Swapping cranks

[Robbo]

G,day all just a couple questions for you mechanical maistro's ... Ok I have a 79 special Im rebuilding/bobbing which includes a complete ground up rebuild both motor and bike.. I have the matching 447 motor that goes with the bike and I have a spare older 256? motor .. Anyway I want to know which is the stronger more reliable of the 2 motors 256 or 447? also can I run the crank from a 72 which I guess would be a 256? in a 447 motor?
Im going to do the cam sprocket swap running the cam sprocket from a 256 on the 447 cam as I was told this is a good cheap and effective performance upgrade,also an upgrade I can do myself and not have to farm out to an engineer or engine shop..
Im a single dad battling to take care of my 3 sons on my own and money isnt plentiful I have had my boys on my own 13 yrs now and I have had my passion for motorcycles on the back burner till now! Basically Im trying to get this bike built as cheaply as possible because thats the only option lol.. Thanks in advance guys this site has really kept me sane lately..

 

[650Skull]

A 256 Cam into a 447? the 447 sprocket has to go on the cam. Never heard of any one putting a 256 crank into 447 cases before usually the other way around, hard to get 256 conrods but mikes sells pistons rings and pins that are set up for the 256 rod.

 

[Robbo]

No I wont be putting a 256 cam in a 447 just swapping the sprockets..

 

[Punkskalar]

If you use a 256 Crank, you'll need to use a 256 Cam gear to match it. They are driven at a 2:1 ratio. So a 256 Crank has 1 less tooth than a 447 Crank will have. Of course, you could disassemble the cranks, and swap all the gears around, but thats a huge pain in the you know what.

AND, if you really want to use a 256 Crank in a later engine, you'll be wanting to swap out all the tensioner and cam guides along with the cam chain to match. Quite a bit of work, but if you have all the parts, not a big deal.

I personally would use the 447 Crank, swap a 447 Cam Gear onto the 256 cam (I like the early 256 cams for my personal builds) and then you have a nice selection of pistons and rods should you need them.

 

[hotdog]

What other bits do you need for your build Robbo..??

 

[Robbo]

g,day hugh.. I was talking about just swapping cam sprockets... I was only asking about using different crank out of interest..
G,day hotdog.. I need a decent pair of engine side cases both clutch and alternator side also a decent set of carbs for a 79 special running the 447 motor.. Would dearly love a set of spoked rims but those are wish items not a necessity as I do have the mag rims for it.. Oh and if you know of anyone with a good working wiring harness that will work with a 79 at a decent price...

 

[hotdog]

Robbo,

I have a set of BS38 carbs you can have if you want, they came of a runner & worked OK, they just look ugly & have a few stripped float bowl threads - nothing that couldn't be fixed, diaphragms also work fine. Let me know if you want a photo or 2.

 

[Robbo]

I will get back to you on that if thats ok? Thanks a million Hotdog..
Im making up my mind on how I want this bike to roll.. bs38,s or the pwk34,s not being a mechanical giant tuning carbs is all japanese to me so to speak and was thinking the pwk,s may be an easier set up to manage for a newb like me?

 

[Robbo]

On a side note.. I have to say the Brotherhood of the road I have experienced on site here on the good days observing the selfless attitudes of some forum members makes me proud to be associated with classy blokes like you all...
Thanks guys Really... Thanks!

.. Chris aka Robbo ..

 

[hotdog]

let me know when you decide, I wont be using them.