1991 Yamaha WR500 & 1991 Yamaha 650 Lx issues - PWC Forum: The best hang-out for Personal WaterCraft enthusiasts
 
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post #1 of 5 (permalink) Old 06-04-2018, 09:03 PM Thread Starter
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1991 Yamaha WR500 & 1991 Yamaha 650 Lx issues

The 500 I can get running and it seems to run good, but if I shut it off I can't get it running again. It fires right up on the trailer as well, but in the water struggles a little initially.

The 650 will start on the trailer. Once in the water I can't get it to fire.

The were both filled up with marine grade mixed gas and had the plugs changed.

I did a compression test on both of them and took pics of the new plugs

500 I got readings of 130 & 115
650 I got readings of 120 & 10

In the pics the red stripe is the 500. Red, black and gray is the 650

What are some ideas what I should try?
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post #2 of 5 (permalink) Old 06-05-2018, 06:47 AM
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Compression is low. Should be in the 145 range and only a 10% variance max.
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post #3 of 5 (permalink) Old 06-05-2018, 08:01 AM Thread Starter
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Quote:
Originally Posted by rodsatheart View Post
Compression is low. Should be in the 145 range and only a 10% variance max.
Ok. So new pistons and rings? I'm more interested in fixing the 650 right now. Would I be better off looking for another motor or a rebuild kit?
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post #4 of 5 (permalink) Old 06-05-2018, 08:34 AM Thread Starter
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Also why will the 500 start on the trailer but struggle in the water? Battery?
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post #5 of 5 (permalink) Old 06-06-2018, 06:28 AM
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Low idle, low speed mixture screw not adjusted right, low compression.
Idle should be about 1100rpm out of water. Do not use the mixture screws on the side of the carb to set idle speed. The idle screw is on the throttle shaft.
Both engines need to be rebuilt.
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