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Author Topic: cb350f lost compression and cylinder 1 popping noise  (Read 663 times)

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Offline Dakotarider

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cb350f lost compression and cylinder 1 popping noise
« on: July 26, 2015, 05:03:01 PM »
I recently lost power while riding accompanied by exhaust popping noise from my 71' cb350f.  Finger compression test shows cylinder 1 is the culprit.  Never torn one of these apart before.  Need some help on what to do next.  Anybody know of a video or some good pics/instructions for a tear down?
thanks
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Offline carnivorous chicken

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #1 on: July 26, 2015, 09:45:12 PM »
Is it a twin or an F? 350Fs were 1972-74. And a "finger compression test" will only tell you if you have next to nothing in terms of compression -- get a gauge or find someone with one so you will know for sure. If your #1 cylinder has zero compression, it's rings or valves. IF you add oil to the spark plug hole and your compression goes up significantly, it's rings.
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Offline Dakotarider

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #2 on: July 27, 2015, 05:20:25 PM »
F, must be confusing it with my other vehicles.  Finger test is noticeably less compression on cylinder one.  I'll try the oil.
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DH

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #3 on: July 27, 2015, 06:36:53 PM »
Make sure the valves are not adjusted too tight for that cyl.
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Offline Dakotarider

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #4 on: August 09, 2015, 05:19:27 AM »
Ok, so it is a rings issue. Drastic change in finger test compression when i put oil in the sparkplug hole.  Next step, is there a good video or instructions w/ pictures online for tearing down the cylinders?  Might as well replace rings in all four. Any valve modifications I should make while I'm at it?  Always helps to male a little more hp.
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Offline skidooextreme

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #5 on: August 09, 2015, 05:42:15 AM »
Make sure you search for suggestions on the head gasket.  Take your time and apply the copper coating to the head gasket and a smear of case sealer around the oil orings otherwise you will end up with a leak. I torqued in stages and left for the night each time because i was so scared of a leak.  In the end, no leaks!  As for dis assembly, it it pretty much straight forward.  Check your valves like DH mentioned just to double check before teardown, but with the oil test already done it looks like you will be ripping her apart. 
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Offline Dakotarider

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #6 on: August 09, 2015, 03:09:07 PM »
Is it necessary/recommended to remove the engine to replace rings? 
Will I need to buy four ring compressing tools to reassemble?
If so, where can I get them?
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Offline calj737

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #7 on: August 09, 2015, 03:59:37 PM »
It's certainly easier to have the engine out of the frame to replace pistons/rings. You only need one tool to install the rings, some use wide band clamps as a DIY tool.
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Offline skidooextreme

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #8 on: August 10, 2015, 04:31:03 AM »
You do not need ring compressors.  Fingers only

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Offline skidooextreme

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Re: cb350f lost compression and cylinder 1 popping noise
« Reply #9 on: August 10, 2015, 04:31:56 AM »
http://forums.sohc4.net/index.php?topic=111517.0

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