Need help with 1975 Yamaha XS500B


New Member
We got the bike a month or so ago. It would start but would not idle. If rpm went below 2500 it would die. I rebuilt the carbs and replaced some seals. Bike would start and run a bit better but still had problems staying at idle. I got it to stay at an idle by means of keeping the choke open a bit. Doing this, the bike would take a long time for rpm to come down to idle after reving engine. The carb mount boots look good.
So next I tried to adjust the timing according to the service manual. The left cylinder points seemed tostart to open when the F mark was far to the right of the indicator. I did the procedure like the manual said and got the points to open right around the F mark. It seemed that I had to move the breaker plate as far as I could in one direction to get there though. Now the bike doesn't fire at all. The point gaps are fine.


Coast to Coast
make sure you have the correct cyl(pts) for timing set max open to aprox .014" to verify tdc for a cyl watch inlet valve open and then close and then that piston rises to max height-aprox tdc- i use a plastic tube from a spray bottle(rigid but will not cause damage) ......if you need to pull the choke to idle you more than likely missed cleaning/opening orifices passages jets etc, in the low speed circuit

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