Will a 250 Mk1 crank go in a 250 Mk3 engine?

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jmwild
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Will a 250 Mk1 crank go in a 250 Mk3 engine?

Post by jmwild » Sat Oct 30, 2010 1:37 am

I have a late 250 Mk3 (1975) which needs a crank. I'm wondering will a MK1 crank fit?

They are both wide case engines aren't they?

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Eldert
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Post by Eldert » Sat Oct 30, 2010 3:12 am

Hi John

all widecase cranks are interchangeable exept for the Swiss army Condor
the Condor has a differend gearbox and the flywheels are smaller to avoid
hitting the gears

Eldert

i forgot there is another exeption : a crank from a Mototrans electric
start wont fit either

jmwild
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Post by jmwild » Sat Oct 30, 2010 3:28 am

Thanks for the quick answer Eldert.
I also have a Condor. I had no idea about the crank differences with that engine!

chimera
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Post by chimera » Mon Nov 22, 2010 12:31 pm

There was no "Mk 1". There is a "Mach 1", it is a narrowcase motor and the cranks are vastly different than a widecase Mk 3.

chimera
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Post by chimera » Mon Nov 22, 2010 12:32 pm

There was no "Mk 1". There is a "Mach 1", it is a narrowcase motor and the cranks are vastly different than a widecase Mk 3.

bobnorton
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Post by bobnorton » Tue Nov 23, 2010 7:56 am

There is also a narrowcase Mark 3 sold up to late 1960s which wont fit either.

jmwild
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Post by jmwild » Wed Nov 24, 2010 4:04 am

I meant "Mach 1", not Mk1. I was under the false impression that the Mach 1 was the first widecase motor. Having had another look at photos, I can see that the widecase rear engine mounts are in a very different place, outside the oil breather. Fortunately I was out bid on the Mach 1 crank I was after!

The 250 crank I have in the Mk3 (non desmo) Widecase motor, is one of the last (1975), and I remember being told that this had the wider crank pin introduced on the very last 250s, and that this was not easy to get hold of at the time (mid 1980s). I was also told that the rod, pin and bearings always needed to be replaced, as the rod was not re-usable. Advice at the time was to find an earlier crank, and use that, as it would be easier to rebuild in future. This is why I was after the earlier crank.

bobnorton
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Post by bobnorton » Wed Nov 24, 2010 8:07 am

I would think that a good engineer could bore out the big end and fit a steel liner to take a new crankpin and bearing.

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Eldert
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Post by Eldert » Thu Nov 25, 2010 4:34 am

Hi John

nowadays its real easy to get a replacement late type complete rod set
( sometimes called the B type ) the italian scrambler club Amici dello Scrambler has those sets made up . cost is 290 euro
you need to order rodset 8030 B

Regards Eldert

machten
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Post by machten » Thu Nov 25, 2010 6:43 am

Eldert,

Do they have one for the 450 mk3 as well (late model 1975)?

Kev

jmwild
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Post by jmwild » Thu Nov 25, 2010 9:11 am

Eldert,

Thanks for the tip about the scrambler club, which I googled. A great website that.

Kev, The 450 big ends are listed in two sizes also.

John.

machten
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Post by machten » Fri Nov 26, 2010 12:19 am

John, Eldert,

Thanks for that. I'll be following that up real soon!

Regards,

Kevin

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