256 vs 447? Here we go...

[Freak]

Ok guys I know ive read this before about the 256 going to pieces in a short order at high rpm's and etc, but i happen to have a 72-256 motor that im wanting to rebuild, just piston and ring for now. I guess I just want to know if im wasting my time and money on this motor and should I just go out and find a 447? Any input would be great. Thanks guys.

 

[xsjohn]

Think they built the 447 so they could rev the wobbly crank even more.......I would like to built a 256 motor for torque someday......probably never will with all the 447 parts I have.....

xsjohn

 

[72XS2]

From what I read on the net, 1972 don't have a 256 but a 306 engine. I don't know the difference , maybe they share a lot of internal parts.

 

[inxs]

- the main difference between the 256 and 306 cranks was the addition of the starter gear on the crank for the e-start...there were slight differences in the crank flywheel and os pistons...the XS1-XS1F cranks were unified to 256-11400-01

 

[72XS2]

Thanks inxs for this info.

 

[cruza]

freak isthe 256 the eariler version of the 447, cause if it is they are the longer conrodded version ,which makes them more effeficient power wise

 

[Freak]

freak isthe 256 the eariler version of the 447, cause if it is they are the longer conrodded version ,which makes them more effeficient power wise

Yes earlier than the 447 and harder to find parts and normaly more expensive. There are many pros and cons. For instance the race guys liked these motors back in the day but they most likey were not using the same rods and pistons just a lot more beefed up. I dont plan on racing it though.

 

[wurlzy]

Hi guys, this might be obvious to some but i'm new to the XS world.
Could someone please explain to me what the reference means when describing the different engines......256, 447, 533.
And where/how does one find out what exactly is in the bike?

Thanks in advance,

Steve

 

[inxs]

- the numbers are cast into the conrod
256...136mm conrod, 22mm wrist pin, 26mm crank pin, no starter cog...306...same with a starter cog
447...130mm rod, 20mm wrist pin, 26mm crank pin, starter cog
533...140mm rod, 20mm wrist pin, 29mm crank pin...mostly sold in europe

- because the bores and strokes are the same each crank type has its own pistons...the cranks can be swapped complete with their rods and pistons...there are other differences in the motors-compression ratios, clutches, cam timing, gearbox etc

 

[JAGUARGOD]

Hi guys, this might be obvious to some but i'm new to the XS world.
Could someone please explain to me what the reference means when describing the different engines......256, 447, 533.
And where/how does one find out what exactly is in the bike?

Thanks in advance,

Steve

WOW! Thanks for asking that Steve...I was feeling really dumb....well I am actually.
Just didnt want to be the ONE....LOL.

 

[wurlzy]

Thanks INXS!

 

[270YAM]

- the numbers are cast into the conrod
256...136mm conrod, 22mm wrist pin, 26mm crank pin, no starter cog...306...same with a starter cog
447...130mm rod, 20mm wrist pin, 26mm crank pin, starter cog
533...140mm rod, 20mm wrist pin, 29mm crank pin...mostly sold in europe

- because the bores and strokes are the same each crank type has its own pistons...the cranks can be swapped complete with their rods and pistons...there are other differences in the motors-compression ratios, clutches, cam timing, gearbox etc

Another difference with the 533 crank: the big ends are 2mm wider than 256/447.
From memory the 256/447 rods are 20 mm wide and 533 is 22 mm wide.

 

[gggGary]

Will 306 crank, rods, pistons etc fit into a 256 block? I have a stuck 256 showing 34,000 miles and a donor low mile 306 if the parts would fit. What about cylinder sleeves, do they interchange throughout the years?

 

[270YAM]

Will 306 crank, rods, pistons etc fit into a 256 block? I have a stuck 256 showing 34,000 miles and a donor low mile 306 if the parts would fit. What about cylinder sleeves, do they interchange throughout the years?

Any crank will should fit in any set of cases, and all the sleeves and barells should be interchangable. The early barrels had a 4 bolt cam chain tensioner, where the later ones have a 6 bolt tensioner.

The only combination I would not recommend is a 256/306/447 crank in 533 cases. Althought they will physically fit, I am told that the 533 cases do not have the oil spray holes at the front to lubricate the big ends.

 

[builder]

so if I am reading this right, the 306 motor can use the 477 crank, con rod and piston combination but what about the bores and head?

 

[ReycleBill]

Subscribed...

 

[builder]

subscribed?

 

[gggGary]

" subscribed? "

It's an option up on the top, under the thread tools menu. Unlike a reply that just gets you the next post and nothing more til you visit the thread again if you subscribe there, you get ALL replies to the thread even if you don't look at it again. Very handy for tech threads of interest or if you are following one of the excellent build threads around here. Or by typing at least 8 letters in reply you will see the next message posted to the thread and can renew by clicking on the thread link in the email.

 

[grizld1]

270YAM, you are misinformed. The same wristpin diameter--22 mm.-- was used in 256 and 306 long rod engines, along with a hotter camshaft and 17/34 crankshaft/camshaft sprocket combination. The 447 short rod engine uses a 20 mm. wristpin, milder camshaft, and 18/36 sprocket combination.

The only significant differences between the 256 and 306 motors, apart from the absence/presence of the electric foot and one of the tranny bearing seats, are in the top end. In 256 cylinders there was a bridge in the cam chain tunnel that forced splitting the cam chain for disassembly, and the head gasket sealing surface pattern on the cylinder top and head was narrower than the pattern on the 306 (which was retained for the 447).

 

[Rabbidmk1]

hi guys,

I need to chime in here for a bit of advice. I came across a 750 kit with a parts bike that I acquired but have come to realize it is a mismatch of parts. I have 79mm pistons with 22mm wrist pins and a regrind cam stamped 447 with a 36 tooth sprocket. Having 2 engines to use for parts, am i correct in thinking I can build this in a 256 engine and swap the 34 tooth sprocket from my stock 256 cam to this larger regrind?