rrperry001 Posted June 22, 2010 Share Posted June 22, 2010 My 1975 Yamaha RD 250 worked fine when i got it two summers ago. While on a road trip my head light got dim and the engine eventually died. I let it sit for a few minutes and restarted it. At that time the headlight was bright and it worked fine, i made it the 100 miles home. However the next day i started it and it ran for about 20min and died. I tested the output going to the battery and there is not voltage going to it. I can charge the battery and the bike runs fine till the voltage drops to amount 5.5v. The local shop charges 85 bucks an hour and doesn't usually work with vintage bikes. Electrical parts for this bike costs up to 500 dollars. I am an engineering student and am component with electrical systems and monitoring equipment. I just have no idea where to start(i obviously checked the fuses and looked for any obvious shorts. I did get caught in the rain on this trip but it didn't quit working till the ride home a week later. Help please! the bike is basically worthless as it now is. It is in mint condition with only 6000 miles and is a blast to ride. Link to comment Share on other sites More sharing options...
Moderator mervin Posted June 23, 2010 Moderator Share Posted June 23, 2010 My 1975 Yamaha RD 250 worked fine when i got it two summers ago. While on a road trip my head light got dim and the engine eventually died. I let it sit for a few minutes and restarted it. At that time the headlight was bright and it worked fine, i made it the 100 miles home. However the next day i started it and it ran for about 20min and died. I tested the output going to the battery and there is not voltage going to it. I can charge the battery and the bike runs fine till the voltage drops to amount 5.5v. The local shop charges 85 bucks an hour and doesn't usually work with vintage bikes. Electrical parts for this bike costs up to 500 dollars. I am an engineering student and am component with electrical systems and monitoring equipment. I just have no idea where to start(i obviously checked the fuses and looked for any obvious shorts. I did get caught in the rain on this trip but it didn't quit working till the ride home a week later. Help please! the bike is basically worthless as it now is. It is in mint condition with only 6000 miles and is a blast to ride. aircooled rd club is your friend here join us, it sounds to me like the brushes on the generator maybe worn out possibly the reg rec packed up which is a known weak point on the B models Merv Link to comment Share on other sites More sharing options...
rrperry001 Posted June 27, 2010 Author Share Posted June 27, 2010 aircooled rd club is your friend here join us, it sounds to me like the brushes on the generator maybe worn out possibly the reg rec packed up which is a known weak point on the B models Merv I fixed it this weekend and that was the problem. I have been asking people for years and no one suggested the brushes, so i just started taking it apart and found one completely gone. When i replaced it, it worked however the surface it rubs on was coming unattached in some places and was probably the cause of the brush wearing out so much more quickly then the other one. Any idea for a good fix for this problem? Link to comment Share on other sites More sharing options...
Moderator mervin Posted June 27, 2010 Moderator Share Posted June 27, 2010 You mean the rotor slip ring that the brush runs on?? 2 things spring too mind 1st and mosr expensive see if you can get it rebuilt somehow , 2nd see if you can get a good secondhand rotor, merv Link to comment Share on other sites More sharing options...
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