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Jul 19, 2014 20:52:00 GMT -5
Post by katmol on Jul 19, 2014 20:52:00 GMT -5
I'm haveing trouble with my "new to me" 1975 XS650. When I bought it the right cylinder would not idle. It would kick in arould 2500 rpms and run ok, but when just cruising at 50 mph or less the right side would just kind of gurgle. Under power it ran good. Me and a very experienced mechanic went through everything for about 6 hours today. Timing, valves, points, carbs... The previous owner had rebuilt the carbs a while ago and told me the right cylinder ran rich, Boy does it! When it idles for a short time the right side smokes like crazy and when I pull the plug it's soaked with gas. We took both carbs down a dozen times. The previous owner had saved all the factory carb parts when he rebuilt them so we put them back to stock. The needles in the rebuitd kit that he had used were about 1/8" shorter then the stock ones. After we put them back together the left ran GREAT, better then with the rebuild kit parts but the right side ran the same. I'm at my wits end. Anybody ran into this before? I'm begining to think the right carb has a cracked passage somewhere. That being said, I guess I'm looking for a right carb body for a '75 XS if anybody's got one laying around. Thanks...
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Jul 20, 2014 9:19:22 GMT -5
Post by grizld1 on Jul 20, 2014 9:19:22 GMT -5
Yes, I've run into that kind of thing before, and so has anyone who's spent much time reviving old motorcycles. Did you and your very experienced helper inspect float levels? Did you check the floats themselves to be sure they haven't sprung leaks and turned into sinks? Did you bench test the right side carburetor to find out if the float valve (needle and seat) is sealing?
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Jul 20, 2014 11:28:19 GMT -5
Post by katmol on Jul 20, 2014 11:28:19 GMT -5
Yes, I've run into that kind of thing before, and so has anyone who's spent much time reviving old motorcycles. Did you and your very experienced helper inspect float levels? Did you check the floats themselves to be sure they haven't sprung leaks and turned into sinks? Did you bench test the right side carburetor to find out if the float valve (needle and seat) is sealing? Hey grild1, we checked everythng concerning the floats I believe. They seemed to be good. Fuel level looked good, valve was working fine. My mechanic friend noticed the float in that carb was collapsed a little but it still seemed to work fine. He's been working on Jap bikes for 60 years and he said it looks like someone has put compressed air to the carb to try and clear it out. I didn't tell him it was me. Anyway, I think we may swap te floats in the two carbs and try that.
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Jul 22, 2014 11:48:39 GMT -5
Post by madmax on Jul 22, 2014 11:48:39 GMT -5
Not sure if this is applicable to '75's but it's worth mentioning.....
Are you running vacuum operated fuel taps? If so, it's possible for the diaphragm in the tap to fail allowing fuel to be sucked down the vacuum pipe and straight into the intake, result is a waaayyy rich mixture.
Max
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Jul 23, 2014 18:08:30 GMT -5
Post by grizld1 on Jul 23, 2014 18:08:30 GMT -5
No vac petcocks before 1978, and those won't install on earlier tanks due to wider centers. Anything's possible, but the PO would have had to change the tank and install carb boots with vac barbs to run the late taps.
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Jul 28, 2014 4:16:55 GMT -5
Post by katmol on Jul 28, 2014 4:16:55 GMT -5
Yes, I've run into that kind of thing before, and so has anyone who's spent much time reviving old motorcycles. Did you and your very experienced helper inspect float levels? Did you check the floats themselves to be sure they haven't sprung leaks and turned into sinks? Did you bench test the right side carburetor to find out if the float valve (needle and seat) is sealing? Hey grild1, we checked everythng concerning the floats I believe. They seemed to be good. Fuel level looked good, valve was working fine. My mechanic friend noticed the float in that carb was collapsed a little but it still seemed to work fine. He's been working on Jap bikes for 60 years and he said it looks like someone has put compressed air to the carb to try and clear it out. I didn't tell him it was me. Anyway, I think we may swap te floats in the two carbs and try that.
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