Absolutely destroyed these pistons!!! Help!!

[Thegreanest]

Let me start by saying, I'm pretty darn mechanically inclined, I work on all my own stuff, but I've never built an engine before.

Soooooo, I was doing some top speed runs with my 99 busa with an rcc stage 1 kit, and after 2 back to back runs the motor gave up.
It just stopped accelerating at 10k rpm in 5th at about 178mph.
As I slowed down motor spewed 90% of it's coolant out of the overflow reservoir cap that must have been blown off and started knocking and died once it dropped down to idle.
I've since completely torn down the motor, and what I found hurt my soul deeply.
Attached is a picture of the piston from cylinder 4.

So some quick background on this bike, it was built in 2012, has.... Well had lol, a balanced gen 2 crank, carillo H-beam rods, je 81mm 8.7:1 turbo pistons, base spacer, web 70-751 cams with ape adjustable sprockets, valve springs, head studs and a few other things.
Along with an rcc stage 1 kit from 2012 when they were using comp turbos.
And was making 9-10psi of boost.

I bought this bike from the guy who had it built only a month ago, so I'm pretty bummed about it giving up so soon, but sometimes that's just the way life goes, right?

Anyway, back to the blown motor...
So as I tore this motor apart, I found that 3 of the 4 pistons had broke, and 1 of those three (the one pictured) had a hole melted in it.
Aluminum bits were everywhere, beaten into the head on cypi

 

[BlueBacon]

sounds horrible, but fyi: no pics up yet

 

[Thegreanest]

Pics

 

[Thegreanest]

Couple more
Interesting to see that coating of aluminum dust in the head

 

[Thegreanest]

sounds horrible, but fyi: no pics up yet

I realize now that I double posted this because the app glitched out on my phone.
The other one has more info and the questions I need answered.
It won't let me edit this one and say "30 minute time limit for editing has passed" or something along those lines

 

[GIXERHP]

What was your air fuel ratio?

 

[GIXERHP]

Also who tuned it?

 

[Thegreanest]

What was your air fuel ratio?

Good question, no idea, no afr gauge.
Previous owner said "it's tuned slightly on the richer side to be safer on the street"
But who knows. It has a pc3 USB, and I was planning on getting it retuned but didn't really get to that

 

[Thegreanest]

Also who tuned it?

Tuned by the brothers power sports in Washington

 

[Thegreanest]

Here's the other half of this post that got cut off from the app glitching out on my phone

"Aluminum bits were everywhere, beaten badly into the head and embedded into the cylinder wall on cylinder 4, in the oil pan, sitting on the pistons.... It was bad.

I don't know much, but I think it was and intake temp and/or fuel issue causing detonation that caused this.

Anyway, from what I can tell (again, new to this) the crank and rods appear to have not taken any damage, and I will be taking them to a machine shop or something to verify that.
Everything else except for the head, pistons and cylinders seem fine.
The cylinders may be reusable but would probably need bored to 83mm.

But... Let's move on to some questions.
How "safe" is an 83mm bore for boost?
I know it'll reduce head gasket surface area by a bit, but is it doable for a street ridden bike?

Do y'all have any insight on what could have caused this?

How much power could I make on the parts listed if I did an intercooler and a secondary fuel system?

Any other advice on rebuilding this motor for a little more power?"

 

[GIXERHP]

As far as i can see the bike went lean as hell, causing the melt down. As for the 83 MM, Stock bore is widely recommended . You need to run a wideband O2 as well as an Air fuel guage, if not you are asking for your wallet to let the hundred dollar bills fall out

As for you asking for more power you need to learn how to run what you have.
Now you could rebuild it, and go out and do the same thing,, Find a good Turbo guy near you..

 

[Berlin Germany]

in my view you had 2 (two) respectively 3 (three) issues

1st - the head and the impacts of foreign parts wherever they come from
2nd - the piston - burnt away because the combustion was seemingly far too lean / the lambda value was too high, well over 1.0 (ideally a value of 0.85-0.90 should be)

(....)
As I slowed down motor spewed 90% of it's coolant out of the overflow reservoir (....)

^^^ 3rd - at least tell me that your head gasket is dead because it for sure burnt through (only once?)

in my view the pre-owner / the shop made all wrong what could be wrong.

now you need a "new" (pre-owned) and crack-free head , a "new" (pre-owned) cyl.-block and 4 new pistons / sets of rings and all gaskets
what makes i guess around 1200-1500 bucks minimum for spare parts only.

and watch the (pre-owned) head with eagle-like-eyes if there are any cracks in the very narrow "bridges" between the inlet valves of each cyl. because they occur especially there.

the cyl.-walls (pre-owned) should have no scratches or else (marks) - they are nikasil coated and standardly very durable
the pistons (pre-owned) should not show scratches / marks at their flanks
their ring grooves must be clinically clean.

and to be safe with a used head and block, flatten their sealing surfaces by 5/100 - 1/10 millimeters.

and a last recommendation : (you already disassambled the top)
open the gearbox and check! (eagle-eyed)
a. the crank and its piston rod bearing surfaces (plus the slide bearings itself too)
and
b. the docks ´n notches at the gear wheels (if they look this way, or similar, they are 100% scrap)

what can happen if a slide bearing stops working see this pic of a deformed rod
and this crank pic too from my hp
(please only follow the links above if your stomach is very resilient - the pictures can be very disturbing)

____________________________________________________________​

or you spend not a cent for parts and throw all the junk at the feet of the previous owner and demand your money back.

 

[busakiller]

You can go up to 83mm bore and they do sell turbo pistons for that bore. I wouldn’t be afraid to go to that bore size if I was you. But from what shown us looks like it went lean or the intake temps were soo hoooot it melted down. On my turbo stage one bike I never do back to back runs like that. I always cruise a bit after a pull to let the temps come down. I would advise getting a intake temp gauge on the bike so you can watch that. Afr gauge ain’t going to matter cause you won’t be looking at that during a pull. But you can look at the iat gauge before doing a pull…. Also after you rebuild the motor upgrade the injectors so you don’t have to run crazy fuel pressure. Is you fuel pump located under the gas tank or down by the swing arm? Best of luck with the rebuild.

 

[pcs]

on one of the pics, looks like the rings might have butted together and damaged the piston. sometimes people incorrectly gap piston rings for their set up. the other pistons with the “speckles” look like it was detonating. could be from low octane fuel, old fuel, or running too hot which could corroborate the loss of ring gap. with aftermarket boosting of anything, good idea to have an a/f gauge and fresh fuel for any hard runs. good luck on the rebuild.

 

[mjl3truck]

Since you are in Vancouver I'd call up Frank at Lyons Technical Machine in Aloha to have him check over your crank and rods plus any machine work you need, not cheap but the best never is.