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The Honda CA95 / Benly 150 Restoration The little brother to the CA160 in our family of Hondas

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  #1  
Unread 11-23-2013, 06:42 PM
62benly 62benly is offline
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Default Left Cylinder Not Firing

Hello,

Just fired up the benly (CA95) tonight after replacing the battery. Before I started her up I put new spark plugs in (after setting the gap) and then adjusted the timing and set the point gap too.

Anyway, she started up OK but the left cylinder is not firing. I know this because she's smoking up a storm and also the left exhaust is cool while the right is stinking hot.

Do any of you know how I might fix this. I think I have had this problem forever now and it sure would be nice to get fixed.

Thank You.
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  #2  
Unread 11-23-2013, 07:25 PM
Spokes Spokes is offline
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We know that the coil is good being that one cylinder is firing.

1. Take the known good firing plug and install it in the non firing cylinder. Take the non firing cylinder plug and install it in the firing cylinder. The reason for doing this is because there is a chance that you have a bad plug. Yes, even new plugs can be bad..especially if purchased off eBay.

2. Make sure the non firing plug cap is screwed in tightly. Fire? Yes. Great! No, then unscrew the cap and cut the spark plug wire about 1/8" off of the end and reinstall the cap. Still not firing?

3. Clean the base of the head at the spark plug hole. Still not firing?

4. Pull the coil and replace the spark plug wire with a 7mm solid core spark plug wire. Snowmobile or lawnmower spark plug wire works great.

IF still no fire..

Check the compression in the cylinder. Low compression won't bang...

You can add about 1/2 oz of clean motor oil to the non firing cylinder to boost compression. If the oil in the cylinder causes combustion then you may have a ring or valve issues.
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  #3  
Unread 11-23-2013, 07:34 PM
62benly 62benly is offline
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OK.

I will check those things asap.

Ah man, I'm feeling the love. Thanks Spokes!!!
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  #4  
Unread 11-23-2013, 08:25 PM
62benly 62benly is offline
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OK, correct me if I'm wrong but don't both left and right plugs fire during the compression and exhaust stroke. So it doesn't matter which spark cable is connected to either cylinder? Given this, what I did was switch spark cables to diagnose if the cables were the problem. I got the same results (No fire in left cylinder). I also switched the plugs around and still no fire. I also disconnected the right plug while she was running. She kept running but slowed and sputtered. I did the same thing to the left and there was not much change in RPM.

I had the cylinders re bored about 2 years ago. I guess the rings could have been placed upside down or something. I think my next step is to find out if that cylinder has comparable compression. Pretty sure this has been an ongoing issue. Been sort of burying my head in the sand about it for quite some time now. Have not been joy riding her or anything. Just will fire her up every once in a while, notice she's not quite right, and then put her away.

I really hope its not a compression issue. I've never done a compression test but its never too late to learn so Ill look into that. I may also try to pour a little bit of oil down there to see if there's any change like spokes suggested. I'll update you all on my progress.

Thanks again.

Last edited by 62benly; 11-23-2013 at 08:31 PM.
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  #5  
Unread 11-23-2013, 08:40 PM
Spokes Spokes is offline
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"I also disconnected the right plug while she was running. She kept running but slowed and sputtered"

Great observations and deductions. Based on your statement above, I will bet on the compression issue.

The oil in the cylinder will help make the engine run better for a short while if it's rings. It won't help if it is a valve issue. If it's a valve issue, perhaps the issue may be just valve adjustment.
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  #6  
Unread 11-24-2013, 04:07 AM
Sam Green Sam Green is offline
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Great info as usual from Chip.

Hear's another reason why asking on here for help is the right thing to do.
Several years ago I was given a load of old Motorcycle Mechanics magazines (British publication) and found this while flicking through them.
This was in an old one from the early days when our Benly's would have been relatively new and was in the Questions and Answers section.
A guy had issues with his bike not running as it should but just on one cylinder.
They told him that ONE of his carbs needed adjustment.

Sam.
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  #7  
Unread 11-24-2013, 04:34 AM
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ByTheLake ByTheLake is offline
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You mention some work that you did before starting the bike up ... replaced the battery, plugs, adjusted the points & timing, etc. By chance did you adjust the valve lash too? I was wondering if a valve wasn't completely closing.

Spokes mentioned the compression test, which would confirm that anyway.
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  #8  
Unread 11-24-2013, 07:30 AM
rhodemon rhodemon is offline
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I've had my share of non firing issues over the years and now use the following technique to trouble shoot them. This procedure only applies to engines w a wasted spark, i.e., those with one set of points and one coil and two cylinders like the CA95 in which both plugs fire at the same time, one of the plugs firing on the compression stroke, and the other at the same time, but on the exhaust stroke.[That combo can make for some beautiful backfires!]

I take off the points cover and ensure the points are riding on the cam flat so I can manually open and close them with my finger or carefully with a screwdriver. If the points are open, i.e. resting in the cam lobe, turn the engine a bit to get them on the cam flat.

Remove both plugs and reconnect them to their wires, and bring the right plug and wire over to the left side of the engine and. after placing the plugs side by side, wrap them together w a bit of bare wire and ground the lot to the side of the engine right in front of your eyes so you can easily see the gaps.

Turn the key to the ignition position and manually open and close the points. [It's not necessary to use the starter unless you want to observe the sparking under load] The plugs should fire equally with the same intensity every time or you've got problems.

I've found unequal firing to be caused by such things as bad or dirty or badly adjusted points or more frequently by a fouled plug. If a plug stays in an engine and never or inconsistently fires, it becomes soaked with gas and isn't right again. Replace it! Maybe sometime in the future it will dry out, but even heating it w a small torch doesn't usually cure it right away.

And don't forget to shut the key off when you're done. Leaving it on will discharge the battery and may burn the points too. I use a small diamond fish hook sharpening file to clean and flatten the points.
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  #9  
Unread 11-24-2013, 08:45 AM
62benly 62benly is offline
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I went out and bought a compression test kit this morning. I came right back home and began with the right cylinder. I turned off the gas and drained the float bowl. Then I took the plug out and connected the pressure gauge. I turned her over and the right cylinder read 90 PSI. Turned her over some more and the gauge red about 90 PSI tops.

I squirted some oil in there, turned her over, and read 130 PSI. Cranked some more and it stayed at 130 PSI.

Did the same on the other side. Screwed in the gauge, turned her over, and read 90 PSI. Squirted some oil in and the gauge jumped and kept rising the more I cranked, unlike the right cylinder, to about 240 PSI.

Kinda weird right? Something's fishy. My re bore job must have been terrible.
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  #10  
Unread 11-24-2013, 09:04 AM
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ByTheLake ByTheLake is offline
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How much oil did you squirt in? You shouldn't get anywhere near 240 PSI, unless you've added quite a bit of oil to the cylinder. Maybe you swapped this engine out for a Diesel and forgot to mention it?

Did you have the choke off and the throttle fully open while taking your compression readings? That's important, and could account for the slightly low reading of 90 PSI before the oil was added.
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  #11  
Unread 11-24-2013, 09:25 AM
62benly 62benly is offline
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Haha, nope not a diesel. Maybe I put too much oil down the hatch?

I just squirted some oil in real quickly. I don't have a funnel, just a nozzle for a lid on the oil bottle. Also, I did not open the throttle fully. I'll see what I can round up for a funnel and try again adding the proper amount (1 oz). But first I'll try again with the throttle open and no oil added.

I ran her for a couple of minutes to burn up what I did put in there.

Thanks for the tips.
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  #12  
Unread 11-24-2013, 09:38 AM
Spokes Spokes is offline
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The oil addition to the cylinders confirmed that the low compression is due to cylinder issue. I can't speak for the 240lb reading.

When you ran the bike to blow the oil out, were both cylinders firing? The next starting after the oil/compression test, take a ride on the bike and confirm that the non firing cylinder exhaust pipe is hot. The bike should run strong for a short while.

The bore of the cylinder may be fine and the rings, or one ring may be installed upside down. An additional ring installation technique is to space the ring gaps at 9 o'clock 1 o'clock and 5 o'clock. Ring gap alignment is also a cause for low compression.

These bikes serve as a great learning curve.
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  #13  
Unread 11-24-2013, 10:08 AM
62benly 62benly is offline
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Does it matter how long I crank the motor for? Is there a general rule of thumb or do I just crank until the pressure stabilizes?

Anyway, I went out and did another test. This time I did not add any oil. Got about the same max PSI in both cylinders (90 PSI) with throttle open wide. No oil added.
Attached Images
File Type: jpg RIGHT.jpg (96.7 KB, 15 views)
File Type: jpg LEFT.jpg (94.8 KB, 10 views)
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  #14  
Unread 11-24-2013, 10:43 AM
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ByTheLake ByTheLake is offline
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Crank or kick until the reading no longer increases.

The numbers appear to be a bit better than 90 PSI in the pics, ironically higher in the cylinder that you say isn't firing. Although these readings are low, if the right cylinder is firing ok while having the lowest compression of the two cylinders, something else may be affecting the left cylinder.

Interesting ... gotta think on this a bit.
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  #15  
Unread 11-24-2013, 11:21 AM
62benly 62benly is offline
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hmm,

A little disappointing that I have low compression after the re-bore. Might be best to take her apart again and make sure everything is lined up as it should. Maybe a good project over Christmas break.

After I had it re bored I was a little overwhelmed so I hired the machine shop that did the re-bore to put the motor back together for me. They seemed like capable dudes.

I did check the Tappet gaps and they all seem OK. I think I definitely have some sort of problem in the left cylinder because the exhaust is always much cooler than the right and also is much more oily/wet at the end of the pipe.

Anyways, I'll sort of play it by ear I guess. I'll update any findings I might have as I go forward.

Thank You
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