Author Topic: PoofKaboom! What Causes The Swiss Cheese Effect? (Read 7211 times)

PilotSniper · « **on:** July 19, 2004, 09:38:49 PM »

I've experienced this problem twice in my short Pilot life.

The first PoofKaboom was due to not knowing that the Pilot I had just purchased was set up for high octane race fuel. By using regular 93 octane fuel, it caused a premature meltdown of my piston and cylinder head (or so I was told). The end result was extensive pitting of the top of the piston, the cylinder head dome and nasty scratching of the cylinder itself.

The second time was Thursday of last week when I unexpectedly drove into Lake Okeechobee during a wide-open throttle run at night (long story). Either way, I could not maintain idle after coming out of the thigh-high water and knew immediately something was wrong. After performing a compression check after cool down and coming up with only 75lbs of compression, I confirmed my fears. Tonight, I tore her down only to find the same thing I had found when I had the unknown race fuel setup. The top of the piston and the cylinder head dome was pitted like swiss cheese. Fortunately, the cylinder itself suffered no scratching at all because I had it coated with the carbide process at Bore-Tech (in my opinion, this process is a VERY necessary must have!).

My dilemma is, I don't have any trashed bearings and my intake is filtered twice. What actually gets in between the piston and the cylinder head to cause the swiss cheese effect? Is it part of the actual piston that breaks off and causes this? Please enlighten me! :?

ludedude · « **Reply #1 on:** July 19, 2004, 09:42:10 PM »

Pieces of the piston, rings, wrist pin clips. They can all do it. I had a wrist pin clip come out once (not inserted correctly??) and made a MESS.

How much compression were you running? Detonation again?

Cool Carbide process works again. Gotta love it

PilotSniper · « **Reply #2 on:** July 19, 2004, 10:22:16 PM »

Quote from: "ludedude"

Pieces of the piston, rings, wrist pin clips. They can all do it. I had a wrist pin clip come out once (not inserted correctly??) and made a MESS.

How much compression were you running? Detonation again?

Cool Carbide process works again. Gotta love it

The rings and wrist pin clips are all there. The only thing missing is the mass from each of the little pits. Wierd!

I was running 167lbs. of compression after the rebuild with a cut down head from PCP. The PoofKaboom brought that number down to 75lbs.

Whatever happened, I hope it never happens again!

And, yes, Bore-Tech rocks!!!

ludedude · « **Reply #3 on:** July 19, 2004, 10:35:16 PM »

I think PH got away with 170 with one of Moskito's heads. But I believe....they say 167 would be on the high (read danger) side for compresion with pump fuel. If you can't find pieces missing from other components, I'd say detonation did you in...that's just my hardly educated in 2-stroke opinion though

PilotSniper · « **Reply #4 on:** July 19, 2004, 10:59:48 PM »

Quote from: "ludedude"

I think PH got away with 170 with one of Moskito's heads. But I believe....they say 167 would be on the high (read danger) side for compresion with pump fuel. If you can't find pieces missing from other components, I'd say detonation did you in...that's just my hardly educated in 2-stroke opinion though

I remember Skeeter saying something about not going over 160 with pump fuel, but when I got the rebuild done, it read 167. I think PCP shaved a little too much on the lathe. She ran hard while she lasted, but now it's time to move on and do things right. I think I'll be going with a standard cylinder head this time around. No more shaved heads for me!

By the way, detonation is a possibility since the underside of the piston is a nice shade of toasted black! I'll post pics once I get them out of the camera.

Thank you for your hardly educated 2-stroke opinion! :lol:

ludedude · « **Reply #5 on:** July 19, 2004, 11:12:23 PM »

Quote from: "PilotSniper

...now it's time to move on and do things right. I think I'll be going with a standard cylinder head this time around. No more shaved heads for me!
Quote

K-Fab head and interchangeable domes....or I have a couple heads that you can have, they need to be cleaned up though. I also have a PCP head that you're welcome to 190 psi!!

PilotSniper · « **Reply #6 on:** July 19, 2004, 11:36:49 PM »

Quote from: "ludedude"

K-Fab head and interchangeable domes....or I have a couple heads that you can have, they need to be cleaned up though. I also have a PCP head that you're welcome to 190 psi!!

K-Fab head = Cool! This is Skeeter's Secret Squirrel Stuff, right?

PCP 190 head = Major PoofKaboom! Nah, I'll pass!!!

I appreciate the offer on the other heads, bud, but I need to pay for my mistakes! Oh, and it looks like I'll be paying... :cry:

ludedude · « **Reply #7 on:** July 19, 2004, 11:39:38 PM »

Well you can pay to have them rechambered.

johnhbd · « **Reply #8 on:** July 19, 2004, 11:57:52 PM »

I ran into the same problem. After two pistons it became apparent that the crank bearing for the rod was breaking apart. I thought I had checked the travel in the bearing but after I disassembled the motor the ends of the bearings were coming off. The top of the piston looked about how you described yours. Hope this helps, if not it was fun trying.

MassOdy · « **Reply #9 on:** July 22, 2004, 03:07:56 PM »

I wouldn't mind hearing the long story.

WOT around the lake at night. Cool.

I hope you get back up and running soon.

PilotSniper · « **Reply #10 on:** July 24, 2004, 06:10:42 PM »

johnbd, thanks for the tip. I've looked as best as I can at the lower crank bearing and all looks well.

MassOdy, it was cool until I took her down to periscope depth, then I remembered I was still in the Pilot! Next time we're out riding, bring the icy beer and I'll fill you in on the details of my escapade into "Hidden Lake". :oops:

I finally found the time to order parts and get pics out of the camera. They're in the gallery here:

http://www.p-o-ps.com/coppermine_dir/thumbnails.php?album=50

Feel free to express your thoughts as to what might have happened.

johnhbd · « **Reply #11 on:** July 25, 2004, 11:09:16 PM »

Sorry to sound like a broken record but I looked at the pictures you posted and the piston and cylinder look identical to mine. The first time I thought the bearing was fine. Does the piston and cylinder grooves appear to have square edges?. I have been a mechnic for over 30 years and it fooled me.
John

PilotSniper · « **Reply #12 on:** July 25, 2004, 11:22:46 PM »

Quote from: "johnhbd"

Sorry to sound like a broken record but I looked at the pictures you posted and the piston and cylinder look identical to mine. The first time I thought the bearing was fine. Does the piston and cylinder grooves appear to have square edges?. I have been a mechnic for over 30 years and it fooled me.
John

John, after speaking to Odykid, Moskito and Ludedude, it seems as though you hit the nail on the head! A bottom-end rebuild is in my immediate future. It's one of the things I told myself I never wanted to get into, but I guess it's unavoidable at this juncture. Thank you for your input. I'll post my findings as I get there.

Thanks again!

ludedude · « **Reply #13 on:** July 26, 2004, 07:53:25 AM »

Sniper, I've got a case splitter tool, you want it? Plus i'll dig up the info I started if I can find it when I rebuilt mine

PilotSniper · « **Reply #14 on:** July 26, 2004, 02:10:44 PM »

Quote from: "ludedude"

Sniper, I've got a case splitter tool, you want it? Plus i'll dig up the info I started if I can find it when I rebuilt mine

Yes, yes and, uh, yes!!! Any tools and info you can send my way will be greatly appreciated!!!

I know I've said this before on more than one occasion, but, where the hell would I be were it not for all of you guys?

Thanks Lude!!!