Wristpin bearing gone or Piston slap
- Thread starter Antec1200X
- Start date
a loud one that appeared out of no where? mine has had a slight slap or ping since i bought it rebuilt from a pro. Been runnin hard for 2 years. No problems
wish i could upload a video.it sounds horrible.
just out of no wheres vill.so i got curious and took the top end off and all bearings seems good.put the top end back on it sounds like nuts in a tin can
just out of no wheres vill.so i got curious and took the top end off and all bearings seems good.put the top end back on it sounds like nuts in a tin can
do a compression test. then pull the head and take a quick peak at the piston. and rings. piston slap comes from the rings not the wrist pin bearing. does it get better or worse when its revved? have you done any mods recently? of any kind... just want to make sure we are dealing with an engine knock and not some other issue? could you post a video?
Check the strangest stuff....
Pull the flywheel and make sure one of the stator bolts isn't hitting the flywheel. It can sound like an engine "knock".
Pull the flywheel and make sure one of the stator bolts isn't hitting the flywheel. It can sound like an engine "knock".
it sounds worse when i turn the flywheel by hand.turn it backwards untill the piston is about to make compression.then it knocks really loud within 2 inches on moving it back and fourth it will keep knocking.
i dont have a usb for my phone so i cant upload
i dont have a usb for my phone so i cant upload
Always at the same location in the stroke?
Sounds like something hitting something, not necessarily piston slap.
Sounds like something hitting something, not necessarily piston slap.
but i had the top end off to check for anything unusual.everything is the way it should be.
ill try and figure out a way to get a video uploaded.i dont think im going to run it the way it is for a bit
btw the compression tester says 135psi.but that was a rigged tester
oh and another thing.it didnt make the sounds the last 3 times i had it out or yesterday,just today thats why im concerned
ill try and figure out a way to get a video uploaded.i dont think im going to run it the way it is for a bit
btw the compression tester says 135psi.but that was a rigged tester
oh and another thing.it didnt make the sounds the last 3 times i had it out or yesterday,just today thats why im concerned
Isn't this a fresh top end? Did you use new pin brg? Check big end of rod just now? Check flywheel then inside clutch cover. Look for chipped/broken teeth on gears, loose gear on counter balance shaft. Maybe loose gear on clutch or kicker idler.
the sounds come from the top end.either play in the wrist pin bearing which was new or the piston is slapping the cylinder walls
That is exactly how mine sounded right before it broke the skirt off. As soon as it would break over from top dead center you could hear it when turning it over by hand. Mine was caused by the wrist pin. When it was running it sounded god awful. I think is was louder than the exhaust. I should have taken it apart as soon as I heard it, but I didn't and now the motor digested the skirt.
If you still have the top end off, grab the con rod to isolate it away from the crankshaft and try to rock the piston around (particularly twisting it). The wrist pin bearing should only be able to slide side-to-side. There should be no movement any other direction. If there is, pop one side circlip out and push the wrist pin out. Inspect the wrist pin bearing to make sure one of the rollers hasn't come out of the cage.
Also, while you have your piston off, turn the crank over by hand and make sure the problem isn't under the clutch cover. Did you "stake" the nuts inside the inner clutch basket and on the balancer shaft gears with their bendable washers? Perhaps one of the screws that holds the input shaft bearing into the case has backed out and it hitting the clutch basket.
Also, while you have your piston off, turn the crank over by hand and make sure the problem isn't under the clutch cover. Did you "stake" the nuts inside the inner clutch basket and on the balancer shaft gears with their bendable washers? Perhaps one of the screws that holds the input shaft bearing into the case has backed out and it hitting the clutch basket.
ill take the cylinder off and inspect the piston and wrist pin bearings like you said.im positive the noise isnt comin from the clutch cover side.but the top end.
it would be a bonus if i could save the piston from shattering,
it would be a bonus if i could save the piston from shattering,
Stuff a clean rag around crank so you don't drop stuff down the case. JMHO, your results may, and will vary.
ok i got the top end off and tryed to twist the piston holding the conectiong rod and it does have alot of play.too much imo.ill have to order a new bearing
Let me see if i can help
I bet its running to rich and not all the fuel is burning fast enough then when the piston comes down and gets a fresh charge from the intake its catching on fire and burning all the feul thats also down in the crankcase and maybe even all the way back to the reeds and its the reeds that are making that noise, better fix it before it completely blows up the bottom end like a grenade and theres peices of shrapnelled blaster motor all over the place.
There, feel better now? I:I
Take the rings off the piston and stick the piston back in the cylinder and see if you can stick a credit card, a peice of paper, 7-11 big gulp straw, feeler guages or anything in between the side of the piston and the cylinder,,,,,,,,,,,,,,,,,,,,,
I bet its running to rich and not all the fuel is burning fast enough then when the piston comes down and gets a fresh charge from the intake its catching on fire and burning all the feul thats also down in the crankcase and maybe even all the way back to the reeds and its the reeds that are making that noise, better fix it before it completely blows up the bottom end like a grenade and theres peices of shrapnelled blaster motor all over the place.
There, feel better now? I:I
Take the rings off the piston and stick the piston back in the cylinder and see if you can stick a credit card, a peice of paper, 7-11 big gulp straw, feeler guages or anything in between the side of the piston and the cylinder,,,,,,,,,,,,,,,,,,,,,
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Pull one circlip out and push the wrist pin out of the piston. Reinstall the wrist pin into the bearing and wiggle it then. That'll give you a much better view of what's going on, whether it's the wrist pin bearing, the wrist pin, or the crankshaft small end hole bad.
ive been dealing with a similar knock i just redid the top end a couple months ago and i had split the cases to make sure everything was good and its been knocking ever since but it does run really good and its a wiseco piston so i guess i should check a few things myself
