5 replies to this topic

[nigelog]

Hi
while assembling the gearbox components I fitted a new camplate spring, second hand camplate (identical) because point at 3rd gear postion on trackway was not worn on the spare I found in a box. Spring was set at correct height, when depressed, in relation to cam pivot and all seemed well. Assembled the cases to check and found that the camplate makes a definate clunk against the bottom of the housing when selecting 4th. Viewing with a bright light spring is engaged in camplate correctly.

Looked at the old camplate and there was no wear mark at the spring/camplate location to indicate that the cam was being held out of place by the lowest point of the camplate meeting the casing.

Re-assembled the old components, including spring, and found 4th still clunked against the bottom on the casing just inside the oilwell.

I cannot assemble all of the components to see where the gears sit at this point because 2 bushes are away for reaming to size.

Is this a "normal" method BSA used to secure the camplate firmly in position in 4th gear or should I remove metal from either the camplate or the casing. As the pinion is traveling towards the sleeve gear to engage it would seem to me that this firm hold between camplate spring and case actually would hold the pinion slightly away from the sleeve gear instead of possibly pushing against it.

Any suggestions or past experiences appreciated or I will have to wait for the rest of the components to see if this will be a problem or not. Many thanks Nigel

Edited by nigelog, 29 October 2008 - 11:25 AM.

[B40RT]

Doesnt clunk on a B40, and theyre all basically the same. You could turn the cam plate upside down and see if it works better that way. ie 1 up and rest down.

[craig10]

Have you seen Rupert Ratio's book on BSA Unit singles, http://www.amazon.co.uk/Rupert-Ratio-Singl...8868&sr=1-1, there's a lot of info in there on the gearboxes.

Sorry I can't be of more help, last time I did one of these was on my B25 Starfire in 1979....

[nigelog]

Hi B40RT - they are essentially the same and if your B40 doesn't clunk I don't think mine should, I only ever used 4th gear once in the time I had the bike running so I cannot say if this is new or not. I was thinking of reversing the gears but I think I'll wait until I get the reamed bushes back and when assembled see how far I can lift the camplate spring, to move everything upwards, while still engaging all the gears. If that fails I might leave it as I am hardly going to hear it with the engine running and it wasn't jumping out of any gears. Maybe a Monday morning assembled bike.

Hi Craig - have the book and find it invaluable. No mention of this particular ailment but then it does say it cannot cover everything in the disclaimer. '79 was the last time I rebuilt an engine and cannot even remember if it was the Yamaha or the Greaves.(Hope I didn't get the parts mixed up)

Rgds Nigel

[sparks2]

Hi
I might just be able to add something to this topic?
Years ago, well, mid 1980's I built or re- built several of the C25, B25 and B40 family of engines.
I found some fairly inacurrately made pattern parts in this area, namely the selector quadrant (camplate).
When the crankcases were assembled the gear selection was 'iffy' - more I cannot remember.
I ended up sending parts back to the supplier with an explanatory drawing. The supplier agreed with my analysis.
Just check any pattern parts very carefully. Just because they look OK may not be enough
Just a thought.
Kind Regards
Sparks2

[nigelog]

Hi Sparks, thanks for input. It appears that not only pattern parts fall into this wandering tolerance area. I think that taking into account it is the springs location in the camplate that should dictate the position I am going to wait until I have all the bits together then either try to raise the spring slightly or remove some material from the bottom of the camplate. 0.5mm over a length of only 5mm should suffice. I'm beginning to believe the adage "never fly to England to buy a bike the day after St Patricks Day".