Getting back in the game.

[loudest143]

It's been about 3 years since I've had a vintage project, and recently I picked up an 82 CB750k. Titled frame, motor removed, tank needs a little pinhole repaired, and the carbs are 42Bs from a donor 750F. Mac 4 into 1 is going to be where I start on the exhaust, and Axxcel coils and wires.

The motor was rebuilt (top end only) by PO. Valve lapping, port and polish, and CB900 cams installed. The motor is in very good shape, and turns freely. When you can pick up a titled frame, spoked wheels with serviceable rubber, and a rebuilt motor for under 5 bills, you buy it! ;D

Carb rebuild went just fine. New o-rings and gaskets for everyone, and they don't leak.

I attempted to get this girl started, and I had some low spark issues. A plug out of the motor sparking off the block showed a teeny tiny little arc. NOT what it should be with aftermarket coils and wires. (Yes, I checked the wiring to the coils, and it is correct as per the manual.)

I found that the spark advance module does not line up when spun (counterclockwise, with the plugs out) the correct markings. (TDC) It's off by about an inch, and even with the adjustment screws, you cannot physically align the advance module with the rotor. SUCKS.

I believe that the cams were installed incorrectly. Meaning, when the spark advance module lines up, (to the 1+4 spark module) it should also be aligned with the 1+4 cam nodes, correct? I believe I'm correct in my assumption, but geez, I'm hoping someone can remind me if that's correct. (Thanks in advance!)

Also, before I dig further into the manual.... Is it possible to remove that rotor between the spark modules and align just that piece, or do I need to realign the camshafts and timing chain? I'd really rather avoid that god awful project. I'm familiar with the process from my old GS850, and I know the Honda is a different animal. Just hoped I could toss out a question, and perhaps someone from the learned panel would reply.

Hope all is well with the regulars here. Good to be back in the vintage world again!

Your Internet Pal,

Loudest143
82 CB750k (still needs a name!)

 

[teazer]

Pop the cam cover off and check cam timing before you do anything else. If that is wrong the motor will never run and may well bend a bunch of valves. Once you are 110% sure it's correct, then look at the advancer and see if a drive pin is missing or something else equally obvious. It's been so long since I built a 900 motor that I cannot remember all those details.

The protrusion on the rotor should line up with the 1-4 pickup module at 1-4 TDC. If it doesn't, I'd remove the pickup plate to get to the advancer and remove that to see what is going on there.

 

[loudest143]

The protrusion on the rotor should line up with the 1-4 pickup module at 1-4 TDC. If it doesn't, I'd remove the pickup plate to get to the advancer and remove that to see what is going on there.

Thanks for the reply, teazer! I was thinking that there has to be SOME WAY to remove the advancer(and its' plate). I bet that will offer some more information.

I can say that when the timing is set to TDC that the correct cam nodes, either 1 or 4 do in fact point towards the spark plugs as they should. At least that part seems right.

Thanks again. Ride safe.