Once again, as I assemble this multi-hand bike, I find more and more things that previous owners have done wrong with it...
I had all the useful motor bits bolted in and got ready to test start. Once I got my faux-fuel tank in place (the real one is in the paint shop), I got around to starting it. It did nothing but pop and smoke a lot. I noticed the ignition was way off and it wasn't long until the real problem became apparent: the points lobe is upside down. Fantastic.
So the bike obviously ran with the lobe upside down before and I assume it was just timed using the points lobe's interaction with the cam sprocket-to-head center line as a valve timing gauge.
Two main questions:
1) Are there any options to flip the points cam 180-degrees without removing and disassembling the head [again]?
2) Are there any side effects to just ignoring the punch mark on the cam and timing the motor based on the direction of the points cam? I'm very tired and not thinking straight. I feel like I'm missing something here and feel like it will NOT work. For it to work, wouldn't the cam lobes have to be separated by exactly 180-degrees and the spade on the points lobe be notched at a right angle to the lobes? I don't know... someone spare my sanity!
P.S.
I'm using the E-Ignition... simplified somehow?
You ever in a hurry to get someplace and you hit every single stop light on the way there? That's what's been going on. I know haste makes waste, but I wanna ride!!!
Another issue... points cam orientation.
EPIPHANY!!!
In theory, wouldn't the most benign way to fix the problem be to just mount the electronic ignition trigger rotor upside down? I can do this VERY accurately which will leave room for as much timing adjustment as I'd need. This way, if there are intricacies with timing the cam 180-degrees off, I can avoid them. Since the trigger rotor replaces the points cam lobes in function, the notch is merely for initial orientation. I know this isn't the purist route, but I'm no purist. I plan on building up a nice performance motor with some MegaCycle cams in the near future, so worst case this is a temporary fix. I'm not missing anything am I?  --> 
Did you take the head off?
Is the line on the points cam up when the cam sprocket marks are up?. ............lm
LM asks a valid question as to whether the cam shafts are correctly aligned wrt the crank.
IF the cams are correctly timed and the only issue is the points cam is 180 degrees out, then you can flip the ignition through 180 degrees and all will be well. The real question is whether the rest of the valve train is correctly timed.
The came appears to be at what-should-be TDC for the right cylinder. I'll double check again before I throw anything back together. The little punch mark on the sprocket itself is at 12-o-clock as is the little "zero" or "G" or whatever on the squared off part that the sprocket is riveted to.
Thanks for the help, I'll keep you guys posted on my findings. I had to get some sleep... I've been up to 3 or 4 every morning working on this bike and up fairly early the next day, every day this week... the mind does weird things when this tired! ...Just so I know I have the right information, at TDC (for the right cylinder) the points cam mark should be DOWN, correct? At "LT" (TDC for the left cylinder), the points cam mark should be pointing to the left, 90-degrees after the first spark, right? EDIT: I don't swear very often, but now is one of those WTF-realization moments. On a 4-stroke engine, the next event after TDC should be the exhaust valve opening, right? On this engine, apparently, the intake valve opens next. What I'm getting at, is the cam itself is upside-down, and the points cam is actually keyed correctly for it. This is all fine and dandy, because in stroke, it does seem to catch all the events correctly. The problem is in setting the cam chain. When using the punch mark and "0 G" as my mark, the marked tooth is exactly in the middle of the squared off portion of the cam (that holds the sprocket), if you turn that 180-degrees to clock the cam correctly, the "middle tooth" is now slightly to one side-- but which one?! Can't I technically just time it to the punch mark as it is, just keeping in mind that the marked tooth is 180-degrees off? As long as the ignition is still oriented correctly (which it would be), it shouldn't matter, right? I now know that my timing was one tooth off, which I knew, and is why I started tearing back into the engine-- I just happened to notice that the timing cam was upside-down as I started the process. Somewhere between TDC and BDC the exhaust valve should open. About 20 degrees or so before TDC, the intake starts to open and about 20 degrees ATDC the exhaust valve closes. Inlet closes around 40 after BDC and exhaust opens about 40 before BDC.
On a Honda CB72 cam timing is quoted as IO 5 ATDC IC 30 ABDC EO 35 BBDC EC 10 ATDC All measured at 1.1mm IIRC. So at TDC on any cylinder either both valves are open (overlap) or both are closed (firing). After TDC the intake closes (overlap cycle) or the exhaust opens. The intake on the "other cylinder" opens 180 degrees later which would be at 110 degrees after TDC on the reference cylinder. It sounds like the cams were set up 180 degrees out (TDC on the wrong cylinder). Take a rest and come back with a clear head and start by determining if the camshaft is at TDC on the correct cylinder and work from there.
I'll try to make this simple.
The engine has a 180 crank not a 360. When the engine runs it fires Right---Left---exhaust---exhaust. Sort of Bang---Bang---coast---coast. Not Bang---Bang every 360 cycle. If as ya say the points cam has the line Down at TDC Right then 9:00 at TDC LT ya have the cams installed correct as long as the Points Cam had the line pointing at the "O" or "DOT" I spent a little time yesterday helping a BMW expert understanding this 180 crank versus the 360 crank on the phone. If I have confused ya let me know and I'll give ya my PHONE NUMBER and explain in simple terms not engineer terms. ..........lm
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||