Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Pre-unit engine sprocket installation

Several years ago,I had my 1960 TR6 engine rebuilt, and I have just now put it back into the frame. My problem is that I'm having trouble getting the engine sprocket back onto the crankshaft. When it wouldn't go on easily I tried light tapping, then warming the sprocket, then freezing the sprocket. It just doesn't want to go on! I've tried reversing the crankshaft nut (E3977) and using that, with spacers, to press the sprocket on, put it's still not going easily, and I'm afraid that if I keep tightening I'll strip the threads on the nut, or worse, the crankshaft.

It's been so long since I took it apart, I don't recall how hard it was to pull the sprocket off. I did get a second used sprocket to see if that would go on any easier, and it won't. I really don't want to have to file the notches and fingers on the sprocket, and it doesn't seem like I should have to. I would appreciate any advice!

Thanks, in advance...

Tim

Can you feel any burrs on the edge of the crank splines? Usually the sprocket goes on fairly easily, in fact, often the splines are worn, with the opposite problem! If you have (or can borrow) a micrometer, you can measure the spline OD at the end and at the engine end, it may have got damaged when fitting the bearing/crankcase half.

Thanks for the information regarding the normal sprocket fit, and for the idea to check the ends of the splines on the crank. I'll take a look this weekend and report back!

if you can, you need to also establish where it is too tight.
The inside diameter, so the smallest diameter ie top of splines
Then the cuts/flutes diameter.
Then the teeth/splines themselves, are they too wide etc
You may need to get a set of inside and outside micrometers, or get a machinist/workshop to do it.

These measurements will tell you where you need to remove metal.
Lastly, any sanding of metal should only be on the sprocket, not the crankshaft....unless there is a burr or bulge etc on the crankshaft.

It sounds like the crankshaft is the issue since a second used sprocket also wouldn't fit. Measure everything like tridentt150v suggested. You may want to have a good machinist do the measurements and remove any metal necessary.

I agree, the splines on the crank are far more likely to have been damaged than the internal splines of 2 sprockets.
Close examination and seeing where the mating splines lock up should give an idea of where the problem is.
Could even get fussy with marker pen or blue, but the shinier patches will usually show anyway.
A spline has probably been bruised by a moment's clumsiness.