Pisto Slap?????

[Blastinit]

Hey guys, I tried posting this in my old thread about engine noise, but it was old enough that no one was reading it anymore. So, here it is.........My Blasty started making a lot of engine noise. Is this piston slap? If so, I will get the top end off ASAP and get it out to KOR! I wanted to get the head modded anyhow

 

[Sruiz67]

Hey man, I am very new to this site so I'm not an expert. I recently bought a 2003 blaster that looks exactly like that one. Checked compression and it was at 90psi. Thinking the bore was stock I ordered a new piston for the stock bore (66mm). Installed everything and started it and it sounded exactly like that. So I pulled the head and saw that the piston had a lot of play. Tore it apart and this time had the cylinder bore mic'd. It was 66.50. Felt like a dumb ass and waisted money but that noise was piston slap in mine. The 66mm piston was to small. Waiting on piston to get here and then we shall see. Live and learn!

 

[Blastinit]

Thanks Sruiz67, that's what I thought. Looks like I better call Ken Oconnor!

 

[Blaner]

possibly your crank bearing too.

 

[ajaysblaster]

I say it is piston slap or you have a bad bearing in the crank area on the rod or main bearings. I would pull the top and look at it

 

[Blaner]

I had a noise similar to that, and after stripping, found a missing circlip on the wrist pin. The wrist pin had been slamming into the cylinder and left some tasty scores, however, these were below the swept area of the rings and so did not affect anything.

 

[Blaner]

Here is a vid of mine, when I realised something was wrong:

 

[Blastinit]

Thanks for all the input guys! I pulled the cylinder head and was able to move the piston around in the bore! I stripped it down, packed it up and sent it to Ken O'Connor. Gonna have it bored, Weisco forged piston, ported and head rechambered. Looking forward to the power that should bring. Next up = bigger carb, just gotta wait for the $$$$. I was really surprised that it was a stock piston/bore size! This thing is 10 years old and still started on the second kick!

 

[briizilla]

huh. mine sounds very similar and has since I got it in January. I was concerned at first but I let my cousin, who has been in motocross(racing and repairing/rebuilding) since before I was born(long ago) listen to it and he said not to worry about it. So I haven't. I did have the head off a few weeks ago and didn't notice anything that raised any concerns.
My property is joined to about 500 acres of woods and I ride trails probably 15-20 hours a week and so far so good. Should I be concerned anyway?

 

[Larry's Shee]

huh. mine sounds very similar and has since I got it in January. I ride trails probably 15-20 hours a week and so far so good. Should I be concerned anyway?

Air cooled 2s are noisey anyhow, add in the extra gears for the counter balancer and the balancer itself and you have lots of noise. If it hasn't gotten worse it's probably OK. next time you have head off, see how much movement the piston has.

 

[briizilla]

Air cooled 2s are noisey anyhow, add in the extra gears for the counter balancer and the balancer itself and you have lots of noise. If it hasn't gotten worse it's probably OK. next time you have head off, see how much movement the piston has.

Thank you sir! I'm thinking of getting a nice port/polish in the fall after a hard summer of riding as it is.

 

[Blaner]

Yes, Larry is correct, aircooled motors do not have the liquid insulation to surppress sound. hence they are always noisy, you can hear reed flutter and all sorts of funny sounds. You can however pick up when something is wrong, as I did on my vids I posted.

Do yourself a favour next time, get a nice big long screwdriver, place the tip at various locations on the engine and press the handle onto the small lobe thingie just at the front of your ear, you can clearly hear different parts moving. You can pick up if you have a noisy crank bearing or similar.