Slapping sound on deceleration (video)

[95jersey]

I had a bad overheat one day and since then I have had this weird slapping sound on deceleration. At least I don't think I ever noticed it before, and when riding in gear and I completely let off the gas, the bike will surge forward a bit when I am coming to a stop when the engine kicks back.

I am thinking I ruined the top end when the bike overheated and have a new forged Wossner piston coming, but in the meantime what do you guys think this is? I would like to continue to ride the bike until I can do the top end but I don't want to do any damage to the cylinder.

http://vid1269.photobucket.com/albums/jj591/95jersey/Gas Idle_zpsxrbwliwr.mp4

If you listen closely you can hear some harder than usual sounding kick backs on deceleration.

 

[john r b]

detonation ? lean jetting?

 

[95jersey]

The jetting was fine before. Yes it has gotten warmer out, but that would only make the bike run richer.

I am thinking I did something to the top end when it overheated.

 

[stian]

The jetting was fine before. Yes it has gotten warmer out, but that would only make the bike run richer.

I am thinking I did something to the top end when it overheated.

Slappy piston rings.

 

[hamilton]

Sure sounds like a exhaust pipe spring to me.
Check the pipe o-rings and put some rubber hose over the springs.

 

[gasgasman]

Sure sounds like a exhaust pipe spring to me.
Check the pipe o-rings and put some rubber hose over the springs.

My vote also.
I put Viton o-rings on my '11 and '15, problem solved.

Aluminum bike stands can make some weird noises too.

 

[desertgasser300]

Pipe O-rings, mine makes the same noise and surging when it gets hot out.

 

[Rick]

Pipe O-rings, mine makes the same noise and surging when it gets hot out.

Pulling a vacuum......non sealing o rings

 

[desertgasser300]

Pulling a vacuum......non sealing o rings

Which o-rings would cause that? Pipe o-rings? My pipe doesn't seal well any more from to many big hits.

 

[djroggen]

Sounds like a pipe to me, mine sounds the same....

 

[95jersey]

Thanks everyone

Got a new top end kit coming so will just redo the whole thing, including exhaust gaskets...

 

[memphis2857]

That is just the pipe o-rings not sealing. Go to a ktm dealer and get some o-rings for a 2010 300 and it will be fine. I certainly wouldn't do a top end solely because of that noise. Correct me if I'm wrong but isn't your bike nearly brand new? How many hours? If it's less than 100 on a 250 and 150 on a 300 I wouldn't even consider a top end. Remember the fewer times you open that engine up unnecessarily the better off you are.


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[desertgasser300]

One of the reasons I wear headphones when I ride. I hear to many noises and get paranoid!!

 

[95jersey]

That is just the pipe o-rings not sealing. Go to a ktm dealer and get some o-rings for a 2010 300 and it will be fine. I certainly wouldn't do a top end solely because of that noise. Correct me if I'm wrong but isn't your bike nearly brand new? How many hours? If it's less than 100 on a 250 and 150 on a 300 I wouldn't even consider a top end. Remember the fewer times you open that engine up unnecessarily the better off you are.


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Thanks, I will absolutely try this. Worst case I shelve the top end for the end of the season. Yes bike is new (Nov 14). I probably got 60 hours on it. I had a bad overheating issue, which is the only reason I considered doing it early. But it sounds like it may have just ruined the O ring seals.

 

[memphis2857]

Yes the gasgas o-rings are garbage. My bike started doing this at 25 hours! Lol. Put the KTM o-rings on and no troubles since


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[95jersey]

Went to local KTM got 2 new O rings and it does not fix the issue. The OEM were in fine shape.

Looks like I will be installing that top end.

 

[bowhunter007]

It sounds like the pipe...it is possible that you've cooked some of the "spring" from your pipe springs, and just not holding as they should. Since it's a relatively easy chore, I vote for a top end inspection...just in case.

 

[memphis2857]

Went to local KTM got 2 new O rings and it does not fix the issue. The OEM were in fine shape.



Looks like I will be installing that top end.

That sucks. One more thing you might try that I know a lot of the guys on here do is put some hi-temp silicone on the o-rings. My bike made that exact sound and it was the pipe not dealing at the head. But as stated above a top end inspection couldn't hurt. Simplest thing to do is check the ring gap.


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[Rick]

Which o-rings would cause that? Pipe o-rings? My pipe doesn't seal well any more from to many big hits.

Pipe spigot o rings, broken mount, pipe not aligned property, not sealing good.

 

[Jakobi]

Pipe spigot o rings, broken mount, pipe not aligned property, not sealing good.

All of the above.

Both the Gas Gas O-rings and the oem lower mount/isolator are garbage and only last a limited time. I've replaced both with ktm parts and checked alignment and all is well.

I've had 2 Gas Gas OEM engines develop strange noises on decal around 65-75hrs which for me were a very BRRRRR odd kind of sound. Just sounded very rattly. New pistons fixed both, but from your video I'm not picking the sound up as the same one I had issues with.