All quiet on the home front ???

unclerob

Been Around the Block
Thanks TJ, it was a quick build for the Bikeshed show as they wanted a bike that hadn't been shown before ....
 

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semmins

Been Around the Block
DTT BOTM WINNER
Took the Guzzi out for another test ride this morning.
 

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beachcomber

TJ - Beachcomber
DTT SUPPORTER
You guys have been remarkably quiet again .... expecting something fantastic to roar out of those sheds and workshops soon !!!! 8) 8)
 

yorkie350

If it runs ride it if it dont polish it & dream !
DTT BOTM WINNER
Quietly tinkering now the days are drawing in but sure we're still building quality as yozzers build proves, another Brit BOTM ;)
 

Titan performance

Titan cafe racer builders.
Sadly, my fave 500 coughed up a lung while on my way to a classic bike meeting in a village just outside Dover....
I limped back home on one cylinder about three miles, which, in hindsight, probably wasn't a good idea. Both skirts had sheared off the left piston, and the debris falling into the crank case has toasted the crank......bugger !
 

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teazer

Over 10,000 Posts
DTT BOTM WINNER
Titan,

How old is that piston? Top looks like there has been detonation but skirts look remarkably shiny. Is that grooved piston design still available or are they all simple (smooth not ribbed) pistons now. Presumably that was for her extra pleasure and sensitivity......
 

Titan performance

Titan cafe racer builders.
To be honest Teazer, the piston is positively ancient, and coupled with the intermittent oil delivery to that cylinder (constant oil bubbles in the line), I guess disaster was inevitable. The poor old thing gets ragged heavily, and the engine has never been rebored. I've got a crank on the way, and some fresh cylinders and pistons to fit. The French tickler, or as we call them, ribbed pistons, were fitted to the T....the plain 750 style were fitted to the GT.
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
Good news is that they lasted way longer than expected. Out with the old and in with the new.
 

CarbsAndCylinders

Careful With That Axe Eugene
Does anyone know the purpose of the ribs on the pistons, I never found that ribs made much difference but then I thought they went on the inside. Seriously, were they to hold oil onto the piston or what.

Would it have been possible to rebuild the crank but cheaper to buy another?

Speaking of cranks, what do you guys think of the scalloped ones, I don't understand why this would not screw up crankcase compression but then I am the guy who put the ribs on the inside, (I wonder where Rosie is today, hmmm).

Brian
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
CrabsAndCylinders said:
Does anyone know the purpose of the ribs on the pistons, I never found that ribs made much difference but then I thought they went on the inside. Seriously, were they to hold oil onto the piston or what.

Contact reduction. Less surface area for friction. They're more often run, especially on cammed motors, above the rings.
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
On that old two stroke design I would suggest that they are there to retain oil rather than reducing friction. At the time a 250cc single was fairly big for a 2 stroke and a 500 twin was really adventurous for the time.

Wiseco et all machine small grooves above the top ring to reduce the flow of combusting gas down to the top ring. They disrupt flow towards the ring.
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
teazer said:
On that old two stroke design I would suggest that they are there to retain oil rather than reducing friction. At the time a 250cc single was fairly big for a 2 stroke and a 500 twin was really adventurous for the time.

Wiseco et all machine small grooves above the top ring to reduce the flow of combusting gas down to the top ring. They disrupt flow towards the ring.
Funny, I thought oil was there to reduce friction. Look up JE pistons. They have diagrams on their site that say exactly why the rings are there.
 

unclerob

Been Around the Block
Yet another Honda built....one day I'll do something different!
 

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beachcomber

TJ - Beachcomber
DTT SUPPORTER
unclerob said:
Yet another Honda built....one day I'll do something different!

You just keep doing the beautiful work you're doing - it's an inspiration for the rest of us mere mortals ............. always an Aer Macchi ?????
 

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