Matt N Posted May 14, 2009 Share Posted May 14, 2009 I've got a 1980 yamaha RS 125 and its totally dead. When i first got it it worked fine but now there doesn't seem to be any life in it at all. I replaced the battery and kicked started it and it sound like it was going to turn over and then after that nothing. I tried bumping it for ages but no luck! I know the bike has got some bad earths and I was thinking about replacing the entire loom as I can get a 2nd hand one on the cheap. As I'm not very clued up with bikes so is there anything I should look for, change etc? Also is the battery 6v? Any help or tips would be greatly appreciated? Here's a picture of my bike: Link to comment Share on other sites More sharing options...
JimR Posted May 14, 2009 Share Posted May 14, 2009 I've got a 1980 yamaha RS 125 and its totally dead. When i first got it it worked fine but now there doesn't seem to be any life in it at all. I replaced the battery and kicked started it and it sound like it was going to turn over and then after that nothing. I tried bumping it for ages but no luck! I know the bike has got some bad earths and I was thinking about replacing the entire loom as I can get a 2nd hand one on the cheap. As I'm not very clued up with bikes so is there anything I should look for, change etc? Also is the battery 6v? Any help or tips would be greatly appreciated? Hi Matt, first off the bike does not need a battery to start, the only wires you need to be concered with are the black/white thro the loom & main switch. It would be good to test for a spark using the following method :- 1) remove the spark plug 2) make sure the main switch is in the on position 3) put the plug into the cap and earth it against the cylinder/cylinder head 4) kick the motor over you should have a nice blue spark between the plug electrodes if not the following might help :- remove the plug & cap & push the ht lead between the cylinder fins & kick the bike over again .. if at this point you get a spark the cap and/or plug are suspect If no spark at this point, obtain a DTI and check that the points open @ 1.8mm btdc, the best method of doing this is to put a fag paper between the points and make sure that @1.8mm btdc the fag paper can be withdrawn with small resistance (the points are opening). If the above is correct then look at the carb, clean it out and make sure the internal drillings (holes) in the carb body /float chamber are clear. If it still refuses to start at this point you will need to to remove the the cylinder (or check the compression) to ensure this part of the engine is ok. Regards Jim Link to comment Share on other sites More sharing options...
Matt N Posted May 15, 2009 Author Share Posted May 15, 2009 Thanks for the write up Jim, that's been really helpful. I did what you said and placed the spark plug near the cylinder head and there was no spark at all. Im going to buy a new plug and cap to see if that eliminates the problem. My dad checked the compression last night and he said it seems fine. If its still not working after I change the plug and cap I will clear out the carb and then look into changing the loom as it looks like a very simple one. Thanks again for your help mate, much appreciated Matt Link to comment Share on other sites More sharing options...
JimR Posted May 15, 2009 Share Posted May 15, 2009 Thanks for the write up Jim, that's been really helpful. I did what you said and placed the spark plug near the cylinder head and there was no spark at all. Im going to buy a new plug and cap to see if that eliminates the problem. My dad checked the compression last night and he said it seems fine. If its still not working after I change the plug and cap I will clear out the carb and then look into changing the loom as it looks like a very simple one. Thanks again for your help mate, much appreciated Matt Hi Matt, I would look at the ignition timming as I would guess that to be the most likley cause ! Regards Jim Link to comment Share on other sites More sharing options...
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