M8 goes into limp mode.

hmm...could it be starving of fuel after 15 seconds..??.. smart valve issues in the tank,letting enough fuel for the first burst and then not enough to sustain it..
is it cold out..??..you put any gasline de-icer in..??

ps...if ya ever get a few extra bucks get rid of that servo and cable and get STM valves...

Arctic Power Valve
(APV) System
NOTE: The servo will activate once at APV cycle
RPM. If the servo cycles three times, cable length
adjustment or valve inspection is required.
NOTE: The 800 cc and 1000 cc have a three-stage
exhaust valve system. The stages are closed, midopen,
and full-open. Each model has a designated
RPM at which the system is synchronized and
checked by the ECU for proper operation. This
occurs once each time the engine is started. The
800 cc system is checked at 4800 RPM and the
1000 cc system is checked at 6100 RPM (Crossfire/
F-Series) or at 6270 RPM (M-Series).

APV Position/RPM
Engine Valve Position Cycle RPM
600 cc Full-Open 7300 (Low Alt)
7400 (High Alt)
800 cc Mid-Open
Full-Open
60-6500 (Low/High Alt)
78-8100 (Low/High Alt)
1000 cc Mid-Open
Full-Open
6300 (Low/High Alt)
6500 (Low/High Alt)




Arctic Power Valve
(APV) System
NOTE: The servo will activate once at APV cycle
RPM. If the servo cycles three times, cable length
adjustment or valve inspection is required.
NOTE: The 800 cc and 1000 cc have a three-stage
exhaust valve system. The stages are closed, midopen,
and full-open. Each model has a designated
RPM at which the system is synchronized and
checked by the ECU for proper operation. This
occurs once each time the engine is started. The
800 cc system is checked at 4800 RPM and the
1000 cc system is checked at 6100 RPM (Crossfire/
F-Series) or at 6270 RPM (M-Series).
APV Position/RPM
Engine Valve

The Arctic Power Valve (APV) System adjusts the size
of the exhaust ports to produce maximum horsepower
on the top end while providing excellent low end
power and increased touring fuel economy.

ENGINE MODEL CENTER ± 1 mm (0.039 in.)
600 cc 36.0 mm (1.417 in.)
800/1000 cc 35.0 mm (1.377 in.)


THEORY
Two-cycle engines and their exhaust systems are
designed to produce maximum horsepower in a given
RPM range. This RPM range will change according to
how high (or low) the exhaust port is in relation to the
cylinder. Engines designed for racing have a “high
port” exhaust system and will produce more horsepower
at higher RPM but only with the loss of low end
power and overall fuel economy. “Low port” engines
will produce maximum horsepower in the low RPM
ranges and provide good mid-range fuel economy, but
they sacrifice top end performance.
The APV system does not increase engine horsepower,
but it does allow the engine to be designed for maximum
top end horsepower without the losses associated
with a “high port” exhaust system.
735-476B
COMPONENTS
The main components of the APV system are the following.
A. Lighting Coil
B. Chassis Control Unit (CCU)
C. ECU
D. Servomotor
E. Power Valve Cables
F. Power Valves
NOTE: On these models, the traditional regulator/
rectifier has been replaced by a chassis control
unit.





Servomotor Test
Care must be taken not to contact the servo yellow,
orange, or black/white terminals, or damage to the
potentiometer circuit will result

NOTE: A 12-volt battery and test leads will be
needed for this test.
1. Remove the servomotor from the snowmobile.
2. Contact the red/black servo terminal with the battery
positive lead; then contact the black/red servo
terminal with the battery negative lead.
3. The servo should rotate when the negative lead
contacts the black/red terminal. Note the direction
of rotation.
4. Reverse the connections on the servo terminals:
positive lead to black/red and negative lead to red/
black. The servomotor should rotate in the opposite
direction.
5. Install the servomotor.
NOTE: If the servo operates correctly in the
above test but fails to operate when connected to
the ECU/CDI at the designated RPM, proceed to
Potentiometer Test.
Potentiometer Test
NOTE: The following test should be made using
MaxiClips (p/n 0744-041) and the Fluke Model 73
Multimeter (p/n 0644-191) set to the ohms scale.
1. Remove the servomotor from the snowmobile.
2. Connect the red maxiclip and meter lead to the
black/white servo terminal; then connect the black
maxiclip and meter lead to the yellow servo terminal.
3. Rotate the servo pulley counterclockwise. The
ohms should increase as the pulley is rotated until
it reaches 4700-5000 ohms.
4. Continue the pulley rotation, and there will be a
small area in the rotation at which the ohm reading
will disappear; then it will return again.
5. Continue the pulley rotation, and the ohms should
appear at a very low value but will again increase
to 4700 ohms. This is normal operation.
6. Install the servomotor.
NOTE: If the servo operates correctly and the
potentiometer test is correct but fails to operate
when connected to the ECU/CDI at the designated
RPM, replace the ECU/CDI

i think the new style is the piston stlye which is an improvement over the bellow...you might notice a bit crisper throttle but the real advantages is the poor performance from cable and servo issues being eliminated..

as well you can adjust the stm for an earlier opening if you want to help bring down temps in mid range if its an issue...but they do come preset and very easy to adjust..

the smart valves are removed through your tank filler neck as a unit and can remain hooked up for inspection...they are a water impervious membrane covering something like a oneway snap disc valve...and maybe you have the valves not opening properly or two out of the three are staying closed...even moisture and not ice can restrict flow as the moisture can impede the membrane..many people have found that removing the fuel from the tank fixed furl delivery issues just because of accumilated moisture over a period of time..

i strongly recommend you go to alpha sports/oregon trail sports/country cat...etc and look at the parts breakdown diagrams for your year sled they offer to really see the smart valve as an assembly etc...the diagrams are valuable tools if your somewhat unfamiliar with some things..

actually it doesn;t hurt to check your pump pressure as well

i would just buy/borrow a cheap guage 0-60 pounds for liquids and put a "T" just as the pressure line comes out of the tank..put a short piece on the T from the tank and the stock line downstream branch and the guage on top...you should have 40 plus pounds running..then just rehook stock line to tank fitting..



.

Before you throw out the baby with the bath water try

unhook boonie box and drive it a little, don't get stupid as it might be lean, the b box can get goofy, have bad connection, be junk

wire your valves open and let power valve motor cycle aginst return springs, ride gently, see what happens

make sure clutching is ok.......secondary bushings in place, weights free and moving, belt deflection/ clean, broken springs ?

while in the area check left side motor mounts

just had to replace a bad ecu on M8, checked lots of possibilites, then tried spare box, yup, just bad electrics.

pipe sensors can cause poor running just as pipe begins to warm up

CATSLEDMAN1 said:

Before you throw out the baby with the bath water try

unhook boonie box and drive it a little, don't get stupid as it might be lean, the b box can get goofy, have bad connection, be junk

wire your valves open and let power valve motor cycle aginst return springs, ride gently, see what happens

make sure clutching is ok.......secondary bushings in place, weights free and moving, belt deflection/ clean, broken springs ?

while in the area check left side motor mounts

just had to replace a bad ecu on M8, checked lots of possibilites, then tried spare box, yup, just bad electrics.

pipe sensors can cause poor running just as pipe begins to warm up

Click to expand...

yikes...didn't notice he had a controller..

RobertTrivanovic said:

Ill defenitly check that out and try to pull out and clean those valves. But I do think it is a servo issue as Iv pulled the plugs numerous times and the sled isnt running to lean. Also STM valves are cheaper $480 Vs a new Servo directly from cat $550 so I would for sure be getting the STM valves... If I know for sure the Servo is the issue.

Click to expand...

if you ever do run into parts needed...lots of servo's cheap in swapmeets...etc..wish you was closer..i have spare ecu/ccu/pipe sensors etc....where are you anyway...any sleds close to swap a part to try..??

RobertTrivanovic said:

If it is the servo ill be getting STM valves to eliminate the possibility of this happening again. Might as well do it right the first time!
Also either you or CATSLEDMAN1 how much is a ECU going to cost if thats needed?

Click to expand...

i bougfht my spare for 300 bucks on swapmeet..it will cost you an arm and leg for new..see if it does end up an issue first and then we can try and help ya out..

your lights working..??...you do have a fuse at the ccu you know...a shorted wire can cause running issues as well...bad spots for these sled to short are tail light wiring..either at back of sled or under tank...reverse and SERVO wiring under fuel tank (they cross from mag side above brake rotor under tank to pto side)..back up alarm from side to side under tank...
and coil wires ar often pinched under tank just behind steering post..

when i went with stms all my wiring came out from under tank and coiled nicely on mag side..

i will pm you my email..i will maybe have time later tomorrow evening to look at it..and i can repost it possibly here...or do you have youtube and you just post youtube link..??