2007 M8 Misfire that alternates cylinders

BennyX

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2007 M8 with Aerocharger 53, Dobeck Box
950km

Symptoms:

-Sled starts and runs on one cylinder at high idle (3200rpm +/-)
-Depending on the amount of fuel pressure (tweaked by partially clamping fuel return line) , sled will alternate which side is running, as indicated by Digitron & IR thermometer. Generally runs terribly and rpms will climb randomly while idling.

Things that have been checked
- compression
- power valves (cleaned and adjusted)
- reeds (replaced with new)
- fuel pump pressure and flow
- regulator pressure tweaked between 38 psi to 44psi
- ECU replaced
- visual inspection of electrical wiring
- coils
- stator
- spark plugs
- Dobeck box unplugged

Any help is greatly appreciated.
 
Last edited:

mountianguy

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2007 M8 with Aerocharger 53, Dobeck Box
950km

Symptoms:

-Sled starts and runs on one cylinder at high idle (3200rpm +/-)
-Depending on the amount of fuel pressure (tweaked by partially clamping fuel return line) , sled will alternate which side is running, as indicated by Digitron & IR thermometer. Generally runs terribly and rpms will climb randomly while idling.

Things that have been checked
- compression
- power valves (cleaned and adjusted)
- reeds (replaced with new)
- fuel pump pressure and flow
- regulator pressure tweaked between 38 psi to 44psi
- ECU replaced
- visual inspection of electrical wiring
- coils
- stator
- spark plugs
- Dobeck box unplugged

Any help is greatly appreciated.

Crank seals possibly. Try spraying ether or any flammable around the seals to see if the rpm changes. If you have a leak it should speed up.
 

Lund

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Its definitely an air intake issue. For a 2 stroke to run at high speed like that is always related to too much air not enough fuel.
I would disconnect the turbo and stick the original pipe back on and see if it settles down. It almost sounds like the wast gate is stuck.
 

BennyX

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Just finished leak down test. Engine as a whole, holds pressure. Cylinder to cylinder leaks heavily.

Upon further research, apparently the centre crank seal isn’t made smog rubber and doesn’t seal completely. Can someone confirm this?
 
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