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

The devil's in the detail----nice way to hide that hole

I am fairly certain that I posted something about breaking a con rod and shredding the 904 motor about 2 years ago, but I am not finding it and there has finally been some development on this bike. Like it is now semi road worthy and a long story to get there.

So back in the summer of 2018 while winding her out and shifting up, there was a big bang and lots of parts and oil scattered about. It had been a hot day and with crappy fuel, knocking pretty hard. The motor was a total loss except for the cams. I decided that I was going to be very busy with work stuff that winter and that I would just have a crate motor built with my cams. It was to be built and delivered by spring 2019, and it was. And that is when the adventure really started.
On Memorial weekend I put the motor in, after sorting some electrical bits, it started right up, ran for 5 minutes or so on the lift. I thought, great, time for a ride. Down off the lift into the driveway, started up and oil spraying all over. Shut it off, back on the lift. It did not take long to find the problem. It seems that the billet cylinder block was not properly machined and the top just cracked off. No compression anymore. Made a little video of the problem, sent it to the builder (who freaked out). We came up with an acceptable plan to fix it. And the first tear down began.

to be continued ...

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.

I have managed to address the various oil leaks (my wife accused me of building a harley) and put some more miles on. Aside from getting caught out in some extreme rain fall that blocked the vent tube of the right hand carb and left me limping home (at least that is my theory), The motor seems to pull stronger with every ride. Definitely more power than the previous motor and I still haven't wound it out yet.

One side issue, with the crank balancing shafts removed there is more vibration throughout the bike. I am feeling the need to take all the bits I can apart and apply lok tite, before they fall off.

I remember the post when the rod went. Hard to type 1 handed, glad it's coming along for you. Not sure if will get to ride this summer with my broken wrist. we will see how long it takes to heal.

I finally got some pictures to go with all this over in the gallery area.

Here's a link to the SM pics: Mag 10 SM Pics

As I get more miles on this motor the buzz seems less (or I am just numb to it!) I think that getting the carbs really dialed in helped.

I was getting some slippage at higher rpms / higher speeds with roll on's. Changed the clutch springs from dark green to red, that seemed to do the trick. Now the tire spins instead.
I have decided to make a new top triple clamp with isolators so as to have rubber mounted handlebars. I really like that feature on my other bikes. So I got some thunderbird isolator rubbers and a block of aluminum, just need some time off to tear into it.
Maybe after the snow starts.

Soon to not be the wicked black speedmaster. The tank and one (remaining) fender are out for paint. After many years of saying 'I really need to paint that bike', it is finally happening.

What's the plan?

this is turning into a not so fun process. An unexpected amount of time has passed since dropping off the gas tank and the shortened rear fender. No dents or repairs needed. Dropped off on a Monday I was told done by the end of the week. Didn't happen, not really concerned. Then I was out of town a couple weeks, thinking it will be done by the time I get back. Not. Yesterday I called and the paint shop guy said tomorrow for sure, or maybe next Friday!

The plan is the tank and bobbed rear fender will be painted 1981 Fiat borduex red. The right side cover will stay the original black as will the (dart manta R3) flyscreen. The rest of the bike is decorated in bits of polished aluminum and a few remaining factory chrome bits.

someday....

http://bonnevilleamerica.com/forums/ubbthreads.php?ubb=showgallery&Number=602922

Now the 'wicked red 1100'
a couple of pictures in the gallery area

Looks good!

Got a few more miles in and the carbs tweaked a bit more. Up a couple jets sizes. Running cooler now. Shifts are very smooth and neutral easy to find after some machine work on the shifter lever.
I also changed the front sprocket from a 17T to an 18T. It was way too jumpy at low speeds. Between the weight reductions (on the bike not rider) and the power increase (also the bike not rider), the bike really wants to go. Very fun. It is like having a new bike that is still the old one.