Author Topic: Need help with 1975 Yamaha XS500B  (Read 1070 times)

Offline da-mack

  • Posts: 1
Need help with 1975 Yamaha XS500B
« on: Sep 05, 2011, 16:04:51 »
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.

Offline joea

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  • Posts: 688
    • cafe' racers
Re: Need help with 1975 Yamaha XS500B
« Reply #1 on: Sep 12, 2011, 05:08:23 »
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