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Author Topic: CB360 compression test and missing tappet screw  (Read 404 times)

Offline Tonnotyetdone

  • Posts: 19
CB360 compression test and missing tappet screw
« on: Jun 04, 2017, 20:16:55 »
As I was going to adjust my tappet clearances, I found that the left hand intake tappet screw is missing.  I know it was in there originally when I got the bike because this is my second go around with adjusting them.  I have yet to perform a compression test, and figured if I'm going to remove the valve cover (hopefully finding the tappet screw tucked away), I might as well go further down the rabbit hole and check pistons, valves, etc. if the compression is low.

My questions are 1) Can I safely perform a compression test knowing there may be a tappet screw floating around somewhere in the crankcase (hopefully bottom, if not luckily still in valve cover) and 2) would a strong magnet on the outside bottom of the crankcase be effective in catching the screw and dragging it towards the drain plug (assuming it has fallen to the bottom)?  I recently pulled the right cover to do an oil change/filter clean, did not notice it sitting at the bottom, so I think I can rule that out - may pull it again just to make sure, wasn't exactly looking for a piece of machinery​ at the time.

Offline irk miller

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Re: CB360 compression test and missing tappet screw
« Reply #1 on: Jun 04, 2017, 21:06:58 »
You can't do a compression test when you have a valve that doesn't open.  It won't show compression since the valve needs to suck air in to compress it. As far as the screw itself-  The sump is not simple a barren open reservoir.  There are chambers and galleys in the way of a clear path.  If you're lucky it's in or around the base of the cam chain and a long retractible magnet fish it out.  Otherwise, you're taking the motor apart to get to it. 

Offline Tonnotyetdone

  • Posts: 19
Re: CB360 compression test and missing tappet screw
« Reply #2 on: Jun 04, 2017, 22:48:47 »
Ah, thank you, good point. Might source a tappet screw from a parts bike and give it a try.  Unless...say the screw fell down the cam chain well.  Could it potentially make its way to the kickstart mechanism?  Or would it most likely stay parked in the front half of the engine under the cylinders?  Not super familiar with the assembled layout of the engine (well...not yet anyway)

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Offline Tonnotyetdone

  • Posts: 19
Re: CB360 compression test and missing tappet screw
« Reply #3 on: Jun 05, 2017, 05:31:53 »
So looking at disassembled engine parts on eBay...if it did fall in to the can shaft channel, most likely it is sitting in the well at the bottom - from what I can tell, oil comes into the well from a valley on the back side of the engine and not underneath it from the sump.  So it looks like, provided the cam chain didn't throw it back into the transmission, your recommended magnetic fishing method should work to get it out of said well.  Jesus, I hope it works, I just want to get it rolling.

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Offline SONIC.

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Re: CB360 compression test and missing tappet screw
« Reply #4 on: Jun 05, 2017, 08:43:17 »
I would not run it without finding that screw.
You never know where it's sitting and when it's going to lodge itself in your cam chain and toast your engine.


Offline alzcbz

  • Posts: 474
Re: CB360 compression test and missing tappet screw
« Reply #5 on: Jun 05, 2017, 21:23:06 »
There will be two pieces rolling around inside your engine.
The screw and the locking nut.
73 CL350 Hardtail somethin turned into café
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Offline Tonnotyetdone

  • Posts: 19
Re: CB360 compression test and missing tappet screw
« Reply #6 on: Jun 07, 2017, 02:02:34 »
Honda god showed mercy - I pulled the valve cover and the tappet screw was sitting tucked away by the valve spring.  Reinstalled, everything reassembled, timing set. etc.  Compression test tomorrow and syncing carbs if all is well.  If it still the will of a loving Honda god, then the bike should be road ready by suppertime.  Thanks for everyone's input and help on the matter!