Cam chain tensioner

[Greg goes wild]

Yeah it was replaced at 2,000 miles under warranty, then I did it again at around 12K miles 2 years ago. Rode it last Friday and no rattle, but speaking from experience, it will start rattling more and more often, so once my 4 tensioners come in, I am just going to replace the current one out of precaution. It seems like they last about 5-8K miles with my style of riding, the climate here and so on. I only use BMW engine oil and filters. I have the engine blocking tool to 'freeze' engine timing when replacing the tensioner, as per the service manual.
At $40 a piece I don't mind all that much - I ride the thing a bit less now that I have the K1600 GTL for my commuting, so it's likely going to be a once-every-three-to-four-years' job. I don't expect BMW will do anything about it. I could convert to the hydraulic tensioner, but that is a lot more expensive and a lot more work. Another alternative would be to install one of those aftermarket manual tensioners, that you can adjust from the outside, but I'd still rather, with all its faults, stick to the original design.
Still very strange that they fail so often - this same tensioner was used in the i3 BMW hybrid car, maybe it's not as prone to failure in that application.

I had the chain tensioner go out at 8k miles. I was STUCK for a couple
of hrs til my nieces husband showed up at my clients property. Once my clients
returned from Germany the CEO client had paid for the bike to be towed to
Wild West Motoplex. That it went there for about 1.5wks. I have NOT had a
issue with the new tensioner in it yet( knock on wood) almost 18k miles on it.
GOOD LUCK with the new ones. WERE THEY USED OR NEW??? for that price
not bad

 

[Ceesie76]

They're new, great price I thought also, which is why I bought all 4 they had available.
Apparently the tensioner is also a KYMCO part that is generally less expensive, but I could not find their part # so went with the BMW one.

 

[BlkBlt]

I have a 2013 C650 GT. I called the NTSA and BMW. They said mine was not covered under the recall. I haven’t had it apart yet to see if it has the hydraulic type or not. I did see a manual tensioner on Amazon but, who would know how tight to set it?

 

[Ceesie76]

I saw a video where the bike owner adjusted the tension on the manual adjuster, with engine running, just to where it stopped rattling.

 

[Sherlock]

Just over a week ago the 650gt was all back together and taken for the MOT. A round trip of 8 miles. Engine running as it should. Last Tuesday getting ready for a run and the Gt at an idle, chain rattling, blip on the throttle and the noise disappears. Back to idle and it’s back. So found some second hand ones on eBay and chose the cleanest one dated 2015. It arrived yesterday, very clean but the plunger is frozen. I thought it should be spring loaded. Any advice apart from doing a hydraulic conversion. Thanks in advance.

 

[Ceesie76]

Never buy these used! Sounds like yours is done for - the 'frozen' part applied to the one I replaced two years ago, when I started to hear the death rattle. They are spring loaded and that's how they keep the chain tight. They freeze up for some reason I don't know, and that's when the rattle starts. They are not very expensive new, I think normally under $100 and you just don't want to take a chance on your engine grenading.

(Although there have been reports of engines that stalled due to jumped timing, due to this chain tensioner issue, brought back to life without any ill effects by bringing the engine back into proper time - so that is always worthwhile to at least try, if it comes that far).

 

[Sherlock]

Just dismantled the tensioner and as you say Ceesie it appears you can manually adjust. May give it a try at the weekend.

 

[Ceesie76]

This is not the manually adjustable (aftermarket) type but good idea to open it up; by cleaning and lubricating you may/should be able to restore its original functionality - I'll try the same with my current one when I replace it, and see if that works. Then no need to keep buying new. Did you see any cause as to why it was 'frozen' when you took it apart?
Looking at it, I wonder now how it works; isn't there a spring inside that pushes the plunger outward?

 

[Sherlock]

So, the spring inside is an expansion type, I would have thought it should be a compression type therefore giving light pressure to take up any chain slack/wear until the tensioner needs replacement. These do appear adjustable but only once removed from the engine. Further investigation needed I think.

 

[Sherlock]

Just removed the tensioner from the bike, fairly straightforward and guess what, nothing broken and the same as the second hand one I got. So over the weekend I will adjust the length of the plunger in very small increments until the chain stops its rattling. I know it will be a long process refitting/removing the tensioner but if it works I will be very happy. Keep you updated.

 

[Ceesie76]

So ... there is a spring inside but it doesn't do anything anymore, and the tensioner is stuck at a certain length? But you can manually turn the thing in or out, and it will just stay where you put it?

 

[Sherlock]

It looks as though the spring stops the threaded part from turning via the slot in the screw head once installed. Still a little puzzling though. Why BMW did not make a manually adjusted version who knows. The alloy case already has a small nut on it for access so halfway there.

 

[Ceesie76]

That small nut is to cover the hole that emerges after you install the new tensioner and pull a small tab that sits inside the hole and, when you pull it (bit like a grenade pin), releases the tension/spring that then pushes the piston against the timing chain and keeps it under pressure. Similar to installing a new timing belt tensioner pulley, some of those come with a pin you remove once it's in place, which then results in the tensioner being pushed the right amount against the belt. So that hole is not made to adjust this thing after installation, AFAIK.

I still wonder how the tensioner is supposed to function, I still think the spring is supposed to supply constant pressure through the piston somehow, so that the tensioner constantly pushes a variable/appropriate amount against the timing chain, and should never 'freeze up'. Once it freezes up, unless you can restore its original functioning, I think it's done for. You'd be better off getting a 'proper' manually adjustable one off ebay or such, rather than trying to convert the original 'automatic' tensioner into a manually adjustable one.

 

[Sherlock]

Thank you for your input, probably the more sensible route to take and install a manual one. Cheers.

 

[Malish]

I think there best idea is to buy Kymco tensioner which is 1:1 OEM BMW, Kymco part number 14550-LKF5-E00, price is about 30$

 

[christo]

You may want to have at it with an impact wrench, with the right size, and a good quality, socket. An impact can get things like this undone safer than applying slow force. What we don't want obviously is to deform/strip the plug. Applying a bit of focused heat at the plug in advance could also help. I did not see the video yet. Think I will be going your route as soon as I get some time and proper workspace. For now, I am thinking about just replacing the current mechanical tensioner with a new one, just to bridge the time until I can do it properly.

BMW recommend heat to release the plug with a caveat to avoid melting plastic panels in the vicinity

 

[Sherlock]

New Kymco chain tensioner fitted today. Gt sounds nice and quiet and does seem a little more lively. Might just be me not having been out on it for a few weeks but glad all that panel removal and refitting is over till next time. Reasonable price for the part with free postage from Poland.