[steveo]

How it Works

The cam chain rides on two guides. The one at the front of the motor is fixed, and rides on the chain. During engine running, the front of the chain is generally pulled tight because the crank is pulling down on the chain, and the cam itself provides load.

The cam chain tensioner blade(back of the engine) works by pressing on the back of the chain, where all the slack is, to keep it tight.

Ideally you want zero slack in the cam chain.

It's made of two parts.

One is a bowed peice of metal that's covered in plastic, that presses on the chain. Think of a flat spring, which is bowed out on one side. The bottom of it sits in a little cup, and to increase tension, the top of the tensioner is pulled down.

The second part is basically a spring-loaded slider. It's held in by a top bolt (to hold it stationary), and a nut on the bottom, which is released/tightened to allow adjustment. They're both accessable without removing anything from the bike. When the nut is released, the spring does its thing and tightens the chain by pulling down on the bowed peice.
This is applicable to the 450 series engines, the 400's tensioner blade is captive between the 2 case halves and can only be replaced by splitting the case. The 400 can be upgraded to the 450 and the 450 downgraded to the 400 by using the appropriate blade and lock plate

[attachment=0:1cybkq9k]14501-MC0-000_1-800x600.jpg[/attachment:1cybkq9k]

 

[steveo]

Re: Cam Chain Tensioner -- Unoffical Manual

Tensioning the Chain - Automatic adjustment with engine running

This is the factory procedure, and should work fine with an engine in good working order.

1. Idle the bike until it's warm (warm enough that it'd burn you if you touched it, i guess)
2. With the bike running, loosen the adjuster nut, wait a few seconds, then re-tighten it. Don't overtorque it. Just snug.
3. If the noise is worse than before, follow manual procedure below

 

[steveo]

Re: Cam Chain Tensioner -- Unoffical Manual

Tensioning the Chain - Manual adjustment

This is necessary if the spring is too weak to overcome the tension of the bowed part of the tensioner, or if it's simply just stuck. It works just as well or better than the automatic procedure if done properly.

It's best done at the same time as valve adjustment.

You should have a helper..

1. Remove seat, tank, valve cover, shifter, and timing cover
2. Rotate the engine (the correct direction.. there's an arrow on the flywheel) until it's near the T mark, but not quite there
3. Loosen the adjuster nut
4. Hold a screwdriver or whatever against the top of the tensioner, pressing it downwards
5. Rotate the engine slowly towards the TDC mark. You might notice the tensioner drop a little extra at this point, that's good, it means the front of the chain has tightened up
6. Snug the adjuster nut up

Now check your work. Check for slack at the front of the chain with a screwdriver. Now rotate the engine backwards a few degrees, this puts all the slack at the front of the chain. It should still be tight. If it isn't, repeat the entire procedure again, this time push a little harder on the tensioner

 

[steveo]

Re: Cam Chain Tensioner -- Unoffical Manual

The Nut

My god don't overtighten it. Just snug. The bolt is likely tempered from years of heating/cooling, and it was too small to begin with. Bad design. It'll break if you muscle it!

There's a copper washer on the adjuster nut. If you remove the nut and washer, you'll find that the threads for the tensioner bolt don't go deep enough to manage snugging up against the casing with a thin or missing washer.

If you've done the tensioning procedure and find the chain quickly becomes noisy again, it's possible that your nut is bottoming out on the bolt, and not the head casting. Adding a second copper washer (or a thicker one) should fix it.

 

[steveo]

Re: Cam Chain Tensioner -- Unoffical Manual

Installation/removal for 450 engines

It's possible to remove the tensioner with the engine still assembled in the frame, to replace parts such as a broken bolt or spring, or a worn guide, but it's a nightmare, and you will swear at it for many hours.

Pulling the engine will make it easier, just because of clearance, but you don't have to.

Removal:

1. unbolt oil pipe and cam gear, remove chain from cam gear, and move it out of the way
2. rotate cam gear so slots are horizontal, and push cam gear forward
3. remove both bolts from the tensioner. poke the lock bolt through its hole with a screwdriver. dont worry, it's captured in the tensioner at this point.. it shouldn't come out.
4. pull the (now free) tensioner upwards, and hold it, remove the pin from the top and seperate the tensioner from the chain guide.. when the pin is out, immediately put a screwdriver in its place. if you drop the tensioner, it's hard to get back
5. with the two peices seperated and the pin removed, the tensioner comes out fairly easily, just turn it around or whatever until it gets past the frame.

Installation:

1. you need to find something to wedge it OPEN a bit ex. with the spring fully extended. a bolt works. it will not go back in if it's contracted at all. you'll need to tie a long peice of wire or something to the wedge, because you need to retrieve it afterwords, and you cant reach it with tools. plan to be able to pull the wedge free with just the string. alternatively, you can try to load the tensioner once it's back in the bike with a bent coathanger or something, but that didn't seem to work for me very well
2. put the tensioner and guide in seperately, and replace the pin. seriously... dont drop the spring loaded part of the tensioner!! that hole is f$^ing deep
3. find the seating position for the bottom of the cam chain guide. it just sits in a U-shaped thing. you need the chain out of the way for this part, tie it to the front of the frame or something. get a screwdriver and put it behind the guide, and push it gently towards the cam (spreading tensioner apart just slightly) until it bottoms out, that'll help ensure it ends up in the cup, instead of falling in the hole. if you miss, either the guide will be so loose that you can push it around, or it'll be so tight that there's no way the bolts will go back in.
4. if you're lucky, you can just fiddle with it and get the bottom bolt in the hole. if you can't, you can try to hold a very strong magnet against the place where the bottom bolt has to go in. move and wiggle and push on the tensioner until the magnet sucks the bolt through the hole. hand tighten the nut
5. install the top bolt. the hole will be lined up, so if it isn't finding it, just push harder.
6. remove the wedge, if you used one
7. work the cam chain back onto the gear. you'll need to fully unload the tensioner (pull it upwards with a hook) and snug the lock nut up.

 

[steveo]

Re: Cam Chain Tensioner -- Unoffical Manual

can i get this stickied?

 

[ryan.hope]

Re: Cam Chain Tensioner -- Unoffical Manual

Do you have any suggestions/recommendations for a replacement for one or both of the bolts if someone happens to already have the adjuster/tensioner out of their engine?

 

[HerrDeacon]

Re: Cam Chain Tensioner -- Unoffical Manual

Have it stickied now stevo, thanks for putting that together, great info!

 

[steveo]

Re: Cam Chain Tensioner -- Unoffical Manual

Do you have any suggestions/recommendations for a replacement for one or both of the bolts if someone happens to already have the adjuster/tensioner out of their engine?

well, you can either go OEM (stick with the OEM bolt on the top at least)

i might consider drilling the bottom hole out and putting a slightly larger bolt in there

the bottom one is a T-bolt, but a regular bolt would work if you modify/grind down the head a little

i thought of oversizing mine a bit, because they're so very breakable, but my motor was still together, so i didnt want to get drill shavings in it

either way if you dont overtighten it, everything should be ok

 

[ryan.hope]

Re: Cam Chain Tensioner -- Unoffical Manual

I just went though this procedure on my own bike and have some comments, they are in blue below...

Installation/removal

It's possible to remove the tensioner with the engine still assembled in the frame, to replace parts such as a broken bolt or spring, or a worn guide, but it's a nightmare, and you will swear at it for many hours.

Pulling the engine will make it easier, just because of clearance, but you don't have to.

Removal:

1. unbolt oil pipe and cam gear, remove chain from cam gear, and move it out of the way
2. rotate cam gear so slots are horizontal, and push cam gear forward You really want to remove the cam chain from the cam and sproket, remove them so that they are out of the way, and tie the chain to the front frame so that there is no slack in the chain.
3. remove both bolts from the tensioner. poke the lock bolt through its hole with a screwdriver. dont worry, it's captured in the tensioner at this point.. it shouldn't come out.
4. pull the (now free) tensioner upwards, and hold it, remove the pin from the top and seperate the tensioner from the chain guide.. when the pin is out, immediately put a screwdriver in its place. if you drop the tensioner, it's hard to get back
5. with the two peices seperated and the pin removed, the tensioner comes out fairly easily, just turn it around or whatever until it gets past the frame. The tensioner will come out with out removing the pin if the cam chain is completely out of the way. Best remove it in one piece so as to not drop the pin or clip.

Installation:

1. you need to find something to wedge it OPEN a bit ex. with the spring fully extended. a bolt works. it will not go back in if it's contracted at all. you'll need to tie a long peice of wire or something to the wedge, because you need to retrieve it afterwords, and you cant reach it with tools. plan to be able to pull the wedge free with just the string. alternatively, you can try to load the tensioner once it's back in the bike with a bent coathanger or something, but that didn't seem to work for me very well The first part of this was a little confusing. It was not clear if you still had the tensioner in 1 or 2 pieces at this point. I can not for the life of me figure out how you put the pin and clip back in if you installed the 2 pieces separately.
2. put the tensioner and guide in seperately, and replace the pin. seriously... dont drop the spring loaded part of the tensioner!! that hole is f$^ing deep
3. find the seating position for the bottom of the cam chain guide. it just sits in a U-shaped thing. you need the chain out of the way for this part, tie it to the front of the frame or something. get a screwdriver and put it behind the guide, and push it gently towards the cam (spreading tensioner apart just slightly) until it bottoms out, that'll help ensure it ends up in the cup, instead of falling in the hole. if you miss, either the guide will be so loose that you can push it around, or it'll be so tight that there's no way the bolts will go back in.
4. if you're lucky, you can just fiddle with it and get the bottom bolt in the hole. if you can't, you can try to hold a very strong magnet against the place where the bottom bolt has to go in. move and wiggle and push on the tensioner until the magnet sucks the bolt through the hole. hand tighten the nut
5. install the top bolt. the hole will be lined up, so if it isn't finding it, just push harder.
6. remove the wedge, if you used one
7. work the cam chain back onto the gear. you'll need to fully unload the tensioner (pull it upwards with a hook) and snug the lock nut up.

I installed my tensioner in 1 piece. First I disconnected the lower spring hook from the tensioner so that I could easily extend the tensioner with out any load on it. In order to keep the tensioner extended while installing I used some paracord. On one end I tied a figure 8 knot, the other end I fed into hole where the top bolt would go. I fed it though the side of the tensioner that would go against the valve head wall. With all the slack removed so that the knot is tight up against the tensioner l looped the other end of the paracord down around the upper spring mount then up and frapped it around the tensioner a few times to keep the tension. While holding the cord tight I reattached the spring to the lower mount. The tensioner is now fully extended and loaded, ready to be installed. Once I got the bottom bolt though the hole with the nut on I used straight and hooked pick to unwind the paracord and pull it out of the hole.

 

[steveo]

Re: Cam Chain Tensioner -- Unoffical Manual

mine wouldn't come past the frame in one peice, there was no way

pin went back in by holding both peices up while slipping the pin back in, no big deal

glad you got it done though!

 

[flytye]

Ok so what do you do when the nut will not loosen or tighten. It turns to the right and to the left with the same tension (med.). I hav a 1985 cb450sc and the nut looks like the one shown in the photo. I'm thinking the bolt is striped going. Into the arm. Any Ideas

 

[longdistancerider]

There's a flat washer under the nut. Use a screwdriver under that prying out as you try to loosen it.

 

[dothetodd]

I just had the top end completely rebuilt on my 1982 CM450E and while I was thinking about things, I'm wondering if I should replace the cam chain. I have a new tensioner, and I plan to adjust it when I assemble the engine, but while I have the engine torn apart, how hard is it to replace the chain itself? I have the head and jugs off, and I'll be splitting the cases, but I don't want to tear into the actual internals of the case, I just want to clean out the inside. When I looked at the Honda FSM, I can't determine if the cam chain is replacable without having to cut/split the chain.

Any help would be appreciated, thanks.

 

[longdistancerider]

These use an endless timing chain. You can cut it off but you have to remove the crankshaft to install a new one, sorry.
Personally? I would inspect the crank bearings while the case is split. Specifically the left rod bearing. Just takes a few minutes to open it. Hardest part is re-assembly and the balancers. Not that big a deal though. It would be a shame to get the top end good and loose the bottom end.

 

[dothetodd]

I'm looking for cam chains online and I'm seeing some aftermarket providers, but no Honda part. Do you know if those aftermarket chains are ok?

Also, do the cam chains typically need to be replaced? The engine was actually in pretty decent shape, so I think that the new tensioner will take care of it, but I'd rather not screw the top end up with one bad piece being reused at the end.

 

[longdistancerider]

I have heard of no instances of this chain breaking. I think it's called a v-drive chain. They have very little stretch and at 60K when I did my engine there were no signs of wear to the chain or sprockets. I replaced my chain and cam sprocket anyway since I had new ones but I think I would have been fine if I hadn't.

 

[dothetodd]

Excellent. My engine only had 23,000 miles before the rebuild, and I'm installing new tensioners, so I think that I'll just stick with the chain that I have in there. It looks like it's in really good shape.

You said "I would inspect the crank bearings while the case is split. Specifically the left rod bearing. Just takes a few minutes to open it. Hardest part is re-assembly and the balancers." I don't have the FSM with me right now to research, but do you have any special tips on doing this that would'nt be noted in the FSM? Unless the crank bearings are actually bad, should I need to replace anything else if I strip it down to check these?

Sorry, I know this is a thread specific to cam chains. I won't post any more on this thread.

 

[jprice90]

this procedure works on the cm400?

 

[longdistancerider]

To remove the tensioner slide only. The 400 tensioner blade is held captive and you have to split the case to remove it.