256 crank fit 447 cases?

[nozila]

Hi all,

I have 2 spare 256 cranks which I was curious to know if it fits and is usable inside a 447 crankcase. Physically, they 256 cranks fit (as I've tried) but I want to know can they be used in there and if so what else is required?

Thanks for any help

Nozila

 

[littlebill31]

Yes, it will fit. But you need a 256 cam. The 447 has a different gear, different cam chain length.

 

[nozila]

Thanks for the quick reply. So in essence, I just need a 256 cam. Though they are pretty rare to come by, yes? The reason for all this is because the 447 crank I have is stuffed, one of the rods have ridiculous play and its extremely expensive to rebuild here in Australia.

 

[littlebill31]

You would need the 256 cam and correct cam chain for it to work,

 

[gggGary]

Isn't there an issue with the RH crank end also?
The biggest problem is the 256 cranks have 22mm small ends on the rods, it's a bit of a story as to why they have those big ass holes in them but they are not a reliable part, the rod end will stretch and can fail under hard use.You also need 256 pistons to match them. Find a good or rebuild a 447 crank it will be cheaper in the long run.

 

[littlebill31]

I just remember Hugh stating that you can use the 256 parts in a 447 case. I know you need to match the internals due to timing. I've never done it, but I can see how basically everything needs to stay with one number (256,447) Something about the transmission as well.

 

[hotdog]

Thanks for the quick reply. So in essence, I just need a 256 cam. Though they are pretty rare to come by, yes? The reason for all this is because the 447 crank I have is stuffed, one of the rods have ridiculous play and its extremely expensive to rebuild here in Australia.

What prices have you been quoted to rebuild the crank - just curious, how expensive is "extremely expensive"...?
IMO you would be better off sticking with 447 internals, they are more readily available in the aftermarket and second hand in Australia.

 

[txxs]

I've been a big fan of "256-" engines etc for a long time.
However in this case unless you have a stockpile of "256" parts or restoring an original 256 bike, I would suggest using "447" internals. Mainly because of the $$$$ and availability.
In any case, it's probably not a good idea to mix and match.
Also there is some motors on local e-bay at the moment (but not cheap).

Just my two cents worth.

 

[member3480]

I have cranks for sale if you need one. $50.00 plus the shipping they came out of 1977 bike

 

[nozila]

dadygcycles - could you give me an idea how much it would cost to send to Australia?
hotdog - mechanic I use says $1k to rebuild my crank.

Funny enough I sold a reasonable useable 447 crank not long ago to fund this crank rebuild.

 

[hotdog]

dadygcycles - could you give me an idea how much it would cost to send to Australia?
hotdog - mechanic I use says $1k to rebuild my crank.

Funny enough I sold a reasonable useable 447 crank not long ago to fund this crank rebuild.

Price is heavily dependent on the condition of your main bearings. If the crank needs a full set of main bearings included in the crank build it's going to cost...
Given their age, all xs6560 cranks should at least be pulled down and inspected prior to installing, I've seen some horror shows as of late and would not recommend installing a crank and hoping for the best.
In Australia with our all-year riding, most motorcycles get a hard life and most cranks I've done require at minimum new rods.
You should be looking at around $300 labor to strip/inspect/clean and reassemble the crankshaft + parts (that's what I used to charge anyway).

 

[MaxPete]

Sorry to butt in late but I really need to emphasize that you must not, under any circumstances, try to use a 256 crank with a 447 camshaft.

ALL 4-stroke engines from the most humble lawnmower to the mighty WW-II in-lines and radials such as the Rolls-Royce Merlin and the Pratt & Whitney R-2800 radial have a 1:2 ratio between crankshaft speed and camshaft speed (the crank turns two revs for each revolution of the camshaft) - BUT - apparently MamaYama changed the number of teeth on the timing sprocket between the 256 crank and the 447 crankshafts.

Nasty trick - but it means that the cranks and cams absolutely must be used in matched sets - regardless of any of the details about bearing g sizes etc. If you don't match them up:
1) the engine will NOT run;
2) a valve WILL crash into a piston;
3) serious or fatal engine damage will result.

Pete

 

[MaxPete]

Sorry to butt in late but I really need to emphasize that you must not, under any circumstances, try to use a 256 crank with a 447 camshaft.

ALL 4-stroke engines from the most humble lawnmower to the mighty WW-II in-lines and radials such as the Rolls-Royce Merlin and the Pratt & Whitney R-2800 radial have a 1:2 ratio between crankshaft speed and camshaft speed (which means that the crankshaft turns TWO revolutions for one revolution of the camshaft).

That is why they are called four-strokes or more correctly, four-stroke cycle engines - the piston travels up and down twice (i.e. it covers the engine stroke four times) for each full engine cycle.

The problem is that MamaYama changed the number of teeth on the timing sprocket between a 256 crank and a 447 crankshaft and so the correct 1:2 ratio will not exist if a 256 crank drives a 447 cam - and that will cause valves to hit pistons.

Nasty trick - but it means that the cranks and cams absolutely must be used in matched sets.

Pete

 

[member3480]

I will get a price for shipping and I have two 447 cranks both came from running bikes and I have a complete 447 bottom end together.
Crank has to weight at least 20 lbs so that's going to put the price up there.

 

[hotdog]

Hi all,

I have 2 spare 256 cranks which I was curious to know if it fits and is usable inside a 447 crankcase. Physically, they 256 cranks fit (as I've tried) but I want to know can they be used in there and if so what else is required?

Thanks for any help

Nozila

Just to be clear, you can use the 256 crank in the 447 cases. You will, however, need to change the rods and cam chain drive sprocket to 447 specs.
So you may just need to source new 447 rods and a cam sprocket.
If you have an early 256 crank there you may have to run starter-less as there will be no ring gear on the crank wheel.

 

[nozila]

hotdog - do you still rebuild cranks?