Cam tensioner question


Maddex
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Cam tensioner question

Post by Maddex »

Hi to all, I start to check valve clearance and figure out that smaller cam chain tensioner is completely loose and hanging down towards the engine. That long pin is not connected to the tensioner. So I googled a bit and looks like some replacement tensioners have that pin welded to the tensioner? How is that pin connected to the rest of the tensioner when it’s new? Also found solid scratches under the right side exhaust cam ( just no 8), assuming some dirt passed under the valve cover gasket. Rest looks good. What are my options here? Its 82 Prolink with 55000 miles ( all cilinders have around 150psi except no2 120)Last owner told me that after they cleaned the carbs, on the way home something banged and engine didn't run smooth anymore. He somehow came home and parked bike for next 15 years, then I took over. I assuming that because of that tensioner, engine lost his proper timing and run roughly.Thanks in advance for any advice.
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Jeff Bennetts
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Re: Cam tensioner question

Post by Jeff Bennetts »

Have you taken the oil sump cover off and removed the oil pump screen to look for any debris? Did you take a good look at the oil filter that came on the bike when you purchased it?

A good place to start.

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Re: Cam tensioner question

Post by Jeff Bennetts »

What the tensioner should look like!
7041F352-BBA2-412F-B547-8E9CE8922DA7.jpeg
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Maddex
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Re: Cam tensioner question

Post by Maddex »

Didn’t remove oil filter and oil sump cover jet, just drained oil before removing the engine from the frame. I’ll try to do that tomorrow and see what kind of surprise is there. Oil was relatively clean without any noticeable shavings. Crossed fingers 🤞

daves79x
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Re: Cam tensioner question

Post by daves79x »

Why are you removing the engine? Yes, the nose broke off of your tensioner. Have never seen that. It looks like a clean break, so I doubt you'll find much debris from that in the sump, but you might find a little from that cam journal. I see the cap shows wear. Does cam show similar wear there? Looks like a lack of oil to just that journal. I'd check the hollow in that cam for debris. Then clean up the journal and cap a bit and Plastigauge the clearance. If out of spec, and just the one cap, you can very carefully work the cap mating surface down on emery paper on a pane of glass or granite to get into correct tolerance. Not the ideal solution, but it works for just one cap. Otherwise, you are looking at replacing the head.

You obviously need a replacement tensioner. Remove the front adjuster and the rubber plug in the nose. Carefully inspect the bore of the nose for burrs and clean it out. Then remove the plugs and crank end cap and check the cam timing per the manual to see if the upper chain jumped a tooth or two when the tensioner broke. A tooth or two will not bend valves, more than that it will. If that checks out, install the new tensioner and adjust. Then do a compression/leakdown test to insure the health of the valve train.

Of course inspect and clean the sump.

Dave

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Re: Cam tensioner question

Post by daves79x »

Looking again, I suppose the broken part could be welded back on. The alignment is not machine-tolerance critical, but has to be close. I say this because the tensioner rubber looks in great shape, and a new or even good used tensioner will set you back significant $$$.

Maddex
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Re: Cam tensioner question

Post by Maddex »

Removed engine so I can properly clean 40 years old grease from back of the engine and bottom part of the frame; also one side of muffler needs attention. Tensioner part does not look broken, looks like that Honda connect those two parts just with tight tolerances?🤔 Cam looks good just by look, didn’t measure nothing yet. Is it possible to put used cap; are they all the same size and shape (no 1,3,8,9,11,14,16)? I think chain didn’t skip any tooth because before taking cams out all markings lined up almost perfectly when I put some tension on the chain. Thanks Dave for the useful info and advice.
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bobcat
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Re: Cam tensioner question

Post by bobcat »

It appears that the end of the cam/cap has overheated from oil starvation.
The center of the camshaft is an oil passage that delivers oil to each of the
caps and it looks like there is a blockage just past the last cam lobe preventing
oil from reaching the last (pictured) cam cap. Don't reinstall the cams without
cleaning the passage bore in the full length of each cam half as well as all oil
tubes, banjo bolts and any other passages all the way back to the main oil galley
where oil is supplied to the top end.
Bob
82 CBX, 81 CBX, CB1100F, 79/82 CB900F (avatar)

daves79x
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Re: Cam tensioner question

Post by daves79x »

I can tell you that the nose of the tensioner is not just pressed into the body. I just checked one I had here and it appears to have been brazed on. I'd just tack weld it back on.

You can use another cam cap, as long as it is the exact same number. However, you will have to clean everything up and smooth the journal and cap a bit, then Plastigauge it to see what you have. As I said before, you can skim the cap to gain correct oil clearance if you have to.

Follow Bob's advice about the top end oiling system.

Dave

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Jeff Bennetts
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Re: Cam tensioner question

Post by Jeff Bennetts »

Here’s an oil flow diagram to help you determine where your blockage could be.

I’m not sure this link will work but here’s a screenshot.

http://www.cbxclub.com/timoil.html


472A9B1E-0CBC-459F-B8DF-C94AA38629A9.png
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Jeff Bennetts
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Re: Cam tensioner question

Post by Jeff Bennetts »

I pulled a couple used tensioners and a NOS from my stash and here are a few observations.

Used #1, the rusty one. The rivets look to be the same diameter but the end of the rivet is not as flattened as the other used #2 tensioner and the orientation of the rivet is the same as the NOS tensioner.

Used #2, the rivet ends are more flattened like the NOS but the rivet heads are on the opposite side of the NOS piece.

All tensioners have been braze tacked from the inside where the rod passes through the tensioner, a little blurry but you get the idea.

Sooner than latter there will be less and less NOS CBX parts available to the public, they are one of the few sources that can tell you exactly what Honda did and the dimensions and tolerances they used.
The shipping date for this NOS tensioner was 04/08.
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AA178BC3-AC4B-4921-AE49-E23A1771C290.jpeg
9CA385CA-77BF-4A4E-A690-C8A2F9C18951.jpeg
DBAB77FC-D53F-449E-A79A-544205A5BEAC.jpeg
FD388FF5-1A39-4F6A-88F5-B4C2030A0496.jpeg
1C9F840A-4284-412C-9DAF-1B24746C995F.jpeg
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bobcat
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Re: Cam tensioner question

Post by bobcat »

Jeff Bennetts wrote:
Thu Mar 23, 2023 10:29 am
Here’s an oil flow diagram to help you determine where your blockage could be.

I’m not sure this link will work but here’s a screenshot.

http://www.cbxclub.com/timoil.html



472A9B1E-0CBC-459F-B8DF-C94AA38629A9.png

If you click on the diagram it will zoom in for a clearer shot but the blockage is most
surely just upstream from the first signs of discoloration on the cam.

Here's a little story about sudden oil starvation; I used to have a Datsun 620 pickup
that I rebuilt the motor at 243k miles mostly to fix abundant oil leaks. Close to 75k miles
later just after an oil change* I was driving at highway speeds when it started to bog down,
loose power and started making a loud squealing noise under the hood. I nursed it home
and raised the hood and burned oily smelling smoke poured out from the valve cover area.
After it cooled off and checked the radiator to find it full of clean coolant I pulled the valve
cover to find the cam and journals all purple to dark blue and all shades in between. I tore
it down to the point of pulling the head to find a wad of teflon tape blocking the oil supply
to the top end. It fried everything beyond that point and I couldn't turn the motor over
by hand.
Nowhere in my rebuild had I used any teflon tape and it had gone many thousands of miles
trouble free until that oil change* using a Fram brand spin on filter. I don't know if Fram uses
teflon tape in their manufacture process but it's the only place it could have come from.

Moral; check your oil filter for correct installation** and foreign matter inside, clean the bolt
thoroughly and don't use cheap filters.
** in this order into the filter housing...spring, washer then the filter. Note the washer usually
is stuck to the old filter grommet and frequently gets thrown away with the old filter. Without
the washer the end of the spring can chew into the grommet and allow bits of rubber to get
beyond the filter going straight to the main oil galley feeding the crank and top end.
Bob
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Re: Cam tensioner question

Post by NobleHops »

We had a bike with bearing/journal trouble in that same location and it was because the restrictor donut at the end of the cam got pushed in too far, blocking the passage to the bearing. Maddex, look carefully at the fiche and you will see there is a rubber restrictor donut that presses in the end of the cam. Sight down into the hollow interior of your camshaft and see if it isn’t in there, pushed in too far. There is a bevel at the end of the hollow shaft, the restrictor properly belongs just at the point where the surface transition from bevel to flat.

We cleaned our journal up with a little wet/dry, swapped on a good cam cap and sailed on, and it worked fine.

N.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

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bobcat
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Re: Cam tensioner question

Post by bobcat »

Nils, that does sound like a better possibility except that if you look at the oil
hole in the cam you can see all the way through it. If the donut was pushed in
too far wouldn't you see it blocking the hole ? It would be interesting to use a
thick wire like a welding rod and stick it into the end of the cam (through the
donut) and see how far it goes before hitting something, if anything. If it doesn't
reach all the way to the end of the passage, mark the wire/rod, remove it and
lay it over the cam and the end is where your blockage is. This can be done
without removing the cam. It would also be interesting to know if the blockage is;
rubber, metal, sealant, etc.
Bob
82 CBX, 81 CBX, CB1100F, 79/82 CB900F (avatar)

Maddex
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Re: Cam tensioner question

Post by Maddex »

Finally got some time to go further with , how it looks now project, CBX. Thank you all for suggestions. I checked the sump screen and looks pretty good to me; didn’t even crack 😅. Checked all cams and didn’t found any blockages (easy to see trough them), checked all perpendicular holes too. Restrictor donuts are where they needs to be. I’ll try to find used journal cap no8 and polish bottom journal in the head, and see what will plastigauge show. Cam chain B probably needs replacement because it’s close to the service limit. Is it possible that if the bike was sitting on the side stand for couple of years, after first start, journal no8 didn’t get oil fast enough for proper lubrication 🤔?
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