1964 Honda Dream CA78 Rebuild-storation

[48lesco]

Bob - I didn't check the 20 pages in this thread, so you may have already done this, and I may even be repeating myself, but make sure the float height is right or even a couple of mm low (less fuel in the bowl). You can also check the actual fuel height in the bowl which is what really matters, with a clear plastic tube connected to the bowl drain. Sounds to me like there's just too much fuel around. You might also shut off the petcock and see if it idles better after half a minute or so. Those coils do get hot. Usually melt whatever that stuff is where the wires attach.
-48

[Bob750]

Here's my plan. Since I have, from this forum and communication from outside the forum, three credible possibilities for this hot idle gone wrong situation, I'm going to try to address them all in the sequence requiring the least amount of work. These possibilities are: float height (which would make mixture adjustments troublesome), coil, head gasket.

Today I'll pull the carb and verify the float is at 26.5 mm. Then I'll tweak it to 27.5 mm and put it back in and go for a ride. (My bowl only has the overflow tube, no drain screw.) But in the past it has idled better a few moments after fuel shut off... Running a new Honda float, seat and valve Since the rebuild over a year ago.

After that test ride, if the problem recurs, I'll try swapping the coil for one of mine from my CB750 To see if that helps or has no effect. The coil on the bike is the cylindrical type. Not sure about the melting of which you speak. But if coils get that hot, I'm less convinced that's the problem.

Remind me what the resistance readings should be? I'll check it cold and hot.

I'll be changing the head gasket next week regardless.

Bob - I didn't check the 20 pages in this thread, so you may have already done this, and I may even be repeating myself, but make sure the float height is right or even a couple of mm low (less fuel in the bowl). You can also check the actual fuel height in the bowl which is what really matters, with a clear plastic tube connected to the bowl drain. Sounds to me like there's just too much fuel around. You might also shut off the petcock and see if it idles better after half a minute or so. Those coils do get hot. Usually melt whatever that stuff is where the wires attach.
-48

[48lesco]

Bob that's a solid plan and I hope increasing the float height worked it out. It's unsatisfying when you use new OEM parts and set everything to spec and you have issues. I wonder if fuel properties like viscosity, vapor pressure, etc are different enough now to cause these issues. I had the same hot idle problem as you with my '66 Dream and a 28mm float height solved it. The OEM coil is about 13K ohms across the secondary and 3-4 ohms for the primary.

[Bob750]

Okay, so, this is a little embarrassing...

I took some advice from a trusted contact of mine, and ran though the normal tune up procedure. Starting with the Points Gap. It had made it all the way out to .017" I remember having a stripped screw last time I wanted to adjust them and decided that since it was "running fine" and was within spec, just barely. I went ahead with timing and the rest.

So yesterday I used my impact driver to get that cammed-out slotted screw loose, reset the points gap to .012" and cleaned them very well.
Then I had to reset the timing due to the massive reduction in gap.
Re-adjusted the cam chain tension for good measure.
Rechecked the valve clearances also. They were just under .004", not even to .003", but I loosened them all up to a nice easy .004".
Then I used a hoist and dunked the whole bike into a giant vat of Run-Rite and let it soak for about 15 minutes. (The label says any longer and it will run too well.)

Bike started and idled nicely, I let it warm up a bit and reset the idle mixture. I set the idle rpm nice and low to help me detect the dreaded hot idle die-out.

Went for a 22-mile ride around town non-stop. No highway, just neighborhoods and boulevards and hills and stop and go stuff to replicate the situation that brings out the mean old bad hot idle. Oh, I forgot to mention I left the points cover off on recommendation just to make sure the points weren't arcing to the cover. And I decided to leave the electrics cover off to allow me to check the temp of the coil while riding. After about 50 minutes and only a couple faint moments of sounding like it was thinking about dying out at a stop light, I pulled over and adjusted the mixture and rpm again. Rode for another 15 minutes back to the garage sounded good at stop lights. I left it running in the alley while I opened the garage, pushed it onto the lift, pumped up the lift and turned on the fan.

I left it like that for 5 minutes.
Plop plop plop plop plop plop plop plop plop plop plop plop plop plop.

It never stalled or faltered. It did seem to slow down a tad at one point, but not much. I touched the mix and throttle stop a bit. Then I reinstalled the points cover and the electrics cover while it continued to idle perfectly for another 5 minutes.
Plop plop plop plop plop plop plop plop plop plop plop plop plop plop.

At this point I decided I had accumulated enough exhaust soot in my hair and clothes, so I closed the fuel petcock and counted. After exactly 30 seconds the idle speed came up significantly to a higher rpm and stabilized there for a solid minute before I turned it off by key.

Today I'll take off the carb and see what pilot jet size is in there. I'll probably tweak the float level by a millimeter to see if that allows it to idle better at a more reasonable mixture screw setting, which currently set at about 2 or 2.5 turns out.

........Om........

[R100]

So Bob, where can I get some of that Run=Rite?
My CB needs to soak in it for at least a week.

[Bob750]

I bought the last drum of it. ;-)

So Bob, where can I get some of that Run=Rite?
My CB needs to soak in it for at least a week.

[Bob750]

So, since my last post, I am sad to say that nothing up until today worked to rid our Dream of it's bad attitude at idle. I do appreciate all of the help and advice during this frustrating troubleshooting chapter. But in the end it was a faulty coil. When it gets to a certain operating temperature it would just start forgetting it's job.

I had convinced myself that there was some carburetor issue. Bill Silver sent me a spare round-bowl carb for me to use to troubleshoot. Two things: Well, Three things: 1) Bill Silver is freaking awesome. 2) His carb made our Dream idle a LOT better. 3) This switching out of the carbs revealed that the problem was not in the carb, because after about 30 minutes of riding the idle problem reared its ugly head again. :-(

So, I'm still running Bill's carb, but I swapped out the Dream's coil for one of my old coils from my '74 CB750K4, since I had upgraded to high-performance coils when I installed my Reg-Rec and electronic ignition.

I went for a 20 mile ride over about 50 minutes yesterday and it ran without any probs, but it began to rain so I had to call it a day. Yay for rain! But I didn't feel I had run the bike long enough to be sure the problem wasn't going to arise again if I had just ridden another 20 minutes; it happened before with a spare condenser I was trying out.

So today I took the Dream out for a nice long ride. I rode all around town and covered 40.5 miles in exactly 2 hours' time including a few longish periods of idling. I never shut the bike off. It never quit. It never hesitated or gave any indication that anything was wrong. After the 2 hour ride was over, I put it up on the lift with the fan on it and let it idle, like a metronome, for about 5 more minutes. No problems.

I am pleased.