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16 XM 800 ETEC Lost Compression

wanderingleif

Member
Lifetime Membership
Nov 6, 2011
57
11
8
Bozeman MT
New to the ETEC's, picked up a 16' with 2400 miles. As far as i could tell it ran like a top! Rode it twice no problem lots of power. Found it has a exhaust leak at the manifold to head due to a missing bolt made appropriate repair and 20 miles into Cooke City lost all compression on the Mag side. Plug looked a little oily but not covered with metal fragments or anything. I have not torn it down yet. Looking for any input or thoughts to start me in the right direction. Thanks
 
S

sledsrock

Well-known member
Nov 26, 2007
1,826
510
113
Grand Junction, Co.
A leak down test before you open it up would be the most proper way to start. If it were me, I’d drop a borescope down in the spark plug hole and see what things look like or just pull the head and look.
 
F
Nov 26, 2007
584
153
43
Minnesota
Check fuel pressure. The fuel pressure regulator can dis-lodge from the housing causing a drop in fuel pressure which can possibly lead to a lean condition. While you are at it, replace the fuel filter. I am going to assume you verified all 8 Y-Pipe bolts are in place after repairs.








The drain what fuel you can and replace with fresh along with a bottle of iso to eliminate possible water in the fuel.




Finally, when the piston is out, take a pic and post it.
 

wanderingleif

Member
Lifetime Membership
Nov 6, 2011
57
11
8
Bozeman MT
All y-pipe bolts present and accounted for. I assume your suggesting possible low fuel pressure could cause the cylinder to burn down? I'm gonna open it up this weekend. I'm guessing ill find either a stuck ring or cylinder lining that has been worn away? I've worked on cars/trucks my whole life but 2-strokes are relativity new to me..... Ill post some picks of my discovery.
 
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