Pilotman top end,

I removed the aluminum on the cylinder wall using muriatic acid then hit it with a hone just enough to check for uneven wear patterns, the bore measures 3.151 the largest measurement I found on the piston was 3.141 giving you a whopping .010 piston to cylinder clearance, did Liewire setup the last piston in this machine? it is a wiseco piston but good god that is .006 too much! There are some lite vertical scratches above the top of the exhaust port that would not hurt anything and you could run it that way but the piston to cylinder clearance is so great you need to bore this out to next bore, there is no out of round, cylinder taper, you can still see the hone marks from the last rebuild, so the bore was not worn over size, looking past the damage from the seizure you can see the piston was low hour because the factory machine marks are still clearly visible so the piston was not worn under size, if you look at the exhaust side of the piston you can still see a shadow of the exhaust port engraved on the piston, this happens when there is excessive piston to cylinder clearances, the weight of the piston is thrown against the cylinder wall on the exhaust side as the piston reaches BDC and the rod angle is changing.

The head has been cut more than once, it has been cut so far that the metal tab used to indicate the rear of the Engine is gone, that tab is usually about 1mm thick on a stock head, I am guessing there has been about 1mm removed from the head, for reliability reasons I suggest you use another head this head has had too much material removed in the past and removing more will not help things, the damage is at least .030 deep.

You can see there is still a chunk of metal stuck in the top of the piston, speaking from experience GRRRRR I suspect that is a rivet out of the bearing separator on the clutch side crank bearing stuck in the top of your piston. http://pilotodyssey.com/Poofkaboom2003.htm

ATVR poofkaboom

Update, Pman sent me his bottom end and I now have it apart, just as I
suspected the heads of the rivets are coming off the clutch side crank
bearing ball seperator, I found 2 of them by the crank seal and one is
still stuck in the top of the piston (see above pic), who knows where the
4th one is...

This has happen to me 3 times, 2 times was with the factory installed bearings,
and the 3rd time was with a bearing I replace (Honda part) but it was 2-1/2
seasons old, now it has happen to Pilotman, his bearings were factory the factory
installed bearings, I suspect the same thing has happen to Pilotsnipers Pilot? He
get his bottom end apart? I would suggest to anybody that has not replaced their
crank bearing to do so, Odykid I will use you as any example here, your first Pilot
was clearly a low hour machine I might let it go a few years and put some more
hours on it then replace your second Pilot clearly had seen a bunch of miles on it
so I would pull the Engine and replace the bearings and seals while it is still running
and before it comes apart and damages the top end like it happen to me and Pilotman,
new head is 150 bux top end kit is 130 bux? if you need to bore the cylinder because
of the damage add another 40-60 bux, so if you let it go it will be doing roughly 300
bux in damage ....

Hoser, should I worry about my new bottom end as well as Odykids?My bearings were factory replacements, didn't Moregoodlier have the same type problem with his aftermarket replacements on 1 of his pilots as well?

Hoser, I showed some or the photos of the bearing failure to one of the test gurus at work (he worked on the Pilot development years ago). He had a few ideas of why the bearing might fail.

1) The crank is not ‘square’. I’m not sure about this one in your case. However it makes sense. if the webs are not aligned correctly it would cause vibration in the bearings.

2) The bearings have some pits on the running surfaces. Could be a problem with the part or from wear (spalling). This would cause vibration like 1) above.

3) Parts history. It is possible that the bearings you get today are not exactly the same as what was fitted originally. Crank bearings are often special bearings. They will be the same size as a standard but they might have closer tolerances or the retainers fit closer or the rivets are stronger. Who knows. Sometimes problems that show up in development get's fixed with a band aid at the last minute.

Do you still have the parts around? Are you willing to send them to me? I am leaving for a week at Atlantic Beach NC in the morning but… I will e-mail you my snail mail address when I get back (it’s a long story but I don’t have e-mail at home right now). I would love to get to the bottom of this to let others know how to avoid it (don’t everybody get your hopes too high, my contacts may not have all the answers and it’s not like I can call the manufacturer up and demand a big investigation).

Yeah I still have some of the failed parts and would like to get an answer, let me know
your address and I will ship you the parts, you can send me a private msg here on
the board if you don't have email....

my person feelings about the bearing issue is that the balls themselves expand dispropotionately (more) to the cage, however slight. when the balls are larger (huh-huh, huh-huh) it tries to spread the cage apart, the rivets are the only thing holding the cage together and in turn the rivets get loose or just start popping like Orville Reddenbocker



As for the Pilotman rebuild (or ANY REBUILD) It would be CRAZY to tear a motor (( Internal Combustion Engine ? )) down that far and not rebuild the crank
hell for another $100. in parts and $50 (or less) in labor the entire motor (( Internal Combustion Engine ? )) would be freshy fresh. Unless it was a just rebuilt crank, that you personally know the history of, I would never waste a bunch of new parts on a unsure foundation.

some things that could be wrong with crank

I little piece of metal melted someplace you can't see it (thrust washer or maybe in the cage corner)

The guy that rebuilt the motor (( Internal Combustion Engine ? )) before might have left the crank sit on a bench not soaked in oil in a plastice bag, unprotected it could start to rust immediately.

I have had perfectly fine cranks in my hand, measured fine, looked fine, known recent rebuild, and still have it fail on me. The one thing I noticed was this happens (crank failure after a rebuild and not rebuilding the crank) more often if the top end had a violent ending or even a seize. Now a days whenever that happens I rebuild the crank too so there is no doubt. If i was replacing a piston or just generally refreshing the top end I would leave the crank alone if it checked oiut good and be sure to not to let it flop around (rubberbands) or have any sideways stress put on it (removeing piston without proper tools)

BTW That was more for general discussion rather than telling Pilotman what to do.

I guess I could agree, when my bearing separator failed the first time
I went with a whole new crank and bearings, my rule of thinking was
if the first crank and bearings lasted 10 years then I could expect at
least 5 years on the new one, I got 2 years then the clutch side bearing
ball separator went again, I rebuilt the bottom end and then shortly there
after the cage that holds and separates the big end rod bearing (bearing
cage) failed and started spitting out pieces so I installed my factory original
crank as a replacement, it looked and felt perfect I had other experienced
Engine builders inspect it, we all agreed there was nothing wrong with it
and that is why it was kept for a spare, then after about 50 hours use the rod
bearing turned blue and locked up my Engine tight, maybe like you said
something I could not see was stuck in the bearing, maybe when it beat the
hell out of the top of my piston it stressed the bearing? Ever try to take a
small chunk of metal and a hammer then try to drive the metal into the
top of the piston, try a nail there is a lot of force put on rod when a chunk
of metal is driven 1/8" into the crown of the piston, perhaps this is doing
hidden damage?

after thinking about that some more it sounds pretty stupid, if the balls got to a size that would spread the cage the bearing would be past the point of no return.

once the cage and balls got to a point where they touching enough to effect the cage they would start melting regardless of the cage or rivets, maybe the rivets are just coming loose

I dunno I don't discount any idea until I can prove it wrong, I want to have an
expert look at the failed parts and see what they say...

http://pilotodyssey.com/pilotboom2.htm

I gotta do some digging I am not sure I still have that bearing that is in that picture..

Pman will be gone until late Sun night I will hold off the assembly of his Engine
until we talk this over..

His crank has one mark on the crank pin using the rod chart at service Honda what
part numbers do I need to use to order a new rod?

Wonder if hillside or Mario can order the Pro-X 500 rod kit ?

Hoser, I was looking for something else when I came across this tidbit of information. From a book, Two Stroke Performance Tuning by A. Graham Bell. 7th printing in ’97. Chapter 7 ‘The Bottom End’, page 147.

“If you wish to use bearings better than those fitted as standard, you may be able to obtain a suitable replacement from the German INA company. There two-stroke bearings are the best available. Try to get main bearings with fatigue resistant plastic or fiber cages rather than riveted steel cages which seam prone to cracking up.”

He goes on to say that some modification is desirable to improve the lubrication of the plastic cage bearings.

Hoser, I was looking for something else when I came across this tidbit of information. From a book, Two Stroke Performance Tuning by A. Graham Bell. 7th printing in ’97. Chapter 7 ‘The Bottom End’, page 147.

“If you wish to use bearings better than those fitted as standard, you may be able to obtain a suitable replacement from the German INA company. There two-stroke bearings are the best available. Try to get main bearings with fatigue resistant plastic or fiber cages rather than riveted steel cages which seam prone to cracking up.”

He goes on to say that some modification is desirable to improve the lubrication of the plastic cage bearings.

http://www.amazon.com/exec/obidos/tg/de ... 9/ref=ase_
successtapcomand/103-1924070-2507048?v=glance&s=books

There is the book! I couldn't find a place to read it online though.

Thanls for the info lee this is probably the same company?
http://www.ina.com/inaupdate/index.asp? ... applet=yes

I have been told about the plastic retainers by others, I have seen them
in other applications like wheel bearings on ATV's I cant get anybody
to tell me the down side of using them I have not seen the ones that
would fit my crank but the ones I have seen that were plastic were
more enclosed and I don't see how they would get lubed as well as the
metal style when used as a crnak bearing, will have to do more research.....


Thanks

Hey guys I have seen bearings that the cages are weld instead of rivets, will those work better than the rivets or plastic ones?

DC do you have access to bearing right? any info on this?



Odykid

This what your talking about Lee ?

We already have the oil feed hole....