- Location
- Australia
Engine failure
- Thread starter Superjet1000
- Start date
SXIPro
JM781 Big Bore
- Location
- Here on the 'X' mostly
Did you leak test it after you built it and before you ran it?
Just4Fun
First World Problems...
- Location
- Southern Oregon
Did your rod bearing let go.. Was it a new crank ?
Blue
Judging your cheapness
- Location
- St Cloud Florida
That is detonation caused from being to lean. It could also be caused from inproper squish clearance but if the squish was correct then you know for sure it was to lean. When you ported the motor did you rejet the carbs ?
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Th3g3rm4n4t0r
Brawlin' n Flippin'
- Location
- Ajax, Ontario, Canada
I know the looks of that first hand... 2 times in one summer. Change your jetting mate.
Th3g3rm4n4t0r
Brawlin' n Flippin'
- Location
- Ajax, Ontario, Canada
OCD Solutions
Original, Clean and Dependable Solutions
- Location
- Rentz, GA
In addition to the above questions, what compression and octane were you running? What head and dome combo?
Who did your porting?
Who did your porting?
- Location
- Australia
Yes I leak tested
No rod bearing did not let go, rebuilt crank.
Squish was checked and ok
Compression was checked but my gauge reads low. Same comp as my XS1000.
Would rather not say who did the porting as its more likely my fault than their's.
ADA head 31cc domes, recommended by porter.
Pump fuel 98 which I think equals 91 in US.
.
Engine was not dialled in properly as yet.
Did just fill my fuel tank with a different brand fuel to what I usually run not long before this happened.
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No rod bearing did not let go, rebuilt crank.
Squish was checked and ok
Compression was checked but my gauge reads low. Same comp as my XS1000.
Would rather not say who did the porting as its more likely my fault than their's.
ADA head 31cc domes, recommended by porter.
Pump fuel 98 which I think equals 91 in US.
.
Engine was not dialled in properly as yet.
Did just fill my fuel tank with a different brand fuel to what I usually run not long before this happened.
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Blue
Judging your cheapness
- Location
- St Cloud Florida
31cc domes would require 100 octane in US measurements.
We typically run 35cc domes on our ported motors with 93 octane but we recommend 100 octane with the use of 33cc domes.
I would guess the 31cc domes is what caused the detination due to the lack of octane in the fuel.
Did you rejet the carbs for a ported motor?
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We typically run 35cc domes on our ported motors with 93 octane but we recommend 100 octane with the use of 33cc domes.
I would guess the 31cc domes is what caused the detination due to the lack of octane in the fuel.
Did you rejet the carbs for a ported motor?
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Last edited:
Nuklear6
I Dream 10' Surf!
Lean lean mean. The aluminum went molten on both exhaust sides. Marks in top of piston are from btoken ring pieces after the top edge of the piston melted and the ring broke. Too much egt from a way lean a/f mixture. 31cc domes are way tight for 91 pump fuel so you'll wanna Def revaluate that when you reassemble but a lean mixture is to blame for this. Imo. Check for air leaks on intake or pulse line issues. Also check to make sure one way valve on tank is working as well as fuel lines and filters are clear. With that much compression it doesn't take long to spike egt when there is a slight fuel delivery problem, especially when at wide open throttle. If all is tight and clear jet it up.
I ran 100oct at 215psi ported case/cyl for a season of race course and surf riding and that seemed like barely enough octane. Needed more like 105-110. It lost compression towards the end of fall, but it lasted basically the whole season and the motor was bought used with an untold no. Of hours on it. Just to give you an idea of how severe your octane issue was...