Crankshaft chop...

[Zepp]

B12 crank....

I need to chop it in half between no2 and 3. What method would be best to join it back up? I know it'll need welding but would a simple spline between the two parts suffice?

[kenty]

there must be easier ways to change a timing chain @Zepp 

[Zepp]

there must be easier ways to change a timing chain @Zepp 

looking to change the whole characteristics Kenty. 

[vizman]

bigbanglittlebang motor?

[Zepp]

bigbanglittlebang motor?

...and why not ;-)

[vizman]

what degree/firing order you looking at doing zepp?

[Gixer1460]

Not doubting your engineering skill but surely a spline and matching spigot is going to be tricky to clock up and keep the crank throws all at 90 / 180 degrees to each other and include a sprocket? I'd suspect a interference fit pin and socket pressed together a la GSX type will allow a bit of 'mallet' adjustment prior to welding?

Edited July 17, 2015 by Gixer1460

[Kid Kearsley]

Pritt-stick 

[Zepp]

Not doubting your engineering skill but surely a spline and matching spigot is going to be tricky to clock up and keep the crank throws all at 90 / 180 degrees to each other and include a sprocket? I'd suspect a interference fit pin and socket pressed together a la GSX type will allow a bit of 'mallet' adjustment prior to welding?

my engineering skills are purely YouTube learnt. 

I now believe the crank may be  en24 and therefore rather unweldable anyway due to being too brittle. On this basis my plan may be a non starter. 

[Zepp]

what degree/firing order you looking at doing zepp?

I was looking at 1/2-4/3.... basically to give a rumble quite like a Yank v8 without the 8 pots. 

[Zepp]

....or maybe even TWO engines strapped together to give the REAL Yank v8 noise. 

I do have one or two engines sitting around. :-)

[kenty]

Heath Robinson solution , cut it , grind 6 equal flats on each half  , chop a long reach socket and hammer the fucker together ,,,, a small dab of Tig will be ok .  

[gsxr884]

Surely its the cams you need to change to change the firing order

[Zepp]

Surely its the cams you need to change to change the firing order

cams too but that's much easier to do. We did this to A series engines 20+ years ago. 

Reason I asked about crank was the far greater load put upon it. 

[gsxr884]

I don't understand why you want to cut the crank unless you want to change from 180 degree firing intervals to something else

[Kristjan]

Obviously it aint cheap, but perhaps it's worth considering getting the crank made?

[Gixer1460]

Obviously it aint cheap, but perhaps it's worth considering getting the crank made?

That's true - couldn't get a 5mm stroke increase from even a std. fresh cast crank + would probably be too weak even if possible so builder pony'd up for a billet one off. That was about £1800 12 years ago but it was done manually on lathe and mill so the man hours racked up - done now, on a CNC machining centre, I guess the cost could be less.

Personally if I was doing anything out of the ordinary and needed a one off crank, i'd make it a flat plane design with the big ends all equally spaced and 90 degrees apart - that'd make an awesome engine, perfect primary balance and rev happy!

[McLean Racing]

Its known that the weld up gsxr cranks dont like going much past 180hp. U could build a plain bearing crank up similar to how the gsx cranks are made. Would be a better solution in my eyes

[kenty]

could you  leave the crank  @Zepp     and just alter the cams so it fires 1+3 together and 4+2 together ........ like a big twin ,, just to see what happens 

[gsxr884]

Without altering the crank you could fire 1&4  and 2&3 together but not any other combo

[kenty]

thats what i meant , @gsxr884 thanks .

[Zepp]

could you  leave the crank  @Zepp     and just alter the cams so it fires 1+3 together and 4+2 together ........ like a big twin ,, just to see what happens 

I could and I've done that before on A series engines. The big twin isn't what I'm after.  

[Zepp]

Without altering the crank you could fire 1&4  and 2&3 together but not any other combo

you still need to chop and join the cams through 180*

[Gixer1460]

Its known that the weld up gsxr cranks dont like going much past 180hp. U could build a plain bearing crank up similar to how the gsx cranks are made. Would be a better solution in my eyes

That doesn't make any sense - firstly GSXR cranks don't need welding - that is unless you are doing the journals to regrind and stroke them. Secondly I know of plenty GSXR cranks that run 180+hp NA that have 100+hp of gas throw in for good measure.......'they' don't break that easily - the other bits do!

You couldn't press together a plain bearing crank - you'd never achieve acceptable journal parallism without regrinding, GSX's have rather 'sloppy' main roller bearings that accept that tolerance of build.

[McLean Racing]

That doesn't make any sense - firstly GSXR cranks don't need welding - that is unless you are doing the journals to regrind and stroke them. Secondly I know of plenty GSXR cranks that run 180+hp NA that have 100+hp of gas throw in for good measure.......'they' don't break that easily - the other bits do!

You couldn't press together a plain bearing crank - you'd never achieve acceptable journal parallism without regrinding, GSX's have rather 'sloppy' main roller bearings that accept that tolerance of build.

what i meant was. I know of people who have stroked gsxr cranks by moving the journals and welding them up and they havent been as stong as the stock crank. Hence why i said it would only be worth doing on a press together crank like a gsx. But as you said. Even then it may not work for the effort involved.

The stock cranks can take alot of power. Ive put approx 300hp on mine no probs and i plan to go more. There was someone in the US who made just over 500hp on a stock crank. 

Is reworking the crank worth the effort? Id personally say it isnt