Twin cyl 2 stroke crank rebuild.

[Mick22]

Twin cyl 2 stroke crank rebuild, I've always just sent these away to be done as I've never had a press in my shed...until recently. I've seen plenty of single cylinder cranks rebuild and had a go at a couple with a bit of help and it wasn't that hard a job.

BUT every time I ask around how to build a twin cylinder crank I can't find anyone that can tell me how to do it. What is the basic way to attack truing up the crank?

I'm guessing you build up each half and get them true before pressing the  2 halfs together and truing them to each other?

Any tricks I need to know

[vmx42]

Hey Mick,
Or you could do a 'How Too' thread, and we could all learn from your mistakes…

Sounds like it could be good to follow.
VMX42

[tony27]

Pretty sure you assemble the lot then either get the centre bearing to webs running true & work outwards or start on 1 side & work across. Trying to keep 2 individually trued cranks that way when pressing them together is next to impossible, you'll end up having to true everything up again

[Mick22]

  yeah pushing 2 true halfs together isn't going to work is it, I'm sure it would even be possible to press them together now that I think of it

[maicomc490t]

Build from one end to the other.

The trick with most cranks irrespective of the number of cylinders is to true as you press up. They are easy to true with the pin only a third home then progressively do the same until done all the way if you can follow what I mean? If you press up in one go and the run-out is excessive you will have great fun chasing it back within limits.

If you do it right the run-out will be next to bugger all and easily 'knocked' into tolerance.

And if all else fails.......

Get a bigger hammer (copper, of course)

Dave Mac 

[Lozza]

What crank Mick?

On top of what Dave said there is the big issue of the crank pin phasing. This of course depends on the engine format, V twin (90 or 70deg V) or parrelel twin 180 or 90 deg format. You cannot press 'through' the centre you must support on the inner web of one cylinder and press the outer on.
There is a fair bit of tooling you will need also.

[Mick22]

Thanks for the help guys, I'll give it a go!

Lozza, unfortunately nothing exciting like an RS or TZ just a crappy ol Jet Ski crank

[Lozza]

Are you pulling it completely apart? You'll need a fat wallet for a TZ750, an ex-Gary Coleman(the bloke that hangs to lap board out for Rossi not the late 'what chu talkin bout Willis') pops up ever 2 years with a bigger price tag

[Mick22]

Yeah its coming completely apart, its got water damage. A new crank is $695 but I picked up a rebuild kit for $100 on ebay (normally $300) so I thought what the hell its about time I learnt how to do twin cranks properly.

TZ's not for me, I still haven't pulled my finger out and got an RS yet!, I'm chasing the TZ750 for a mate who has a fat wallet but no time, he asked me to chase one down for him (He worked with Gary C until recently) I can't beleive the price they are pulling at the moment but as always there are a few bargains to be found. A guy in QLD picked up a good 700 from Japan for $18000 recently

I would have liked to see the other Gary Coleman on a TZ 750.... that would be an impressive power to weight equation

[Lozza]

After you have pressed it up $700 will seem like way to cheap.

[vmxrider]

Have a look here, there's some info on rebuilding and truing kawasaki triple cranks, some of which may be of help for a twin.
http://kawtriple.com/mraxl/

[Mick22]

Thanks vmxrider that is really helpfull info!

After you have pressed it up $700 will seem like way to cheap.

I hear what your saying Lozza but unfortunately the left side or "tight arse" side of my brain seems to have power over the "logic" side at the moment.....at worst I might end up with a new $100 piece of artwork for the shed wall loosley based on a crankshaft

[Lozza]

I hear what your saying Lozza but unfortunately the left side or "tight arse" side of my brain seems to have power over the "logic" side at the moment.....at worst I might end up with a new $100 piece of artwork for the shed wall loosley based on a crankshaft

Been there and now I listen to that little voice

I have at least $300 worth of tooling(a copper hammer is $100) to do twin cranks that's without the press, V blocks, dial indicators and lathe. You'll have some knowledge at the end of it though