Hello everyone,
I'm new to the forum so a short introduction. I own a Sloper S30-13 which I restored three years ago. After a catastrophic failure of the old piston, I rebuilt the engine again - I redid the main bearing which was already quite worn, new piston, rings and pin, new small end bush, rebore, new valve guides and springs. Amazing - after the rebuild she started on the first kick without complaints.
After an initial running in phase, I have now been doing tuning rides to see how she performs at top speed, but the results were somewhat disappointing. She starts reliably on the first kick and settles in a stable idle, pulls very well, and accelerates up to 70-75km/h without any problems and can cruise at those speeds all day. Beyond that it's a struggle. After a very loooong straight at WOT she eventually reaches 80km/h and tops at about 85km/h. After that there's nothing.
Since there are no signs of an ignition timing problem, I started experimenting with the needle setting on the carburettor. After trying all 5 needle positions, the best performance on mine seems to be on the third notch from the bottom.
However, none of the needle positions made a change on the top speed. To be noted, at this top speed of 85km/h the engine doesn't seem to be struggling or being tortured - it just seems to not be able to increase the rpms beyond that. So now I'm out of ideas and hoping for some pointers from the experts here in the forum.
My gearing is for solo work: engine 21t, g’box 19t and final drive 42t. Timing is set at TDC, fully retarded, fag paper just pulling out of the points. Carburetter is an Amal 6/024. I also double checked that the slider and choke are closing and opening fully, which I can confirm. After warming up, my choke lever can be anywhere between 3/4 and fully opened. If below that, there is a drop in performance, so the mixture also seems to be OK.
The only other "problem" I have since the rebuild is a somewhat large oil leak from the middle of the pushrod covers, where they telescope into each other. There is no seal there as far as I know. Is this a known issue? and if so are there are any known cures?
Cheers,
Gui