03 Viper Missing at high rpm on one cylinder

01sxr700

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Joined
May 9, 2001
Messages
285
Age
73
Location
Thunder Bay, On.Ca.
As the title says the pto cyl is missing on high rpm, runs good at low and mid range. Checked plugs all good.
Fresh rebuild on engine top end.
Compression is 120/120/105, The one cyl is low because of the lower compression ratio on the pto cylinder.
Dry/wet compression test same result.
Interchanged coils to check coil, same problem.
Full throttle run, shut the engine off with throttle wide open and the pto plug is wet and the others are dry and brown.
Do the same thing at mid range and all the plus are dry and brown.
Checked the crank seal with starter fluid and no change in rpm.
Checked carbs/clean, and because the plug is wet it would indicate its getting fuel.
Checked for grounding out of wire from CDI to coil all indicate good.
Reeds are good
Power valves operating the same.

Anyone have any insight to my problem?
 

These carbs vent into the airbox so make sure all the hoses and fittings are in good condition, especially for that cylinder.
Is the machine completely stock?
 
So I put it back together after moving the reeds to the center cylinder and cleaning the pto carb. Now it runs like a champ, the only other thing I did was unplug and replug in the cdi to check the wires going to the coils for a short to ground. Go figure. On another note anyone know which weight goes non the inner hole of the clutch weight. Machine is revving at 9,000.(I remove a the rivets when it wasn't getting the proper rpm not realizing it wasn't firing at high rpm). The manual says one thing and the tech page on the site say another.
 
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