I sent the carbs off to Jack at Old school carbs to get rebuilt properly, as they were seized and terrible, and after he finished them up, reinstalled them on the bike, tried to start it up, and got nothing. After a few weekends of idly tinkering with the bike here and there, I eventually discovered that the bike had been rebuilt at some point in the past, and the previous owner had reinstalled the ignition jackshaft out of time, as is easy to do with the errors in the old manuals.
A little hackery with some gaffers tape:
And she fired right up!
At this point, though, I decided it needed to be torn down to be checked over right - in the process of diagnosing the ignition issue I had discovered a few other things, and realized I wouldn't be happy unless I completely checked every bolt and put everything back together myself.
But before I came to that conclusion, I built something else:
This is, IMO, the supermoto that KTM should have built. If you'd like to read about it, more details are here.
Here's a picture of my 1290 and the one I built at the track:
But apologies! You're not here for KTMs!
Back to the CBX - I finally got the time to begin the teardown. Pulled the engine from the frame:
And pulled the engine apart - took some hammering to get the top end off, as the previous owner had spraybombed the entire thing.
At this point, I begin to spec out the bores, and I notice something strange...the honda spec says the pistons should be 64.5mm, but mine are just barely under 67mm. I double check my measurements, and sure as hell, the pistons and the very straight, nicely crosshatched bores are 67mm. What is this?!?!
Props to anyone who can identify these pistons before scrolling down...
Anyways, as it turns out, there is an Ontario bore kit in the bike, taking it up to 1130ccs.
They also a use head gasket which interestingly doesn't match the bores exactly:
Anyways, after some fears about locating rings and such (the ring look, thankfully, brand new - I doubt this engine has ever been run with the bore kit, as the crosshatch is so fresh that it looks like it has never run since the rebuild where they installed the primary shaft out of time), I managed to find appropriate replacement head/base gaskets, piston ring clips, and I'll be reusing the rings.
As I'm a sucker for cool stuff, the external stuff is all going off for vapor blasting by Restocycle (Hey NobleHops!), and most of the internals including the gearbox will be going off for WPC treatment, as I've always wanted to do a build with that engine treatment. I don't anticipate any performance gain from it, but I do hope it provides more reliability and long term wear benefits. I'll be replacing the cam chains, and other wear items while I'm in the engine, hopefully setting the bike up for 50k miles of reliable normal operation with nothing more than valve adjustments and normal maintenance.
Tonight I managed to pull half of the valves, got hung up on one of them that needed to have a high spot knocked down before it would move smoothly out of the valve guide:
I'll also be setting the bike up with a ZRX swingarm and forks, a Ducati Scrambler headlight, ABS, and a number of other things to get it looking like what I think we all dream of: A CBX made in 2016. I've got an open trackday that I do each year, and this year it's on October 3rd - the goal is to have the bike ready for that trackday. Following that test, we'll ride it around for a little bit, and then break it down again so the frame, wheels, and swingarm can be powdercoated, and all the parts can go off for a custom paint job, that is still TBD. I'll also be leaning on GP Frame and Wheel to do some measuring of the frame, to make sure it's straight, and to allow us to validate that rake, trail, and other numbers are in an acceptable range.
Longer term plans include an RFID ignition, a more modern looking gauge cluster using the OEM gauges, and maybe a few other neat things.
But until then, I've got a CBX in the garage in pieces, and any tips that members might have of good things to look out for when doing a rebuild of a questionable rebuild would be much appreciated!
Hope you all have enjoyed my ramblings, and safe riding out there!
-Mike
