Topic: 1980 cb650 cam timing

[REDTR4]

try this again - so the starter clutch went out on my 1980 cb650 had to split cases to replace - did that got back together and starter works - but wont run carbs cleaned 3x compression good ignition timing checked and think cam is in correctly but that may be the issue = with carbs off an little starting fluid shot in each cyl engine pops and sputters occasional backfire - similar to plug wires miss directed (they are not) so stumped - i know the notch on the end of the cam needs to face forward when tdc on cyl 1 and that's the way it looks... any suggestions or help GREATLY APPRECIATED  thanks Kurt

[scottly]

The ignition pulse generators are polarity sensitive, and if the wires are reversed there will be spark but at the wrong time. There is a white band on one of the blue and yellow wires which need to be connected to matching wires in the harness. Also, the coils should have a resistance of something like 480 ohms +/- 50 ohms.

[HondaMan]

If the bike was running before all this (implying the carbs were working OK) and you disassembled those carbs, make sure the seal on the air-inject port (that odd round thing on the side of the carb) is sealing well. If it isn't, it can be really hard to start because it is letting in extra air, diluting the idle mixture too much to fire.

I went thru this on a 1979 version of the bike after someone else had "cleaned" the carbs, and then set all 4 at random float depths and random idle-mix screw settings between 1/2 and 4 turns out.

Some people's kids...

[REDTR4]

Thanks for responding - will check on the pick ups but since the carbs are off and it wont run on starting fluid its not the carbs at this point... any advice on checking cam timing/settings would be greatly appreciated!

[scottly]

i know the notch on the end of the cam needs to face forward when tdc on cyl 1 and that's the way it looks...

That sounds correct. Remember, the ignition is on the crankshaft, so the cam timing has nothing to do with ignition timing.

[scottly]

Here's the 650 schematic. The pulse generator wires go to the spark units under the seat, which then feed the ignition coils. If there are no white bands on the generator wires, a timing strobe would be one way to check the ignition timing, or you could try just swapping two yellows or two blues and see if the bike runs on two cylinders.
 

[REDTR4]

Thanks for info sorry about pvt msg I'm just getting used to how to use the site!!