Motorcycle Repair: 73 RD350 fuel problem, yamaha rd350, weisco pistons

Question
I have a 1973 Yamaha RD350 which I picked up with a burnt hole in the left piston.  I smoothed out the cylinder and put in stock pistons and rings in.  I had it running good but it was smoking a lot.  Turns out the left piston did not seal properly and was covered with oil when I took it back apart.  I decided to go another route and bought new Weisco pistons and rings (4th over) and picked up a set of used cylinders which I had bored, etc.. I put the engine back together but could not get it started.  It was not getting gas for some reason.  If you put gas into the cylinder it would start briefly.  The carbs were pulled off a cleaned but it still does not seem to be getting any gas. There is gas in the fuel line and in the carb bowl but the gas is not getting into the cylinders.  Everything (except for the excessive smoking) worked fine before until I put the Weisco pistons in.  What did I do wrong? What am I missing? Any help would be appreciated.

Answer
Hi Brad,

First, sorry for the delay in responding to your question. I usually reply with in a couple of hours. My sucky ISP is causing problems. Soon to have a cable connection.

Have you measured cylinder compression? If so, what were the results? If not, do so and advise.

Wiseco makes quality pistons. A very good choice.

Do you have the RD350LC?

I recommend starting with the gas tank and trace/watch fuel flow. Verify that gas is flowing to the float bowls. If so, is gas passing thru jets? Are the intake reeds in good condition and properly installed? Are piston rings properly installed (printed sides up)?

I suspect the compression is low and not creating enough vacuum to draw fuel up thru the carbs and into the crankcase. So , do the compression test and we'll go from there.

Send replies to my email address: mcso429@netzero.com

Respectfully,
Mark Shively