1964 Honda Dream CA78 Rebuild-storation

[G-Man]

Bob

You're getting close.The coil might have an issue but it might also show up when you're riding, too. If the carb is clean and the float height is correct then you only have the throttle stop and idle mixture screw to play with.

It might be worth doing the carb tuning when the engine is hot and then see if you can live with that when it is cold....

G

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.

[48lesco]

+1 on carb tuning after it's hot. Even with that "insulator" the carb gets hot and fuel properties change at temperature. You probably have, but if not I'd re-check the valve clearances too. Your issue seems too repeatable to be coil or condenser related...

[Bob750]

Thank you guys for the insight. I hope I'm finally homing in on the real issue. Or, maybe it was a combination of issues all at once that was driving me crazy. I think the failing condenser was forcing me to compensate in other places that now, with a good condenser, are out-of whack.

At the end of the short ride yesterday, I did fiddle with the idle mixture and got the idle stable before shutting it down. If it's a little hard to start today, I'll know I'm on the right track; Bill "MrHonda" Silver says that if you can start one of these bikes really easily when cold, then it's not tuned right. ;-)

Just a few weeks ago I did the full tune-up after ultrasonically cleaning the carburetor and its parts and spending a lot of time making sure the float level was spot on.:

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.

Admittedly however, it wasn't HOT after only a 2-mile warm-up ride, and it did have the old condenser on it which may have been "fogging my goggles" enough for me to not to see the over-rich condition when it does get HOT, rather than just really warm. Previously, when trying to get it to idle when really HOT (as it was kicking and sputtering with a bad condenser), I could never get it dialed in because... hot, failing, condenser. So now maybe this is it.

I'll report back!

Bob

You're getting close. The coil might have an issue but it might also show up when you're riding, too. If the carb is clean and the float height is correct then you only have the throttle stop and idle mixture screw to play with.

It might be worth doing the carb tuning when the engine is hot and then see if you can live with that when it is cold....

G

+1 on carb tuning after it's hot. Even with that "insulator" the carb gets hot and fuel properties change at temperature. You probably have, but if not I'd re-check the valve clearances too. Your issue seems too repeatable to be coil or condenser related...

[Tim Miller]

Bob,

My advice is to fix the head gasket leakage first. If your leaking any combustion your never going to make this run right. Before you take it apart tell us what your initial and total timing is, using a strobe timing light. You might need to repair the advancer too. I've used plenty of aftermarket head gasket and copper ones too with no problems. Yours sleeves have probably dropped.

Tim

Thank you guys for the insight. I hope I'm finally homing in on the real issue. Or, maybe it was a combination of issues all at once that was driving me crazy. I think the failing condenser was forcing me to compensate in other places that now, with a good condenser, are out-of whack.

At the end of the short ride yesterday, I did fiddle with the idle mixture and got the idle stable before shutting it down. If it's a little hard to start today, I'll know I'm on the right track; Bill "MrHonda" Silver says that if you can start one of these bikes really easily when cold, then it's not tuned right. ;-)

Just a few weeks ago I did the full tune-up after ultrasonically cleaning the carburetor and its parts and spending a lot of time making sure the float level was spot on.:

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.

Admittedly however, it wasn't HOT after only a 2-mile warm-up ride, and it did have the old condenser on it which may have been "fogging my goggles" enough for me to not to see the over-rich condition when it does get HOT, rather than just really warm. Previously, when trying to get it to idle when really HOT (as it was kicking and sputtering with a bad condenser), I could never get it dialed in because... hot, failing, condenser. So now maybe this is it.

I'll report back!

Bob

You're getting close. The coil might have an issue but it might also show up when you're riding, too. If the carb is clean and the float height is correct then you only have the throttle stop and idle mixture screw to play with.

It might be worth doing the carb tuning when the engine is hot and then see if you can live with that when it is cold....

G

+1 on carb tuning after it's hot. Even with that "insulator" the carb gets hot and fuel properties change at temperature. You probably have, but if not I'd re-check the valve clearances too. Your issue seems too repeatable to be coil or condenser related...

[G-Man]

Tim

Sound advice. I forgot about the head gasket problem.

G

Bob,

My advice is to fix the head gasket leakage first. If your leaking any combustion your never going to make this run right. Before you take it apart tell us what your initial and total timing is, using a strobe timing light. You might need to repair the advancer too. I've used plenty of aftermarket head gasket and copper ones too with no problems. Yours sleeves have probably dropped.

Tim

Thank you guys for the insight. I hope I'm finally homing in on the real issue. Or, maybe it was a combination of issues all at once that was driving me crazy. I think the failing condenser was forcing me to compensate in other places that now, with a good condenser, are out-of whack.

At the end of the short ride yesterday, I did fiddle with the idle mixture and got the idle stable before shutting it down. If it's a little hard to start today, I'll know I'm on the right track; Bill "MrHonda" Silver says that if you can start one of these bikes really easily when cold, then it's not tuned right. ;-)

Just a few weeks ago I did the full tune-up after ultrasonically cleaning the carburetor and its parts and spending a lot of time making sure the float level was spot on.:

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.

Admittedly however, it wasn't HOT after only a 2-mile warm-up ride, and it did have the old condenser on it which may have been "fogging my goggles" enough for me to not to see the over-rich condition when it does get HOT, rather than just really warm. Previously, when trying to get it to idle when really HOT (as it was kicking and sputtering with a bad condenser), I could never get it dialed in because... hot, failing, condenser. So now maybe this is it.

I'll report back!

Bob

You're getting close. The coil might have an issue but it might also show up when you're riding, too. If the carb is clean and the float height is correct then you only have the throttle stop and idle mixture screw to play with.

It might be worth doing the carb tuning when the engine is hot and then see if you can live with that when it is cold....

G

+1 on carb tuning after it's hot. Even with that "insulator" the carb gets hot and fuel properties change at temperature. You probably have, but if not I'd re-check the valve clearances too. Your issue seems too repeatable to be coil or condenser related...

[Bob750]

So I took it out today.

Sadly, it started a little easier than I was hoping. It was starting to behave funny at idle again around 12 miles out. After a bit more at about 17 miles, I pulled into a parking lot and let it idle while I adjusted the mixture. I could make improvements but It still wants to quit and occasionally sounds like it's missing. I rev it. It's fine for a short bit then starts running rough again and will occasionally just quit. On my way back it stalled a couple of times at traffic lights. After I got it home. I let it idle but it wouldn't for very long. There was a point on the ride, during acceleration that it "missed" a couple spark cycles.

I took off the side cover once the bike was up on the lift. I could only hold my palm against the coil for about 30 seconds before I had to start fighting my reflexes to remove my hand. Do coils usually get that hot? How might a coil fail or become intermittent when hot? Yesterday I thought it was just an idle mixture issue since I'd eliminated the condenser as the (sole) problem. Now I'm not so sure. Unless the needle needs to be moved to a different slot.

Tim.
I checked the timing with a strobe last month. It was idling at F, and it went smoothly to full advance within a "good" RPM sweep and locked right on the || all the way to "really fast". As you know, Dreams have no tach. :-( The advancer is working fine. Loudmouse would have caught a bad one when he rebuilt the head, anyway. And even if it wasn't working properly this problem only happens when the bike's been running a while and is hot. I don't see how an advancer failure would allow the bike to run great at all throttle settings and then only when the bike gets hot it cause the bike's idle to drop rpm and die. (I can't recheck it now anyway though because my cheapo hand-me-down strobe died while I was checking my CB750 after putting in my electronic ignition. Luckily I had finished the job before it died.) This is the new strobe I will be buying when I get the budget approval. It had the RPM feature. ;-)

The new OEM head gasket will be ordered this week, along with the new o-rings for the oil galleries. Mind you, the gasket isn't blown. No combustion leaks to the outside, just a little oil seepage after long rides (top and base gasket don't leak.) I do fear oil is seeping into the combustion chamber though. I doubt the cans have slipped; they were perfectly smooth with the cylinder block when I disassembled it, cleaned it, honed the cylinders and reassembled it. I don't think after being fine for 8500 miles and a 1st-over bore job at some point long ago, that they would slip at this point only 500 miles after a rebuild. But we'll see what things look like when I drop the motor and get back in there. (Reassembly photo album.) (Dissassembly album.)

[Tim Miller]

Bob,

Remember I'm just trying to help you out. If your leaking oil/ fuel around the plugs / skull and you think oil in getting in chambers then the head gasket is not holding. Your leaking high pressure during compression stroke. I've been there done that. I have had this same problem myself, it's all fine when cold then runs poor hot. I'm glad you have verified your advancer is in good condition. I not only mill all gasket surface I also lap them in.

All the best,
Tim

So I took it out today.

Sadly, it started a little easier than I was hoping. It was starting to behave funny at idle again around 12 miles out. After a bit more at about 17 miles, I pulled into a parking lot and let it idle while I adjusted the mixture. I could make improvements but It still wants to quit and occasionally sounds like it's missing. I rev it. It's fine for a short bit then starts running rough again and will occasionally just quit. On my way back it stalled a couple of times at traffic lights. After I got it home. I let it idle but it wouldn't for very long. There was a point on the ride, during acceleration that it "missed" a couple spark cycles.

I took off the side cover once the bike was up on the lift. I could only hold my palm against the coil for about 30 seconds before I had to start fighting my reflexes to remove my hand. Do coils usually get that hot? How might a coil fail or become intermittent when hot? Yesterday I thought it was just an idle mixture issue since I'd eliminated the condenser as the (sole) problem. Now I'm not so sure. Unless the needle needs to be moved to a different slot.

Tim.
I checked the timing with a strobe last month. It was idling at F, and it went smoothly to full advance within a "good" RPM sweep and locked right on the || all the way to "really fast". As you know, Dreams have no tach. :-( The advancer is working fine. Loudmouse would have caught a bad one when he rebuilt the head, anyway. And even if it wasn't working properly this problem only happens when the bike's been running a while and is hot. I don't see how an advancer failure would allow the bike to run great at all throttle settings and then only when the bike gets hot it cause the bike's idle to drop rpm and die. (I can't recheck it now anyway though because my cheapo hand-me-down strobe died while I was checking my CB750 after putting in my electronic ignition. Luckily I had finished the job before it died.) This is the new strobe I will be buying when I get the budget approval. It had the RPM feature. ;-)

The new OEM head gasket will be ordered this week, along with the new o-rings for the oil galleries. Mind you, the gasket isn't blown. No combustion leaks to the outside, just a little oil seepage after long rides (top and base gasket don't leak.) I do fear oil is seeping into the combustion chamber though. I doubt the cans have slipped; they were perfectly smooth with the cylinder block when I disassembled it, cleaned it, honed the cylinders and reassembled it. I don't think after being fine for 8500 miles and a 1st-over bore job at some point long ago, that they would slip at this point only 500 miles after a rebuild. But we'll see what things look like when I drop the motor and get back in there. (Reassembly photo album.) (Dissassembly album.)