1980 won't rev over 4000 rpm

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stingrayboxing

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First off, let me start by saying I love my xs650. It is my first bike and I got it for $150 as a project. Anyways, I had it running good, until the alternator rotor went out and I had to replace it. The bike was then running great. I then took it for a short trip, about 30 miles each way. When I was on my way back (it sat for about an hour after riding it there), I lost any acceleration and power. The bike will not go over 3500-4000rpm's. I have replaced the spark plugs, the compression is not bad, somewhere around 150 on one side, and 143 on the other side, checked and adjusted the valves. Like I said, this is my first bike and I have been learning and doing everything on my own...(with help from my clymers and this site) (thanks everyone btw!) But I am puzzled and clueless.

Thanks in advance for any suggestions!
 
charging good now? battery ok? volts at battery at 2-2500rpm? must have a good power supply on these. cheers
 
thanks guys.
yes, the charging is good now.
as for the carb diaphrams, when I lift them and cover the hole they just stay up, maybe come down like 1/4 of the way and stop...when I remove my thumb they come the rest of the way down. Is that correct?
 
i was getting the same deal with a spare am working on, it would start and idle like a champ but would breakup with some RPM. compression was about 140 for both. put lil oil in chamber compression went to 180. took Pamcopete's advise and put eye dropper full of restore in from sparkplug hole, smoke like a champ for a few min. but runs great for now.
 
retiredgent: I don't have a timing light, but am looking at getting one asap....
wacobrian: when I added the oil the compression jumped to 170 on the lower side and 190 on the higher side...
also, noticed the exhaust valve cover on lower side was loose...idk if that had anything to do with anything, but the problem was occuring before I had checked the clearance, so not sure...
 
i was also having some issues with the advance weights one was too tight ones from mikes are too loose, got it working good but still stumbing. i know the carbs are on the money just pulled them off black beauty. i had another motor doing about the same thing it turned out to be the valves not seating
 
weekendrider: thanks! went out and unhooked the wire to the brush and it ran like a charm! The headlight didn't work, but I assume they are connected somehow, which would explain why the headlight indicator light kept coming on...now I just have to figure out how exactly and find the time to fix the problem...
 
update: got a new magnet put on and she runs good! just have a little carb tinkering and she'll be ready to go!
 
On your bike the headlight gets turned on b y the safety relay at the same time it cuts power to the starter. It is controled by ther voltage on thne yellow wire from the stator. When you unplugged the reg/rec you stopped the voltage on the yellow wire. It will work right after you plug the reg/rec back in.
Leo
 

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