TOPIC:

I'm new here and hope to find support towards resolving a mystery. I just bought a 77 twin that was a barn find. No title or keys. After some time and money I've arrived at a point where the engine will not fire- except out the pipe. Good solid spark at both new plugs. Both plugs get damp with gas but no ignition. The carbs are clean with air screws out a turn and a half and the air filter removed. Adding gas to the intakes still won't create ignition. I watched the valves actuate through the plug holes and- from what's visible- they seem in time. Certainly they are closed at TDC. I have 12VDC but a new battery is on the way. I'd like 13VDC and hope a replacement helps. The points are set around halfway through the range of adjustment.
Any thoughts or experiences are appreciated.

Well, a more accurate point adjustment may help. (half way through their range?) It effects timing and dwell time, having the correct gap. Also a good solid battery. Cranking it with marginal current and voltage will also kill the starter if not already. Starting fluid (either) is the thing to use to check if something will fire. pouring gas in floods it. Of course either can cause problems too. Just a shot, not a flood. lol

Download a service manual and read up. Of course the best advice in the world does no good if it is not followed through. (probably the best advice I can give)

Take care of the obvious things first. Battery and points first, and the other things seem to fall into place by themselves. Popping out the pipes is an indication of timing, in my wild guessing clairvoyant viewpoint.

Sounds like carb problems. I'd do a full teardown and soak with carb dip followed by reinstallation with new O-rings and gaskets. Make sure the carb boots on both sides of the carbs are sealing fully and you have a good air filter too.

Make use of some type of air filter. The CV carbs will be way lean without any one.

Nessism wrote: Sounds like carb problems. I'd do a full teardown and soak with carb dip followed by reinstallation with new O-rings and gaskets. Make sure the carb boots on both sides of the carbs are sealing fully and you have a good air filter too.

I would tend to agree with Nessim here too. gas turns into varnish after sitting for years, and plugs up jets and internal passages. With the exception that you say they are clean.

Usually a motor will start briefly after a shot of gas, (or either) so it also sounds like your "half" adjustment on the points may be a timing issue.

Pull the plugs after cranking. Wet or dry will tell the story.

Does cranking sound normal, or more of a free-spin due to no compression?

If wet and free-spinning. Shoot some oil in the plug holes, clean the plugs, shoot carb cleaner in the intake, and try again.

Plugs dry and no free-spin, It's carbs or fuel feed.

First thing I would do is a compression test. You know you have spark and gas. You also need compression.

Thanks to all for the comments and advice.
The starter turns the engine over using my 12VDC power cart- I expect the new battery will perform the same. I'm shy to use the electric starter and prefer the kick starter due to the starter clutch being a weak link in this design. That said, the machine has crazy compression requiring huge effort to kick. So much so I took out the plugs when it arrived thinking the valves were hitting or the pistons were stuck. Nope, just nutso compression.
Today I will get some spray ether and more carb cleaner.
A question- If the cam chain jumped a link what obvious clues would arise? Right now it rotates free of any interference.

A jumped cam chain is very, very rare. I would not even have that on the list at this point.

I'd put my mony on clogged carbs and mis-adjusted points.

In your first post you indicated that you had removed the air filter. As I said above without any air filter the cv carbs will be way lean.

A teaching moment for others to benefit from. Please Please learn from my mistakes.
When the ignition advance is reassembled wrong the eccentric cam will be 180 degrees out of phase. Points will close instead of open. Using the starter motor w/ plugs removed this is verified when a timing light shows the F and T marks through the bottom plate window instead of the top window. 180 degrees out. Won't run. At all. Pipe fills with gas and will only fart. Like me. Probably fifty hours of labor and half way to a divorce.
I will begin balancing the carbs now.

Moments like this are the best personal teacher, sadly but true....