Manual cam chain tensioner

[Jim813]

I've had been looking for a manual cam chain tensioner form my 2008 YZ450F for quite a while with no luck. Eventually, after a recommendation from a TT member, I called APE. They didn't have a tensioner for the aluminum framed YZ, but offered to built one. I sent them my stock tensioner, and after a few weeks they sent me what I was looking for:

This is the first one they made. It's a nice piece, installed easily, and I will never have to worry about the stock tensioner failing. Anodized tensioners will be produced in the future, but I like the natural look myself. APE can be reached at 661-256-7309

[rjcook450]

How often are you having to check the tension since its not auto anymore?

[Jim813]

I have talked to a few competent riders who run manual tensioners and every three or four oil changes, or every 15-20 hours seems to be just fine. It only takes about 5-10 minutes to check.

Another upside to the manual tensioner is the cam chain and the other components involved will last longer. With the stock tensioner, the cam chain sliders are always slammed against the chain, causing increased pressure on the cams, cam chain, and others. With the manual tensioner, only the pressure that's needed is applied ( when adjusted correctly).

[FinchFan194]

Cost? How do you adjust it? Do they give you directions when you buy it?

[Jim813]

Cost? How do you adjust it? Do they give you directions when you buy it?

Well, since this was the first one they built and I had to send in my stock tensioner, they sent it for free. Normally they offer tensioners for around $50. I received no directions, but installing and adjusting is rather simple. Adjusting is easier with two people.

Installing( for adjusting skip first step):

First: Remove stock tensioner and replace with manual one, and tighten evenly and completely with stock bolts. Check the stock gasket, as it is most likely reusable. There will be no need for the copper washer that comes on the inside tensioner bolt( the one holding the tensioner to the engine), so throw it in a bag with the stock tensioner.

Second: Remove seat, tank, and spark plug. The spark plug is removed to help the engine turn over easier.

Third: If the tensioner has an o-ring that seals the adjuster bolt( chain tension bolt for cam chain), pull it back to make turning the bolt easier ( the APE unit has an o-ring). Tighten the chain tension adjuster bolt until finger tight. Then, turn the engine over. On my YZ it was easy enough to use the kickstarter, rather than taking the ignition cover plug off and turning over the engine with a socket( a friend helps here, as they can turn the engine over why you focus on the tensioner). As the engine is turned over, keep turning the adjuster bolt in until your fingers can no longer turn it.

Fourth: Back the adjuster bolt out 1/4 turn, then push back the o-ring. Next, tighten the nut that keeps the adjustment set.

Fifth: Replace spark plug, tank, and seat.

Sixth: Go ride!

[grayracer513]

As long as the chain is kept in good condition, I see no compelling reason to replace the stock tensioner with a manual one. The only thing that can be gained by it is that due to the frequency of inspection necessary with a manual adjuster, a chain that starts to kink and bind can't sneak up on you, as can happen with the automatic unit.

The stock chain adjuster virtually never fails in the first place, as far as I've seen. Once it has run in, it cannot be pushed back out by the chain. Try it on the bench sometime. The manual tensioner shown here differs from stock in essentially one way only; there's no spring to turn the bolt. Otherwise they work the same, and you can no more push the stock plunger back in than the bolt in the manual unit.

What happens is that as the chain starts binding over enough of it's length, it tends not to straighten out as it runs up the back side against the tensioner shoe. As it wears, and real slack develops, the kinked links keep the chain artificially tight enough on the back side to keep the tensioner from rolling in on the slack that would be there were the chain healthy. Then, eventually the engine kicks back, or rolls backward for any reason, pulls the kinks out on the back side, and pulls the suddenly slackened chain over the cams. Bingo. Out of time. Either that, or it finally gets so bad that it's able to skip out while running, which of course is usually disastrous.

This can be avoided by periodically inspecting the chain for any tight links, which can be done by removing the cam cover, parking the engine at TDC, slacking the tensioner, and checking the visible section of chain. Restore the tension, turn the engine to the next compression stroke, and check another section. If you check the condition of your cam chain every 3-4 rides, your stock tensioner should work perfectly well.

If you do decide to go with manual tensioning, the instructions here are flawed:

• No caution was given regarding removing the tensioner. It should never be done until after the engine has been moved to the timing position (TDC on the compression stroke), and the engine should never be rotated to where a valve starts to open without tension on the chain. It will jump time.
  
• The instruction to turn the bolt in finger tight, then back off a quarter is also dangerous. First, it's not enough tension. Second, it assumes that the front and top runs of chain are tight, that you are working only against true slack, and that the threads are perfect. What should be done is to again place the engine at TDC/Comp with the cam cover open and tighten the screw until you can no longer feel any slack in the top run of chain between cams, and it has become taut. Then back off until there is light pressure on the adjuster bolt.
  
• As to frequency of inspection and adjustment, it should be looked at at least every 5 hours, probably every ride day. 15-20 is way too long.
  
• As far as the adjuster guide running against the chain, it's supposed to. In 350 hours of running with a stock tensioner (same one the whole time, BTW) none of the guides in my '03 had worn significantly.
  
• Remember that a manual tensioner will not prevent a chain from kinking, and because of the way they are adjusted, a binding chain can be overlooked during the adjustment process. Be sure to back the adjuster off and check the chain for kinks as described above.
  

[Jim813]

What happens is that as the chain starts binding over enough of it's length, it tends not to straighten out as it runs up the back side against the tensioner shoe. As it wears, and real slack develops, the kinked links keep the chain artificially tight enough on the back side to keep the tensioner from rolling in on the slack that would be there were the chain healthy. Then, eventually the engine kicks back, or rolls backward for any reason, pulls the kinks out on the back side, and pulls the suddenly slackened chain over the cams. Bingo. Out of time. Either that, or it finally gets so bad that it's able to skip out while running, which of course is usually disastrous.

Gray, with this senario, it sounds like this condition could generally happen with either tensioner, given that the chain isn't inspected, correct?

If you do decide to go with manual tensioning, the instructions here are flawed:

• No caution was given regarding removing the tensioner. It should never be done until after the engine has been moved to the timing position (TDC on the compression stroke), and the engine should never be rotated to where a valve starts to open without tension on the chain. It will jump time.
  

I don't quite understand this. Why does the engine have to be at TDC on the compression stroke, if the engine is never turned over until there is tension on the chain?

If you do decide to go with manual tensioning, the instructions here are flawed:

• ...and that the threads are perfect.
  

You are talking about the adjuster bolt threads, correct?

If you do decide to go with manual tensioning, the instructions here are flawed:

• As to frequency of inspection and adjustment, it should be looked at at least every 5 hours, probably every ride day. 15-20 is way too long.
  

Is a cam chain expected to stretch quite this rapidly? Also, is every five hours a precautionary measure, or will their actually be noticeable slack that has to be taken up by the adjuster bolt after this time.

Gray, thanks for the input. This is simply an alternative to the stock tensioner, in which I hope will eliminate another possibility of a mechanical failure. My instructions may be flawed by the book, but I have yet to see an issue with them.

[grayracer513]

Gray, with this senario, it sounds like this condition could generally happen with either tensioner, given that the chain isn't inspected, correct?

Yes and no. If you use your finger tight method, the same thing may happen. Using my method forces all slack out and puts tension on the chain during the adjustment, which pushes out any kinks and sets the correct tension regardless of the chain condition. However, in that case, the binding condition would be masked, and could go overlooked until the chain actually breaks.

I don't quite understand this. Why does the engine have to be at TDC on the compression stroke, if the engine is never turned over until there is tension on the chain?

If tensioner is removed while the cam lobes are bearing down on a valve lifter at less than peak lift, the spring force can cause the camshaft to rotate with enough force to skip time as soon as the tensioner is removed. Even if that doesn't happen, valve spring force could push the cam forward against the chain and give you a false indication of the true overall tension by pulling the back run of chain tight.

You are talking about the adjuster bolt threads, correct?

Yes.

Is a cam chain expected to stretch quite this rapidly? Also, is every five hours a precautionary measure, or will their actually be noticeable slack that has to be taken up by the adjuster bolt after this time.

Gray, thanks for the input. This is simply an alternative to the stock tensioner, in which I hope will eliminate another possibility of a mechanical failure. My instructions may be flawed by the book, but I have yet to see an issue with them.

The chain should not normally need an adjustment that often, but what if it did and you missed it? With the automatic unit, any slack that appears is immediately taken up as it occurs, and the chain is always at optimum tension. With a manual setup, it goes from ideal to some degree less than ideal for however long you go between adjustments. Should some event occur that caused an unusual amount of slack 5 hours into your 20 service interval, it could be a problem.

Otherwise, I think perhaps my biggest objection is that I don't think your way of setting the tension results in the chain being quite tight enough.

[Jim813]

Yes and no. If you use your finger tight method, the same thing may happen. Using my method forces all slack out and puts tension on the chain during the adjustment, which pushes out any kinks and sets the correct tension regardless of the chain condition. However, in that case, the binding condition would be masked, and could go overlooked until the chain actually breaks.

If tensioner is removed while the cam lobes are bearing down on a valve lifter at less than peak lift, the spring force can cause the camshaft to rotate with enough force to skip time as soon as the tensioner is removed. Even if that doesn't happen, valve spring force could push the cam forward against the chain and give you a false indication of the true overall tension by pulling the back run of chain tight.

Yes.

The chain should not normally need an adjustment that often, but what if it did and you missed it? With the automatic unit, any slack that appears is immediately taken up as it occurs, and the chain is always at optimum tension. With a manual setup, it goes from ideal to some degree less than ideal for however long you go between adjustments. Should some event occur that caused an unusual amount of slack 5 hours into your 20 service interval, it could be a problem.

Otherwise, I think perhaps my biggest objection is that I don't think your way of setting the tension results in the chain being quite tight enough.

I understand. My method could most likely use some revising. I may experiment with your method in the near future. My only question about your method is that I think I would be guessing what " light pressure on the adjuster bolt" really means. Do you mind explaining?

Is it possible to overtighten the cam chain? What would happen if the chain was overtightened?

[grayracer513]

Over-tightening would accelerate wear and increase the tensile load on the chain, and yes, of course, it's possible. Under tightening is obviously also possible, and carries what should be obvious risks.

The tensioning method is something like that used to set steering head bearings, wherein the bearing is torqued well beyond what it is actually set to in order to "settle" it completely. Then you back off and come back against the bearing with 5 ft/lb on the ring nut.

Same principal with the chain tensioner, but you have to understand that the chain is going to be a good deal less solid that the head bearings when tensioned. Run the adjuster down to where the chain feels too tight (no slack, and is difficult to deflect by pushing on the top run). I'll guess this would be somewhere around 30-40 inch pounds on the adjuster bolt, but don't hold me to that. Then back off to the point where the bolt has run down to "just snug", say about 3-5 inch pounds more than the rotating torque needed to turn the screw, if any. Very much like your 'finger tight" reference, except for the pre-tensioning step you left out.

The best thing I can recommend is to reinstall the stock tensioner, kick the engine over a few times, and see what the tension on the top run of chain feels like, then duplicate that same feel with your manual adjuster.

[KJ790]

As long as the chain is kept in good condition, I see no compelling reason to replace the stock tensioner with a manual one. The only thing that can be gained by it is that due to the frequency of inspection necessary with a manual adjuster, a chain that starts to kink and bind can't sneak up on you, as can happen with the automatic unit.

I agree with you on a stock engine, but on a heavily modded engine I have seen the automatic tensioners fail causing the timing to jump. It generally happens when the throttle is chopped. I recently had this happen on one of my YZ250F's, and it is possible with the YZ450F as well. I had a high compression piston, Web cams, and stiffer valve springs. The motor ran great for two races, then quit half way through the third race. I only put 0.8 hours on the hour meter. I found that the cam chain jumped timing on the exhaust cam and bent the exhaust valves. The tensioner seems to work perfectly normal, and I knew it wasn't an issue of the cam chain or anything else being worn, so I was baffled. I talked to a few good engine builders and a couple told me that they have seen the stock tensioners lose tension momentarily and jump time on engines with aggressive cams and heavy duty valve springs. One told me that he will only run MCCT's on mod motors that he builds for just this reason. I just bought a MCCT from APE to make sure I don't have this problem again.

[grayracer513]

There are only two ways the automatic tensioner in a YZF can loosen up the cam chain:

• The chain forcibly pushes the tensioner plunger straight back in by causing the internal screw ramp to "skid" or "strip" over itself, or,
  
• The drive screw (what the spring bears against) is rotated in the reverse direction
  

While I'm willing to concede the possibility of either one of these conditions occurring, at least in theory, I count them either one as being extremely unlikely, and bordering on incredible. In an engine with that much money involved, there's no harm in the precaution, I suppose. But manual tensioners are not perfect, either, owing simply to the fact that they are unable to accommodate changes in tension on the fly, which is a consideration in any endurance event.

If ever you run across a tensioner that you believe has failed and caused such a problem, I'd like to get my hands on it, if possible.

[Wes Woodin]

In 350 hours of running with a stock tensioner (same one the whole time, BTW) none of the guides in my '03 had worn significantly.

I rode my Yami 08 what seems forever and never had to do anything to anything. I sold my bike to my friend and he rode forever. I haven't spoken to him in a long time but I would assume he has 90-100 hours on it now. Still no problem

[NVDESERTPETE]

"05" and "06" RMZ450's both use manual cam chain adjusters. Suzuki went to automatic in "07". They're really is no down side to a manual cam chain adjust if it's adjusted correctly and adjusted per manufacturers recommendations other than in my opinion it's just another unneccessary maintenance step when automatics work fine!

Engine must be at top dead center as Grayracer recommended. This removes the valve spring tension on the cam lobes and gives you the best adjustment range. The Suzuki design still uses an internal spring for the tension and a lock nut and bolt which places tension on a flat area machined on one side of the plunger so it won't back out. Correct tension on the lock bolt and nut is critical so that the plunger flat does not deform or if left to loose the plunger backs out!

The danger I see with the APE design is because it can be easily overtightened. I would say finger tight only and do not back-off the adjustment 1/4 turn.

Suzuki recommends every 6 hours after break-in you perform the cam chain adjust. Plan on every few hours until the machine is broke-in or if a new cam chain is installed. I can go about 12 to 16 hours now depending on how hard I ride it before I start to hear some cam chain noise.

If it was me I'd keep the automatic. The manual cam chain adjust is really the only thing I hate about my RMZ450 and there are no aftermarket automatics being made! The "07" and up will not work on my "05".

[grayracer513]

"05" and "06" RMZ450's both use manual cam chain adjusters. Suzuki went to automatic in "07". They're really is no down side to a manual cam chain adjust if it's adjusted correctly and adjusted per manufacturers recommendations other than in my opinion it's just another unneccessary maintenance step when automatics work fine!

The manual cam chain adjust is really the only thing I hate about my RMZ450 and there are no aftermarket automatics being made! The "07" and up will not work on my "05".

Out of curiosity, what is the Suzuki service manual procedure for determining correct tension, and the recommended interval?

[Jim813]

Gray, do any of the wear characteristics of the cam chain, such as: stretching, binding, or kinking, relate to the tension on the chain?

[grayracer513]

"Stretching", which is actually pin/plate wear added up over the length of the chain will obviously make the chain looser. Likewise, wear at the rear guide does the same.

The effect of kinking is discussed in my first post in this thread (#6).

[Jim813]

Maybe I should make my question more clear. I have some insignificant thoughts that the stock automatic tensioner is possibly putting too much tension on the chain. Why are cam chains stretching, binding, and/or kinking within 60-70 hours of use or less? Is there that much load on the chains, or are they made from lesser materials. Or, does the chain tension play a roll in what is possibly accelerated wear? Although they are most likely non-comparable, I am comparing my thoughts with the cam chain and a drive chain. I'm sure you would agree that a correctly adjusted chain will last much much longer, as many will (such as your ORN6) easily last over 150 hours. So why can't a cam chain?

[grayracer513]

To begin with, there was more tension applied by the older tensioners on the '05 an earlier models. The kinked chain issue was extremely uncommon then.

Cam chains run at vastly higher speeds than rear chains do, but are lubed better and kept away from dirt. In the automotive world, they last more or less the life of the engine without a particular problem. My thought on the matter is that Yamaha was dealt a bad batch by its vendor. Hopefully those are used up now.

An alternative is the Pro-X cam chain, made by Borg-Warner

[NVDESERTPETE]

Out of curiosity, what is the Suzuki service manual procedure for determining correct tension, and the recommended interval?

The Zook tensioner still uses a spring. Make sure the engine is at TDC and loosen the lock bolt and nut located on the side of the tensioner instead of the rear like the APE design. The spring inside the tensioner does all the tensioning forcing the plunger forward just like an automatic. You then just tighten the lock bolt and nut. There is no ratchet system or pawl to keep the tensioner from backing off if the lock bolt comes loose. The plunger is a smooth bore design with one side machined flat for the lock nut. Sounds screwy but if done right it works fine. The Zook microfiche has a good breakdown of how it works. I really wish it was an automatic as I get tired of dealing with it!