68 Dream CA77 won't run

[hoodooman1]

I have a 68 dream 305. I recently cleaned/gapped the points, rebuilt the carb and changed the plugs which got the bike running - for a while. I didn't have an MC battery on hand, so I used my marine battery to start the bike. After a minute, I noticed some light smoke coming from the rectifier so I promptly unplugged the battery. I then went and got an MC battery and actually rode the bike about 5 miles without issue. After that ride I parked it for a day or so.

Since, I haven't been able to get the bike to run more than a second or so. The spark looks to be weak but is there. I'm getting plenty of fuel it seems as the plugs are wet. Additionally, if I spray starting fluid, the bike will barely bark, if at all. I don't have a spare condenser on hand and have realized that they are $$$$ on ebay, etc. The headlight and starter still function and there are no burned wires anywhere. I think the smoke was the rubber cover on a hot rectifier. Maybe I burned up the rectifier, but wouldn't that only impact charging, not necessarily spark?

Where do I start to troubleshoot this thing? I appreciate any input.

[mike horvath]

I’m not so sure the marine battery (if 12v) would smoke the rectifier. Is it the original rectifier?
My thoughts are you mentioned after gapping plugs and adjusting points etc, that you know it getting plenty of fuel because the plugs are WET.
They shouldn’t be “wet”. I think you’ve fouled them out trying desperately to get the bike started.
I’d start with two fresh plugs (properly gapped) and follow normal starting procedures.
Be sure the battery has at least 12.5 volts standing before cranking. Let’s try to get it running to check charging.
All was fine prior to maintenance steps I presume.

[Muddy]

I agree, the marine battery should not make a difference - IF it is connected to the bike in the same way as the original battery was. These bikes do not like running without a battery connected for any period of time.

Carby rebuilds can also lead to a lot of unexpected problems - especially if new jets have been fitted. There are lots of reports of carb kits being sold for these bikes with incorrect jets and incorrect needle/seats. Did you ensure to get the float height correct - this is essential.

Finally, Mike's suggestion of new, correctly gapped plugs is essential. If the new plugs foul quickly, you can suspect there is a carb issue.

Good luck.

[Michael Stoic]

As a general principle, the baseline is the gold standard of where to start troubleshooting. Properly charged correct battery. Confirmed good (cleaned) grounds. Bench tested variables like the rectifier and the condenser.

Sometimes routine wiring testing - cleaning bullet connections and ground points - leads to discovery of an obvious fault (short or break in the wiring), but I'd start with the baseline first. Your bike ran so you're close...

--
Mike Stoic

[hoodooman1]

Thanks folks for the input. I appreciate your time in helping me! The bike sat for maybe 5 years before I got it, but was a regular runner for many years. When I used the marine battery, I connected it with jumper cables. Maybe they touched something and shorted? And yes, the rectifier is original. At the time of my post:

MC Battery was new and fully charged and verified with a multimeter
Carb was disassembled, briefly chemdipped, and cleaned. All existing jets, needles, seat, etc. were reused. I only replaced the bowl gasket. I reset the float height which was already pretty much spot-on.
I did replace the D8HA NGKs again with new, properly gapped plugs a second time with no change
Points were cleaned (sanded) and sprayed with electrical cleaner and regapped
I adjusted the cam chain tensioner, which was stuck. Bike had new cam chain 15 years ago with maybe 3,000 miles on it.
Bike has had aftermarket 5ohm coil on it for 20 years, which still tests at 5 ohms
Condenser is also 20 years old. I haven't pulled it off to bench test it.
I went through many (not all) wires in the harness and cleaned connectors with deoxit spray


Electricals all seem to work: horn, starter, headlight, etc.

How can I bench test the rectifier? Although, I don't think that the rectifier should affect spark, is that correct?

Additionally, is it possible that my cam chain jumped a tooth while I adjusted the tensioner? It was stuck so I had to tap it with a hammer and pull it out with vice grips to get the tensioner freed up.

[Muddy]

Sounds like you have all the basics covered off and checked.

It is really surprising that the motor will not fire when you use starter fluid and use fresh spark plugs.

I'm guessing you have timed the points using the static method, which only leaves valve timing in the basics list. Might be worth just checking that?

Compression test OK?

[mike horvath]

“Carb was disassembled, briefly chemdipped, and cleaned. All existing jets, needles, seat, etc. were reused. I only replaced the bowl gasket.“

Ok. One more hit on the carb topic;
Did you use canned air or low pressure air nozzle to blow out all air passages?

Not sure the cam chain would jump a tooth, I think there’d be a better chance of it jumping completely off (oh noooo Mr. Bill!) if there’s that much slack in the loop, but you’d not only hear it in the bottom end while cranking, the valves wouldn’t open and close and you might damage the crank.
Man, short of popping the top to see the TDC punch mark, I’ve only one thought;
Might it be possible to remove the plugs, set #1 piston at the top, and see where the timing F mark is? You'd need an extra hand for this one.