Bonneville America Forums Forums General Motorcycle Forums Member's Rides mag10's wicked black speedmaster

Rather than pull the whole motor and ship it back I elected to just pull the top end and send the cylinders, pistons, rings back and a replacement set would be returned, with new gaskets and i would be back in business.
What actually happened was the root problem effected all of the lot of cylinders that had been made in a batch, so all were suspect. The fix was a redesign (which I had a hand in) and re-manufacture. This was in June of 2019.

Forward to mid November and the new parts arrived, unfortunately winter had arrived sooner and my shop was snowed in. I got a break in the weather right after thanksgiving and put the motor back together. However, it would not start, I attributed that to the cold weather and waited it out.

Now into March of 2020 and I am working from home and have time to sort out this bike. After some investigation of all the usual reasons, turns out to have no compression. So I tear it down, measure everything, check flatness on the head and the cylinders, call the builder compare specs, put it back together but with no cams, still no compression. It just bleeds away fast.

Back apart, but this time I notice that the cylinder liners are not flush with the deck, but are .005 below. It was not like that a couple days before. Delving into that showed the liners were loose in the cylinder block and moving around as the pistons traveled, not good. So back it went.

A month or so later I received the same cylinders back with a properly fitted set of liners, another set of gaskets as so on. Back together again and this time it fired up on the first turnover. I seems to run good, very strong. I am fine tuning the carbs and sorting thru a small oil weep from the starter as well as oil mist collection issues with the secondary breather. Going from 90 mm pistons to 101 mm pistons changes the case displacement as well!

So far a 100 plus miles on and keeping it under 5000 rpm for some break in. If work would stop interfering I would get the break in done quicker. I expect the breathing issue will reduce as the rings get seated.