Started Engine Build

[Hook]

Finally I have started converting the vast boxes of bits and pieces into a Motorcycle.
I fitted the crankshaft into the crankcases and have found that I do not need any shims on the engine sprocket side and as there is no way of fitting the large hole thrust washer on the ignition side and that there is no movement or end float it would be pointless trying.
It never ceases to amaze me on the subtle differences the different years and marks have, I did check on the board regarding the thrust washer and it seems that some models omitted it.
Now to unbolt everything, fit the con rods and camshaft, gasket cement the two halves and bolt it all back up again.
Regarding the con rods, I can see the L & R stamp on each (left to the engine sprocket and right to the ignition sides) but in the workshop manual it also states "the right way around"?... laying them on an engineers plate there seems to be no difference which way up they sit.

[DAVE BRADY]

Hi,

Do the rods have small drillings in the big end?

Dave.

[Hook]

I'll have a look

[Hook]

No drllings in the big end.

[DAVE BRADY]

Hi,

Depending on the year the left/drive side rod had a small drilling through from the journal to the side of the rod.  This hole was to face the flywheel with the idea being that oil would bleed under pressure to be splashed up the bore by the flywheel helping to lubricate the bore.  It also served to even up the oil supply to the big ends.

Dave.

[Hook]

The year would be anybodies guess  These are all sourced parts from different sellers, the frame is a Thunerbolt and the matched cases are also thunderbolt...found the year on the owners club library and promptly forgot where I wrote it...this will be a proper phoenix risen from the ashes.

[Gup holland]

This is the easy way to see if you got a long or short crank.

[Hook]

Thank you for that info, I had no idea that there were two sizes, mine is of the standard shorter version.
Rummaging through the piles of part I have gathered it has dawned on me that I have an awful lot of parts I'm going to sell off.

[Gup holland]

Ok it's an early one, the did not use a thrustwasher, the timingside bush flange was thicker than the late ones with thrustwasher.
It is also impossible to place one.

[Hook]

funnily enough in the box I found one con rod with a small hole, it has blue permanent marker A65 written on it and one of the pair that I was going to use has the same blue marks on it so I'm guessing that they are the pair.

[DAVE BRADY]

Hi,

There should be a 3 digit number on the rod and cap and they should be the same and indicate that they have been machined as pair so the big end 'eye' is round.
Ideally the two rods should be only one number different indicating that they were made and machined one after the other and so should be very close weight/balance/tolerances etc.
If the ones with the blues marks do not have consecutive numbers it could be that one is a replaced but may have been filed/polished to match.  Check this with small scale kitchen scales.
Total weight, big end weight and small end weight should be the same.

Dave.

[Hook]

Thank you for that invaluable information, I would have ended up with some form of vibration.
These are the rods weights and numbers...

Blue writing, no hole, 368g with nuts and small end bush fitted, rod and cup number 357, stamped R, moulded number R2R2R
Blue writing, with oil hole, 360g with nuts and small end bush, rod and cup number 975, Stamped L, moulded number R2R2R
Black writing Spare rod, 968g with nuts and small end bush, rod and cup number 8, stamped ? looks like T but the black writing states RHS, moulded number R2R1Z
Looks like I need to get a matched pair.

[DAVE BRADY]

Hi,

The two with the blue writing could be made to match.
The constants are the bolts and nuts so they are left alone but the rods can be equalled up by taking some material from the heavier one.
If you have some digital kitchen scales that measure down to the gram that may be enough although professional balancers go down to fractions of a gram.

The rods need to be supported horizontally on their edge.
Sit one rod with the big end on the table and the small end on the scales.  Raise the rod or the scales to get the centre line of the rod horizontal.  Record the reading and do this for both rods.
Then sit the big end on the scales whilst supporting the small end to get the rod centre line horizontal and record this weight.
The idea now is to remove material from the heavier rod to match the lighter one end for end and overall.

There are some vids. on youtube that may explain it better
It can take a bit of time.

Dave.

[Hook]

Thank you, I'll check that out.

[cdsdorset2]

Simple answer with conrods is replace with new if you can afford them. You have no idea of their history or condition. I always fit thunder rods.