79yz400 Posted May 20, 2007 Share Posted May 20, 2007 Hey guys, Im new to this whole thing. A little over a year ago I picked up an older Yamaha 400, believe it's a YZ from what I've seen, though I am unsure of what year it is. To make a long story short I bought it off the guy for cheap, because it had a blown head gasket. I purchased the new head gasket, installed it properly according to a little bit of help I got from a motorcycle mechanic at the shop. I put some new fuel in it mixed with some nice synthetic 2 stroke oil. It took a while, but it ended up starting, very excited the first time I heard it run. However this was short lived, the bike was idling very high, so I adjusted one screw, believe it was the air screw, and brought the idle down. I than took it for a little ride. As I was riding it, I punched the throttle, but the bike didn't seem to go anywhere, just revved up?? I continued driving and all of sudden the throttle was stuck, in a panic I hit the kill switch....nothing. The bike was hitting its rev-limiter or something. So the first thing that came into my mind was clutch, and gear up, did this and dropped the clutch, stalling the bike. I was now officially afraid of the bike, it was the first time I've ever ridden a bike... I was a little disappointed but the guy did mention something about throttle sticking, so it wasn't something I didn't know, I just didn't think that it would happen right away. I than proceeded to pull the carb off, and try to possibly untwist the thottle cable. I than also (for some stupid reason) thought it would be a good idea to fool around with the screws on the carb. Now the bike doesn't start It's been about 6 months since I've touched it, not having or making much time for it. I think it needs new clutches, and new plugs, but I don't know how to tune the carb. Is there anybody out there that can tell me what to set the carb at, so that it will at least start?? or should I just bring the bike to a bike shop?? And is there anything I can do about that kill switch not working?? Thanks guys, hope someone can help me Brian Link to comment Share on other sites More sharing options...
derwood Posted May 25, 2007 Share Posted May 25, 2007 Well.. for the spark plug.. pull it out and go at it with a wire brush. For the carb.. twist both screws out until they almost come all the way out.. but not off the threads... it's quite the process.. but give them a half or qaurter turn in.. then try and start it. and keep doing this till it starts. Tired of kicking it over? go up a slight incline.. my DT 400 will bum start in 2nd gear.. I bet your bike will to. so yeah.. if you get tired of kicking and kicking.. just roll it down the hill in second.. pop the clutch and see if she starts. Also.. as for the throtle sticking.. pull the carb right out.. open it up.. make sure the needle is going all the way down.. if not.. or it looks dull.. some very fine grit sandpaper will put the point back on it.. but be super careful to do it evenly. that's all I can think of for the problems you mentioned. Also.. if there's any way you can get your hands on a compression gauge.. check the spec's for your bike.. and see if the compression is good. You may need new piston rings. So yeah before doing any of that.. check the compression first. Hope that helps. -Derwood. Link to comment Share on other sites More sharing options...
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