Friday, July 5, 2013

On growing up.

There comes a time in any person's motorcycle's life when it's time to grow up.
This is what's happening to Marcolino's BMW R45, as it grows up to become an R65. Last year, before "der Korsika blitzkrieg", Witold and Marcolino scoured the ads for a suitable bike and found the R45 on the island of Elba. It handled the trip to Corsica really well all things considered, but it deserved more. The two of them tore into the venerable Bavarian flat twin with gusto and replaced (among other things) barrels and pistons with those off an R65. That's more like it.

Once again, it's all about that one-two-three...
And now, after nearly twenty years as a stock 883, my Sportster is growing up (perhaps out would be more appropriate) to a brash 1200cc of tarmac-ripping, fire-breathing, grin-inducing fun. 'Oorah...

As you may recall, earlier this year I had started noticing smoking and other problems with the Sportster and took it to Roberto who did his best to fix it: at first it looked like there wouldn't be a need for anything too invasive, so we decided to be as conservative as possible and simply replaced the piston rings and valve oil seals. The rest of the components was examined and cleaned, then the whole thing was put together with new gaskets, of course. The bike ran great. Seriously it was like I had gotten an extra 10 hp out of the engine. It was smooth and purposeful.
But, there is a but.
Only a few hundred miles after I got it back, the engine started blowing smoke again, this time twice as bad. The bike wouldn't start either, so I carted it off back to Roberto who was very good about it and provided me with a no-questions-asked warranty: there had obviously been something wrong and he was going to take care of it: that's a class act. During the second tear-down and examination, he found that the valve stems were scored (perhaps a rogue particle of grinding paste from when we cleaned the valves the previous time?) so they got replaced. New seals again, new gaskets. We think that the new piston rings, being harder than the original ones after 60.000kms, may have eaten into the cylinder liners, which, if you recall, had shown signs of discoloration, probably from when the bike was left to one side in the garage for a couple of years. Whether or not that's the case, let that be a lesson to us all: do not leave your bike sitting still, use it or it will perish.
Now, examining all the various top-end components, what's tricky is that there is no blatant culprit: it's not like you pull the heads and find a cracked piston. Everything shows the signs of wear you'd expect after 60.000kms, with maybe a few very small anomalies. Another thing I hadn't considered, which Roberto pointed out, is that having a balanced exhaust system can give you a "false positive" if you will, as to where smoke is truly coming from.
So, not having a clear cut root cause, and rather than "risking" another top-end rebuild only to find the same problem again, I've decided to start from scratch with the cylinders bored out to the standard 1200 size. New pistons. New rings. Of course, that's assuming the "machine shop" doesn't screw up (yes, it's all back with those folks again, don't get me started).
But for now, here's a few recent shots:

If you get past the blurriness, I'm sure you can appreciate the difference between the standard 883 and the 1200. Size matters, let's not kid ourselves yeah?

Here's a few more self-explanatory shots of engine bits, though I will direct your attention to those crazy knife & fork conrods:


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