Prior to removing  my timing chain I found I could press the tensioner downwards, which, according to the forum  is worn and needs replacing.

The chain was showing sideways wear but not on its length.. none of the guides were worn.,after 60k miles.

The K75 unit has a facility to hold oil pressure and thus tension on the chain via a ball bearing and spring in its spigot in the oilway.

The k100 tensioner does not have any obvious way of holding oil pressure with the engine stationary that I can see.

If the engine oil pressure has dissapated naturally with the engine stopped, then I should be able to press down against the internal tensioner spring.

Should the oil pressure remain constant , even with the engine off ?

If it should, then either my tensioner is duff, or my engine oil pressure relief valve may be suspect.

I would love to fit the k75 tensioner with its back pressure valve, which also helps to prevent overloading the rachet mechanism

I wonder whether the k75 unit spigot would fit in to the recess on the k100, 

or , to be adventurous, fit the k75  unit minus its spigot , and cut an access hole in the timing cover and use a small lever to lift the rachet mechanism manually to take up any wear on the chain.

Fabricate a small inspection plate and tri bond to seal it.

Anyone else been able to push down on their tensioner on their k100, and what did they do to cure it..

Anyways, spare k100 tensioner ordered. 

Then I have another problem.

In order to see if the second unit is holding its pressure and tension, I have to remove the cover I have just fitted with its new pain in the ass to fit teflon seal..

Wished I had kept the old type seal in the cover until I was satisfied with the tensioner



Bob

The K75 unit has a facility to hold oil pressure and thus tension on the chain via a ball bearing and spring in its spigot in the oilway.

The k100 tensioner does not have any obvious way of holding oil pressure with the engine stationary that I can see.

Where do you get this information Bob.

Hi Rick,

My information is only from what I can see from looking at both types of tensioner.

The k75 unit shows the ball bearing and I presume a return spring ,in the rear spigot, but I cannot see how the k100 unit will hold pressure, unless it depends on the engine holding oil pressure whilst the engine is shut off.

I am not a trained mechanic , so if someone can explain how the k100 unit does hold pressure,  with the engine shut off,  even for long periods, then as mine could be pressed down ,  my unit must be faulty.

As I could press down on my tensioner , then I presume with a slight drop of oil pressure,  and  no obvious way 
 ( to me at least ) of preventing a drop of pressure, then I am compressing the spring . 

It then begs the question, why did BMW change the design , the k75 unit looks far superior.

The rachet design together with the non return valve is better, but there are thousands of k100,s running 
perfectly happy ,with the early tensioner,   

Bob

I have found a forum post on this subject back in 2013

This a reply from " TheMason" 

What year is your bike Brickee? Early K cam chain tensioners didn't have the rachet mechanism in them, relying only on oil pressure. You can replace the early part with the later part. It is a direct swap. Be careful you don't skip timing turning a lose cam chain, not that I know anything about that mind you ..... Just check the timing marks carefully before going forward. Just saying .....................



This a link to BMW OE catalogue showing a timing cover with an inspection hole .

I wonder why 

Possibly to inspect chain or tensioner  ?

http://www.realoem.com/bmw/enUS/showparts?id=0516-USA-09-1989-K589-BMW-K_100_LT_87_0506,0516_&diagId=11_4679

this link shows the new superceded  tensioner part number which I presume is the rachet type 

http://www.realoem.com/bmw/enUS/partxref?q=11311460834

Does this mean BMW realised the need to hold oil pressure in the tensioner ?

I presume the price of £150  I was quoted was for the k75 type tensioner

I will find a k75 tensioner and fit it.


Bob

Motoworks uk have them in stock for £15.00

will arrive friday. 

Part number shows for k75 and all k1100 models

Bob

The tension after the engine stops is not held by residual oil pressure as there is none. The pressure is from a small spring and a ratchet mechanism to prevent the tensioner from collapsing completely back into itself and letting the chain totally slack on its return run. The ratchet mechanism is different on the K100 and K75 but AFAIK the K1100 has the same tensioner as the K100 at least any K1100 I have pulled down does.
The K100 tensioner has a circular array of teeth where the K75 has a straight forward ratchet on the side of the piston of the tensioner.

Would be interesting to know why  BMW decided to change the design for the k75, given the number of K100 built.

 Were there so many complaints from owners through the dealers,  to force a change of design.

I will fit the k75 unit when it arrives

Do the BMW car tensioners have a back pressure check valve.

At least this lay up is giving me the time to do other jobs that needed doing

bob

They changed the gear type to straight cut on the crank to balance output shaft because they said the firing pulses would wreck spiral gears and the rubbers in a rubbered balance shaft, I'd bet a bob or two on it being tied to the firing pulses, they have decided to make the 75 one stronger perhaps.

I’ve just replaced my chain and guides and could press down on the tensioner at certain points during the turning of the crank but only a small amount. I could not push it all the way in. If you take the tensioner off and turn the piston in all the way then release a bit, you should not be able to compress the piston. Ratchet mechanism working correctly. If you can compress and expand just against spring pressure then the ratchet is not working.
Engine oil pressure while running will take up the small amount of movement that the ratchet cannot when the engine is not running.
My chain showed a decent amount of bow and the lower and side guides had wear ridges after 87k kms. The new design side guide needs 2 longer hex heads than the early type. I used 2 from the ignition pick up cover. I cannot see any advantage to using a k75 tensioner if your ratchet works as above and you have oil pressure.

Bob,
I cut down a plastic bottle to make a seal guide for the new type seal. Push the tube through the seal and as the cover is fitted the tube is pushed out forwards. The lip of the seal then relaxes back onto the crank turning surface.
regards john

There might be another reason for the change of design for the tensioner.

After an oil change, if the mechanic fires the motor straight away, without  disconnecting the fuel pump connector
 
first, then perhaps the original tensioner without the ability to hold its pressure and tension on the chain, could 

jump .

I know this from experience.

Having completed a rear main seal job, my motor was shut off for best part of a month.

I decided to change the oil, but stupidly forgot to disconnect the fuel pump connector, prime the system via the starter and then fire the motor up.

The noise from the timing cover was not pleasant, but did quieten down fairly quickly.

Whilst riding, i could hear a droning from the front of the bike  ,

hence the timing chain removal.

If the original tensioner had a back pressure valve like the k75 has, I would refit it.

Nobbylon, 

I will be scouring the chemist with my vernier looking for a suitable pill bottle...looking forward to that.

I found one for the rear main seal in the house,but not this time.

Bob

I will share a trick I learned some time ago about the teflon seals and getting them on.
They can stretch quite a lot and return to the original size fairly well so oil them up and run your finger round and round them on the inside puting outward pressure so they slowly expand then while expanded you can slip them on and they then contract onto the shaft.
Takes a bit of practice when you also need to co-ordinate getting the sealant on as well but it can be done.

Thanks for the tip Rick.

With all the work nearly done, she will be good for many a year .

Taking her to Germany next year so  its a good time to get all the necessary age related stuff out of the way.

Bob