Broken mainshaft????

tigman88 · Mar 27, 2011

Hi, I was wondering what could be the reason a mainshaft could break??

bill · Mar 27, 2011

tigman88 said:
Hi, I was wondering what could be the reason a mainshaft could break??

it is a weak design. stress riser built in where the clutch locating circlip grove is machined. WAY to much weight outboard of ANY support. abuse IE drag racing and power shift's. to tight of a primary chain.

ML · Mar 27, 2011

If the layshaft has the old ball bearing collapse, then the mainshaft can get jammed and fracture.

Mick

swooshdave · Mar 27, 2011

bill said:
tigman88 said:

Hi, I was wondering what could be the reason a mainshaft could break??

Click to expand...

it is a weak design. stress riser built in where the clutch locating circlip grove is machined. WAY to much weight outboard of ANY support. abuse IE drag racing and power shift's. to tight of a primary chain.

Big ass clutch hanging way off the side of a spindly mainshaft?

willh · Mar 27, 2011

Wheelies :twisted: , plus everything everyone else said. but what came first? broken mainshaft, the bent layshaft, or cracked box.

Can you say outrigger

Hobot · Mar 28, 2011

Unclviny · Mar 28, 2011

Somewhere around here is the Mainshaft from my '73 850, it twisted in 2 pieces and I write it off to stress for all of the above reason's. Bear in mind that the Commando gearbox was designed a LONG time ago!

Vince

T95 · Mar 29, 2011

hobot said:

What you got there Hobot?
I can guess, but rather you set me straight!

Unclviny · Mar 29, 2011

That is the Steve Maney Outrigger, because of the modifying of the inner primary case you must use a primary belt but it works very well.

Vince

tigman88 · Mar 29, 2011

How common is this ???

Rohan · Mar 29, 2011

tigman88 said:
How common is this ???

What year is your Commando ?

There was a bulletin or advisory out about checking mainshafts for straightness, somewhere early in the 850 series. If they are not straight, they tend to break...

If it has lasted all this time, thats pretty good...

Not all of them do this, later ones were made of better steel or better made, or something, to fix this ? As someone said though, if they cop a hiding, they are not the best design....

hth.

Hobot · Mar 29, 2011

Yes, Steve Manny out rigger, which requires a big hole in inner primary case to make room for the mount face so close to clutch. I was able to seal mine, but likely the only one to do so. Next time I intend to make out rigger part of inner case. Helps clutch wobble wear stay away too.

Is there an upgrade after market main shaft available that fits factory box?

What happened when the main shafts broke, I need to know as I expect to break some before upgrading to $4000 TT - someday.

willh · Mar 30, 2011

hobot said:
What happened when the main shafts broke, I need to know as I expect to break some before upgrading to $4000 TT - someday.

No more go :evil: :lol: clutch spins in the primary for a second before shutting down upon realization that something has gone horribly wrong.

For me, a cracked case, bent layshaft. Pulled the primary cover on the side of the road and the clutch practically fell out.

Will