Harsh Reality Pics - The Black Museum

It looks like a Grenade went off. The damage I have done to pistons was a tiny melted hole in a Bonnie once and a few melted ring lands on the inlet face in my 3C
 
I had those electronica pistons in my SF - yes I know they don't suit the motor - and both of them developed those cracks, from the oil hole in the ring land through to the gudgeon. There was no contact with the squish and the compression was not up to spec.
 
Yamaha YZF750 do exactly the same - most go un recognised and probably run for ages.
If your small end bush is rotating has the rod end gone oval ? Again oval small ends is a Yamaha problem, gives an off load rattle on overrun , I’ve done a lot of V Max’s with this all caused by over revving. The knocking would also bring on the crack in the gudgeon pin boss in the piston.
 
Thomas aus LAU said:
Originally we only wanted to replace a defective (rotating) connecting rod bearing from a friend´s 750 SFC Electronica.
We came across several cracks in both pistons (see red color). I've never seen it like this before.

Does anyone have any idea where this can come from?

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Thomas aus LAU
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I've got an unused pair of them here, if anyone wants to buy 'em! I suspect detonation. Perhaps the lack of a swish band contributes? Running 40 degrees advance on those is pretty extreme, even if CR isn't up to spec.
 
Exmoor beast said:
Yamaha YZF750 do exactly the same - most go un recognised and probably run for ages.
If your small end bush is rotating has the rod end gone oval ? Again oval small ends is a Yamaha problem, gives an off load rattle on overrun , I’ve done a lot of V Max’s with this all caused by over revving. The knocking would also bring on the crack in the gudgeon pin boss in the piston.
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Agreed. The first Yamaha oval small ends i saw were first gen FZR1000. The H**** V4's do it too.
Those pistons I'd say are simply not up to the job. The internal strutting around the pin bosses is unusual too. Which may have contributed to the cracking.
It's good practise to crack test reused parts. Cheap but good insurance.
 
Just as a counter, sometimes it goes right.
Out with mate, Steve, night before last. He stopped me after he noticed something dangling from underneath the bike. Turned out to be the battery breather, which had caught the back tyre and been spat out, as I stopped.
I put it in my pocket and carried on for many miles of spirited riding.
Went out to the garage to refit it, today, only to find that the elbow which attaches it to the battery was missing.
Crap! I thought but, upon searching, I found it trapped in the cable tie that normally secures the hose to the swing arm.
Question is, should I buy a Lottery ticket?IMG_2916.JPG
 
it is likely that the elbow fell out before the hose became detached from it, almost definite in fact, is this a £10 Halfords battery? doesn't really matter, but clean the male and female parts for the elbow with spirit and glue it in place with superglue of some sort.

I had better have a look at mine

CLEM
 
CLEMTOG said:
it is likely that the elbow fell out before the hose became detached from it, almost definite in fact, is this a £10 Halfords battery? doesn't really matter, but clean the male and female parts for the elbow with spirit and glue it in place with superglue of some sort.

I had better have a look at mine

CLEM
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Agreed, Clem.
It seems the hole in the Yuasa ( David 'Truffle-Sniffer of the Year' Finch's Halfords Special £10 Laverda Battery) is slightly larger than the previous Banner. A wrap of PVC tape has it in there securely. Always a nice feeling. ;)
 
Hello Hamish,
is it possible that the breather hose for the battery was secured with a cable tie down there? And that when the hose was caught by the rear wheel and pulled along with it, it then pulled the elbow out from the battery at the top? But only until the elbow got to the cable tie, it finally got stuck there ...

Cheers,
Jo
 
Jo said:
Hello Hamish,
is it possible that the breather hose for the battery was secured with a cable tie down there? And that when the hose was caught by the rear wheel and pulled along with it, it then pulled the elbow out from the battery at the top? But only until the elbow got to the cable tie, it finally got stuck there ...

Cheers,
Jo
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Yes, Jo, as Clem said, above.
But I was slightly surprised that it hadn't fallen out during 60+miles of spirited riding (obviously, complying with all posted Speed Limits), on frequently dubious road surfaces.
 
v2ventiler said:
original pistons? I mean what make?
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Original ASSO (no. 2077) in 80.0 for the 1975 Electronica.
The pistons were the type, that only had one reinforcing rib in the piston crown.
There is also a second version with several ribs.
The pistons have been driven about 2000 km on the road, no race and with a sensible driver.
Ignition-timing, sparks, balancing of carbs, valve-clearance,....... where ok.

Thomas aus LAU
 
Dellortoman said:
Just an idle thought ... attaching the hose to the swing arm (which oscillates) may have imparted oscillating forces that were transmitted up the hose to the spigot on the battery, which shook it out.
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Thanks, Dellortoman. The hose is loose in the tie allowing it to move freely. The problem was that the orifice, in the battery was a little larger than the elbow, now resolved.
 
Thomas aus LAU said:
Before you invest money in the lottery, I recommend that you first invest money in sealants or new sealing rings. The housing looks a bit (too) oily. The way to the rear tire is not far ... Loctite and friends will help you. ;)

Thomas aus LAU
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Thanks, Thomas. That's, probably, 25,000 miles worth, since I last degreased the back of the engine. It stops the winter road salt whitening the alloy. ;)
 
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