Zach_J
XS400 Member
Hi everyone,
My name is Zach, and my father and I just picked up our first project bike, an early XS400. Im not 100% sure what year/ model it is, as it seems it has some conflicting equipment on it. I know it is an early bike because it has wire wheels and drum brakes, but it also has electric start w/ the kick backup. I was under the impression that teh "economy" models with drum brakes didn't come with electric start. It has ~7800 miles on the ODO, but the speedo cable broke some time before we got it so who knows if that is acurrate or not.
I did have a few questions about the carburetors though. I am fairly mechanically inclined, since I have 3 years experience as an Audi Technician, however bikes and carbs are somewhat new territory for me. (The downside of growing up and working in an age of EFI)
This bike seems to have a few quirks to it, which I'm pretty sure are fueling/ carb related. The bike fires right up, and seems to settle into a nice idle around 750rpm(im guessing, the Tach is not functioning right now either) after a few minutes of warm up. However once it gets warm, it starts backfiring and popping at idle every 100rpm or so. If I give it some gas it seems to rev up just fine, but then settles into an idle aruond ~2200rpm and won't drop below that, even if I snap the throttles open then closed(they do seem to be closing, and not hanging up on anythign.)
To me the first issue sounds like either the pilot jet is clogged, or the main jet/ both jets are wrong. Does anyone know what size the stock jets are? I can find the parts online, but it doesn't list a specification with them. I do live at altitude, approx 5300ft above sea level, which could have an effect on what size jet it should have. Anyone have any ideas to help me out? As far as I know the bike is stock, with the black plastic airboxes and chrome exhaust (which looks factory to me). My father and I do eventually want to put a 2-1 exhaust and Air filter pods on it, which im sure will affect what size jets we should put in it.
Thanks for all your help. I am stoked I found this forum. I will try to post a picture later tonight when I get home from work.
-Zach J
My name is Zach, and my father and I just picked up our first project bike, an early XS400. Im not 100% sure what year/ model it is, as it seems it has some conflicting equipment on it. I know it is an early bike because it has wire wheels and drum brakes, but it also has electric start w/ the kick backup. I was under the impression that teh "economy" models with drum brakes didn't come with electric start. It has ~7800 miles on the ODO, but the speedo cable broke some time before we got it so who knows if that is acurrate or not.
I did have a few questions about the carburetors though. I am fairly mechanically inclined, since I have 3 years experience as an Audi Technician, however bikes and carbs are somewhat new territory for me. (The downside of growing up and working in an age of EFI)
This bike seems to have a few quirks to it, which I'm pretty sure are fueling/ carb related. The bike fires right up, and seems to settle into a nice idle around 750rpm(im guessing, the Tach is not functioning right now either) after a few minutes of warm up. However once it gets warm, it starts backfiring and popping at idle every 100rpm or so. If I give it some gas it seems to rev up just fine, but then settles into an idle aruond ~2200rpm and won't drop below that, even if I snap the throttles open then closed(they do seem to be closing, and not hanging up on anythign.)
To me the first issue sounds like either the pilot jet is clogged, or the main jet/ both jets are wrong. Does anyone know what size the stock jets are? I can find the parts online, but it doesn't list a specification with them. I do live at altitude, approx 5300ft above sea level, which could have an effect on what size jet it should have. Anyone have any ideas to help me out? As far as I know the bike is stock, with the black plastic airboxes and chrome exhaust (which looks factory to me). My father and I do eventually want to put a 2-1 exhaust and Air filter pods on it, which im sure will affect what size jets we should put in it.
Thanks for all your help. I am stoked I found this forum. I will try to post a picture later tonight when I get home from work.
-Zach J