Hi Barry..The first thing you need to do is check that the back of the piece that carries the engine sprocket is not contacting the crankcase. If it is you will need a thicker spacer.(but bear in mind alignment of the clutch and engine sprockets).
If that is not contacting the crankcase you will need to check the spacer that is fitted between the main bearings (on the drive side) to ensure it is within tolerance..(1.000"-1.005")..in fact that should be checked anyway if you haven't already done so as it positions the crank within the cases.
Also, if you have the crank in the cases with the timing gear fitted but no nut (or a loose nut) on the timing side, as you turn the engine it will force the crankshaft pinion against the back of the bush in the timing side outrigger plate making the engine go tight. If that is the situation you will find the engine loosens off again if you turn it backwards, or in the opposite direction to normal running....Ian
email (option): ian@wright52.plus.com
I agree, which was why I suggested checking the sprocket carrier first.(Always start with the easiest things first!) However, it is important that the main bearing spacer is within tolerance to ensure correct meshing of the oil pump drive spindle teeth and the crank pinion. A spacer which is substantially undersize may cause tightness as the drive side nut is tightened and the gears become incorrectly meshed.
Even if the fault is not that extreme though, the spacer should be within tolerance to avoid excessive wear..so it still needs to be checked if the correct dimensions have not been confirmed prior to assembly...
...Ian
email (option): ian@wright52.plus.com
my main bearing does have the separate spacer, russell motors gave me the parts i need, the spacer is about 8mm and the shims about 1mm,
i tightened the nut on the timing side and i could turn the shaft easier.
barry
email (option): mrsbfuller@hotmail.co.uk
Hi Andrew...You need to start in the same place as Barry...first confirm that with everything fitted to the end of the crank the engine sprocket sleeve is not contacting the crankcase...Ian
email (option): ian@wright52.plus.com
Hi Andrew...I don't recognise the splined washer you mentioned...it sounds like the shock absorber nut tab washer but that is not fitted on before the cush drive parts
...Ian
email (option): ian@wright52.plus.com
Hi Andrew..So did you just removed the chain?..Did you fit the complete shock absorber assembly including spring, sprocket etc. etc.?..and tighten everything fully?
Barry....The connecting rod should lie centrally in relation to the crankcase joint..the cutouts in the cases can be used as a guide and you also have the crankcase joint to sight across. Although this provides a rough guide to everything being correct it is not, in my opinion, a sufficiently accurate 'test' to rely on and isn't even necessary if the crankcase/crank assembly has been correctly assembled. The crankshaft 'floats' within the cases (ie. it is not shimmed to control end float and positioning.) However, the outer drive side bearing is fixed in position in the crankcase (this is why the circlip is fitted, to eliminate any possibility of the bearing moving) and when the shock absorber assembly is tightened up the crank is pulled over to that side of the engine, thus fixing the cranks position in relation to the fixed bearing.
How far the crank is pulled over is controlled primarily by the spacer that fits between the main bearings on the drive side. The length of this spacer is specified to ensure correct positioning of the crank.
It should measure 1.000"-1.005"..so there is a 5 thou tolerance...or put another way a 5 thou maximum variation in the position of the crank within the cases.(at least theoretically...all the other components such as flywheels, crank pinion,oilflinger etc. will also have had a production tolerance and there remains the possibility that these were selectively assembled originally to achieve a specified overall tolerance..no information exists on this subject so unfortunately it cannot be allowed for..)
Positioning of the crank central to the cases has nothing directly to do with the conrod/piston. The rod could be 1/16" off centre and it wouldn't matter as there is ample free movement either side of the small end bush.
It is done this way to ensure correct meshing of the crank pinion and oil pump drive spindle teeth.
Therefore everything that affects the position of the crank within the cases ,on the drive side, should be checked during assembly.
So, the spacer should be within specified tolerances...the boss on the side of the flywheels which the oil flinger plate sits against should be flat with no raised burrs or damage evident. The oil flinger plate should be flat, not reduced in thickness by wear and sitting flat against the flywheel boss.
If these conditions are all met the crank will inevitably be located in the correct position when the shock absorber assembly is fitted and tightened.
As the conrod is a forging with no clearly defined centre line, the irregularities on its surface tend to 'distract the eye' and it has a side to side clearance in the flywheels of at least .010", using this to estimate the cranks position visually to a tolerance of .005" or less is never going to be accurate enough...and even if it were, there doesn't seem much sense in finding out it is wrong after the cases are assembled...Ian
email (option): ian@wright52.plus.com