Honda Twins banner

1 - 20 of 29 Posts

·
Registered
Joined
·
29 Posts
Discussion Starter #1
Hi,
This a newbie question. I'm noob both in mechanics and classic motorcycles. My bike is a CB450 K7. I have adjusted my valves yesterday, it's only the second time i do this job, and at my first attempt, everything went fine. The bike ran very well for another 3k miles, so the time has come for another valve check/adjust. I followed the procedure and double checked everything, except maybe one thing: I think i did the job with the cam chain tensioner nut loose and i'm pretty sure i did not properly tightened it. I think i have just tightened it against the lock nut. (i try to remember what i fu** up).

When i started the bike after the job, everything looked normal. I went out for a ride and i noticed engine hesitation on acceleration that was not present before. After about 30 miles, on my way back home, the engine become very noisy. Now i ear a very loud "clicking" from the top end but i'm not sure where excatly the noise is coming from.

What is the effect of running the engine with the cam chain tensioner loose? It's clear than i fu** up something, i just don't know what exactly.

Any ideas?

Thank you
 

·
Sensei
Joined
·
27,164 Posts
If you did not loosen the tensioner's bolt , just the locknut, the tensioner SHOULD have remained where it was previously ...... The situation you discribe sounds more like the valves were adjusted to the correct lash "gap", but with the excentrics in the wrong position (There are TWO positions of the excentric that give the correct lash, but one of them actually changes the leverage angle of the tappets, causing excessive wear to tappets and camshaft)
ARE YOU SURE the adjuster indexes (the small secondary lines 90 degrees off the screw slots) are set "away" from the sparkplugs?... If they are, we'll investigate the next step....IF NOT, you'll need to open the tappet covers to inspect/re-adjust the valves/tappets etc....Riding 30 miles (improperly adjusted) is long enough to cause serious damage.....
LET us know what you find regarding the positioning of the adjusters, and we'll go from there....Hopefully, Bill (our primary 450 expert) will chime in..... Steve
 

·
Registered
Joined
·
29 Posts
Discussion Starter #3
Hi Steve,
Thank you for your quick reply! In fact, "double checked everything" is not totally exact :oops: , the adjuster index is actually in wrong position on the left exhaust valve. This morning, i re-opened everything and re-did the valve adjustment, but in my noob ignorance, i just did not knew about the index mark. The cams looked fine but i did not pay particular attention to this one.

I am going to re-open everything and have a look at the left exhaust cam.

Thank you very much for the advice!
 

·
Registered
Joined
·
703 Posts
Well you could have done what I did. If you left the bolt loose then your tensioner has just come apart inside the engine. I just finished a rebuild today with new tensioner dampers.




and now back together almost.

 

·
Sensei
Joined
·
27,164 Posts
Completely different set-up in a 450 (parts-wise)....
 

·
Registered
Joined
·
29 Posts
Discussion Starter #6
Hi,

I gave a look under the valve covers and things does not look too bad. The cams and the tappets looks good, at least, they look pretty much the same they looked before that sad 30 miles ride. On the left side exhaust cam however, there is some tiny spots but the cam surface feels soft to the touch even after the oil whipped off. There is no gouges or scratches. To my noobs eyes, this cam looks more worn than the others, but not seriously injured. Am i right?

I found that the cam chain is very loose! I can turn the crank almost as much as the space between two magnets on the magneto with no movement at all on the cams! :shock: I have not removed the tensioner yet, but it seems clear that it's service life is now over :(

For now, i feel like i am quite a lucky guy, but i guess i may discover a mess in the crankcase... I must give a look there. By the way, some gaskets are due, so i guess the time has come to remove the engine, and replace them.

Thank you very much for your input.
 

Attachments

·
Sensei
Joined
·
27,164 Posts
From the pix, it appears the left INTAKE cam lobe suffered the damage (I believe that's a carb top right under it in the pic) Somehow your tensioner wasn't applying any tension to the cam chain... (stuck possibly?... remove from engine and verify it will adjust when both the nut and bolt are loosed)
(BTW, the intake cam is MUCH easier to obtain a replacement for as it's usually the exhaust cam that is destroyed first) I may even have one and one good tappet (rocker) to facilitate the process of the repairs..... (E-mail me as [email protected] if interested in those)
I would venture that a tear-down is appropriate at this time,... Might as well go for a fresh engine to have for the Spring return to riding..... Bill (tbpmusic) is our 450 expert, and I'll be happy to assist in any way I can.... Steve
 

·
Registered
Joined
·
29 Posts
Discussion Starter #8
You're right Steve, i have not twisted my tongue long enough before writing ;) the pic shows the intake cam... I will keep you tuned on what i am going to find next.

Thanks again!
 

·
Registered
Joined
·
6,495 Posts
Your cam chain is shot, need a new one.
When installing a new cam chain, there's barely enough slack to get it in place, and that's with the tensioner removed.

Like Steve said, pull the tensioner off and check its operation.
Then push the plunger all the way in and lock it down - then install it back on the bike.
Rotate the engine to Left TDC compression stroke and release the advancer bolt - you should see/hear the tensioner snap back in towards the cam chain.

I doubt if the cam chain "jumped" on you - even being a single tooth off would cause a 450 to not start or run.
With the 450's roller/tensioner setup, it's very difficult to jump the cam chain, there's just not enough room in there. It's most likely to happen if one of the rollers (or the tensioner) self-destructs, that creates enough room for the chain to jump teeth on you.

Many 450's continue to run even with substantial top end damage, they're incredibly tough engines.......

A running 450 is a symphony of top end noises - takes a long time to get used to and know what's supposed to be there and what's not.........
 

·
Registered
Joined
·
6,495 Posts
HerrDeacon said:
tbpmusic said:
A running 450 is a symphony of top end noises
I've never heard one, but I just love this line :D
The song writer in me at work.............

But there are three steel cam chain rollers up top, one rubber roller below the cylinders, the tensioner itself, the chain, two cams, valves, tappets, pistons - all moving in perfect synchronization (hopefully).
And the 180 degree engine gives the exhaust that off-center ba-doom-badoom sound.

It is music, to me anyway...........
 

·
Registered
Joined
·
29 Posts
Discussion Starter #12
Thanks a lot for your input Bill. I was wondering if the chain could have jumped but i guess it's not the case since the engine still starts easily.

Besides replacing the intake camshaft, the cam chain and related parts depending on what i am going to discover next, should i be aware of other particular things?

For now my 450 is no longer symphonic... :(
 

·
Registered
Joined
·
6,495 Posts
Guydraud said:
Thanks a lot for your input Bill. I was wondering if the chain could have jumped but i guess it's not the case since the engine still starts easily.

Besides replacing the intake camshaft, the cam chain and related parts depending on what i am going to discover next, should i be aware of other particular things?

For now my 450 is no longer symphonic... :(
Not really - can't tell until you can look at the parts.
I can't really tell from a photo if your cams/tappets are shot.
Check the 4 cam "bearings" of course.
No real reason to remove the torsion bars unless you need to take the valves out.
The lower cam chain roller is rubber (Roller B), and is usually shot.
They're nearly impossible to find in the US, but I think some of our Aussie/Kiwi friends may be able to help there????
The upper rollers/sprockets are all steel, usually never fail, but examine their teeth.
Tensioner roller is also rubber - check it too.
Also replace the 4 big o-rings that go on the cam sprockets - they're still available, and they do help quiet things down a little........
Replace the 4 little rubber o-rings that go around the adjuster shafts, use new gaskets.

Have somebody mike your cylinders while you have it apart, might as well check - specs are in the manual.

While you have the head off, turn it "sideways" on the bench and pour acetone into the intake/exhaust ports.
Look for any leakage around the valves - none is permissible.

When you get it back together, use 0.002" as a valve setting, then static time.
Once running, check for top end oiling immediately - either loosen one of the two far (rider's) right head nuts (with the copper washers), or loosen the big bolt head on the back of the tach drive. You should see oil in short order.....

If you see gouges/scrapes inside the head or cylinder castings where the cam chain was slapping around, you need to think about maybe splitting the cases and getting rid of aluminum shavings, depending on how bad it is.......
 

·
Registered
Joined
·
29 Posts
Discussion Starter #14
Thank you very much for all this invaluable information Bill! It's going to take me quite a while to complete the job though, i'll keep you tuned.

Please excuse my ignorance but what does "mike the cylinders" means? (English is not my mother tongue on top of that...)

What a mess for such an idiot mistake i've done... :( By a simple maintenance task incorrectly done, i turned my sweet running engine into a quite serious wrenching project. I wanted to learn, i'm learning now!
 

·
Registered
Joined
·
6,495 Posts
Guydraud said:
Thank you very much for all this invaluable information Bill! It's going to take me quite a while to complete the job though, i'll keep you tuned.

Please excuse my ignorance but what does "mike the cylinders" means? (English is not my mother tongue on top of that...)

What a mess for such an idiot mistake i've done... :( By a simple maintenance task incorrectly done, i turned my sweet running engine into a quite serious wrenching project. I wanted to learn, i'm learning now!
Sorry - "mike" means to use micrometers to measure something - any machine shop, sometimes large auto part stores. Just bribe them (beer usually works), it only takes them a minute.

Stop fretting - you may not have hurt the engine all that much. A loose cam chain wouldn't tear up your cams and followers.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #16
At last, after my precious and rare spare time wasted on annoying things like fixing my house's roof ;) i'm back on something really important: working to make my beloved 450 sing again! :)

Things are not looking too bad so far. I followed the procedure you teached me to check plunger operation on the cam chain tensioner and it is working fine. Teeth are also very good, seems top shape.

The cam gears teeth however are showing signs of wear near their base, just above the 'U' space between each of them. To my noob eyes, it does not look very good... Is it bad enough to consider the cam no longer usable?

The (hard to find) roller B is also not looking good, but i can't tell if it's bad enough to replace it.

I had quite a bad surprise when i opened the engine, the combustion chambers and pistons are covered with thick carbon deposits and one of the previous owners already removed some in a really careless fashion :( I'll start another thread for this.

Thank you again for your precious help!
 

Attachments

·
Registered
Joined
·
29 Posts
Discussion Starter #17
I forgot to ask: is it a good idea to replace the cam chain with one that have a master link? I tought it could make future maintenance easier but is it as reliable as the continuous oem chain?

Should i be aware of brands to avoid?

Thanks!
 

·
Registered
Joined
·
6,495 Posts
No master links, please. Must use a riveted link....the chains you see on EBay will be ok.

That Roller B looks shot to me. The last one I got was from one of our friends Down Under here - hopefully he'll see this and let you know.

The cam sprocket looks ok to me - just replace those rubber o-rings on the cam sprockets. You'll need a total of four, and they're still available form Honda.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #19
Thanks again for your input Bill! I have just placed an order to my local Honda dealer. I'll keep you tuned as i progress.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #20
Hi,

Before doing any attempt to unmount the valves, i checked for leaks with acetone. Both intake valves are leaking, the right one more seriously. The exhaust valves are ok. I guess removing the valves is no longer an option... I don't have the special tool for torsion bars, is there any other safe way to unmount them?

Thanks!
 

Attachments

1 - 20 of 29 Posts
Top