infbearing Posted May 1, 2009 Share Posted May 1, 2009 Hello anyone, please help. My XS360 is bogging down over 60MPH, basically loses all power. I had my bike dyno'd and it is running real rich all the way and then at the very end way way lean, it just drops off. A local shop told me that it probably shouldn't go over 60mph anyway, which I think is BS. Anyone know a good mechanic in Atlanta, GA area who can get the carb straight? Thanks! Link to comment Share on other sites More sharing options...
JimR Posted May 1, 2009 Share Posted May 1, 2009 Hello anyone, please help. My XS360 is bogging down over 60MPH, basically loses all power. I had my bike dyno'd and it is running real rich all the way and then at the very end way way lean, it just drops off. A local shop told me that it probably shouldn't go over 60mph anyway, which I think is BS. Anyone know a good mechanic in Atlanta, GA area who can get the carb straight? Thanks! Hi, so doing the translation the bike is rich at low RPM & weak at high rpm ? which may indicate a few problems .. I guess you adjusted all service items to the spec and found the bike did not perform ? (XS360's would do about 90 uk mph). If you have not done the setup it would be good to start with a wet & dry compression test (in order to work out if the engine internals are fine), then check that the timming & dwell angle are correct then move to the carbs .. UK XS400/360's had awful carbs ... the mix screws could be broken with them being screwed in too hard, the rubber bungs covering the jets falling out or just falling to bits causing all sorts of mid range/high speed problems. i repaired a brand new bike back in 79 (with low milage) with a brand new set of carbs, which after looking at the old set it would appear the above problems. To dyno a bike of this age may not give a correct picture (I guess you used an up to date Dyno) as the old fashioned carbs will give different results to modern FI bikes. So the bike may supply a very rich result under certain conditions but bear in mind that this may not be an error condition and you may need to wind back from modern tech. Regards Jim Link to comment Share on other sites More sharing options...
infbearing Posted May 1, 2009 Author Share Posted May 1, 2009 Hi, so doing the translation the bike is rich at low RPM & weak at high rpm ? which may indicate a few problems .. I guess you adjusted all service items to the spec and found the bike did not perform ? (XS360's would do about 90 uk mph). If you have not done the setup it would be good to start with a wet & dry compression test (in order to work out if the engine internals are fine), then check that the timming & dwell angle are correct then move to the carbs .. UK XS400/360's had awful carbs ... the mix screws could be broken with them being screwed in too hard, the rubber bungs covering the jets falling out or just falling to bits causing all sorts of mid range/high speed problems. i repaired a brand new bike back in 79 (with low milage) with a brand new set of carbs, which after looking at the old set it would appear the above problems. To dyno a bike of this age may not give a correct picture (I guess you used an up to date Dyno) as the old fashioned carbs will give different results to modern FI bikes. So the bike may supply a very rich result under certain conditions but bear in mind that this may not be an error condition and you may need to wind back from modern tech. Regards Jim Jim, thank you for your feedback. The bike overall runs fine, it idles well, starts very easily and in general doesn't seem to have any major problems. Although I have not done and further tests as far as the compression or timing, I'm not smart to those things and really don't know a lot about the mechanics of motorcycles or cars for that matter. I do want to learn though. The biggest thing is that it just tends to "cut out" anywhere from 4000-6000 rpms, lower rpm's are fine. As far as the dyno it was a modern dyno and on the print out the bike did not have any problems until it go over the 4,000 rpm mark and at that point is when it was completely lean, before then it was rich. The mechainc said it need to be re-jetted. Is this something i can do in a weekend with some patience, does that sound like the problem? Link to comment Share on other sites More sharing options...
yoda Posted May 1, 2009 Share Posted May 1, 2009 First it could be fuel starvation, so clean the tank out and the petcock and lines. Secondly, if you have diaphragm carbs, it could be caused by a hole in the diaphragms. What ever it is, it most certainly is fuel problems. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 1, 2009 Moderator Share Posted May 1, 2009 4k is when the main jet kicks in, have you cleaned the spray bar holes? have a look here as it gives good tips Link to comment Share on other sites More sharing options...
JimR Posted May 2, 2009 Share Posted May 2, 2009 4k is when the main jet kicks in, have you cleaned the spray bar holes? have a look here as it gives good tips Hi Drewp, what happens in this case with the rubber jet covers missing ? this may show a rich miture when the main jet takes over, but if the motor/carbs are not healthy (diaphram issues etc) there may be extra issues in order to fix the bike. with that section is clean (main jet) there is a posibility that ancilary carb componets take over, but without assuring that the engine is sound there is little that can be done with the carbs... It may be quite easy to diagnose that problem but if the rest is in poo order you could be wrong and may spend loads of time diagnosing the wrong problems.. we need to know if the motor is in exact Yamaha health if not ... you do a bodge thing if not the motor needs to be std Regards Jim Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 2, 2009 Moderator Share Posted May 2, 2009 Hi Drewp, what happens in this case with the rubber jet covers missing ? this may show a rich miture when the main jet takes over, but if the motor/carbs are not healthy (diaphram issues etc) there may be extra issues in order to fix the bike. with that section is clean (main jet) there is a posibility that ancilary carb componets take over, but without assuring that the engine is sound there is little that can be done with the carbs... It may be quite easy to diagnose that problem but if the rest is in poo order you could be wrong and may spend loads of time diagnosing the wrong problems.. we need to know if the motor is in exact Yamaha health if not ... you do a bodge thing if not the motor needs to be std Regards Jim I agree the rest of the bike should be as spec, just adding to that really. what is/are rubber jet covers? the only rubber i have are the diaphrams and the choke boot! Link to comment Share on other sites More sharing options...
JimR Posted May 3, 2009 Share Posted May 3, 2009 I agree the rest of the bike should be as spec, just adding to that really. what is/are rubber jet covers? the only rubber i have are the diaphrams and the choke boot! Hi Drewps this will be P/n 93210-03142-00 part 5 on the parts book illustration which lives which lives on the Nozzle Main (2A2-14941-06-00) part 6 as per illustration .... I should have said o ring but it was trying to give it a location within its description rather than just o ring Regards Jim Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 3, 2009 Moderator Share Posted May 3, 2009 Hi Drewps this will be P/n 93210-03142-00 part 5 on the parts book illustration which lives which lives on the Nozzle Main (2A2-14941-06-00) part 6 as per illustration .... I should have said o ring but it was trying to give it a location within its description rather than just o ring Regards Jim yep I can see it now. I thought the 360 had the same carb as the 400 but it has the O ring like the 250 carbs Link to comment Share on other sites More sharing options...
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