4x4van Posted March 4, 2011 Posted March 4, 2011 I have a 1985 BW200 that is driving me crazy. It will run for 5-10 minutes, then suddenly die. No amount of kicking will restart it, choke or not, gas or not, nothing. If I shut the fuel petcock off, drain the carb bowl, then turn the petcock back on...it will restart immediately and run fine again. 5 minutes later...repeat the process. I've disassembled and cleaned the carb, no change. I've tried putting the jets, needle, etc. from a different carb in mine and it still has the problem. But if I put the entire different carb (from my brother's BW) on mine, it solves the problem. It almost seems like it is getting an air bubble somewhere that fuel can't get past. Draining the float bowl & starting over solves the problem, but only temporarily. Could the float level be causing the prob? Too high or too low? And if so, how can I set the float level? I can get a whole new carb on eBay for about $50, but it's a cheap knock-off, and I'm not sure if I want to chance it. On the other hand, a new carb from Yamaha is more than I can spend right now. Any suggestions?
Moderator DirtyDT Posted March 4, 2011 Moderator Posted March 4, 2011 Floats or main jet sticking. Fuel usage is greater than fuel getting into the carb. Carb cleaner and bowl off.
4x4van Posted March 4, 2011 Author Posted March 4, 2011 Floats or main jet sticking. If the float was sticking in the "up" position (needle valve closed), the the bike would be running out of fuel. But the float bowl is full, and requires a full draining before the bike will restart. If the float was sticking in the "down" position (needle valve open), the carb would be overfilling and fuel would be running out of the overflow tube. That isn't happening. A main jet has no moving parts to "stick", and there is no debris clogging it. Fuel usage is greater than fuel getting into the carb. Carb cleaner and bowl off. If the fuel usage was greater than fuel getting into the carb, then the float bowl would be empty and sitting for just a minute or so would refill it and allow it to restart. But it will not restart at all untill float bowl is completely drained, no matter how long you wait. The carb has already been completely disassembled and cleaned.
Moderator Airhead Posted March 4, 2011 Moderator Posted March 4, 2011 what about vacuum? runs for 5 mins as vacuum gradually builds then stops? fuel starvation? open the gas tank filler try again...blocked vent? Draining the bowl will release vacuum but fuel will still be there, vacuum with oppose the vacuum developed in the manifold. Also check the carb vent is clear.
4x4van Posted March 7, 2011 Author Posted March 7, 2011 what about vacuum? runs for 5 mins as vacuum gradually builds then stops? fuel starvation? open the gas tank filler try again...blocked vent? Draining the bowl will release vacuum but fuel will still be there, vacuum with oppose the vacuum developed in the manifold. Also check the carb vent is clear. Vacuum...hmmm...Definitely something to look into. I'll double check gas cap vent and the carb vent. Also going to disassemble the entire carb (again) and soak for 24-48 hours in Seafoam. Maybe I missed a clogged passage somewhere the last time I cleaned it. Was out in the desert this weekend and still had the problem, checked the floats but there is really no way to adjust the float level. When it does run, it seems to run better with the choke part way on (first "click"), as if it's running lean. Funny thing is this; if I leave the carb bowl drain open so that fuel is pouring out of the bottom of the carb, it will run fine. But once that drain screw is closed, 30 seconds to a minute later it dies and requires a carb drain again to restart. Hmmm...does sound a bit like a carb vent issue, doesn't it? OK, well that gives me a direction to pursue, at least. Once I get a chance to dig into it again, I'll post back with results or lack thereof. Thanks for the tips.
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