Domo
XS400 Member
My bike will not run consistently. I get it running a few days, then the idle degrades until it wont run long enough to make it more than a block or two of riding.
I'm out of ideas, and the only thing I can find wrong with my bike, is the left exhaust pipe. The bike always seemed weak on the left exhaust. The right side was always pumping healthy, but the left side was always weak, backfired, and sputtered when I shut er down. The baffle plate blew off in a backfire while I was riding, no idea where it is. Now somethings rattling around inside, and the bike runs really loud.
I've checked timing, compression, and tested for vacuum leaks and nothing ever shows definitive signs of trouble. I always fix/tighten everything I check anyway, but nothing ever shows any sign that it would be the problem. And the problems persist regardless.
Would a bad muffler cause the idle to degrade over time. Or, cause ANY issues with the carbs?
The only thing that fixes it, is either cleaning the carb, or re-syncing the carb. I do both each time, so I cant tell if its just one OR the other. But that gets it working..for a few days. Something is causing it to go out of sync. But, Im jumping ahead a little bit. Read on, I explain more..
An important thing to note as you read this post is; This has been happening, almost like clock work, for a few months. I am determined to fix this problem, but I need help diagnosing it, as nothing I've tried has worked.
It always SEEMS to work, for a few days. But it never lasts, and its usually as soon as I start thinking, its finally solved.
Here's my story.
What's happening to me is, I clean the carbs in the oxidization tank over night, then blow everything with compressed air. Every hole. Every jet. Then, I repeat. Despite the fact I've pulled these things, cleaned them, and SEEM to have fixed the problem by cleaning them. I have yet to see even the tiniest, microscopic suggestion of any dirt, grit, or grain. I wear a jewler eyepiece to inspect the jets as I go. They are ALWAYS, spotless. And each time, I resync the carbs afterwards.
Install them. They run like an effing top (can we swear here?) for about 4-5 days.
Then, it stops idling high on the most open choke if I stand the bike up from its side stand. The next day it doesn't high idle with any choke at all, side stand or upright. It just idles low. The fact that the choked idle changes at first whether the bikes is tilted or upright is strange, isnt it? Dont focus on this TOO much, as far as I can tell, its only happened once. Its more about the choke in general.
Next, the idle is messed completely. It starts to hang really high. I can feel the carburetor "coughing." Maybe not getting enough air. And if I adjust it, it takes several turns before it makes any changes, and all that happens is, its either too high, or too low. No inbetween. Just stall, or 4000 RPM idle.
This is always within a week of getting it running. Every time, it starts great, runs great for a few days, then within a day or two all this happens.
I have replaced the air filters (new OEM), float bowl gaskets, and some of the jets. I've re-routed my throttle to make sure its free from being pulled on turns.
My floats are not stock. Nor are they from an xs400. When I bought the bike, it had different floats in it, from an xs650. They are set to the manuals reco'd settings for float height, and I've read online that they're compatible with the xs400. I just received OEM floats, but I have yet to put them in.
So thats it. Clean the carbs, nothing comes out, at all. Re-sync, runs fine a few days. Slowly gets worse over the next 2 or 3. Then it barely runs, if at all.
Something is causing it to slowly degrade, and since the carbs seem to stay clean when I clean them, I can only start assuming the problem lies elsewhere.
Ive changed spark plugs a few times, the only thing they were telling me at the time, is that its running too rich.
remember, I've checked a lot of things. And nothing points to any hint of a problem. Im probably forgetting a few other things I've checked or tested, so Im open to suggestions still. I'll just say whether I've checked it, and how thoroughly I did so.
Oh, I also checked all fuses, and the battery. Both were 100%.
One more thing. Today as I pulled up to my house, and stalled. I noticed some white smoke coming out of my left airbox. I opened it and checked inside. Spotless. Could have been exhaust? Left side is the troubled side.... although the smoke was white.
I have a new 2-2 MAC exhaust in the mail, and need to install my OEM floats. Until then, I am WIDE open to any and every suggestion, or question.
Help me xs400.com, you're my only hope.
I'm out of ideas, and the only thing I can find wrong with my bike, is the left exhaust pipe. The bike always seemed weak on the left exhaust. The right side was always pumping healthy, but the left side was always weak, backfired, and sputtered when I shut er down. The baffle plate blew off in a backfire while I was riding, no idea where it is. Now somethings rattling around inside, and the bike runs really loud.
I've checked timing, compression, and tested for vacuum leaks and nothing ever shows definitive signs of trouble. I always fix/tighten everything I check anyway, but nothing ever shows any sign that it would be the problem. And the problems persist regardless.
Would a bad muffler cause the idle to degrade over time. Or, cause ANY issues with the carbs?
The only thing that fixes it, is either cleaning the carb, or re-syncing the carb. I do both each time, so I cant tell if its just one OR the other. But that gets it working..for a few days. Something is causing it to go out of sync. But, Im jumping ahead a little bit. Read on, I explain more..
An important thing to note as you read this post is; This has been happening, almost like clock work, for a few months. I am determined to fix this problem, but I need help diagnosing it, as nothing I've tried has worked.
It always SEEMS to work, for a few days. But it never lasts, and its usually as soon as I start thinking, its finally solved.
Here's my story.
What's happening to me is, I clean the carbs in the oxidization tank over night, then blow everything with compressed air. Every hole. Every jet. Then, I repeat. Despite the fact I've pulled these things, cleaned them, and SEEM to have fixed the problem by cleaning them. I have yet to see even the tiniest, microscopic suggestion of any dirt, grit, or grain. I wear a jewler eyepiece to inspect the jets as I go. They are ALWAYS, spotless. And each time, I resync the carbs afterwards.
Install them. They run like an effing top (can we swear here?) for about 4-5 days.
Then, it stops idling high on the most open choke if I stand the bike up from its side stand. The next day it doesn't high idle with any choke at all, side stand or upright. It just idles low. The fact that the choked idle changes at first whether the bikes is tilted or upright is strange, isnt it? Dont focus on this TOO much, as far as I can tell, its only happened once. Its more about the choke in general.
Next, the idle is messed completely. It starts to hang really high. I can feel the carburetor "coughing." Maybe not getting enough air. And if I adjust it, it takes several turns before it makes any changes, and all that happens is, its either too high, or too low. No inbetween. Just stall, or 4000 RPM idle.
This is always within a week of getting it running. Every time, it starts great, runs great for a few days, then within a day or two all this happens.
I have replaced the air filters (new OEM), float bowl gaskets, and some of the jets. I've re-routed my throttle to make sure its free from being pulled on turns.
My floats are not stock. Nor are they from an xs400. When I bought the bike, it had different floats in it, from an xs650. They are set to the manuals reco'd settings for float height, and I've read online that they're compatible with the xs400. I just received OEM floats, but I have yet to put them in.
So thats it. Clean the carbs, nothing comes out, at all. Re-sync, runs fine a few days. Slowly gets worse over the next 2 or 3. Then it barely runs, if at all.
Something is causing it to slowly degrade, and since the carbs seem to stay clean when I clean them, I can only start assuming the problem lies elsewhere.
Ive changed spark plugs a few times, the only thing they were telling me at the time, is that its running too rich.
remember, I've checked a lot of things. And nothing points to any hint of a problem. Im probably forgetting a few other things I've checked or tested, so Im open to suggestions still. I'll just say whether I've checked it, and how thoroughly I did so.
Oh, I also checked all fuses, and the battery. Both were 100%.
One more thing. Today as I pulled up to my house, and stalled. I noticed some white smoke coming out of my left airbox. I opened it and checked inside. Spotless. Could have been exhaust? Left side is the troubled side.... although the smoke was white.
I have a new 2-2 MAC exhaust in the mail, and need to install my OEM floats. Until then, I am WIDE open to any and every suggestion, or question.
Help me xs400.com, you're my only hope.