Motor strip

[chaterlea25]

Hi Mark,
Is the shrapnel steel or alloy? and from where?
It looks like you caught it just in time 

John

[tlmark]

Yeah it steel there’s no shim’s on the crank so I’m suspicious it could be the remains of that possibly?  Big end shells are scored  And the plain timing bearing doesn’t look too good either 

[tlmark]

Close up of the cleaned main bearing you can see traces of material around the boss on the inner race.
So do you guys think this the remains of an end float shim? 

[berger]

it could well be, mine did similar a few years ago , I think the crank end nut shifted a tad and this made the crank hammer the shim and destroyed it. I still ran the bike and thrashed it for miles after a triumph expert? told me the crank would find its own run. anyway I also was told it could end in a snapped crank so it was stripped and put right

[berger]

mark just looked at your crank web pic, it seems to me something has gone very wrong if ime right in assuming it has a recess , it should be slightly proud where the shims and bearing but up to it

[tlmark]

Er... really?

[chaterlea25]

Hi Mark,
Oh Burger  

That recess will need to be faced off so the new shimming has a flat face to work from
Was the cush drive nut tight?
The mangled shims are almost always due to the nut not being done up properly 65ft/lbs

John

[tlmark]

Hmm as I didn’t have anything to fit the Cush drive “nut” I tapped it loose with a drift and then used a C spanner to take it off. I don’t think it was that tight so that sounds likely    glad I decided to pull it apart my wallet isn’t though.

[muskrat]

G'day Mark
That face should be approx 25thou" proud of the web.
Looks like the radius is undercut. It should be a nice 90thou" radius with no perceivable step from shaft to bearing surface.
With the nut done up to 65ft/lb it should take a good whack to get it moving. (your tap might be as big as my whack)
Cheers

[duTch]

 I discovered my crank was same when I stripped it 7 years ago, and in addition the shaft was worn, which only became apparent when I was shimming it after a re-grind...the main journal has a well-made sleeve over it, so not obvious until it dislodged when pulling the bearing off a second time....

 With very little options and already in deep, I shimmed it out and loctited the sleeve gone with it, ~ 12K miles later is hanging in there, but I don't flog it (I think)..

 Not ideal, but you may have better resources available to deal with it. good luck

[tlmark]

Ok, guys, I've been discussing this with a colleague at work (he's a Toolmaker) he says we could turn a spacer to fit the crank instead of shims?
and loctite the bearing to the shaft once end float has been dealt with. Maybe even make it from bronze?

[chaterlea25]

Hi Mark,
Yes a solid spacer is better than a stack of shims, all depending how thick it will need to be
I have done this on various projects but it takes time and probably repeated dismantling to get it right
a slip fit bearing on the crank makes this easier, maybe hone out the old bearing so it will slide onto the crank end
I would go for decent steel as a material

John

[Billybream]

The use of a dummy bearing to gauge end float is good advice, because for sure you will have to split cases a lot to determine shim size.
As for the cush nut, treat yourself to the SRM version with hex nut arrangement, makes tightening procedure easier and secure with addition of Loctite.

[a101960]

As for the cush nut, treat yourself to the SRM version with hex nut arrangement, makes tightening procedure easier and secure with addition of Loctite.

Yep, I second that. tighten to 65 ft lbs.

[tlmark]

Cheers Guys
I put a mic on the plain bearing big end pins and they are still round!!! quite pleasantly surprised and -.020" undersize. the timing side is round too and I need to double check but only -.010" undersize.  so I'm hoping if I can sort the drive side I'm good to rebuild.