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Mberg9000

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  1. Good news! I finally found some time today to set up a strobe and check the timing. It was more retarded than it should have been, firing about halfway in between the LF and LT mark. I advanced it as neccessary, and it runs fine now, even better than it did before! Thanks for the help, drewpy especially. You're the man!
  2. I took some photos of my timing module just to be clear about what I'm doing: The Haynes manual said that it was first necessary to match the left cylinder timing up with the LF mark on the rotor by loosening the two screws (top right and bottom left in the pictures, kinda hard to see) and rotating the whole timing unit. They then said you need to set the right cylinder timing with the RF mark by rotating an "inner" section of the timing unit accordingly. In my case, there is NO RF mark on the rotor. (There IS an RT mark... I don't know if it's relevant, but I posted the photo anyways.) I assume that since the left and right points can't be adjusted seperately, just the LF mark is to be set at the appropriate point? Is there any method of setting this without using a strobe? If not and I buy (or find) a strobe for this purpose, what is the method exactly? By the way, thanks again for all of the replies. It's really great to have such practical and knowledgeable help, especially when I'm learning all of this for the first time.
  3. I picked up a Haynes manual from my local library today and checked a few things out. I opened the cover for the timing points (one of the screw heads was very stripped, somebody has obviously been in there before...). Inside was not the adjustable mechanism that the Haynes manual detailed, but instead a round black plastic unit with fixed points built in. I also opened up the circular observation panel on the left side of the engine. The LF marker appears to line up properly with the firing point/cam shaft, but the marker for right cylinder lines up when the points are almost past each other. I don't know if this is a bad thing or not, but I didn't think rotating the entire black plastic unit was a good idea. I also checked the valves by opening up the four "observation ports" underneath the gastank on the top of the engine. Unfortunately I didn't have the proper feeler gauges to reach down and check the gaps (I only have straight feeler gauges, something with a 90 degree bend would be needed for that). Just by moving the valves around though, they didn't seem to have an unusual amount of play (or a lack of ANY play for that matter). I checked the fuel filter; no problem there. I also checked the sparkplugs, which also appear to be fine. I guess the next thing on the list would be to dismantle the carb? Hopefully it's easier than it sounds...
  4. Thanks for the reply drewpy. I'm hoping that it really IS just some small basic problem. But my lack of experience with bikes especially makes it difficult for me to know where to check for all of these things. Ignition timing, for example. How would I go about checking that? What exactly do you mean by "valves gapped"?
  5. Hello everybody! This is my first post and I'm hoping that I will find some good advice. To start, I'd like to thank everybody in advance who gives me any information. I am by no means very knowledgeable when it comes to bikes... I'm pretty green. But I do have SOME mechanical knowledge, as well as a well equiped garage at my disposal. Ok, so here's the problem: I bought a 1981 Yamaha XS400 Special last summer. It worked without any problems for 4 months last summer and for the majority of this summer as well, except recently there has definitely been somthing wrong with it. When idling, it will occasionally "die" for about half a second. The engine will lose most power, the RPM needle will dip down getting further and further each time, and the neutral light will flicker a bit as a result. Sometimes it takes several minutes before this starts happening, and sometimes it happens about every five seconds. Regardless, it eventually does it more and more frequently until it dies completely. Also, when starting the bike cold the engine "putters" more than it has in the past and acts a bit jumpy. A friend thinks it may be backfiring through the carbuerator. When driving the bike in higher RPMs than an idle there are no signs that anything is wrong. In my effort to find out what's wrong, I think I've ruled out a few potential areas. I've charged the battery and have even run the bike with the battery charger attached and running; the problem persists. I have checked the air filters; they seem relatively clean to me, and I've blown them out just to make sure. I've also tried some spray-in carb cleaner into the air intake on the carbeurators, but there was no noticeable difference at all. The problem persists regardless of where the petcock is. Has anybody had a similar problem? Does anybody have any ideas what the problem might be? Is it a timing issue? Is it not recieveing enough fuel? A wiring issue? Would it help if I created a short video of the symptom? Any help is really, truly appreciated. Thanks!
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