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A A A A Author Topic: CX500 - Source of Tapping Noise in Engine  (Read 670 times)

Barocca

CX500 - Source of Tapping Noise in Engine
« Started on: 11-Nov-19, 13:54 »
I'm hoping that one of our experienced members can help me to identify the source of a noise that is worrying me. 
The bike has been off the road for many months whilst triple bypass surgery was performed.  It runs standard exhaust system and air filter, has new timing chain, new piston rings (negligible wear on bores or pistons), Rae-san ignition, carbs rebuilt by CX guru.  The bike has been ridden about 40km and has had cylinder heads re-torqued and valve clearances set.  The noise is particularly noticeable at idle and low throttle openings.  There does not appear to be any leak around the exhaust system that might explain it.  Any ideas? 
Note that, given the other problems on the bike prior to the rebuild, it is possible that the noise was present before the bike was pulled apart.


Seagrass

Re: CX500 - Source of Tapping Noise in Engine
« Reply #1 on: 11-Nov-19, 15:56 »
Barocca that sounds like a very loud tappet noise.

How did you set the tappets (engine cold, drag fit with feeler gauge etc) and what gap did you set the tappets to? Did you turn the engien the correct way when setting the tappets?

Did you happen to start the engine before pouring 200 Ml's of oil down into the "camshaft well" (via the heads). If so this can cause excessive camshaft lobe wear so you may need to reset the tappet clearance again.

Seagrass

CX PHREAK

Re: CX500 - Source of Tapping Noise in Engine
« Reply #2 on: 11-Nov-19, 16:44 »
Tappets set on the right stroke?

 Did the gaps seem non existent when making the adjustment?

 Left you a post on the US forum.

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #3 on: 13-Nov-19, 17:42 »
Seagrass & CXPhreak:  -  Tappets set on correct stroke(s), turning clockwise from front, at 3thou in, 4thou ex.  Cam lobes etc lubed before starting.

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #4 on: 13-Nov-19, 18:02 »
I have just inspected the tappet clearances and found, in thou:
Left    -  Inlets 5 & 6  ,  Exhausts 5 & 6
Right  -  Inlets 5 & 5  ,  Exhausts 6 & 8

Have carefully reset these to 3thou and 4thou.  On start-up the same noise as before is present.  It appears to be coming from the right hand side of the engine. 

fab

Re: CX500 - Source of Tapping Noise in Engine
« Reply #5 on: 14-Nov-19, 16:46 »
maybe a bent or blocked pushrod? I would start it up and leave the tappet cover off and make sure you are getting oil up at the tappet and make sure everything is moving as its supposed too.

doddsy1000

Re: CX500 - Source of Tapping Noise in Engine
« Reply #6 on: 14-Nov-19, 20:06 »
It certainly seems like a tappet noise, doesn't it?

I've heard stories of worn rocker arms moving around fractionally while running.

Stories of a sticky valve also spring to mind.

Other than that, what everyone else has said. 

Especially running with the rocker cover off to isolate the location.

Wrap a big towel around the cylinder first to catch the oil. :grandpa:

Cass

Re: CX500 - Source of Tapping Noise in Engine
« Reply #7 on: 16-Nov-19, 15:08 »
I had the same problem so I threw the manual out the window and each time the valves were rocking I checked the gap took a few cycles however!

Cass

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #8 on: 16-Nov-19, 15:28 »
Thanks All

UPDATE:
1978 CX500 with standard carbs, airbox and exhaust system;
Done triple bypass;
Rae-San Hall Effect ignition;
Carbs rebuilt by CXPhreak;
Big-ends plasti-gauged, minimal wear;
Piston/Bore wear minimal, new rings fitted, bores lightly honed;
Valve guides given only cursory inspection, valves lapped, new valve oil-seals fitted;
Rocker shafts are worn but have now been swapped (In<>Ex);
Oil circulation in cylinder head is good;
Compression test cold (psi): L-175 R-165, with oil down plugholes L-175 R-175;
Fan, housing and surrounds inspected.  All OK, no signs of any cracks, knocking or rubbing;
No exhaust leaks apparent near cylinder heads;
Mechanic's stethoscope confirms the noise is coming from upper right of engine (inside cylinder head?);

I got to thinking back to 2015 when I first took the bike off the road.  My post https://www.australiancx.asn.au/forum/index.php?topic=13721.msg141483#msg141483 includes the following: "The last time I rode the CX500 it started to make a clicking sound as we neared home.  It was sufficiently different from normal for me to consider whether to stop immediately or continue the remaining km to home.  There was no misfiring or loss of power, so I nursed the bike home.  I’d only done the basics after buying the bike (comp. test, tappets, oil and filters, plugs, flush and change coolant)." 
I'm increasingly wondering whether my current engine noise is the same one that alarmed me in 2015, it certainly sounds very similar.  If it has the same origin, then it may provide some pointers.  For instance, the noise seemed to begin suddenly near the end of a 100km ride, and, the work that I have done since has neither unveiled the source of the noise nor remedied it.  Curiouser and curiouser!

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #9 on: 11-Jan-20, 12:47 »
Possible Culprit?
I eventually got an experienced mechanic to listen to the bike and probe it with his mechanic's stethoscope.  He opined that the source of the noise was from behind the fan, probably worn camshaft and/or bearing.  The noise was detectable at the water-pump end, but more pronounced at the front.  I'd appreciate any opinions on this diagnosis and what I can do to verify it.  Thanks all.

Onetrack

Re: CX500 - Source of Tapping Noise in Engine
« Reply #10 on: 11-Jan-20, 18:57 »
Is the cam chain adjusted correctly?

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #11 on: 11-Jan-20, 19:00 »
Yes, cam chain adjusted correctly.

Seagrass

Re: CX500 - Source of Tapping Noise in Engine
« Reply #12 on: 11-Jan-20, 19:48 »
There is no bearing as such. The camshaft runs in the front camshaft cover (floating on a film of oil) and in a “journal” at the water pump end.

If you did not install a thrust washer on the camshaft behind the water pump impeller, the impeller could be rubbing somewhere and making the noise.

Alternately as the camshaft operates the pushrods which in turn operate the valve rockers it is possible the noise is coming from the camshaft lobes. Have you had the camshaft out to inspect it?

Seagrass

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #13 on: 11-Jan-20, 20:10 »
Thanks Seagrass.  I neglected to inspect the camshaft whilst the engine was out.  In my inexperience, I would have thought that the load on the camshaft was predominantly downwards but cyclical switching in the directions of the two sets of pushrods.  Could wear on the front and/or rear housings produce the noise I'm hearing?   

CX PHREAK

Re: CX500 - Source of Tapping Noise in Engine
« Reply #14 on: 11-Jan-20, 21:15 »

Seagrass

Re: CX500 - Source of Tapping Noise in Engine
« Reply #15 on: 11-Jan-20, 21:16 »
Thanks Seagrass.  I neglected to inspect the camshaft whilst the engine was out.  In my inexperience, I would have thought that the load on the camshaft was predominantly downwards but cyclical switching in the directions of the two sets of pushrods.  Could wear on the front and/or rear housings produce the noise I'm hearing?   

I do not believe the tapping sound could be caused by wear in the camshaft journals, more likely to be a camshaft lobe or something else.

Maybe CX Phreak may have some other ideas.

Seagrass

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #16 on: 11-Jan-20, 21:20 »
CXPhreak, I firmly believe that I installed the camshaft thrust washer. 

CX PHREAK

Re: CX500 - Source of Tapping Noise in Engine
« Reply #17 on: 11-Jan-20, 21:37 »
Not worn upper rocker shafts?

 Excuse me if we've been over some of this stuff.

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #18 on: 11-Jan-20, 23:50 »
Not worn upper rocker shafts?

 Excuse me if we've been over some of this stuff.
Rocker shafts are worn but have now been swapped (In<>Ex)

Barocca

Re: CX500 - Source of Tapping Noise in Engine
« Reply #19 on: 16-Jan-20, 12:55 »
Thanks for the input from members.  I took the bike to a well-regarded mechanic, and he thought that the most likely cause was from a worn cam lobe.  It looks like I'll have to pull the engine out and strip it all down again to verify and remedy.  Is there somewhere that can do a good job of reclaiming worn camshafts and followers?

fab

Re: CX500 - Source of Tapping Noise in Engine
« Reply #20 on: 16-Jan-20, 15:59 »
I use Tighe cams in Queensland and they have always done a great job.

Seagrass

Re: CX500 - Source of Tapping Noise in Engine
« Reply #21 on: 16-Jan-20, 19:03 »
I have used Waggot Cams in NSW and they were also very good.

Seagrass

Cass

Re: CX500 - Source of Tapping Noise in Engine
« Reply #22 on: 17-Jan-20, 16:35 »
Mate,
Before I'd go down the road cam lobes, I'd re-adjusts those tappet , the motor sounds tight but maybe just play around with the clearance. Put it on TDC and check and check on non compression stroke, maybe a heavier oil like 15 weight or maybe 20 weight . Sounds like that right side is just not set right, have you adjusted the  timing chain on Tl/ TDC on the compression stroke, maybe check in mm instead of thou of inch, just trying to help I would hate to see  you spend all that money for nothing.

denuto

Re: CX500 - Source of Tapping Noise in Engine
« Reply #23 on: 17-Jan-20, 18:06 »
The comments from Cass make good sense, no poit in paying someone to pull out and strip down the engine without doing as much diagnosing as you reasonabl can. Which got me thinking.... My suggestion is to check the valve moment at the push rod, comparing the two cylinders. It would require a dial guage but if your cam lobe is worn down to the point it is making that noise, it might be possible to measure difference in lift from one cylinder to the other, as the push rods for each cylinder are operated by different camshaft lobes.

CX PHREAK

Re: CX500 - Source of Tapping Noise in Engine
« Reply #24 on: 17-Jan-20, 18:29 »
I doubt if a worn lobe will make a noise. It would just lose lift. But a chipped one will though. You may be able to rotate the motor and visually check for chips if you remove the pushrods and lift the subrockers out of the way. Two don't lift very far though.

Make sure the clearances are done on compression or the clearances end up huge, particularly on the exhaust valve and a lot of noise results.

 


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