9 replies to this topic

[minimanjay]

Was just wondering what's the possibilitys in stroking a 1380 what's needed and would it take it over 1400 if stroke it I'm not after a revvy engine ?

[Guess-Works.com]

Not uncommon, this is how they build 1430's, 1460s and higher.

but you will need an offset ground A Series crank and cooper S rods... or something special and very expensive.

For example an offset ground crank @ 84.3mm stroke with a 73.5mm piston will give a capacity approx 1430cc, crank will cost iro £500 + an exchange A SERIES Crank ( You cannot offset an A+ crank ). Then you need the rods and a set of std cooper S rods will cost in excess of £100.

[minimanjay]

So can u get a series crank offset or is it a special crank full stop and I take it a rods because stronger ? How much am I looking in total ? It's either a long stroked 73.5mm bore or jut a 1071 set up both engines I've always wanted so I don't mine I got bout 1200 pound to spend on short engine I have a sccr gear box for it to go on and a quaife diff

[Guess-Works.com]

Yes it's an A series crank which has been offset ground. The offset is only possible as you're changing the size of the big end from 1.75" to 1.625" which is why you need cooper S rods.

and yes, once you've changed the crank, replaced the pistons and rods ( unless you manage to get the pistons off the old rods without damaging them ) you will not have much change from 1k.

A lot of money for 50cc !

[minimanjay]

Do I got for a 1071 or a long stroke 1380 :snot sure

[Guess-Works.com]

For a 1071 you will need the correct block as it's shorter than a 1275, or have some longer rods made.

[KernowCooper]

MED offer a 1500 long stroke crank and last months Mini Magazine had a article on it but the cost is very expensive.

[bmcecosse]

Just curious - but why can an A+ crank not be offset ground? Does it break into the oilways??

[Guess-Works.com]

Because of the roller fillet radius on the A+ crank...

[bmcecosse]

I did wonder if it was that - I've got an old crank in stock for that reason!