What causes piston slap??

[dnoftz]

What causes piston slap and how can I diagnose the problem?0613021807.3g2 - YouTube this is the motor running not sure if it will help

not sure how to post video

 

[Triple_B]

I can't hear sh*t in the video.


But piston slap is caused my too much gap between the piston and the cylinder wall, so the piston actually rattles around inside the cylinder. This can cause a piston skirt to break off

 

[scotj77]

take it out of the garage and shoot the video. too much echo to here the motor. get down close to the cylinder withthe camera

 

[DirtDiggler]

Pull your intake and look at the intake windows , look for cracks on the piston .

 

[dnoftz]

My dad seems to think that the crank can cause this as well. How do i check the the ring gap to see if that is causing it. also when the motor is not running i can turn the clutch fast hand hear what i believe is the piston slap. I put new bearing in the crank case and it seemed tight when I was turning the crank with my hand can that be part of the issue or is piston slap always from the rings?

 

[dnoftz]

This is a brand new piston and rings Fresh rebuild I haven't even tried braking it in. I am afraid if I run it with it making the noise I may damage something. May have like 5 min run time in total.

 

[blasterBruce]

Did you do the 3 Heat Cycles ? , What about a Compression Check before you started it ?

 

[Blaaster]

I have a horrible feeling that the problem may be caused by either poor assembly or ill fitting parts.

Bearings when correctly installed should never seem tight.

Ring gap should be checked prior to assembly by inserting the rings in the jug and then measuring the gap.

Did you fit the correct size piston?

Did you do anything else other than fit a piston and rings?

Rings do not usually cause piston slap, it is usually caused by a sloppy piston in the bore.

If it is making noise when it is turned over by hand, I recommend that you dissasemble things bit, by bit to find the cause of your problem.

 

[dnoftz]

I built the motor from the ground up. I took the jug in and had it looked at when I got it. the machine shop told me it was a good cylinder it still had fresh hash marks. Told me it was 67mm so I ordered a 1mm over piston and ring top end kit. No I have not done the heat cycles yet. when I started it I hear some noise so I shut it down other then to shoot the video i posted. I did not do a compression test though.

 

[brandoz28]

i can't hear anything in that video.....sounds like the mic is clipping.


the only way to know that it's right is to put a mic to the piston, and then use a bore gauge in the cylinder.