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Discussion Starter · #1 ·
My otherwise mint condition and low mileage CB360T has gotten more and more difficult to start. It has also started backfiring under load and quite often one cylinder won't fire...

I'll skip all the carbrelated work I have done and would like to ask you about the coils.

- Do my coils seem OK?
- My spark plug caps seem like they are toast (no reading). If so, should I get 5 or 10 K Ohm ones?


I have measured them as follows:

Coil 1
Primary: 7,4 Ohm
Secondary: 15,13 K Ohm
Secondary (no spark plug Cap): 10,4 K Ohm
Spark Plug Cap: 0 Ohm

Coil 2
Primary: 7,3 Ohm
Secondary: 15,09 K Ohm
Secondary (no spark plug Cap): 10,33 K Ohm
Spark Plug Cap: 0 Ohm

New Spark Plug Cap (NGK)
Spark Plug Cap: 4,74 K Ohm

I have made this test:
SimpleCoilTest.jpg
(http://i201.photobucket.com/albums/aa158/66Sprint_album/SimpleCoilTest.jpg)

With both coils, a spark would appear. It made no difference whether i used the old spark plug caps or the new NGK.
 

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Getting full battery voltage at the coils? Maybe you could do a voltage drop test on the coil + terminal with the engine running under load. One lead on the battery + terminal and the other lead on coil + , with the meter set to volts, should tell you if there are losses in the ignition switch or wiring.
 

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Sensei
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Well, when you tested JUST the plug caps your meter was set to the "wrong" scale.....
Your previous numbers show about a 5K ohm difference between readings with and without the caps... (15. K vs 10. K)...So, caps are 5K not "0"...
Your coils appear to be fine....

I have run across cases of intermittent " backfiring/afterfiring" on bikes with poor contact at the "kill" switch, but it SOUNDS like you would be best-off adjusting/verifying the points timing, installing new good plugs, and calling the ignition good .......(What do the old plugs look like?)....

IF your compression is within range, (155 to 180 PSI), I would suggest that it's a fuel supply problem.....
Carbs out of sync or misadjusted, incorrect float height, bad shut-off needle, etc....
 

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Discussion Starter · #4 ·
Thanks for the quick replys! Great!

Mike
I'll have to try that when spring comes, as the bike is in winter storage. I have taken a few parts off for light restoration and testing, so I can't run it right now.

66sprint
Thank you for chiming in. I know you are very knowledgeable about these bikes. I'll tell you as much as I can about my bike in the following:
I follow your logic with the 5 K ohm difference. However, I checked to 3 different caps at the same setting and right after eachother. I just went out and re-did the measuring, and the result is the same: No reading on the old caps and 4,74 K ohm on the new one.

The spark plugs are less than a month old. The old plugs actually looked OK. They were maybe slightly dark (as in a bit too rich), but we are talking very slightly!
I have recently fitted Mark "Hondaman"'s, ignition (Transistorized Ignition for Dual Points, SOHC4shop.com) and it has made the bike run quite a lot smoother, especially at idle.

I have not tested the compression lately. I do have a tester, so the next time I'll go by my friends house (where the bike is stored), I'll give it a go. (Allthough it only has 8000 miles racked up).
I also have a carb-sync thingy (also have a CB550), but haven't sync'd the 360 in a while - I'll get to that in the spring.

About the carbs: I have taken them apart several times. They have been cleaned with carb spray, 'strands' of a wire (right word to use?). I have checked the diaphragms and they seem to be intact. All brass look fine and is original.
I have tried float heights of 18 and 21 mm. The bike did not like the 21 mm setting, didn't run well. (Found mention of this setting on the forum somewhere). They are now at 18 mm. Have used the cleartube method to check, and it seems to check out.

I have fitted new, original carb manifolds about a year ago.

One of the mufflers has a small hole about 4 mm in diameter right behind the pipe/muffler connection clamp.

When it actually runs, is warmed up, it runs wonderfully and very smooth. Only when pressured in low gears, it pops, backfires. It doesn't do this, if I apply the throttle gently and steadily. It starts well too.

Regards, Frank
 

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Sensei
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Have you considered that the problem MAY lie in the timing advance mechanism?....
The more you tell us about the overall performance, the more that and the low speed to midrange transition in the carbs might come into play....Are you running the stock air-boxes?....A lack of "still-air" volume within pods (for instance) can cause the transitional "stumbles", as can overall intake tract length/ability to induce laminar flow...."Dirty" air filters should be a consideration as well.....Pods alone require several changes to the internal air jets in these CV carbs, as well as fuel jetting changes.....

AS to the 5K difference, were RESISTOR plugs used previously? (Iridium plugs maybe?)
 

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Here is how I tested my coils - tested them alone...to ensure they were working.

 

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Discussion Starter · #7 ·
Thanks for the video Rob D. It's actually one of the videos I followed! I had the coils/condenser off the bike as I was testing them.

The bike is completely stock (except for the Hondaman ignition). New original condensors and airfilters were fitted in 2007. Plugs are the standard NGK B8ES.
Maybe I should take apart the timing advance mechanism and give it a good clean/oiling. As far as I have heard, they can get a litle "sticky" and not function properly.

I'm not ruling out the possibility of the problem being carb-related, in fact, I'm not ruling out anything! I'm very grateful for all your suggestions. I am not a complete idiot at motorcycles, having wrenched for about 7 years, but I'm no expert either :)
 

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Well, according to David silver spares (UK), it looks like the bike needs 5k ohm spark plug caps.
I should be able to borrow those from other bikes/mopeds I have, so it'll be easy to check out...

Sendt fra min LG-D802 med Tapatalk
 
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