1964 Honda Dream CA78 Rebuild-storation

Bob750 · Post by **Bob750** » Mon Mar 16, 2015 10:52 am

Thanks for the discussion, G!

Is there an intermediate failure mode for the condenser? Wouldn't it just stop the bike from receiving spark? And would it return to normal operation after cooling a bit?

This is intriguing. If this is all just a bad condenser, that'd be nice, since I have a spare condenser that I bought when the bike was new to us and thought it might be why the bike would not start. (Turns out the condenser wire had been pulled apart at a connection hidden in some electrical tape.) Plugged it back and boom! Off to the races. But I kept the new condenser as a spare. :-)

Someone on the Carb-fuel thread also suggested heating the condenser with hot air before riding to see if it changes the behavior or ride-time-to-failure. Perhaps I'll give that a shot. And I may wire up the spare, bypassing the one on the top of the motor, and see if that eliminates the symptom.

Why did they put the condenser up there? For cooling? Too big to fit under the point cover, where it's also very hot?

G-Man wrote:Bob

The condenser snuffs out voltage spikes as the points operate and stops arcing. The traditional condenser failure is when the engine gets hot.

Bad spark means poor running which may look like un burnt fuel,,,,,,

G

G-Man · Post by **G-Man** » Mon Mar 16, 2015 10:55 am

Bob

The heat thing is a classic condenser failure symptom.
G

Bob750 · Post by **Bob750** » Mon Mar 16, 2015 9:17 pm

Well, I think it was just really dirty points. I cleaned the points by dragging a folded piece of 600 grit wet-dry sandpaper spritzed with 'Lectra-motive cleaning spray through the closed contacts; then I followed that with a business card wetted with contact cleaner. I also repaired a couple of wiring connections that were needing it (one being the wire from the harness to the condenser). No more points arcing. Then I went riding.

I rode "hard" for 25 miles for a period of one hour without turning off the engine. Up hills. In stop and go traffic. Wide open throttle on PCH. Heavy acceleration at most lights and stops. Whatever I could do to get it HOT.

After my butt became too numb to continue, I pulled into the garage and let it idle for a few minutes. Not once did it develop the business it had been recently.

I guess I need to clean these points every 500 miles. I don't think the condenser is the problem this time. But if it ever does fail, I have one on hand.

Look at these:

G-Man · Post by **G-Man** » Tue Mar 17, 2015 12:27 am

Bob

The condenser is there to stop the points arcing, with subsequent transfer of metal from one point surface to the other. This causes a tiny hole on one contact and a matching pimple on the other. The effect of the two damaged surfaces is to alter the effective points gap and timing. The condenser is there to slow that proces down.

By 'cleaning' the points with the 600 grit paper, you have reset the clock on the process but you might not have eliminated the problem.

I would keep the condenser in you pocket - just in case....... :-)

G

Bob750 · Post by **Bob750** » Tue Mar 17, 2015 12:33 pm

Okay, G-Man.

Good advice. I think I'm staring to understand the finer aspects of this stuff.

Cheers!

G-Man · Post by **G-Man** » Tue Mar 17, 2015 12:44 pm

Bob

You're welcome. Let us know if the problem comes back and if you can make it go away again in the same way. It's all useful information to share.

G

Bob750 · Post by **Bob750** » Sun May 10, 2015 6:38 pm

Okay. I'm back. 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.