Big-bore short-stroke?

[DanielMc]

I'm planning to build an R65 framed special and was going to put a big valve 1000cc engine in it but a friend suggested I tried cutting down a set of 1000cc barrels and assembled the engine using these cut-down barrels, 1000cc pistons and heads.

He reckons that would give a short-stroke motor of around 850cc with the same cornering clearance as the narrow R65 engine.

I like the idea, but I'm wondering how easy/difficult that sort of engineering job might be.

[chasbmw]

I have a feeling that Richard Difazio from Frome somerset,built something very similar around 5/7 years ago and he reported verygood results. It was written up in classic bike I think?

He is semi retired now but the website is still active when I lastlooked, so worth a call

[DanielMc]

Thanks Chas - I've got Richard's email address so I'll ask him directly.

[Garnet]

I have a feeling that Richard Difazio from Frome somerset,built something very similar around 5/7 years ago and he reported verygood results. It was written up in classic bike I think?

He is semi retired now but the website is still active when I lastlooked, so worth a call

Wow, is he still going? I have read a couple of articles about his hub steering forks/frames. Does he still build them?

[DanielMc]

I have a feeling that Richard Difazio from Frome somerset,built something very similar around 5/7 years ago and he reported verygood results. It was written up in classic bike I think?

He is semi retired now but the website is still active when I lastlooked, so worth a call

Wow, is he still going? I have read a couple of articles about his hub steering forks/frames. Does he still build them?

Unfortunately no - the shop closed a couple of years ago. There's a lot more to the family than the hub-steering too - a book most definitely should to be written about the Difazios.

Meanwhile Richard replied to my email, text below:

Hello Daniel,

I think you must be as daft as I am !

Yes, over the last twenty five or so years, I have made several short stroke special R65's, mostly 94m/m bore 850cc, and they are all in regular use with their current owners and I hardly ever see them, so perhaps they are trouble free ? currently I use a monolever chassis with an R65 bottom end, and 88m/m bore which makes a very useful short stroke 750cc.

I have always gone down the road of using an all R65 (or 45) bottom end with rods, with appropriate bigger bore and 1981 on R65 heads, it is probably the most economical and simple route.

In the beginning I always bought Venolia pistons, they are forged, lightweight, slipper type three ring pistons and very strong, and I have never had any trouble with them.

When I thought I was going to do so some sprinting/hillclimbing with a special BMW, I had some R65 cylinders sleeved and bored to suit a pair of 95m/m Guzzi pistons, fitted with a pair of R100RS heads this would probably have been an outrageous machine, however, common sense prevailed.

The popularist theory of 'machining down' R100 cylnders and using R100 pistons and heads, is a bit too simplistic........the R45/65 shorter stroke is achieved by a different crank throw dimension, with shorter rods, and, pistons with the gudgeon pin hole nearer the crown.......so those three things are critical.

Has this given you something to think about ?

Regards,

Richard.

Thanks again to Chas for suggesting I contact him.

[chasbmw]

Daneil,
Sounds as if Richard would build you one if you asked nicely. he has done some work for me in the past and i was pleased with the results. Its a pity that the business is closed as they were very much old school family bike business. i think that the motorcyle jounalist with the surname Difazio, may be a son..........Charles

[Hunsta]

I have a feeling that Richard Difazio from Frome somerset,built something very similar around 5/7 years ago and he reported verygood results. It was written up in classic bike I think?

He is semi retired now but the website is still active when I lastlooked, so worth a call

Wow, is he still going? I have read a couple of articles about his hub steering forks/frames. Does he still build them?

Unfortunately no - the shop closed a couple of years ago. There's a lot more to the family than the hub-steering too - a book most definitely should to be written about the Difazios.

Meanwhile Richard replied to my email, text below:

Hello Daniel,

I think you must be as daft as I am !

Yes, over the last twenty five or so years, I have made several short stroke special R65's, mostly 94m/m bore 850cc, and they are all in regular use with their current owners and I hardly ever see them, so perhaps they are trouble free ? currently I use a monolever chassis with an R65 bottom end, and 88m/m bore which makes a very useful short stroke 750cc.

I have always gone down the road of using an all R65 (or 45) bottom end with rods, with appropriate bigger bore and 1981 on R65 heads, it is probably the most economical and simple route.

In the beginning I always bought Venolia pistons, they are forged, lightweight, slipper type three ring pistons and very strong, and I have never had any trouble with them.

When I thought I was going to do so some sprinting/hillclimbing with a special BMW, I had some R65 cylinders sleeved and bored to suit a pair of 95m/m Guzzi pistons, fitted with a pair of R100RS heads this would probably have been an outrageous machine, however, common sense prevailed.

The popularist theory of 'machining down' R100 cylnders and using R100 pistons and heads, is a bit too simplistic........the R45/65 shorter stroke is achieved by a different crank throw dimension, with shorter rods, and, pistons with the gudgeon pin hole nearer the crown.......so those three things are critical.

Has this given you something to think about ?

Regards,

Richard.

Thanks again to Chas for suggesting I contact him.

Oh god we just cant leave this here. I need details. Details people. Please.
Could we possibley get a Mod to move this thread into the R65 thread. With the permission of the initiator of course.
Craig

[Chuey]

He reckons that would give a short-stroke motor of around 850cc with the same cornering clearance as the narrow R65 engine.

Have you ever run out of cornering clearance on a normal R100 bike? I haven't. I want to scrape those valve covers and have come close but have not done it yet. Or is it for the theoretical clearance? For me that's what it would be.

Chuey

[Major Softie]

Have you ever run out of cornering clearance on a normal R100 bike? I haven't. I want to scrape those valve covers and have come close but have not done it yet. Or is it for the theoretical clearance? For me that's what it would be.
Chuey

It's certainly a genuine problem on a track bike - one which is usually dealt with by raising and angling the motor. On the street, it shouldn't be an issue for any sane rider, but can we all claim ownership of that title?

[Chuey]

It's certainly a genuine problem on a track bike - one which is usually dealt with by raising and angling the motor. On the street, it shouldn't be an issue for any sane rider, but can we all claim ownership of that title?

I guess I can. I've never scraped my valve covers and it wasn't because I was on the street instead of the track.

Chuey