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    1982 XS400 - right cylinder dies after a few seconds

    If it's not the petcock filter than it can be the tube that connect the valve in the petcock to the right cylinder boot that is between the cylinder and the carburetor. This tube transfer the vacuum created by the piston to the valve in the petcock and opens it so that the fuel can go down to...
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    1982 XS400 - right cylinder dies after a few seconds

    Please, tell us if that was the issue so that the next person going through the same problem can find its answer here!
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    1982 XS400 - right cylinder dies after a few seconds

    Hi Rob. Yes, it is safe to run the bike on prime; just don't forget to close it after riding otherwise, the pressure can force the fuel in the carbs and fload them. The problem you have is simple: the petcock filter is cloged and does not let enough fuel to the carbs and since the left carb is...
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    1980 Yamaha XS400

    As tstidham said, valve adjustment has to be verified. Be careful because this engine has a 180 degrees crank and it is possible to try to adjust the valves when the engine is not on compression stroke TDC; you should be able to move the rocker up and down with your finger. Also, maybe first...
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    battery

    A car battery (the type that we use on our bikes) is designed to give a short but high burst of electricity to energise the starter motor (because it needs it!). If you use only the kick start, then you can use a smaller battery. I would make sure, though, that the alternator does not send more...
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    1982 XS400 - right cylinder dies after a few seconds

    Is it possible that the tube between the 2 carbs would be partially blocked? That way, the bowl would be emptied while you run and slowly refill when you stop!
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    RPM not going back down

    I prefer to have my mirrors attached closer to the steering stem because the further you are from it, the more amplitude the vibrations will have, buzzing the image even more. But you could find a way to use the mirror stem to make it heavier to reduce the vibrations....
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    RPM not going back down

    That's what I thought!
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    RPM not going back down

    Almost. I have some pops when I close the throttle but I believe that it will be easy now to prevent them since the pilot screw is only 1 1/2 turn out!
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    RPM not going back down

    Here is a copy of the drawing done with Google SketchUp (free); the black pieces are rubber seals that are expanded in the handlebar tube by the nut (the white end round piece - plastic) and bolt (steel) that squeeze them when tightening so that the assembly stays inside the bar. The bolt goes...
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    RPM not going back down

    Somebody (I can't find who!) told me to balance my carbs, that it would make a huge difference. I did. And the effect is humonguous! This bike has never felt like that before. It accelerate much more strongly, even in 6th at 3500rpm! No more problem of the rpm not gong back fast enough and this...
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    RPM not going back down

    Original air filters
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    RPM not going back down

    I have visually balanced them but I will check with my vacuum testers which might give me interesting infos. Also, I want to swap the air filters to see if it makes a difference...
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    RPM not going back down

    kebabs: The only problem I had when I decided to open the carbs was starting when the engine was cold. It would start with only one cylinder (the left) until the revs would reach 2,500; then the second one would come in and after 30 secs, it would idle perfectly. Other than that, it was working...
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    RPM not going back down

    tstidham, I checked and rechecked the passages and the jets and they are all free flowing. I can spray brake fluid and see it spaying out at the right place. The problem is not there. I thought that it could be caused by the rubber cap on the pilot jet inlet that would prevent fuel from entering...
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    RPM not going back down

    I am done with it for this year! Too many other things to do before the snow covers the land (normally, it begins by mid october and stays from mid-novemeber to end of april!). I was working the two carbs together to adjust it and, just to see, I completely screwed in the pilot screw on the left...
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    RPM not going back down

    Thanks, Kebabs. Those infos are precious as they will help me understand what is going on. I rode my bike again and things didn't go so well so I am back to changing the float height again. I have read this article...
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    RPM not going back down

    So the problem was that the idle adjustment screw has been set very high to compensate for the pilot jet which was not set properly. I reajusted the idle adjusment screw to have a minimal idle then adjusted the pilot jet unscrewing it until the rpm stop raising and then brought back the idle...
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    RPM not going back down

    Good to know! Thanks. One thing, though: the bike only had a starting problem; other than that, it was running just fine!
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    RPM not going back down

    carb holders are brand new! Vacuum hose and cap have been verified. No change to the bike; it is all original. I will shoot compressed air at the pivot of the butterfly (which, by the way, is barely opened while the adjustment screw is full in!). I remember one detail: when the engine spins...
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