98 500 rotory valve help

[rockymountainking2004]

A friend of mines 98 formula DL 500, is running really bad, and he told me that last year he and another guy took the motor apart to replace the pistons,and they did not know how to put the valve back in the right spot. In some positions it would not even run he said, then they found a notch that worked and he took it home. I think it must be off a tooth or so, but I am a polaris guy and dont know much about the older rotory valve motors.

It gets to about 6000 rpm and then the power drops off, and starts kinda sputtering. On a stand with no load on the motor it runs fine.

Also, he said they put a small chip in it the size of a pencil tip in it, but I dont think that would hurt it

Just thought someone coule throw some advice my way, and could tell me how to get the timming specs, and how to set the timming on it.

 

[rockymountainking2004]

Ttt

 

[Skidoo xtc]

According to my Specification booklet on the 98 500 motor it should open at 135 degrees and close at 64 degrees.

I copied this out of the shop manual

ROTARY VALVE TIMING
To correctly install rotary valve, proceed as follows:
– Turning crankshaft, bring MAG side piston to
Top Dead Center.
Use a dial indicator (P/N 414 1047 00).
2. MAG piston at TDC

A degree wheel (P/N 414 3529 00) is required to
measure rotary valve opening and closing angles
in relation with MAG side piston. Degree wheel
will be installed on rotary valve shaft for measurements.

For the following instructions, use these specifications
as an example:
OPENING: 132° BTDC
CLOSING: 52° BTDC

Proceed as follows:
– Turning crankshaft, bring MAG side piston to
Top Dead Center as done before with a crankcase
having a ridge.

– For opening mark, first align 360° line of degree
wheel with BOTTOM of MAG side inlet port.
Then, find 132° line on degree wheel and mark
crankcase at this point.


For closing mark, first align 360° line of degree
wheel with TOP of MAG side inlet port. Then,
find 52° line on degree wheel and mark crankcase
at this point.

Position rotary valve on shaft splines to have
edges as close as possible to marks.
NOTE: Rotary valve is asymmetrical. Therefore,
try turning it inside out then reinstall on splines to
determine best installation position.
Apply injection oil on rotary valve before closing
rotary valve cover.