64mm stroke crank with 125mm rod

[RManson]

Got a new project going and it's time to sort out a crank.

Specs call for 64mm stroke with a 125mm rod. I know the rod is a not a common Lamby deal, but who's doing 64mm stroke crank webs? I'd like to just get a set of webs as I'll need to sort out the rod and have it assembled/balanced and possibly welded as opposed to buying a crank and taking it apart.

Spoke with MBD and as has been noted elsewhere on this forum, his supplier has gone away, so he's a no go. Worb 5 can do it, but it's big bucks. Lambretta Evergreen offer a 64mm crank, anyone have any experience using those in high(er) HP engines?

Thanks!

-Ryan

[Train Driver]

http://www.alpha-bearings.com/
Jb tuning
I have a Mb 64x120 crank but they don't come cheap
£500 from Mb

[Darrell Taylor]

could also try 62 with offset pin

ps 290cc! that will shift

[Adam_Winstone]

Watching this thread with interest as I'd like to get my hands on another 64+mm crank for a project. The one in my 260 is an AF 62mm web crank with MB eccentric pin (supposed to add 3mm to stroke), which was built and welded by Jerome at Readspeed. Again, mine uses a 120mm rod with 18mm gudgeon pin.

If the Evergreen one was reliable then I'd probably be up for trying one but I refuse to pay more than £300 for a crank.

Adam

[RManson]

I've emailed a handful of shops, including those recommended above. I'll let you guys know what I turn up! Thanks for your help!

[grimspeed]

Readspeed do a 64mm crank ! Martin at Chiselspeed keep Kawasaki rods of 125mm in stock !
He could also stroke that to 68mm if you wanted to go realy mad !

[mattyp]

as above jb tuning sell 64mm cranks

[Adam_Winstone]

Most crank webs will not allow a straight pin to go beyond 62mm stroke as you are getting too close to the edge of the web. You can then use an ecentric pin to take it a bit further, e.g. 64-65mm so do we know if the longer stroke item mentioned above use a bigger diameter web and need the casing machined out to suit? At that stroke you would need some serious welding and maching to the trench that would be required for rotation too.

I guess that we are talking BIG bucks too? That said, I don't mind spending money if an item is REALLY special but something like a 62mm stroke crank should be fairly run of the mill and benefit from the economy of scale. If a 64mm item is simply a 62mm assembled with an eccentric pin then it should be little more expensive than the 62mm as the only difference is the cost of sourcing the pin, assembly is the same.

Thanks for the feedback on this thread. Who knows, it may lead to another project motor (like I need one!!!).

Adam

[Rich_T]

For all the faffing around with eccentric pins and machining the case to accept the increased big end throw you might as well skim out the case an extra 3mm, make larger crank webs and utilise a straight pin with something like an RD400 rod (115mm). The RD400 rod has a smaller big end than say a CR250 rod (125.5mm) so the RD400 would be a vey good candidate as less would need to be removed from the casing.

Additionally, larger crank webs help with crank balance, running with the original size would make it a bit of a bone shaker.

[Adam_Winstone]

^... agree 100% but the question is WHO and HOW MUCH? (mainly about crank webs, rather than casing work)

Adam