New member with a 1967 CL77 and questions about losing power

[coydogsf]

Hey All,

I recently acquired the bike I've been drooling over, a 1967 CL77. The previous owner and his son had done a nice job going through most everything with an eye towards function if not always perfect restoration. Not a problem for me as I plan on riding and enjoying this thing.

So I took it out the other day. It had been having trouble starting, but a few days on the trickle charger and some new plugs and it fired right up and was running great. I shifted through the gears until I was up to about 50-55 mph (pretty exciting on this bike, but that's what traffic on the country road was doing). All was well until the first hill when I felt the first sputter.

Now, I'm used to sputters. I've felt them on my other old Hondas, usually when I forget to turn on the fuel petcock. But this time the fuel was on and the bike kept running, just with an intermittent decrease in power, even with the throttle wide open.

I've actually felt something like this one other time on my '73 CB750 and eventually traced it to cracking boots between the carb and air filter. Fresh, soft rubber and new clamps, and I never felt it again. Looking at my CL, I noticed that the boots don't have any type of clamp at all. I looked online and found these spring types but wondered a) is this what people are using vs. ring clamps with tightening screws and b) does this sound to anyone else like an air leak here could be the problem c) what else should I be thinking about?

Thanks in advance for any input!

Dave

[LOUD MOUSE]

These bikes had a tendency to have the cap go bad and not allow air in.
We would open the cap to prove this was the problem then leave the cap half open until we could replace it.
HONDA did offer this- Drill a small hole across the one already there under/near the seal gasket.
I did that once but found I cured the vacuum problem with gas on the tank. .............lm

Hey All,

I recently acquired the bike I've been drooling over, a 1967 CL77. The previous owner and his son had done a nice job going through most everything with an eye towards function if not always perfect restoration. Not a problem for me as I plan on riding and enjoying this thing.

So I took it out the other day. It had been having trouble starting, but a few days on the trickle charger and some new plugs and it fired right up and was running great. I shifted through the gears until I was up to about 50-55 mph (pretty exciting on this bike, but that's what traffic on the country road was doing). All was well until the first hill when I felt the first sputter.

Now, I'm used to sputters. I've felt them on my other old Hondas, usually when I forget to turn on the fuel petcock. But this time the fuel was on and the bike kept running, just with an intermittent decrease in power, even with the throttle wide open.

I've actually felt something like this one other time on my '73 CB750 and eventually traced it to cracking boots between the carb and air filter. Fresh, soft rubber and new clamps, and I never felt it again. Looking at my CL, I noticed that the boots don't have any type of clamp at all. I looked online and found these spring types but wondered a) is this what people are using vs. ring clamps with tightening screws and b) does this sound to anyone else like an air leak here could be the problem c) what else should I be thinking about?

Thanks in advance for any input!

Dave

[LOUD MOUSE]

The spring thing works fine.
Also check the vent tube on the bottom of the bowl for blockage. .............lm

Hey All,

I recently acquired the bike I've been drooling over, a 1967 CL77. The previous owner and his son had done a nice job going through most everything with an eye towards function if not always perfect restoration. Not a problem for me as I plan on riding and enjoying this thing.

So I took it out the other day. It had been having trouble starting, but a few days on the trickle charger and some new plugs and it fired right up and was running great. I shifted through the gears until I was up to about 50-55 mph (pretty exciting on this bike, but that's what traffic on the country road was doing). All was well until the first hill when I felt the first sputter.

Now, I'm used to sputters. I've felt them on my other old Hondas, usually when I forget to turn on the fuel petcock. But this time the fuel was on and the bike kept running, just with an intermittent decrease in power, even with the throttle wide open.

I've actually felt something like this one other time on my '73 CB750 and eventually traced it to cracking boots between the carb and air filter. Fresh, soft rubber and new clamps, and I never felt it again. Looking at my CL, I noticed that the boots don't have any type of clamp at all. I looked online and found these spring types but wondered a) is this what people are using vs. ring clamps with tightening screws and b) does this sound to anyone else like an air leak here could be the problem c) what else should I be thinking about?

Thanks in advance for any input!

Dave

[coydogsf]

Finally got a chance to get the bike back out on a long ride after cleaning the float bowls and adding spring clamps on the boots between the carbs and air filters. Unfortunately, no change, but I did gather some more info.

First, bike starts up and runs for the first 15 minutes absolutely perfectly. Smooth throttle through all the gears. The problem first appears after about 3-5 minutes of 50-55 mph. I rode it around town at low speeds the other day for much longer with no problems. It really only seems to happen after getting it up to speed. There's a sputter, loss of power and the sound of the engine changes. I'm assuming it's running on one cylinder.

Tips on how to tell which one it's running on?

As I slow to pull off the road, the engine usually dies. If I try to kick it over right away, it won't work. If I wait 30 seconds, it starts on the first kick with full throttle/power response. I can usually ride about 3-5 minutes (at any speed) before the problem comes back.

My thoughts (please correct if/when I'm wrong!):

Doesn't seem like a clog (fuel line/filter/carbs/jets) because it comes back so predictably and is resolved at least momentarily by restarting. Yeah, maybe stuff gets blown out a bit by the startup, but once the problem occurs, it always comes back in the same period of time. The next day, it will start right up and run no problem.

The above makes me think it's heat related. The air boots were a thought and may still need to replaced with some new flexible rubber to get a good seal once they start expanding from the heat?

Coils? I found a post on testing them and will do so, but I'm worried that the problem would only show up when they were hot. BTW, both spark plugs look identical and a nice tan/white.

Anything else anyone can think of I should test? Trying to get her ready for a 300+ mile three day vintage ride this coming weekend!!!

Thanks in advance.
Dave

[G-Man]

Did you try loosening the gas cap?

You can test to see which cylinder is firing by pulling off one of the plug leads. If it keeps running it's that one. If it stops - its the other one.

If it runs on one fro a long time the non running ctlinder / pipe will be cooler


G

[coydogsf]

Did you try loosening the gas cap?

You can test to see which cylinder is firing by pulling off one of the plug leads. If it keeps running it's that one. If it stops - its the other one.

If it runs on one fro a long time the non running ctlinder / pipe will be cooler


G

Thanks for the response! You know, I didn't think to try venting the gas cap since it didn't seem to make sense to me that that would affect only one cylinder. That being said, I will certainly try.

As for figuring out which cylinder is affected, my problem is that I'd need to remove a plug wire *while underway* since it dies when I pull to a stop and runs on both when I fire it back up. Maybe I can figure out a way to do that as I coast to a stop using the foot brake in neutral and reving the engine to keep it alive! And good thought on the checking the pipe temp, tho the problem only seems to happen when everything is already nice and hot.

I really do appreciate the input and helping me think this thing through.

Dave

[G-Man]

Depending on how the carbs are set up, a vacuum in the tank could affect one side before the other.

If you're not happy touching the hot pipes you could get hold of a thermomenter.

http://www.ebay.com/itm/Dual-2-Probe-Se ... rkt%3D1%26


G

Did you try loosening the gas cap?

You can test to see which cylinder is firing by pulling off one of the plug leads. If it keeps running it's that one. If it stops - its the other one.

If it runs on one fro a long time the non running ctlinder / pipe will be cooler


G

Thanks for the response! You know, I didn't think to try venting the gas cap since it didn't seem to make sense to me that that would affect only one cylinder. That being said, I will certainly try.

As for figuring out which cylinder is affected, my problem is that I'd need to remove a plug wire *while underway* since it dies when I pull to a stop and runs on both when I fire it back up. Maybe I can figure out a way to do that as I coast to a stop using the foot brake in neutral and reving the engine to keep it alive! And good thought on the checking the pipe temp, tho the problem only seems to happen when everything is already nice and hot.

I really do appreciate the input and helping me think this thing through.

Dave