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Bike Pings at idle!

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I'm not used to hi performance 2 stroke (we have sleds and an old Polaris quad though) but I guess this is normal and definitively not detonation.

Anyway, my bike is loud! Specially at idle speed, even worse when cold and the idle is higher then normal. At idle, the bike have 2 sounds On the background there's an usual engine sound (4 stroke like) that goes like Brrrrrrrrrrrrrrr, then on top of it you have some loud (really loud) Pings that goes like this: PING...PING...PING...PING.PING........PING.PING.PING.......PING..PING.. You get the idea. :bonk:

Now it's not that usual 2 stroke ping (like with other 2 strokes) But it sounds exactly like if you take the sharp, needle like part of a big hammer and slammed it as hard a you could on a THICK piece of of metal. The sound is enough to make my ears tickle listening to it close to the engine (exactly like the hammer on metal). When I slowly rev the bike the pings get closer together to a point where the overall engine noise cover it and it sounds normal again (loud, but normal). No sings of detonation anywhere even when on hard load the bike revs nicely.

So what's up with those loud pings at idle? Is every 250 doing this?

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aww that sucks..wasnt that the nice new bike 2 weeks ago you were bragging about from some canadian motocrosser you baught it from? sounds like they he shoulda fixed it first or you been puttin alot of hours on it since and messed the piston up, or the pipe needs a repack, but im not very mechanicly inclined lol i know just enough to get by, glad we have this awesome helpful site full of nice guys:applause:

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Bikes runs great and it got 200psi of compression. Guy told me the piston and repack was done 2 hours (of riding) ago. I say it's loud but I don't have anything to compare it to. To me it's just the usual 2 stroke ping but louder. :bonk: I wish I could record it.

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I think I found a way to record it. Won't be high quality but I think it will work. Can't wait to let her rip after work! :bonk:

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If the topend is fresh they probably installed a forged piston which will give alot of piston to cylinderwall slap. Another thing to check and make sure it's clean is the exhaust valve and it's parts.

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Here you go! I got it on tape! The ping is obviously louder (or should I say "sharper") in real life but it's pretty much it. It seems normal to me but you make the call. :bonk:

The file (60sec. about 2.5MB)

http://quickimg.com/uploads/64c2a15591df791d510558d490ae23c4.wav

I also got some pic of the inside of the beast and was really pleased with what I saw. Considering I took a little ride with it being way rich (sponge dripping) before jetting it correctly and taking another ride. Those pics have been taken after letting it idle for the sound sample so I guess it loaded up but the exhaust port was still pretty clean (wet and oily but not full of carbon). But then again, you make the call:

Here's the cylinder. We can cleanly see the perfect cross hatch:

piston1.jpg

Here we see the piston with really minimal blowout (if any) and the surprisingly clean head:

piston2.jpg

Here we see a closer look at the piston (blurry):

piston3.jpg

So, anything wrong doc? :naughty:

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Looks good and sounds normal just ride it like you stole it and don't worry it's a 2 stroke after all.:bonk:

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Looks good and sounds normal just ride it like you stole it and don't worry it's a 2 stroke after all.:bonk:
Thank you. :naughty: So it's not a piston slapping sound after all?

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I'm no expert, but it sounds exactly like our two CR85s, only a little deeper.

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iunno i know my 250 doesnt really sound like that

that bike even sounds rich man

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If the topend is fresh they probably installed a forged piston which will give alot of piston to cylinderwall slap. Another thing to check and make sure it's clean is the exhaust valve and it's parts.

Where are you coming up with this missinformation?

A late model 250 GP forging is at .0015 piston to cylinder clearance.

My OE casting is set up at .0023-.003

How can a piston set up with a tighter piston to cylinder clearance slap and make more noise.

All modern forging's are running as tight or tighter piston to cylinder

clearance compared to there cast counterparts.

1970 forging technology was a long time ago, let it go!

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Where are you coming up with this missinformation?

A late model 250 GP forging is at .0015 piston to cylinder clearance.

My OE casting is set up at .0023-.003

How can a piston set up with a tighter piston to cylinder clearance slap and make more noise.

All modern forging's are running as tight or tighter piston to cylinder

clearance compared to there cast counterparts.

1970 forging technology was a long time ago, let it go!

...and about my bike? :bonk:

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...and about my bike? :bonk:

Your bike sounds fine.

What pipe is on it?

Some pipes have a more brassy sound than some others.

The piston appears to have had some trash go through there.

There is more wear on it with only two hours than I would like to see.

I would imagine it has more than two hours on it.

She's startin to rub up high towards the rings more than it should with a tight piston to cylinder clearance.

Still looks plenty good to leave it alone and ride it.

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my bike does that too, but not as bad, although i have heard worse, it seems like it should be ok. but than again im no expert on this subject

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