the rubber inlets, so i would like to think this is not the problem. 2) you need to get a keyster carb kit and replace everything with the kit where can i find a keyster carb kit? i found this on ebay, but i dont know if it will work, its for an xs400 xs400 keyster carb kit i live san diego, california, if it makes a difference 3) tune the bike by setting the valves, points gap, timing and finally balance the carbs. If you get the vaccum guages there will be instructions in there. you need to find a way of supplying fuel with the tank off the bike and you use the stubs on the inlet rubbers as vaccum take-off. i will do the points gap as soon as i get points. i have two lefts, but i need to order a right. at the moment im going to pretend the valves are fine, i dont want to touch them if i dont have to. im going to go buy a pair of vacuum gauges today to try to sync the carbs, but i have a feeling i wont know what im doing. thank you for your time and help, i will let you know how it turns out. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted March 31, 2007 Moderator Share Posted March 31, 2007 Those are the carb kits, in fact the exact same ones I bought. Don't forget you need two! The valves are really easy, just use your manual to set the crank to the timing marks and 10mm spanner and feeler gauge. rtv on the inlets is not a good idea, use a gasket and check rubbers for cracks/splits Link to comment Share on other sites More sharing options...
apathetic Posted March 31, 2007 Author Share Posted March 31, 2007 Those are the carb kits, in fact the exact same ones I bought. Don't forget you need two! The valves are really easy, just use your manual to set the crank to the timing marks and 10mm spanner and feeler gauge. rtv on the inlets is not a good idea, use a gasket and check rubbers for cracks/splits i just bought a pair of vacuum gauges but i hooked them up and the needle just bounces from one side to the other there was no way to get an accurate reading, or even near accurate reading, with those gauges so i am going to return them, but i still an stuck with unsynced carbs i used wd40 to check for leaks but i couldnt see anything i guess its easier to see pressure (bubbles) than vacuum before i buy a pair of those carb kits, i just wanted to make sure one more time so i dont buy the wrong things. my bike is a 360 and the carb kit is for a 400, but its still the same parts, right? ill try the timing either tomorrow (sunday) or next weekend thank you so much for the help drewpy the problem has to be an issue with the carbs and/or timing im positive of it although i got it running again it still has problems even at idle coughing/choking, hesitation and sticking... but it has to be a carb/timing issue thanks again drewpy, and i await your response on the carb kit Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 1, 2007 Moderator Share Posted April 1, 2007 If the vaccum gauges do flutter, there is a knurled knob on the pipe which needs tightening up till the fluttering stops. this acts as a damper due to the engine characteristics and is normal on all bikes. checking my manual, the carbs are the same as the 400 but have different sized jets, so you need to ask them for a 360 kit. the 360 has; 135 mains, 0.6 air jet, 4FP21-3 jet needle, X-6 needle jet, needle position 3, pilot jet 17.5, starter jet 40. air screw 1 to 1.5 turns out from stop. send them an email, as they have tons of stock. if they don't have any try NRP in Manchester UK! Link to comment Share on other sites More sharing options...
apathetic Posted April 3, 2007 Author Share Posted April 3, 2007 If the vaccum gauges do flutter, there is a knurled knob on the pipe which needs tightening up till the fluttering stops. this acts as a damper due to the engine characteristics and is normal on all bikes. checking my manual, the carbs are the same as the 400 but have different sized jets, so you need to ask them for a 360 kit. the 360 has; 135 mains, 0.6 air jet, 4FP21-3 jet needle, X-6 needle jet, needle position 3, pilot jet 17.5, starter jet 40. air screw 1 to 1.5 turns out from stop. send them an email, as they have tons of stock. if they don't have any try NRP in Manchester UK! wow youre great thanks for the help at this point i still am going to try a couple more things before i start ordering parts im going to go buy a gallon of carb cleaner and soak the entire thing for at least 24 hours (minus the diaphrams) my only question is other than the diaphrams, are there any other rubber parts that should be removed? also, i cant figure out how to remove the jets. the floats are easy, and so is the float needle and the seat the float needle sits in. but other than those, i cant find anything to unscrew. what am i missing? i also need to try replacing the points (as soon as i get a right, i have a left) and checking the gap (which i can do now anyway) possibly valve timing too once again, i need to thank you for your help. you kick arse. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 3, 2007 Moderator Share Posted April 3, 2007 I don't recommend soaking in solvent as there are rubber bits in the choke mechanism. what you need to do is get them vapour blasted ( for looks) and then ultrasonic cleaned. I use jrs in Uk but you will have to do a google search if your in the USA. these will come out ultra clean and JRS even replaced the parts of the carb with my keyster kit and built it up for me! approx £100 for ultrasonic clean. Link to comment Share on other sites More sharing options...
apathetic Posted April 6, 2007 Author Share Posted April 6, 2007 I don't recommend soaking in solvent as there are rubber bits in the choke mechanism. what you need to do is get them vapour blasted ( for looks) and then ultrasonic cleaned. I use jrs in Uk but you will have to do a google search if your in the USA. these will come out ultra clean and JRS even replaced the parts of the carb with my keyster kit and built it up for me! approx £100 for ultrasonic clean. ok now that the weekend has arrived i once again have time to work on my bike i spent what little time i had this week getting more familiar with these carbs i can basically rebuild the entire thing now with my eyes closed although that doesnt necessarily mean i know what each part does anyway i cleaned the entire thing as well as i could on my own while inquiring where i can send them to be sonic cleaned if need be i woke up early this morning and put the carbs back in and i just got back and had some time to tinker with the bike basically i had initially opened the throttle screw until the butterflies were closed that way i could tighten them (therefore opening the butterflies) little by little until i found the perfect idle initially the bike did not start at all (with closed butterflies) eventually when they opened up enough i still encountered the same ongoing problem the bike just revs to 4k and stays there it idles better with the choke partially on but thats no way to run a bike all the time so this is what i did i took the spark plugs out the left one was black (too rich) and the right one was gray (it is my understanding that this is a good thing) i cleaned the plugs and then i counted how many turns of the pilot screw it took to close the left one and applied the same many turns out on the left one i must have done something wrong because then the right one was black and the left one was gray so i closed them both and opened them up 1 full turn then i started the bike and each time i turned them each 1/2 turn until the bike seemed to rev fine i now messed with the idle screw until it found a happy place now the bike seemed to rev and idle fine so i pushed the bike up the alley to the street (the alley is a hill, this may prove to be an important factor) now i am on a level surface as soon as i turned the bike on it revd to about 3.5k give or take 0.5k i was sad and pushed the bike back to its spot in the alley i dont know why the bike seemed to perform fine on the hill and not fine on a flat surface the only thing i think it could affect is the float levels but i dont know why the floats would mess with the idle then again im not carb genius at this point i believe that it is a mixture problem whether its the position of the pilot screws (which i understand adjusts the mixture, i think closed is lean and open is rich) or the position of the idle screw (although at times it seems not to make a difference and always revs at 4k) or a faulty choke (it seems to work fine to me but once again im not carb genius) through the process of elimination i come to the conclusion that this is the problem can you help me drewpy? /hail /salute /thanks Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 7, 2007 Moderator Share Posted April 7, 2007 the pilot system affects the lower rev range to 4k 'ish and the mains take over. The galleries in the carbs are very small and even after i cleaned them they were still blocked. that is why i ended up sending them away to be cleaned. the reving you encounter is a weak mixture in the pilot system, but any tweaking of the screw will not overcome the reving. BTW its 1.5 turns from the bottom. Another fault i have found is the pilot screws snapping off at the bottom due to wear of the brass and hamfisted tighteneing (an interference fit into a conical seat) you can check by completely removing the pilot screws and they should have a really fine needle on the end, if they are "dumpy" ie rounded then the end has snapped off, this has happened on both sets of carbs i have had! the float height is very important:- yamaha say 26.6 +/- 2.5mm using a venier caliper, measure the distance of float arm from the top of the float chamber gasket seat (no gasket) to the top of the float. (the float should be resting on, but not depressing the spring loaded inlet needle) bend the tang to achieve level amont both right and left floats have to read the same. Drewpy Link to comment Share on other sites More sharing options...
apathetic Posted April 7, 2007 Author Share Posted April 7, 2007 wow... youre awesome! thank you!! i guess ill take my carbs off, again... Link to comment Share on other sites More sharing options...
jakwi Posted May 31, 2007 Share Posted May 31, 2007 Hey there, I have pretty much the same bike doing pretty much the same thing, but I've come to the conclusion that it's the intake carb boots/holders as when I spray starting fluid on the boot while the engine is running it revves up. Did you every figure out what was going on with yours? Jason hello im a noob and i need help any help would be much appreciated i recently bought a 1977 xs360 i rode it home and it gave me no problems the next day it started having hesitation and choking issues while it was in gear and at speed this problem continued to get worse until the bike no longer ran the previous owner told me to replace the spark plug wires and points i spliced in new wires and boots i installed new spark plugs i installed a nos condenser i removed the carbs and cleaned them (although i had no idea what i was doing, i reassembled them correctly, i at least know this for sure) one thing that should be noted is that the one of the needle valve assemblies (the little needle with the spring inside that touches the float) is more springy (stiff) than the other i am not sure if this causes problems or not but i thought it was an important item to mention also when i cleaned the carbs i did not have a manual i just took apart what looked easy to take apart and cleaned it with carb cleaner i am 100% sure i reassembled the carb correctly as i read the manual afterwards and had luckily done all the right steps the bike now runs there are still a number of problems at idle, the motor would rev to 4000 and stick i eventually got it down to 1200 by adjusting the idle screw if i revved the bike, the revs would stick to however high i opened the throttle i somewhat fixed this problem (once again with the idle screw); it still persists although not as bad the real problem is after getting it into gear, i get the same hesitation and choking problem i had before after reading a haynes shop manual, i believe that i have to sync the carbs, but i am not sure the manual has instructions on how to sync the carbs, but they are hard to follow apparently i have to get a pair of vacuum gauges hook one to the hose that goes from the carb to the backside of the petcock and the other to the same corresponding hose on the other carb (this hose is connected to nothing and plugged with a bolt) and then adjust some screw i cant find until both gauges read 5 hg cm while the motor revs at 1200 is what i have talked about a common problem? have i diagnosed the problem correctly? is a carb sync the next step? is there an issue with how i described the needle valve assembly? did i describe the carb sync process correctly? i still need to do the points the previous owner gave me 2 points but they are 2 lefts i need to order a right thank you for your time thank you for your help your time is much appreciated Link to comment Share on other sites More sharing options...
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