CA77 Dream running GREAT! ... Until it gets HOT.

[LOUD MOUSE]

Looks like I lucked out again. :-)
Thanks for the comment on the head. .........................lm

Gas cap loose to prevent vacuum? Our cap is perfectly clean and and vents very well--too well, judging by the top of the tank on a hot day... ;-) I'll check the valves again, but just cleaning the points cleared things up nicely. Thanks, LM! Your valvetrain and head work you did for us is, well, still awesome.

If you did a full rebuild you may want to readjust all parts which have required clearances.
With cold engine adjust all valves. (they be tight now)
Clean and adjust points. (the phenolic area which contacts the points cam will wear in and close the gap and change the "F" timing).
Worth a try I guess. ....................lm)
OH. And leave the gas cap loose.

If it's not a carburetion issue, maybe it's a fuel related issue. Have you tried a different grade of gas? Maybe some ethanol free blend(if you can find it). Maybe it's electrical, do you have a way to heat up the coil/condenser(with a heat gun or a hair dryer) to see if it acts up?

[Bob750]

No problem, Ed!

I took the opportunity to do the full checkup.

1) Checked tappet clearances. Intakes were a tad tight. Exhaust was fine.
2) Reset cam chain tension at BDC per user manual. A slight forward movement was noticed when I loosened the lock bolt. So I'm glad I did that.
3) Cleaned the points again.
4) Cleaned the points cam & felt. Re-lubed the felt.
5) Checked point gap. OK.
6) Checked static timing with a light bulb. Was off a tad, so adjusted it.
7) Set the carb screws to initial settings. Warmed up the bike and adjusted the mixture and idle.

I'm very happy. More importantly, my wife is happier. (It's her bike, after all!)

Since I checked the advance with a strobe last week and found it working well, I'm confident there's no need to do it again. Besides, my cheapo strobe died while I was revving it--luckily, after I had already verified the advance's proper operation.

So... in the end it wasn't a carburetion or fuel issue after all. It was dirty points. Problem is, if they get fouled again soon or the bad hot idle returns soon, it's an indication of a failing condenser, since the condenser's job is to quench the arcing that's causing the fouling. So I'll be replacing it when I replace my leaky head gasket with an OEM one next month or so. (Too much of a pain to do it with the motor in the frame.)

Cheers, all!

[Bob750]

Okay. I'm back.

It might be mixture related after all (hidden by a bad condenser and oil fouling from a seeing gasket)...

Here's the update:

I wired up an NOS condenser--zip-tied it to the right dust cover screw hole boss. Bike runs the same as before when cold, but when it gets hot there is no more coughing and sputtering, so it seems that there was/is a problem with the old condenser (that is still mounted on the top of the motor.) So the new condenser has indeed alleviated some issues.

But after getting hot, there is still the tendency for the idle RPM to slow and then quit, unless I blip (or more) the throttle. It will however continue to run apparently indefinitely as long as speed and rpm are maintained. Before the new condenser, no matter what, it would be fighting with me all the way home. Now it's only unhappy at idle and even then I can work the throttle to keep it running.

It may be worth mentioning that it's definitely temp-related not distance-related, because I can reproduce this issue after going 25 miles in 1 hour on an overcast day, or after only going 3 miles in stop and go city traffic in less than 10 minutes on a 72'F day.

Is there anything I can check with regards to mixture? Does this engine run richer when it's hot due to the intake behind the head heating the air and reducing its density, thus enriching the mixture? Could that cause it to die of an over-rich idle-mixture, but only when hot enough? I made a 1/4 turn mixture adjustment (slowed down--richer), made the opposite adjustment to a 1/4 turn in the other direction (sped up--leaner) and was able to get the idle stable albeit at a little higher RPM than I had it set at.

I'm still going to redo the head gasket with OEM item. But if it is oil fouling at hot temps killing the spark, wouldn't the plugs still be fouled an hour later when the thing's cooled down but starts with a slight tap of the button and then putts happily along without quitting or dropping RPM?

Could the coil be showing age when it gets warmed up but not when it's cool?

What component behaves significantly differently at high operating temps than at low ones. I've learned the Condenser is one, and I replaced it, noting some improvement but not elimination of the remaining hot idle issue.

Gonna go test the bike with various mixture settings to see if that's now the primary problem. Later though; I've had beerz.

[Bob750]

{If you follow my restoration thread, you can skip this post.}

I just wanted to check in and say that I solved the problem, and it was not fuel related.

It was a faulty coil. At present I'm running one of my CB750 coils, which were left over after I upgraded that bike to high-perf coils, a reg-rec, and electronic ignition.

I was able to determine the problem had nothing to do with carburetion by swapping my carb out for one on loan from Bill Silver. (That man is awesome.) His carb did allow our Dream to idle better, but when the coil got to it's "i'm getting belligerent" temperature, it started to only give out some sparks, instead of all the sparks.

So my main problem is now solved. I'll run my CB750 coil until I replace it with a nice new Dyna D8-1A from Charlie's Place.

In the meantime, and to keep this thread about carburation and Fuel, I'm going to see which parts from Bill's carb give my carb better idle characteristics. Then I'll try to source whatever those are. Check with my restoration thread.