Piston slap? Or...

[Vmaxrider]

I have a 2007 FJR with about 9000 miles on it. I have noticed when it is cold out(below 40 degrees F.) that it has a knocking sound coming from the left side of the engine. The sound goes away once the engine has a little heat in it or about one bar showing on the gauge. I am using Mobil 1 full synthetic 10 w 40 oil and change it every 3000 miles. The sound goes away with revs. And just knocks at idle at about 1500 rpm. I have tried pulling and releasing the clutch while idling but it doesn't change the sound (my FZ1 had a noisy clutch) any thoughts? Or has anyone else experienced something similiar? I don't think it's the CCTV since it is mostly on the left side. Also the bike runs great otherwise with no issues at all. What do you guys think? Piston slap? Normal?

 

[RadioHowie]

Sounds like a symptom reported quite frequently...

When the FJR is cold, running an EPA-mandated VERY lean fuel injection map, sometimes the fuel load doesn't vaporize well in a cold cylinder and doesn't fire. So the piston hits a "dead hole" and clunks as it attempts to rebound from the compression. There is very little inertia in the FJR motor -- no "flywheel effect" like you get with a car with a 30-40 pound flywheel rotating -- so for a fraction of a millisecond, the piston slams into a brick wall.

Then, as the bike warms up, the mis-fires go away and the bike idles fine.

That's pretty much it.

 

[Vmaxrider]

Every so often it does the clunk/backfire noise when cold. That is the one I thought was because of the fuel map. This noise is more of a dull knock with every revolution of the engine until warm. I don't think it's a bearing though because it is not there when the engine speeds up or when warm. Do you think it's still maybe the EPA's fuel map? Does anyone else have a similar sound?

 

[Fred W]

Visualizing your verbal description will be fruitless beyond compare. Capture an accurate sounding file and post it up.

 

[NMRoadRunner]

The pistons are only about 1" tall if that, I doubt you could detect piston slap from the short skirt. If it is, it won't take long before you find out. :glare:

 

[FJReady]

Every so often it does the clunk/backfire noise when cold. That is the one I thought was because of the fuel map. This noise is more of a dull knock with every revolution of the engine until warm. I don't think it's a bearing though because it is not there when the engine speeds up or when warm. Do you think it's still maybe the EPA's fuel map? Does anyone else have a similar sound?

I wear ear plugs, so my engine sounds great. Really though, I think all FJR motors 'hiccup' just a tiny bit when cold. 1-2 minutes after starting all is well. Sorry this doesn't help much.

 

[wmadoty]

Somtimes, I think I hear a slight knock when the engine is cold as well. It goes away after it has warmed up. I have a 2010 with 10,000 miles. I doubt you really have a problem. My noise does not bother me at all, and I doubt there is anything wrong with it. My noise has been there since day one.

 

[BwanaDik]

Sounds familiar...

Knockin' on FJR's Door

 

[BlueRidgeFJR]

Hi, my name is mike and im a throttle junkie, When I got my FJR I had came off a 86' FJ 1200. It had good old carbs, so when it was time to light it up you had to pour a little fuel with the throttle to wake him up. When I got my new FJR I had the same old habit and it stumbled on warmup, sounding like s*^t! Finnaly I figured out to turn the key on, do not touch the throttle, push the red launch button and let it warm up then all was well. Technology!!! Whowudda-thunkit!