Author Topic: cycle -x pistons (Read 13209 times)

MRieck · « **Reply #25 on:** September 16, 2009, 05:12:18 AM »

Quote from: mick7504 on September 16, 2009, 02:44:31 AM

The Post Mortem will be interesting.
Curious $:-\$

Me too.

754 · « **Reply #26 on:** September 16, 2009, 08:27:06 AM »

try running a second plug gasket under the plugs that hit & see if it runs . (new plug, of course)

Big Bob · « **Reply #27 on:** November 11, 2009, 08:58:34 AM »

The engine has been opened. It ain't pretty. Pics to follow.

MRieck · « **Reply #28 on:** November 11, 2009, 09:02:17 AM »

Quote from: Big Bob on November 11, 2009, 08:58:34 AM

The engine has been opened. It ain't pretty. Pics to follow.

That sucks Bob.

MRieck · « **Reply #29 on:** November 11, 2009, 09:05:23 AM »

What is your initial diagnosis?

Big Bob · « **Reply #30 on:** November 11, 2009, 09:32:52 AM »

Piston failure, intake side. Chunks of ring got loose and bounced around for a while. Downloading pics, emailing consulants, etc. Watch this space.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #31 on:** November 11, 2009, 09:44:44 AM »

1 piece oil rings?

Big Bob · « **Reply #32 on:** November 11, 2009, 09:52:24 AM »

kos · « **Reply #33 on:** November 11, 2009, 10:14:20 AM »

OK Bob, this is how it works. First you take some truth serum (ie: cold biers) and then you tell us just what RPM this engine sees on acceleration or more importantly deceleration. How many hours on these new pistons and who put it together?

Inquiring minds want to know.

JLeather · « **Reply #34 on:** November 11, 2009, 10:18:06 AM »

Yeah, I second that. That's a really odd place for a piston to fail. Looks to me like it overheated. Cast pistons don't take overheating very well.

Big Bob · « **Reply #35 on:** November 11, 2009, 10:32:50 AM »

This engine came out of Garry Bird's old race bike which I bought from him when the engine quit.

Engine was never, ever over 9,000 rpm. Pistons are Cycle X 850cc kit. Garry came over last night and we tore into the engine this morning and this is what we found.

Hours? Don't know an exact number. I can say that the engine ran at a total of 4 practice/track days and 3 race days. Garry doesn't exactly ride like an animal, he treats his machines well. Garry assembled the engine. He's been doing this for a few years. Like 40 or so. Crewed for some pros back in the day, etc. He knows what he's doing.

More pics:

So. What says the SOHC4 brain trust?

Toxic · « **Reply #36 on:** November 11, 2009, 11:03:19 AM »

Common spot for a piston to fail. Looks like it ran lean and overheated.

paulages · « **Reply #37 on:** November 11, 2009, 11:11:17 AM »

Quote from: Big Bob on November 11, 2009, 10:32:50 AM

This engine came out of Garry Bird's old race bike which I bought from him when the engine quit.

Engine was never, ever over 9,000 rpm. Pistons are Cycle X 850cc kit. Garry came over last night and we tore into the engine this morning and this is what we found.

Hours? Don't know an exact number. I can say that the engine ran at a total of 4 practice/track days and 3 race days. Garry doesn't exactly ride like an animal, he treats his machines well. Garry assembled the engine. He's been doing this for a few years. Like 40 or so. Crewed for some pros back in the day, etc. He knows what he's doing.

More pics:

So. What says the SOHC4 brain trust?

looks like an overheat to me... you can see where the skirt was grabbing the cylinder wall, and the exploded section looks like it has side wear as well. if you weren't saying how skilled your builder is, i'd suspect tight ring gaps with the bits of ring everywhere, but i guess they could have simply failed when the piston expanded. do you know what your piston to wall clearances were?

mec · « **Reply #38 on:** November 11, 2009, 11:40:59 AM »

one time we had a similar failure.
pistoncrown and pockets self machined......too less material between the in-valve pocket and the compression piston ring groove, 3mm top ring land (oem piston had 4.5mm, racing >6mm).

mec

kos · « **Reply #39 on:** November 11, 2009, 11:51:38 AM »

Looks lean to me..can we see the other spark plugs?

KOS

Big Bob · « **Reply #40 on:** November 11, 2009, 02:44:16 PM »

Garry and I have been debating the failure and consuming truth serum while smoking giant cigars and cleaning my garage. Garry's pet Scary Genius Jan Svensen (formar pro racer, bad-ass mechanical engineer) agrees that it's heat related. Garry does not think the engine was running lean, it was jetted properly and ran great, plugs showed a nice even burn.

Now I have to decide what to do next. I want to run a bike in AHRMA Heavyweight Superbike next year. I'm on a tight budget though - gotta pay for the house, pay bills, feed kid, etc. And the overtime at work ain't what it used to be. I know I can't build a bike that will run at the front, aside from not having the budget there's also the fact that I am too big to be doing this stuff. And I suck.

Hmmph. More beer first.

Old Scrambler · « **Reply #41 on:** November 11, 2009, 05:17:55 PM »

I am +1 with mec..............Lets see what the other failed piston looks like. Bob....at your size, I'll give you a few cc's over stock but I don't know about 100.

kos · « **Reply #42 on:** November 11, 2009, 05:50:47 PM »

Those die cast pistons are OK for street, but if you want to go Racing look into the JE 836cc kit. Forged, each piston is made to fit in it's proper bore. IR: Right handed or left handed...due to valve offsets in heads.

I'll help you out with prices.

KOS

750Caferider · « **Reply #43 on:** November 11, 2009, 09:28:11 PM »

For those of you that have a bent spark plug you can do what I did to limp along the #4 cylinder on my bug... Add some washers to the new plug gapped at .28 and away you go... Don't do it for to long as you may end up welding the plug to the head if it's real bad... That piston just looks ugly... Any chance it was due to detonation? Effing noobs and their questions...

Cheers,

Anders

bryanj · « **Reply #44 on:** November 11, 2009, 10:19:00 PM »

Used to see similar on CB250K4 way back when if the engine was "thrashed" from cold. Best reason we ever came up with was that warming too quick nipped the ring causing it to shatter then a piece would work its way out upwards but that was just an unproved theory

Big Bob · « **Reply #45 on:** November 12, 2009, 03:27:53 AM »

Quote from: Old Scrambler on November 11, 2009, 05:17:55 PM

Bob....at your size, I'll give you a few cc's over stock but I don't know about 100.

No, no - I will not be running this engine in my former class, Production Heavyweight. This is for Superbike Heavyweight. Different rules. I can't even afford to build an engine as big as the rules allow.

Big Bob · « **Reply #46 on:** November 12, 2009, 03:29:36 AM »

Quote from: kos on November 11, 2009, 05:50:47 PM

Those die cast pistons are OK for street, but if you want to go Racing look into the JE 836cc kit. Forged, each piston is made to fit in it's proper bore. IR: Right handed or left handed...due to valve offsets in heads.

Is there a difference between the JE parts and Wiseco? I mean besides the fact that I've got the Wiseco parts in my basement right now?

754 · « **Reply #47 on:** November 12, 2009, 07:40:50 AM »

Is it just me, or is the valve cutout rather large/ & maybe a bit close to the ring land? Slight radius on edge of cut would not hurt it either?

Are those 10.5 to 1 CR ?

JLeather · « **Reply #48 on:** November 12, 2009, 08:30:03 AM »

Those valve cutouts look exactly the same as my set of old Wiseco forged pistons. Same piston across all 4 cylinders, and fairly sharp in the pocket. I think a number of other piston makers used an almost identical style in some of the cast ones too, maybe ART?

kos · « **Reply #49 on:** November 12, 2009, 02:50:27 PM »

Wiseco & JE. I sell both, but the JE pistons are more custom fit to cylinder head especially in valve cut out department. I have won a lot of races with Wiseco, but I like the JE 836cc kit best. More money of course.

KOS

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Author Topic: cycle -x pistons (Read 13209 times)