2000 TC88 with 100" S & S kit, S & S 570 gear drive cams, Magnetti Marelli open-loop EFI, ported heads, mixture adjusted on Dyno but timing pretty much left alone @ Stage I flash.

Very no bueno hot day noise under freeway acceleration - thought I lost a valve spring or con rod on fresh motor undergoing final tuning. Taking away timing solved it, but I'm left wondering about damage done, if any.

When I first experienced the knock I had spent some time in 85 degree city traffic before getting on the freeway. I rolled on the throttle pretty good around mid 2000's and the noise I heard scared the bejezus out of me - it didn't sound like knock; for lack of a better way to describe it, it sounded... springier, it resonated and sounded more like metal distorting under duress. I taped a mic by the front jug and reproduced the noise. The Mike picked up classic knock, but not the sound my ears did. I actually thought I lost a valve spring or something, but taking away timing solved the problem and 500 miles or so later the engine runs fine.

I know these noise questions are real eye rollers for people, but just wondering if this rings a bell with any of you, and if I should have reservations about my 6000 mile ride I'm about to take.

 

If you’ve now ride 500 miles and got on it some, with no more noise, I’d consider it happy.

 

That's what I'm hoping. Having tried this trip last summer only to loose a front piston a few hindred miles in, I'm probably more cautious than most. Damn, that noise was loud and sounded like a debacle in the making. Gotten on it plenty in the miles since taking away timing and all seems well. I just worry about the ticking time bomb issue.

 

Severe detonation can break up pistons and ruin the rings. Fortunately the piston kit you used has forged pistons which can take a bit of punishment over cast pistons. If you are not using oil, have any piston rattle or excessive oil out the breathers, chances are you are OK. You can perform a leakdown test to get the condition of the rings but IMO probably not needed.

 

@Max Headflow , that's great re-assurance, thanks once again for the benefit of your experience.

I had a lot of carbon build-up on my pistons from a cautious break-in on a rich tune. I've been giving it some good hard pulls which seems to be breaking up the carbon.

I've scoped my cylinders and pistons a few times and have sometimes noticed oil on the pistons to the extent that a small amount had pooled in the valve reliefs. While idling the hot engine a few days ago to adjust the idle speed and then cracking the throttle I thought I saw a touch of smoke from the exhaust but can't swear to it (might have just been a heat shadow), which is what prompted this renewed last-minute line of inquiry about possible engine damage. I'm not sure that's anything to be concerned about, but with the oil on the pistons, it does raise questions. I scoped it again today and the pistons look pretty good to my untrained eye. You can see the clean patches appearing on the pistons where before there was carbon, so I'm assuming that getting my mixture dialed in better on the dyno and doing some good hard pulls is cleaning some away.

Here are two pics of both pistons and an example of an oily shot I took several days ago. The fresh pics were after running the cold engine long enough to pull it into the garage (20 seconds?) and revving it a bit before shutting down. I don't recall the conditions under which the "oily" pic was taken.

Anyway, unless you ( @Max Headflow @TriGeezer or any of you other more experienced members) see anything that makes you think otherwise, it looks like she may be ready to roll on this trip! After last summer's fiasco, it'll be nice to actually get this one under my belt.



Front Piston - right side

Front Piston - left side

Rear Piston - right side

Rear Piston - left side

oily

 

Well,

After looking at the pictures I'd be concerned. The carbon flaking marks are a sure sign off severe pinging. The ping blasts the carbon off the piston top. Hope you got that fixed. What also concerns me is the intake valve pockets. It looks like the intake valves are catching the edge of the pocket and might even be bottoming out in the pocket. I would have thought that SnS kit pistons would have provided plenty of clearance but from what I see here it looks like the valve is hitting. Not sure how many miles but at this point you should not have oil on the pistons.

Personally I would not take this bike very far based on what I see in the pics.

 

@Max Headflow Damn, not at all what I wanted to hear, but I appreciate hearing it now from you instead of from a shop 1000 miles away. I'll have to take it to a shop at this point and get it looked at. Thanks man. I'll also try to scope those intake eyebrows a little better. I wonder if that crazy sound I heard might have been valves tapping the pistons. Hot day, rolling hard on the throttle at freeway speed in the 2500 - 3000 rev range (I think). As I mentioned, my mind went straight to valve springs but it only happened under load and my RPMs weren't high.

 

On monday, I'd call SnS. Send them a picture and tell them you are running 0.060 over valves. See what they say.. I always check valve reliefs to make sure there is adequate clearance. I would have thought that the aftermarket pistons would have plenty. The only 4 inch bore pistons I messed with were SnS but for a 4 5/8 stroke motor (older SnS stuff). They had plenty clearance for 2 inch valves. I've not used these new ones but to me the reliefs do look like they are catching the edge of the valve.

 

It looks like the heads are coming off.

 

I wonder if this could be related to the larger intake valves the builder installed - I think he said they were 0.060" larger than factory.