Motorcycle Repair: Gas/oil mixture, oil mixture, premix

Question
Chris,
     Hi, I just bought a 1983 Yamaha YZ490K, in excellent condition I might add. The service manual says to use Yamalube "R" at 24:1. Is this too much oil?. Also, I have an exhaust leak where the pipe meets the cylinder but the manual says this is typical of these bikes. It says to put high temp silicone around the area. The thing that consurnes me is the amount of premix oil pissing out from the leak. Does this indicate that I need new rings or will this happen anyway.

                                     Thanks,
                                      John

Answer
Hi John.
 24:1 is not a big mix.  I have seen and ridden bikes that require a 50:1 mix.  As far as what the manual says in that regard, follow the manual.  It was written by the factroy, so it is correct.

If you are getting excess oil spitting out, then make sure that it is the premix and not engine oil.  If it's engine oil, then new rings may well be in order.  If it is premix, then you could be looking at a problem with insufficient spark, valve gap and/or ignition timing or (and least likely) the fuel/oil not mixing properly and staying mixed.

Check those and see what you get.
Good luck.
FALCON