Thwaites Type BA1

[Jeremy Rowland]

Hi Terry I am not exactly sure how the de-compressor works on this engine but I'd guess that when you operate it then it should partially open the exhaust valve so try operating the lever with the rocker cover off and see what moves and which valve/s the lever operates, it may be that the lever operating shaft has come loose on the shaft and so nothing is happening.

Jeremy

[imp]

Thanks i"ll check

[imp]

When you turn the starting handle , the small cog in the foreground rotates and catches the 'L' shaped bracket to the left of the picture, one side of the cog has no teeth , I am assuming it should be against the bracket while trying to start? any help will be gratefully received, Terry.
Original URL: http://i1121.photobucket.com/albums/l515/TerryChamberlain/WP_20161125_11_18_10_Pro.jpg

[Jeremy Rowland]

Does the cog look like the teeth have worn off the one side? Does the mechanism hold the exhaust valve slightly open?

Jeremy

[imp]

The face of the cog (dog) looks correct, with a smooth side. The exhaust valve opens and closes very slightly, hope that helps. while turning the starting handle I am unable to decompress the engine even rotating the cog(dog) in line with the bracket (spring pawl) . I am able to turn the starting handle, maybe half a turn before feeling resistance from the engine . many thanks Terry.

[Jeremy Rowland]

Terry unless I was actually looking at it I can't see from the photos how it works, basically all a de-compressor is, is a method to slightly open usually the exhaust valve of the engine to allow compression to be lost to enable you to swing the engine over, the idea being to get the engine to turn easier so you can swing it over the compression stroke and close the de-compressor lever as the engine goes over the compression stroke.

There is a method for starting these small single or twin cylinder dumper diesels but I have never started one myself; if you can get somebody to physically operate the de-compressor lever and it opens the valve okay then I cannot see what the problem is?

If the lever was loose on its operating shaft and not turning thus not opening the valve as it should I could understand that, if the mechanism displayed signs of wear I could also understand that but if it opens the valve okay I'm at a loss to guess what could be wrong?

Jeremy

[imp]

thanks for your help