TO start Off I recieved a bored cylinder that was in pretty good condition. When I felt the inside I felt just a very very very tiny grove where the piston skirt runs. I installed this cylinder with a 10:1 wiseco piston bored 2.00mm over. My problem is that i hear a noise from my engine in low RPM ONLY. It never happens unless it is at a little over idle speed. I can hammer it down the road in 4 gear and it doesnt make a sound. The noise it makes is not a ping or a loud nock. It is a muffled nock. It is noticable when starting off from idle. I mainly run my engine at higher speeds. My rod is fine because i checked that aready. I am positive that it is piston slap off idle. My question is will this hurt my engine, since it does not do it very much. WIll my engine last. If I put in synthetic oil will that help.

 

I'm just a tad bit confused by your definition of "Piston Slap". Are you saying there is play in the wrist pin (from rod to piston)? Or are you saying the piston / valve clearance is not enough?

If it's the wrist pin you'll wear the bearing out quickly and eventually result in improper piston / valve clearance (KABOOM). Or if it IS piston / valve clearance, perhaps try a thicker head gasket, or you may even have to take the piston into a machine shop and shave .010 or .020 off the top.

Hope this helps, or if I'm completely in La-La land, try to elaborate a bit more and I'll try again.

Cya

 

sorry kawasakaikid I mean't the piston to cylinder spacinging. I think my piston is slapping againsnt my cylinder walls.

 

is it a 4 stroke or 2 stroke?if its a 4 stroke then its probably the cam chain

 

It is a 4 stroke and I know that it is piston slap. There are groves worn in the cylinder from the piston skirt. I was just wondering if it will hurt it if it only does it at low rpm

 

if there are grooves worn from the skirt you need to have the cylinder bored out to the next size (maybe 2 sizes over) and install the proper size piston. running a piston with slop will eventually lead to motor failure

 

I think I know the kind of slap you are talking about. This usually occurs in worn engines but it has been an issue recently with some modern engines designed to be very loose. The piston skirt slaps against the cylinder walls a little bit at low RPM.

My answer is it is risky. It might not ever fail and actually run better because it’s loose. Then again I broke a piston in a worn engine while making a rapid change in RPM, a blip for a gear change, on an early shift to a lower gear.

If this happens, you will have deep gashes in the cylinder walls and the engine will be pumped full of metal fragments. Especially true on a multi cylinder engine but I suppose a single cylinder will just stop immediately.

The only difference I see in a tear down now versus a dear down after it fails is the potential walk when it breaks twenty miles from the road.

 

I hate to ask a dumb question, but did you put in a new piston or ring into a worn cyclinder? If you put new pistons or rings in you have to have the cyclinder honed or the rings will not seat and they will not last very long. Also did you measure the the distance between the piston and the cyclinder. I am not sure of the numbers for the clerance, but it sounds like you need to check this if you did not.

 

I agree with Dill, you're only asking for trouble by leaving it the way it is. Plus you're losing HP, Torque, and compression due to blow-by. More than likely you may need to have the cylinder honed and buy a new (correct size) piston & rings.

 

well guys My cylinder is worn and I have a good stock one that I got from a friend. I brought the one from my friend to the dealer and he checked it out and said the new one was good and the one I am using now was way to worn. So I am going to use the cylinder I got from my friend with a new piston. I want one that has about 9:1 compression or 9.5:1. What brand should I use.