no1chevyboy
New member
looking to help a friend, this was a fresh rebuild crank seals up, i have an idea what caused this but would like input,was running double oil, damage only on intake side here are some pics
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Pistons grew too big for cylinders. So what can cause this?
1] Improper piston/cylinder clearance
2] Over heated engine:
-low coolant
-coolant vapour lock
-defective water pump
-hard running with not enough snow to cool heat exchangers
3] No oil circulation
-defective oil pump
-low or no oil
-oil lines not properly bled
1] Improper piston/cylinder clearance
2] Over heated engine:
-low coolant
-coolant vapour lock
-defective water pump
-hard running with not enough snow to cool heat exchangers
3] No oil circulation
-defective oil pump
-low or no oil
-oil lines not properly bled
bluemonster1
LIFE MEMBER ONLY ONCE!!!
maybe wrong pistons!!!!
im gunna guess that the problem has something to do with that five letter word on the side of the jug??? (rotax) haha surprised no one beat me to it.
goody_700
New member
I would say either wrong pistons, or wrong bore size for pistons that were bought, or not warmed up enough before cranking on it (cold seize), or too much dirt in the engine when reassembled, it wasn't cleaned properly.
horkn
New member
goody_700 said:
That would be my guess.
Those series 3 rotax had issues with bore sizes and maybe the wrong pistons were used.
no1chevyboy
New member
all the scoring is on the intake side no scoreing on exhaust side so the coolest side of the piston wouldnt out grow the hotter side, and everything spotless clean hes a fanatic about clean,oil pump primed,plus 50:1 in fuel tank
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madzx2
Member
maybe too much extra oil premixed in the tank?
How was the motor run from the time it was fired up to the time it quit? Was it rode hard or babied? Did he run through any light and fluffy powder?
no1chevyboy
New member
it was run pretty much like baby with some blips,he only rebuilt it because it looked like a crank seal was leaking and it had 7500 miles on it
extremelyfastmax4
New member
to much oil in the gas will lean them out, it looks like cold seize, or u sucked some snow on the intake and that will cause the cold seize possible not proper clearance.
no1chevyboy
New member
yes to much oil will lean out combustion mixture( less fuel molecules more oil molecules) but will lube more and if there was a lean problem this would show up on the hottest part of the piston not the coolest
no1chevyboy said:
This isn't a rotory valve engine, correct?
toydoc
Member
I have seen that when you run without a air box. Snow dust will wash the oil off the intake side. Even with K&N, you still need per-chagers on them.
I run my open fuel sled at 16:1, so it will slow down before you take a piston out like that. Too much oil just wont burn and runs out the pipes, shouldn't take out pistons
I run my open fuel sled at 16:1, so it will slow down before you take a piston out like that. Too much oil just wont burn and runs out the pipes, shouldn't take out pistons
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9801srx
Member
imo.that really looks like damage from no oil. if it cold seized there would be damage on the exhaust side also because the pistons would have got tight in the cyl. if it was lean the damage would be on the top of the piston . the intake side is the thrust side of the piston and will scuff just like that with out oil,the exhaust side not so much because it's pushed away from the cyl on the power stroke. i would tripple check that he indeed put extra oil in the tank and that the oil pump is working.
no1chevyboy
New member
snomofo its not a rotary valve motor. 9801srx yes he for sure put in 50:1 in tank. he finished the motor in july he put in high octaine fuel mixed with oil (3 gallons) at 50:1 along with seafoam he heat cycled the motor at least once then put to bed until nov. when he filled the tank up with 50:1 trails opened dec.15 when on maiden voyage stoping and checking under hood at stop signs to make sure all was good , sled was running great stoped to eat line was to long got back on sled and in 100 yards he noticed something was not right turned around drove back to bar and motor died.
Something nobody mentioned but the carb boots are a known weak area on Rotax engines,I've seen too many of them around here crack and cause engine failure so if he hasn't checked/changed them I'd for sure give them a VERY close inspection.
Are the pistons, Wisco? What is the bore dia? Measure the piston's. Is this a Nicasel cyl? The scuff marks look exactly like I see in a lot of Sea Doos, from water injestion. The story of the seazer just doesn't make sence. Al
horkn
New member
snomofo said:
For me just seeing the cylinder makes it a non rotary motor .
Fourbarrel is right about the rotaxes of this ilk having known problems with boots leaking. A bit extra air will easily ruin a motor quickly.
Also, running wisecos is not a problem provided they are sized properly. Also it's been noted many times that you also want to let a sled with wisecos warm up properly, although my 87 indy trail 488 has had wisecos in it for at least 6k with no issues even before the advice to let them warm up a good while before beating on it came around.
