Today for the first time I took the bike for a little spin, the motor fired up on the first kick full choke, I let it warm up and took the choke off it seemed to idle Ok but the left exhaust pipe was cold when I took it for a little ride maybe a quarter mile at 15mph,i got back and it was firing on both cylinders (both pipes nice and hot, I was thinking maybe the pilot jet, but I let it idle and it continued to fire on both, my thought was on idle fuel flows through the pilot then at higher rpm it uses the main jet, correct? But it always does this, fires only on the right side, then I sit it on the center stand and goose the throttle and eventually it fires on both, Wtf? It's so dam cold here I think I need to get this thing out on the high way and just fly, clean it out maybe, also I removed both carbs and really meticulously cleaned them per the write up I found here, that's on other thing I have never torn apart a carb, I had the bike for a few weeks before I cleaned them, I was intimidated to dismantle them, so any noobs out there don't be afraid it was really easy, just take your time!
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Left piston not working
- Thread starter Nate7504
- Start date
Tombo
XS400 Addict
My first guess would be that the carbs are still dirty (ask me how I know). Pay special attention to the jets. Took me 3 tries before I got the carbs clean enough to tune on this bike, before that it wouldn't run on both cylinders at start up. After that it ran poorly, but at last both cylinders were firing. Pay special attention to the the jets, especially the needle jet. All 16 holes need to be perfectly clean.
You got a fuel filter yet?
flying on this bike in this state will not fix your problems, I promise
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You got a fuel filter yet?
flying on this bike in this state will not fix your problems, I promise
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Yes I put one on, a universal inline type, now that I think about it I didn't remove the tube that the main jet sits in, the one with all the small holes, I removed the jet and the washer but didn't want to force it out the top, so I left it and just sprayed cleaner in it. I only lightly tapped it, would not budge so I let it alone.
Tombo
XS400 Addict
There's your problem. No bullshit, give yourself an hour just for the cleaning part, spend the entire hour, scrub. Spraying air and carb cleaner is not enough. Its part off the process, but the scrubbing is what its important. Rob the strings off a guitar our but wire scrubbers, make sure the passage of each jet, every single one is immaculate. You won't regret it, but if you do another half assed job, you probably will. You got this thing boy! 
Cheers
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Cheers
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Ok so tore it all apart, cleaned it, then took it for a ride everything ran very well, but I noticed it takes a while for the engine to return to normal idle after I let off the gas,? It's now running smoothly and both cylinders are working now, just takes a while to return to 1200rpm
Tombo
XS400 Addict
Nice! Good to hear you made a difference. You need to sync carbs, set timing, set idle mixture screws. I am also thinking you might have an air leak causing the bike to run lean. Run a leak test with starter fluid or butane our propane before you get to tuning.
Did you set the float heights while you had the carbs off? Mine were way lean when I got the bike, common because if a misprint in the manual
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Did you set the float heights while you had the carbs off? Mine were way lean when I got the bike, common because if a misprint in the manual
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Turn your idle mixture screws out more. You're either a little lean in the idle circuit or the pilot jets/circuit is still dirty.
Some of the later models have o-rings under the idle mixture screws that can deteriorate and cause issues with idle if they are not replaced.
Some of the later models have o-rings under the idle mixture screws that can deteriorate and cause issues with idle if they are not replaced.
Tombo
XS400 Addict
They are the flathead screws on both carbs in the topside next to where the intake boots connect. Turn them slowly to the right until they come to the stop. Be careful that you don't tighten them, just enough that they stop moving. Now back them out 2.5 turns, see how that does
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Tombo
XS400 Addict
They are brass
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You can turn the idle mix screws while the carbs are on the bike, but cutting the caps off may be difficult. I'd probably pull them off. Get used to it! You're not going to get off that easy
YES. There should be clamps on the carb boots! Without clamps they could actually pop right off the engine.
YES. There should be clamps on the carb boots! Without clamps they could actually pop right off the engine.
The clamps may solve your problem alone. That does look like a pilot screw to me, but I have a different model of carb. Mine looks different. There will be one on each side though and it is very likely that they are on the side near the carb boot facing the sky/gas tank.
you guys are awesome thanks a lot both of them are only turned out one and a half turn so I reset them to 2&a half, I also put some hose clamps on it seems to idle a lot better now, what affected them only being out one and a half turns have on the bike?
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Tombo
XS400 Addict
Great news! Did the revs start acting normal after gas let off?
Depending on the jetting if the bike, it could have made you're bike run lean (which based on your description, seemed to be the case). Turning them another turn to the left allows moregas to flow at idle.
Nice work dude, keep on looking for gremlins using this forum, you will find them, and with diligence you will have that bitch riding awesome
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Depending on the jetting if the bike, it could have made you're bike run lean (which based on your description, seemed to be the case). Turning them another turn to the left allows moregas to flow at idle.
Nice work dude, keep on looking for gremlins using this forum, you will find them, and with diligence you will have that bitch riding awesome
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Sorry I chimed in too late on this thread glad you got it running and figured your problem out.
A while back I had a problem with my bike cutting out on one cylinder,come to find out even though the plugs were new one of them was bad.My bike had flooded several times cause of a sticking float.I took the carbs and fixed that problem,then I removed the spark plugs.One of them was wet,so as soon as I changed it problem solved.
A while back I had a problem with my bike cutting out on one cylinder,come to find out even though the plugs were new one of them was bad.My bike had flooded several times cause of a sticking float.I took the carbs and fixed that problem,then I removed the spark plugs.One of them was wet,so as soon as I changed it problem solved.
