Problems With Ignition Advance?

[Tom W.]

I finally got plates for my rusty '64 CB77 and went on a longer ride. Up to ~1/4 throttle the engine runs fine. But at around half throttle or more, the engine bogs and sometimes backfires. This was very noticeable going up hills. I'm guessing it's a problem with the ignition not advancing? What do you guys think? In Bill Silver's book he talks about hooking up automotive timing light to check total advance. Where would I shine the strobe light? I'm use to working on cars but there ain't no front pulley on this engine. I also remember reading somewhere about lubing the mechanical advance parts but can't seem to find the info. Maybe it was on an email list?.
Any advice appreciated.
Thanks,
Tom

[piecutter]

The timing marks can be found under the round cover on the right hand side of the engine case. Easy enough.<br /> The advance mechanism is the tough part, since it's in the middle of the cam! Unfortunately you have to drop the motor and take the top cover off to get to it. They usually get plenty of lube, being where they are, but I suppose if it sits for a VERY long time it's possible for it to get stuck. I'd check with the timing light first just to see if it's advancing

[FLYHAVEN2001]

You sure it is not the carb's?Are they synchronized(opening at the same time)? My single carb CA77 would bogg out on hills and miss when I first got it on the road and the problem was my plugs were fouling due to being too rich. I had to move my jet needle clip up one notch to reduce gas flow and checked float level. Problem solved.There's a procedure I think under repair log or superhawk forum how to set carbs up.

[Tom W.]

Thanks Piecutter, I'll try the timing light tonight. I actually pulled the cover off after the ride but everything was still hot so I didn't do anything else.<br /><br />Flyhaven: Yes, it could be a Carb. problem. But since I've pulled the slides and cleaned them a bit, I thought it was less suspect. I did check to make sure they open at the same time.<br />I guess the bogging could be due to the lack of fuel. I pulled the plugs and they had that light brown color that I thought meant mixture was good.<br /><br />Tom

[Pigeonalley]

I could be wrong but it sounds as if you’re leaning out at higher RPM and when going uphill. Is one side backfiring more then the other? If so reset that float first. <br /> You should also check your fuel flow to the carburetors. If there is a restriction that reduces the flow at higher RPM you bowls may not stay full.<br /> My CA had a partially restricted petcock. It would idle fine, run great at low RPM but there was no way I could get up to high RPM. Pulled all the nasty stuff out of the screen and then every thing was fine.<br /> Please keep us updated<br />

[Tom W.]

I hooked up my trusty Sears timing light and shined it on the end of the camshaft (I assume) and fired up the engine. Nothing, zero advance. That timing mark didn't move even when I rev'd it up to 4K RPM. I'm guessing I should see some movement by then.<br /><br />What now?<br /><br />Pigionalley: I could still have carb problems, but probably not the petcock. I put in a rebuild kit a couple of weeks ago.<br /><br />Thanks,<br />Tom

[piecutter]

Ok, easy check first. take off the points cover and remove the points plate. Hold the crank in position and you should be able to grab the points cam and turn it clockwise a bit. it should spring back when you release it. If your extremely lucky you will have now unstuck the advancer. Yeah, I WISH i had that kind of luck! If it doesn't turn, or spring back, well, it looks like your in for some more disassembly. Pipes off. Left hand peg and shifter off. Take off the tank. Unscrew the carb tops and pull the slides out and tie them to the frame so they are out of the way. Disconnect the plug wires, points wires, stator harness and pull out all the engine mount bolts except for the bottom rear one, that is, after youv'e put a jack under it. Loosen the last bolt a little bit and lower the motor until it rocks far enough forward so the top cover is clear of the frame. Keep an I out for anything that I forgot to mention to disconnect, it should make itself painfully obvious at this point!<br /> When you get the top cover off you'll see the cam sprocket in the middle of the head. The advance mechanism is on the left hand side of the sprocket. It actually advances the points cam with a shaft right down the center of the right cam. First thing to check is wether or not the springs are still in one piece and haven't popped off and fallen into the case. They are attached to the weights which you should now be able to get a finger on. You shoul be able to pull the end of the weight opposite it's pivot outward and see the points cam moving. If not, well, yeah it's stuck! But I guess I don't need to tell you that at this point. If you need replacement parts I'm sure emo or someone else here should be able to help you.<br />