Rebuilding GB7 Gearbox

[daveleek]

I have a problem with the mainshaft third gear which locks up when the kick - start end nut is tightened , it took me ages to to discover why the gears were locked , do I remove material from the 3rd gear mainshaft bush's face ? I dont know what to do . There is plenty of imformation about stripping the box and replacing the 2 ball-bearings and oil seal but no information about clearances , all gears ,selector forks , bushes lay and mainshaft have been replaced

[Simon.Gardiner]

Long shot - needs a (thicker?) gasket??
viewtopic.php?f=21&t=10929&p=75825

SG

[will_curry]

Is there any end float on the mainshaft when the nut is tightened up? There needs to be
some, at least enough to feel.

[JohnnyBeckett]

hi i had this when i rebuilt my box and used the club spares gaskets that was to thin , i had some of drags gaskets in stock that are thicker and now the box is OK , also check the bushes in the gears are fitted in right

[daveleek]

It is just as the photo , just the two gears on the mainshaft and tightened on the kickstart end , 3rd gear is locked against the splines where the arrow is , all the bushes in the gears were fitted by Geoff and are correct

[daveleek]

I have removed 20 thou from the shoulder of the 3 rd gear as it is wider than the original gear , reassembled and tightened the nut and the gear spins freely with 2 thou clearance , thanks for the response . I now have another problem , the 19 t chain drive sprocket will not go on the splines and files wont touch it , the splines are angled rather than square , is this a common occurance or am I just unlucky

[Roger Gwynn]

I think they should have parallel sides, in any case they should be the same as the sleeve gear.

[daveleek]

I have just recieved my 19t chain sprocket from a Dutch supplier and it is identical to the one from the UK , so I am back to square one , down 80 odd euros and in posession of two sprockets that are of no use . Are the splines on sprockets for a Burman CP/B52 Box different to the GB 7 Box sprocket splines ?

[Paul Gasson]

I found the same problem with a new sprocket for my CP gearbox sourced from the club spares scheme but I was able to file it in the corners to straighten the spline enough for it to fit. The spline shape on new sprockets is definitely different from the original shape. Do you have a Dremel tool, it only took a few strokes of the file on each spline to make mine fit.

[daveleek]

Paul , I spent ages over the weekend trying to file the UK sprocket and also two hacksaw blades together would'nt touch it , are these part of a bad batch or are they correct for CP box but not for the GB7 box ?