Triumphrat

Old Cafe Racer

Thanks Mr.Pete.
Looks like I'm on the right track here for shims;
http://www.circlips.com.au/contentbl...ips&sec3=shims

Available from CBC bearings the local supplier for me up here.

.

1963wak

there are no shims as standard the timing ball bearing locates the crank, if end float developes the bearing is shaged or is moving in the case,as for cenralising the crank its worth checking but unless the side of the cranks worn it should be ok.i use late t140 3 piece roller bearings in my engines instead of balls,a lot stronger and still locates the crank.

Old Cafe Racer

Well my bearings are brand new (200 miles) and the original bearings hadn't been spinning in the cases and were real tight to remove but there is nothing to stop the crank and bearings moving side to side in the cases if the side to side space is bigger than the bearing to bearing distance which it must be.
The crank assembly simply slides side to side in the single lipped roller bearing (which has an allowance in the outer race width to allow for it to do so) and the crank slips easily side to side in the timing side ball bearings inner race.
I could Loctite it but that's not the proper way to do it.
This engine I got complete but suspect was built from different parts which could be why the end float is out of spec.
Originally Triumph probably used selective assembly to achieve the correct side float seeing as they didn't use shims.
There is a reason for using a ball on one side and a roller the other, a ball is self aligning but a roller isn't so using two rollers isn't normal engineering practice in these applications as the ball will tolerate a little misalignment but rollers won't to any great extent especially when the crank starts to flex in the middle so I'll stick to the normal ball and roller arangement I think.

1963wak

if the crank slides in the ball then you will have to use loctite,the crank will have end float until the timing side crank nut is tightened.triumph went to double rollers because the ball kept failing on the t140, the reason they didnt fit one from the start is the 3 piece type didnt exist.

Mr.Pete

The crank shouldn't move easily when the engine is cold and the crank pinion nut is tight.
It can move when things get hot.There is almost no interference fit on the TS bearing when the engine is hot Smetimes it will even have clearance ib the crankcase.The bearings surely do rotate in the crankcase.

JohnA

Well they might rotate in the cases but they certainly aren't meant to! The idea is that, when tightening the nut on the timing side of the crank, the crank is pulled hard against the inner race of the timing side bearing, meaning that the only end float possible is the few microns worth of play in the bearing itself. Unlees there is movement either of the crank in the timing side bearing's inner race, or of the timing side bearing's outer race in the crankcase housing - either of which would be technically wrong and definitely not designed-in at the factory.

Crank flexure is not a problem [bearing-wise] if using the 'superblend' type bearings (as fitted to Commandos). The roller timing side bearing as fitted to post 1980 T140s & TR7s is a big improvement. Superblend conversions for the drive side bearing are available (try Kirby Rowbotham).

Mr.Pete

The only thing that keeps the bearings in place on a hot engine is the shoulders in the crankcase,to the outside of the bearings.Without theses shoulders,the crank would surely walk right out of the crankcase.

It may be difficult to comprehend,but shafts and bearings do "walk",even when they appear to be tightly held.The crank is only clamped to the timing side bearing.If the outer race of that bearing has no interference fit in the case at running temperarure,it causes no problem.Outer bearing races are not generally meant to be tightly fitted.The inner race must always be clamped tightly to the shaft.

The outer races can.and do, rotate even when they still have some interference fit at running temperature.

DerryUK

A couple of thoughts, my T100 manual talks about heating the crankcases to 100deg C to aid main bearing removal; now 100 deg C doesn't seem very hot to me and I can imagine a running engine reaching that temperature. Also in my manual supplement it talks about applying Loctite to the roller bearing outer which to me implies they can move.

However, if things do move then over time you would expect to see witness marks I would have thought.

__________________
DerryUK

'69 T100S being rebuilt - very s-l-o-w-l-y
VFR800 VTEC

1963wak

i always loctite the outer races and the inners if they need it,i dont see what the fuss is about if the primary chains in line and the bores are central why would the crank want to move ? these engines have done at least 40 years like this !

Old Cafe Racer

Well I resurected this thread and asked my two questions because regardless of how old my engine is, 31 thou end float is well out of spec and believe it or not makes a bell like noise at low speed in town which initially put me onto the problem so I've pulled the cases apart and am going to fix it properly with shims between the bearings and crank shoulders so it can't move too far and keeps the rods properly centered in the bores.
I don't have a primary chain, using a BNR belt drive so no real issue there but a crank flogging side to side like that is asking for trouble if left as it is.