Cam Chain Noise CB400F

400four · Posted: Wed Mar 21, 2007 1:07 pm Post subject: Cam Chain Noise CB400F

Can anyone tell me how to quiet down the cam chain noise on a Honda four. The Honda manual says to: Start the engine, idle at 1200, loosen the tensioner nut and bolt and finally retighten. This proceedure doesn't do squat. The tensioner screw is all the way in. Why is there even an adjustment if it's a "self-adjusting type". I would appreciate anybody's comment if you have experienced this before. Thanks, Jon

fasterspider · Posted: Wed Mar 21, 2007 1:56 pm Post subject:

It is time for a new chain, the old one is stretched beyond service limits.
Nothing can be done to quiet a stretched chain except replace it.

400four · Posted: Wed Mar 21, 2007 2:29 pm Post subject:

fasterspider · Posted: Wed Mar 21, 2007 3:45 pm Post subject:

KirkN · Posted: Thu Mar 22, 2007 5:23 am Post subject:

stretched because there was too much slack

Hmmm..... not sure about that one. I thought slack was on the "unloaded" side of a chain. The "loaded" side would always be pulled taut. Having excess slack on the unloaded side of a chain wouldn't cause the chain to stretch. It would, however, allow the chain to slap back and forth against the tensioner surfaces, causing them to wear prematurely. So that when 400four tries to adjust the tensioner, the bolt runs all the way in because there's not enough "meat" on the tensioners to push against the chain.

I seem to recall that all the SOHC Honda fours seemed to wear out the adjusters pretty quickly. At least the 2 I've owned over the years were that way.

fasterspider · Posted: Thu Mar 22, 2007 8:40 am Post subject:

Brian42 · Posted: Thu Mar 22, 2007 9:25 pm Post subject:

When doing the cam chain adjustment how can you tell if the adjuster is actually pushing in to the maximum when you lock it back down? I understand, fundamentally, I believe, the concept. The bolt at the front and the two at the back are merely holding down the position that the spring takes the adjuster to. You are not actually pushing the adjuster, just relieving the hold on the thing so it adjusts itself. Then locking it back down. But, without actually taking off the valve cover and getting right into it, how can one be assured it is actually adjusting? If you took out the front bolt can you see into the hole to see if the shaft is moving?

I recall seeing a long series of postings on another site about a year ago where a couple of guys were going at each other as to the best way to actually do the thing and as to when to tighten the bolt. Like turning the crank through a certain distance and then slightly backing up the crank to introduce the most slack in the chain and then tightening the bolts. Or something like that. I have been trying to locate these postings because it seemed like some good advise was in some of the crap being tossed around but it was getting lost.

ManOnBike · Posted: Mon Apr 09, 2007 4:07 pm Post subject:

There is a very good way of fixing this..
I was a despatch rider did over 500,000 miles on two 400 fours and both on their original cam chains!

1.. obtain a 8mmx30mm Allen bolt, 2x8mm nut, and 8mm fibre washer. you will also need a long allen key or allen bit in a set that can reach between hot exhausts

2 lock two nuts on the bolt so that 7 mm of thread is exposed.

3 File off ALL the threads so you end up with a bolt with 7mm protruding beyond the end of the thread. remove the locknuts and ditch the one that the filing will have damaged but leave other one on bolt.

4. Remove the front engine mounting plates ( 3 bolts)

5. Clean area between engine plates (so no crap can get into engine in next step) and you will find a 10mm hexagon on a plug at right angles to the tensioner adjuster. remove this and throw it away, now put the fibre washer and the bolt you prepared earlier into the threaded hole where you removed the plug. don't try to go too far in at this stage.. spin the nut down to the washer

6. Slacken the normal tensioner bolt ( which acts just as a grub screw on the tensioner rod) it is worth removing it and checking for signs of stress as often people have tried overtightening them in the hope it might cure the noise.. a broken bolt in the hole is a complete pain!

7. Make sue you have an allen key that can reach between the centre two exhausts and you can turn it without burning your fingers before you run the engine!

8. Start engine and allow to warm up to operating temperature

9. Slowly turn the allen key clockwise a quarter turn at a time .. it will not appear to do anything for ages and quite suddenly will make contact and LISTEN CAREFULLY you are assisting the (far too weak) springs directly on the end of the tensioner rod and it would be easy to over do it and unwittingly put huge tension on the cam chain.. when the rattle disappears back it off lightly and accept a slight rattle at this stage.. tighten the normal tensioner bolt and locknut

10. Replace the engine mounting plates and bolts and take the bike out and ride it fast and hard to get the engine really cooking hot.. as everything expands the chain tensions slightly

11. now the engine is properly hot, slacken the tensioner bolt and then back off the allen bolt till you have rattle then re tighten again LISTENING CAREFULLY.. if you go too tight a different noise of stressed too tight comes in.. if this happens back off and bring it up again till the rattle just disappears. tighten the tensioner bolt when you are happy its spot on.

If the chain has been rattling for a long time it is likely that the slipper blades will "run in" to a now non rattling chain and re adjustment needed in a few hundred miles.. subsequently you should find that it will be several thousand miles before a touch of rattle appears.. always judge by a hot engine .. it may have a touch of rattle cold that disappears when it warms up.

I have done this modification around 30 times to bikes with as much as 60,000 miles on the clock and only once has it failed where subsequent dismantling revealed the slipper blade had worn right through.

the other occasional pitfall is that the rattling chain hits the pivot of the arm that the tensioner rod pushes causing partial seizure. in this case the chain will tension ok as you have plenty of leverage.. but when you slacken the allen bolt off the rattle does not return // hence why i said listen carefully .. i have only seen this on bikes that have had their chain rattling in the breeze for 50,000 plus. but i have never had to replace a chain.. have bought and sold many bikes that sounded like a bag of nails and with this mod done sold on for a quick profit! Not one has ever been returned with complications

Ride free brothers and sisters

boldorboy · Posted: Tue Apr 10, 2007 8:51 am Post subject:

Sounds like you have your answer... but... Fasterspider is right... slack chains stretch faster... why? Because the slack chain is slack and then suddenly "loaded" a couple times each time the engine turns over... like jerking the slack out of a rope... A tight chain has steadier tension through the engine rotation. Therefore exerting less force on the part... Also, the slack chain will ride up and down the teeth of the chain wheels (or sprockets) wearing the rollers and the chain wheel prematurely.

Cam chains can also be worn prematurely by excessive idling, and /or low RPM operation.

boldorboy · Posted: Tue Apr 10, 2007 8:53 am Post subject:

Sounds like you have your answer... but... Fasterspider is right... slack chains stretch faster... why? Because the slack chain is slack and then suddenly "loaded" a couple times each time the engine turns over... like jerking the slack out of a rope... A tight chain has steadier tension through the engine rotation. Therefore exerting less force on the part... Also, the slack chain will ride up and down the teeth of the chain wheels (or sprockets) wearing the rollers and the chain wheel prematurely.

Cam chains can also be worn prematurely by excessive idling, and /or low RPM operation.

ManOnBike · Posted: Wed Apr 11, 2007 3:56 am Post subject:

All i can say is that this has been done by myself and several mates countless times..

When i was a courier i used to carry a bolt the tools to do the job ( it can be done without removing engine plates) .. just.. and would offer to fix a noisy cam on the spot for 20 quid.. must have done about 50 of them.. many happy guys ( and girls) rode away rattle free in less than 10 mins

The cam chain don't need to be very stretched to rattle and most of the noise is what it is hitting into...(the pivot of the U shaped tensioner arm that transfers the push to the slipper blade).. and the cam chain tunnel acts like a soundbox on a guitar making it sound far worse than it actually is ..as I said my own two bikes did over 500,000 miles between them both on their original chains the first one had done 48.000 before i came up with the fix and had been rattling for at least 30,000 miles yet was silenced ok and went on to do 270,000 miles when the primary chain gave up seizing solid with a big bang!

Honda fitted a system bound to fail.. as the chain stretches so the slipper blade will need to be bent more.. as the bike ages the rubber face of the slipper blade hardens making it harder to bend the blade and this is all supposed to be achieved by a relatively light compression spring which as you adjust it lengthens and thus looses force so its never long before an equilibrium is arrived at with a slack chain.. you hear of other people removing the plug and using a screwdriver to push on the adjusting rod.. thats ok to a point but its hard to be accurate.. my method gives precise adjustment and years of rattle free riding

One other fault that older/higher mileage bikes tend to show is the bolt on the end of the primary shaft comes undone and punches a hole in the clutch cover.. so anytime you have that over off it is worth removing the bolt.. cleaning it up.. get the threads of both bolt and layshaft dry with brake cleaner..use loctite and re-torque it..

Whether it is worth removing the cover just to check it is a hard one.. but it is only one cheap gasket and two hours work so a caring owner may say yes.. its getting hard to find good secondhand clutch covers as result of this problem..

As for your comment of excessive idling/ low speed riding.. my first bike was despatched in London, hence bucketloads of idling/low speed from new to 48000 miles before this mod was sucessfully done..

boldorboy · Posted: Wed Apr 11, 2007 10:32 am Post subject:

Wasn't trying to discredit you, ManOnBike.

Actually, your answer had some great advice from someone with first hand riding experience..

My answer came from a number of years as a Honda tech and seeing a countless number of poorly maintained, highly polished bikes come through our shop.

I was merely trying to address the question of how a poorly adjusted or "slack" chain wears quicker than a properly adjusted chain... Also pointing out that excessive idling may contribute to wearing of engine components... That's just text book... BUT.. I'm glad you haven't' had that experience.

ManOnBike · Posted: Sat Apr 14, 2007 3:42 am Post subject:

hey boldor how opposite we are.. my bikes always look, at a glance, dreadful.. yet are always well maintained.. in London weather you cant keep a bike both polished and ride it 10 hours 5 days a week.. I would just keep greasing all moving parts and WD40 over the dirt on the rest of the bike. Annual steam clean and it would look a million dollars whereas other couriers who tried to keep their bikes cleanish had rust/flaky metalwork everywhere.. the beauty of the 400four is it would run on an on with compression barely above atmospheric.. my first bike finally had its head off for the first time at 83,000 miles.. a rebore to +50 and it was right as rain and went on to do over 100,000 before a more major strip was needed.. I still think this model is one of the most reliable bikes anyone has ever made..

Brian42 · Posted: Sat Apr 14, 2007 10:49 am Post subject:

Is this a technique that can be applied to a CB900 engine, putting an assist bolt to help push the adjuster rod in from the front?

boldorboy · Posted: Mon Apr 16, 2007 9:39 am Post subject:

The polished bikes where customers... I like to ride and not polish as well...

I rode a 78 BMW R100 with 605,000 before selling it... Looked like absolute doo-doo but runs great.. My daily Honda is a 900F with a little over 140,000... Last year was my lowest mileage year since 92... I only put on 23,000 miles because of the new baby in the house.

So... we're probably not that opposite... as a shop mechanic I was required to work of these machines that the owners just never rode... It broke my heart...

If you want to come over and ride the Rockies... I'm here... with a bike I'm sure you'd feel at home on.