Pictures of what happens when u run 13:1 on pump gas

[d3ktrix]

I was looking through my old photobucket pictures and found this.
Cell phone picture of my friends head after it popped.

It was an 04 450R with a 12.5:1 piston and a +3 crank, which makes it just under 13:1.
Stock valves, Hotcams S2

There was so much detonation that a large amount of metal was eaten away from the head around each valve and plug. You can actually see the valve seats exposed.
The spark plug looked like a x-mas tree of metal flakes too.

Then I'm guessing some large chunk of the head cam off and shot out through the side of the chamber.

http://i252.photobucket.com/albums/hh6/d3ktrix/PIC-0132.jpg

Here is a picture of a normal head so u can see how much was really eaten away.
http://i252.photobucket.com/albums/hh6/d3ktrix/cleanhead001.jpg

[Honda5]

WOW how lean was that motor? and how did it last that long?

[Ruf Racing]

That goes to show, 13:1 is the edge for pump gas. Some guys can
get away with that ratio without issue. Some can't.

[ds268]

I would argue that was cause by an extreme lean condition for some amount of time. Running premium pump with 13:1 is normal here. Lower elevation will probably need more octane but that's exactly what the head looks like even on some local turbo drag cars that are tuned too lean.

[BlaineKaiser450]

That looks nasty haha

[d3ktrix]

Originally posted by ds268
I would argue that was cause by an extreme lean condition for some amount of time. Running premium pump with 13:1 is normal here. Lower elevation will probably need more octane but that's exactly what the head looks like even on some local turbo drag cars that are tuned too lean.

Bike had a bored CRF carb with a 180MJ and 50pilot. Dasa exhaust, Uni filter, no lid.
600ft elevation at the place it was ridden most, summer weather when it blew. Engine had low hours on it when it blew since its last rebuild.

Unless it had an air leak that jetting should be rich if anything.

[Butter]

Was that McDermott's motor?

[d3ktrix]

Originally posted by Butter
Was that McDermott's motor?

Ya his practice bike, mostly used for pit ridding.

[Butter]

LOL, that kid has gone through more engines than anyone I know, lol. He even destroyed a "stock" motor on that '08 he had. Always liked racing with him though. Sucks he stopped.

[d3ktrix]

Yeah he has had bad luck with engines, and rear shocks. lol
He always took care of them too.

He never blew up the stock 08 that I know of, it was kind of messed up when he bought it used. I think that engine had some kind of heat problem before he bought it.
The timing chain was super kinked up and so stretched that the tensioner didn't even touch it. And while we were putting the flywheel back on with the new cam chain, the end of the crank snapped off so we had to split the cases because of that. lol Either a casting flaw or heat damage IMO, some stuff was weird colored in that engine, and smelled like horribly burnt oil.

[Butter]

Damn, I guess with that kinda luck, I would of just gave up too. Blows *** when you can't even make it through race day cause your bike won't let you. Had all that when I had my Yama-bomb.