I'm confused about cam chain tension

[SirSquid1300]

I just serviced the valves on the left bank/side of the engine. I'm confused about how this cam chain tensioner really works.

I used a small flat head screwdriver to reduce tension so I could get the cam back in the head. So... am I supposed to screw the tensioner counter clock wise to add back tension, until a certain threshold? Maybe I misinterpreted some of the threads... but does the tensioner just re-tension it's self when you let go of the screw driver?

Any help would be appreciated.

Btw... easiest valve job hands down.

 

[jfheath]

Yes, The cam tensioner adjusts itself. It has a coiled spring which turns the screw / helix it in the correct direction (ccw) to press the cam chain tensioner guide against the cam chain. As the chain 'stretches' over time the spring is always trying to turn the adjusting screw to ensure the tensioner guide rail takes up the slack. This added tension cannot be reversed without using a screwdriver to turn the screw cw)

ie if the chain becomes too tight (it won't), it is unable to push the the adjusting screw back to gain more slack.

However, it is not unknown for the adjuster to stick a bit after it has been held in place for a while in its fully released position. (it happened twice on mine) - so yes give it a hand with a screwdriver, but then exercise the screw a few times and check that it can move in by itself. You will fell the spring pressure as you wind the tensioner out (cw) - and it is plenty strong enough to turn the screw back the other way (ccw) without help. If it doesn't then it might be necessary to replace the device, or service it if possible. Its only a couple of bolts and a gasket. But the right hand side one would be a pain to get at.

Once the tensioner is in place, turn the engine by hand in the correct direction and revisit the timing marks to check that you are not a tooth out. The instructions say to check the marks against the top surface of the cylinder head. It is easy to be one tooth out if your viewing position is a tad too high. Your line of sight must be such that you cannot see any of the mating surface. This can be difficult for the inlet cam. I use a mirror and a fine beam torch/flashlght to cast a shadow.

But another useful check is the position of the inner timing marks on the exhaust / inlet cam sprockets where they face each other. I noticed that they aligned with each other and can make the one tooth out error easier to spot.

 

[sirbike]

Yes. Automatic tensioner. Not sure if it matters, however, I let the screwdriver unwind gently, then turn the motor over by hand a couple of revs to let it settle in.

 

[SirSquid1300]

Thanks everyone. Looks like I need to hit eBay and fine a new tensioner. Why my shop manual can't just say "self-adjusting " is beyond me. Instead they use some obscure language that prompted this question.

 

[Kevcules]

Good to hear that someone else has had a head scratching moment like I did when working on the left side tensioner. I had the same issue when I did my valves some months ago.
The right side tensioner could be wound back and locked in place, then once released it would easily and quickly spring back into position visually tightening the chain. Then as the engine rotates and warms up, the tensioner continues to adjust if necessary.

The left side is another story. The tensioner would NOT extend and tension the chain once the tool was removed from it. I could clearly see the chain being loose sitting on the chain guide where the tensioner was and it wasn't doing it's job. I tried rotating the engine a little with no difference. The only option was to crank the tensioner the other way (counter clockwise) to snug it up. Starting the engine with the chain that loose could be catastrophic I think. Once the chain was a bit more snug, I could then see that I was off one tooth on the cams so off it came again. Rotating the engine slowly, I was now good with the cam timing after using the tensioner to manually snug up the chain again. Then backed off a bit so I could see the chain get slightly slack between the cams, I left it there for the tensioner to do the rest of the job when the engine started and warmed up.

I initially thought my tensioner was bad also with only 48,000 kms but I was wrong. I wasted $120 on a tensioner that did the exact same thing. When you reach inside the hole where the tensioner goes, that chain guide is very hard to push in. That's why the tensioner struggles to do it at least when the engine is cold. I thought maybe the chain guide was stuck on it's pivot or something was broken. From what I could see, nothing looked bad.

When I asked my local dealership about the problem I was having, he didn't seem to understand what I was saying. You would think that anyone who has done a shim swap would have encountered this issue when re-assembling the left side if it plagues all of our bikes. He did say that he would never change a tensioner without removing the valve cover as I had suggested which in this case is very sound advice! I've seen many videos on replacing cam chain tensioners on cars, trucks and motorcycles and most of them just removed the tensioner and re-installed the new one. In most cases you could hear the audible "click" that the tensioner had extended and was working normally. I've don't that before also on other machines without issue.

There's also some instances where you can disassemble the tensioner and add a few revolutions of tension on a worn tensioner instead of replacing them. On a Honda Rincon forum, it's commonly done. That's for another discussion.

I wondered if the issue I was seeing was just isolated to my bike, but happy to hear it may just be the nature of the beast!

 

[jfheath]

Thinking about what @Kevcules has just said - if you turn the screw out as far as it will go, the tensioner will not be in contact with the exhaust side guide rail. It should just turn. But put 'ST1300 cam chain tensioner' into ebay - I've just found 5 singles and a pair for not very much money - about 1/10 of list price - all in the USA.

 

[Kevcules]

Thinking about what @Kevcules has just said - if you turn the screw out as far as it will go, the tensioner will not be in contact with the exhaust side guide rail. It should just turn. But put 'ST1300 cam chain tensioner' into ebay - I've just found 5 singles and a pair for not very much money - about 1/10 of list price - all in the USA.

I checked Ebay and most of the tensioners shown were "pre owned" or used. I didn't see any new ones available.

I didn't want to mess around with an aftermarket possibly inferior part anyways when it cam to cam timing, but I definitely did waste my money thinking the tensioner was bad with such little miles on my bike.

I highly doubt the op needs a new tensioner.

Good luck....

 

[SirSquid1300]

Good to hear that someone else has had a head scratching moment like I did when working on the left side tensioner. I had the same issue when I did my valves some months ago.
The right side tensioner could be wound back and locked in place, then once released it would easily and quickly spring back into position visually tightening the chain. Then as the engine rotates and warms up, the tensioner continues to adjust if necessary.

The left side is another story. The tensioner would NOT extend and tension the chain once the tool was removed from it. I could clearly see the chain being loose sitting on the chain guide where the tensioner was and it wasn't doing it's job. I tried rotating the engine a little with no difference. The only option was to crank the tensioner the other way (counter clockwise) to snug it up. Starting the engine with the chain that loose could be catastrophic I think. Once the chain was a bit more snug, I could then see that I was off one tooth on the cams so off it came again. Rotating the engine slowly, I was now good with the cam timing after using the tensioner to manually snug up the chain again. Then backed off a bit so I could see the chain get slightly slack between the cams, I left it there for the tensioner to do the rest of the job when the engine started and warmed up.

I initially thought my tensioner was bad also with only 48,000 kms but I was wrong. I wasted $120 on a tensioner that did the exact same thing. When you reach inside the hole where the tensioner goes, that chain guide is very hard to push in. That's why the tensioner struggles to do it at least when the engine is cold. I thought maybe the chain guide was stuck on it's pivot or something was broken. From what I could see, nothing looked bad.

When I asked my local dealership about the problem I was having, he didn't seem to understand what I was saying. You would think that anyone who has done a shim swap would have encountered this issue when re-assembling the left side if it plagues all of our bikes. He did say that he would never change a tensioner without removing the valve cover as I had suggested which in this case is very sound advice! I've seen many videos on replacing cam chain tensioners on cars, trucks and motorcycles and most of them just removed the tensioner and re-installed the new one. In most cases you could hear the audible "click" that the tensioner had extended and was working normally. I've don't that before also on other machines without issue.

There's also some instances where you can disassemble the tensioner and add a few revolutions of tension on a worn tensioner instead of replacing them. On a Honda Rincon forum, it's commonly done. That's for another discussion.

I wondered if the issue I was seeing was just isolated to my bike, but happy to hear it may just be the nature of the beast!

Sweet. That's what I did too - just enough slack between the cam gears to ensure I didn't over tighten. Given your feedback, I'm not going to buy a new or used tensioner. The bike only has 50K miles (ST1300 humor har har har).

 

[SirSquid1300]

I checked Ebay and most of the tensioners shown were "pre owned" or used. I didn't see any new ones available.

I didn't want to mess around with an aftermarket possibly inferior part anyways when it cam to cam timing, but I definitely did waste my money thinking the tensioner was bad with such little miles on my bike.

I highly doubt the op needs a new tensioner.

Good luck....

I was able to get the tensioner to work as described in the manual! I guess it needed a little help to usher it along the way. I wiggled the screw driver in and out and it eventually took hold using the spring loaded tension.

Weird.