piston slap?

[We1Dont7Die]

was riding today and in the mid to high rpms i was hearing a tapping sound...it almost sounds like something is just smacking on the frame. I rode by a friend who immediately recognized it as piston slap.
He had two suggestions.
1. just ride it, but not too hard, until it completely breaks and then do an engine rebuild.
2.Take engine out and either fix or replace it.

How difficult of a job is this to tackle? He mentioned that things have to be pressed and NEEDING to take it to a machine shop.

I've had nothing but problems with this warrior since i got it this year and now piston slap...I feel like piston slapping myself :argh:. any input is appreciated.

 

[87warrior917]

hmm. is the piston stock? what kinda gas you running? could just be spark knock, which means ur not runing high enough octane. i have always ran 93 in all mine stock or not. but i wouldnt think it would just all of a sudden start slapping. it would gradually get worse once it starts. but its really not that hard to replace the piston, you would just have to take the aftermarket piston and cylinder to a shop and get it bored. which should be around 50-60...

 

[We1Dont7Die]

I'm not sure if the piston is stock. I have been running mid grade gas. I've also noticed it now smokes for a minute or two after starting but it goes away.

 

[87warrior917]

hmm my 87 smokes on initial start up but clears after its warmed up... i think it the valve seals leting it smoke. if it was a ring thats broke it would smoke all the time. i say adjust the valves change the oil and see what it sounds like after that...oooorr maybe its the timing chain slapping. they will stretch over time and start slapping against the chain guides...

 

[dirtrider73068]

If its piston slap, then you need to stop riding it, and look at rebuilding. Keep riding it and look at replacing the motor, its slapping the the side of cylinder it will eventfully bust the piston if not already marred the cylinder. I would troubleshoot this and do not ride it till you find out, exactly the problem is. Try adjusting the valves, if it still does it, change fuels, if it still does it, may need to do a compression test to see how much the rings are sealing in the cylinder, if the test is low then may need to as a last resort take the head of and check the piston in the cylinder and see if its piston slap.

 

[We1Dont7Die]

I adjusted the valves about a month ago but I will check them again. I will also do another compression test. if it is piston slap wouldnt that mean the piston is loose in there and the compression reading should be low?

 

[dirtrider73068]

Yes if the piston is slapping it means its hitting the wall of the cylinder so you should get a low reading. If it still a high reading then everything should be good. Could be timing chain, or if its doing it at idle and at speed. If its doing just at speed it could be gear noise your hearing. I know my chain was loose, and it sounds like valves or something was rattling, might check the tension of your chain.

 

[We1Dont7Die]

I haven't checked things out yet. I will tomorrow most likely but I had a thought..

if it is piston slap, would you hear it all the time or only under stress? (I hear it more when i am on the bike and gunning it rather than sitting in neutral and revving it)

Could i install a new piston and rings and fix it or would i HAVE to bore? I haven't ever done any engine work.

 

[1998yamahawarrior]

if you do find out its piston slap. youll want to take it apart before you get any parts. then take the jug to an engine machine shop unless you have the tools to measure it. chances are it will need at least a small amount of boring if its piston slap, but at any rate get a shops advice on the jug. if that is your problem look at it this way, go with a higher compression piston and its an upgrade for more power.

 

[We1Dont7Die]

Would i be able to fix this just by working on the top end? I have never taken an engine apart.

 

[elwood]

top end is easy just read the manual, print any pages you need. It's only a few bolts to take it apart. No need to teear into the bottom half

 

[dirtrider73068]

Pretty much thats what is wrong with it is just the top end. Its pretty straight forward to work on it, I haven't taken my top end off, but from what i have seen there should be 4 bolts that hold the jug and head on, plus the timeing chain, carb, all that little stuff. It shouldn't be that hard, just take your time follow the manual.

 

[1998yamahawarrior]

the hardest thing about the top end is when you have it apart, dont let the timing chain fall into the crankcase. if it does it can be a bitch to get right in place agian.

 

[elwood]

yeah take a wire and hook it to the timing chain and tie it to something like the frame, then when you put the jug on just slide the wire though to pull the chain though, same with the head

 

[elwood]

if you are changing the timing chain you will need to take off the left side cover and pull the fly wheel. For pulling the fly wheel you will need a puller.