I have a lot of noise coming from the front of the motor. Been gradually getting worse over the past 12 months. Noise is not too bad when cold but very rattly when hot. Pretty sure it's the timing chain.  Anyone got any thoughts on this? Is there anything else I need to consider when doing this?

Cheers

Could just be a stuck tensioner.  I've been into two of my K's, one with 70k miles and one with 110k.    The k100RS with 110k had a worn chain with a bit of side bend, the 75RT with 70k had a near perfect chain compared to a new one.  Neither bike showed any visible wear to the guides or tensioner. 

If you decide to replace anything I would just do the chain.  The tensioner can be cleaned and checked for a plugged oil passage.  The guides will probably last forever.

check the plastic rails

the whole chain kit including rails isn't too exxy  

but worth cleaning up the tensioner whilst in there
 .

According to BMW, the chain/guide should be replaced every 60,000 kms.
Personally, I replace them at 100k.

A bit of history. The old girl has done 157k klm. I bought her with 125k on the odo. There were a couple of receipts for work done after 110k but not for the timing chain.

The chain usually outlasts the guides and tensioner. have a look is about the only way to check. If you need any bits I have heaps of those here just give me a yell and I'll post them down.

I'll just order a chain then. Thanks Rick.
Hope to get this done before the Snowy trip.

What'sthe best stuff to use for a gasket? Permatex Ultra??

At just over 120K (kms) my K100RS' plastic guides had grooves in 'em, all three. I replaced the tensioner as well since I already had a spare. Aside from a debacle where 'Bins sent the wrong length chain in the correct box, it's a pleasant afternoon job in the garage. Charlie saved me by offering up his spare and I replaced his when they sent the correct chain. Be sure to have a front seal and the method/tool to easily do the job. I prefer OEM Drei Bond (or Yama bond/Honda bond/Fuji bond) but any good anaerobic sealant works - stays flexible in the absence of air.

I use permatex RTV blue. Be aware the parcel delivery is slow now as the international flights are chockers with people so not much freight space. I'm still waiting for fork seals that were sent over 2 weeks ago.

+1 on the Permatex RTV blue.

The timing chain kit from Motorworks arrived last week. So that I had a before and after comparison I recorded the motor running at idle. It's at running temperature with the fan cutting in and out as normal. You can definitely hear the noisy chain at the front left corner of the block.


One of the timing cover bolts (6M 20mm) stripped inside the head as I was taking it out. A couple of different ezy-outs failed to remove it so I sacrificed one of Tom's allen keys and welded it to the bolt head....snap!

Apart from an extra 2 or 3 mm, the timing chain looked pretty good. No more bendy than the new one. However the guides were worn especially the shorter side guide rail which had deep grooves (I'll post a pic tomorrow). The tensioner mechanism looks to be working fine. Oil holes were unblocked. Everything went back together without a hitch.

Unfortunately one of the valve cover bolt holes stripped. Picking up a helicoil compatible NuCoil kit in the morning.

Replaced the cover bolt rubber seals while I was at it.

Should be BOTR by lunchtime tomorrow.

Thanks to Tom for allowing me to use his workshop and for his help and ingenuity.

New timing chain and guides has made a big difference to the engine noise. The old girl is purring nicely now with a noticeable increase in engine performance. Better acceleration and quicker throttle responce. I'm expecting a big improvement in fuel consumption.
The guides were very worn.



Helicoil went in but unfortunately after the offending hole was cleaned out after tapping a thread for the coil I found the surrounding metal had cracked. Coil went in anyway and the cover bolt torqued up ok BUT I think the bushing block taking the bolt hole will need to be repaired or replaced. Anyone got any ideas on this.
Anyone have an old motor with a spare camshaft bushing block thingy I can buy?
Cheers

yeah have a couple here mate

but remember they are tunnel bored and as such might have some offset to the camshaft journals

I think sidecar paul posted a fix for this involving a new piece of aluminium across the bridge of the affected piece ...was a neat solution indeed

Yes Charlie it was me. I made two for forum members in America so if you need one Nigel, give me a shout.




In the meantime, I'd put a small hose clamp on the stub to prevent it spreading.

Paul.

Could you make a bar of aluminum with two holes for the mounting studs, and the center hole a press fit over the cracked part?  That would be the simple fix to me as long as the helicoil is doing it's job.

An informative thread thank you Kaptain and contributors...

Please keep us posted on your fuel consumption findings. I found your observations regarding significant gains when setting valve stem clearances particularly interesting. Do you think the improvements were due only to better valve timing (the percentage increase in flow losses due to too big a clearance must surely be minimal?) or did you - I hate even to say it - have cylinder pressure losses due to incomplete sealing of the valves (i.e too small a clearance)? I know that if you had this latter case for any length of time then adjusting the clearances would not have brought you back to the consumption figures you were quoting. I feel I might be getting myself into deep water here - please don't take this the wrong way!

Point-Seven-five wrote:Could you make a bar of aluminum with two holes for the mounting studs, and the center hole a press fit over the cracked part?  That would be the simple fix to me as long as the helicoil is doing it's job.

That sounds like a neat idea. I'll investigate.
Also got a guy looking at the possibility of welding it up but that may be a problem if the piece warps due to the heat.
Paul, thanks for the offer of fabricating a bridge, I'll let you know.

Of course I'd have to say that there must've been a problem with the thread previously. I've had the covers of quite a few times but I've always been very easy when tightening those bolts up. However, how the crack appeared has got me wondering. Was it there to begin with, covered over with oil etc or did it appear when tapping out the hole? The guy that sold me the NuCoil kit seemed to know what he was talking about and he suggested I should be able to just tap out the hole as is with out drilling the old threads out. I feel this may have been a mistake as that may have placed greater stress on the surrounding metal. I think if I were to do that again I would drill it out and brace it with a hose clamp re Paul suggestion. The good thing is I can see there's a remedy.

Rawdon. Your reference to valve clearances was probably regarding my post on the recent Fuel consumption thread. The other symptoms I referred to in that post relate to a problem I had back in 2014 with my engine cutting out (Engine cutout on throttle off and solution here). What I found was that the exhaust valve clearances on the front 3 pots were far too tight and undoubtedly got worse once the engine reached operating temp. Most likely the valves were not fully closing as you suggested. I also had a bit of backfiring sounding similar to a rifle going off. What I do know is that once the exhaust valve clearances were brought back into spec, the symptoms of engine failure instantly disappeared and my fuel consumption fell dramatically. There's no "maybe" about that. I keep meticulous fuel and service records so it's well documented.

Rawdonball wrote:I know that if you had this latter case for any length of time then adjusting the clearances would not have brought you back to the consumption figures you were quoting

I'm interested to hear your thoughts. Can you elaborate on this old mate?  Cheers

Kaptain, with the bearing cap off, cut a strip of 3mm aluminum and put a press fit hole in the center.  Press it onto the cap and use the holes in the cap as guides for the other two holes in the strip.  I would figure under an hour in a shade tree machine shop and about a buck in material cost.

All the dimensions you need Nigel for the replacement cap

Thanks Rick. That's a big help. Cheers.

Would there be any advantage in having that bridge hole an interference fit? Perhaps help keep the bridge thread together. If you put the cap in the fridge and the Ali strip in the sun then it will slip over the cap and shrink onto it. Anyone see an issue with that???

yeah I see an issue mate ....

once the metal is gone from the thread hole ...there is no going back, no amount of retapping will achieve the same tensile strength of the original

keep in mind that its a cam cover fixing ...and shouldn't be under too much stress ....but as always we like to go a little too firm with the tighten up process

good thought but naaa    I wouldn't go there

Rawdonball wrote:I know that if you had this latter case for any length of time then adjusting the clearances would not have brought you back to the consumption figures you were quoting

I'm interested to hear your thoughts. Can you elaborate on this old mate?  Cheers

Hey Kaptain, thanks for posting those links to other threads as regards your fuel consumption and valve clearance issues - I thought I had read all your posts!

When I said a problem resulting from valves clearances being too small, was unlikely to be fully rectified by adjustment only if it had been around for a while - this was due to me thinking that exhaust valves that fail to close fully would soon burn/overheat. In this case restoration of good sealing and hence engine performance would need valve and valve seat sealing area reconditioning. The theory (which I've only read about recently) is that a significant proportion of the heat loss from a valve, is via conduction through the valve seat while the valve is closed - if valve isn't closing properly you get overheating as well as the destructive action of burning gas being forced between the sealing surfaces. It would be interesting to see how the cylinder compression readings for those with previously tight valve clearances compare with the cylinder which had the ok valve clearances.

Your expose' on the engine cut out on throttle off was fascinating and has given me my latest 'pet theory' - if it was caused by compression related problems from valve clearances being too small then no wonder it seemed intermittent (and likewise your fuel consumption issue). All down to the fact that the instances in which these problems were noticed were dependent on many factors including the way you had been riding, the ambient temperature conditions, the fuel you were using, the load you were carrying etc etc....

Anyway - while i'm enjoying my theorizing I hope you are enjoying your silent timing chain. How about posting another video clip for 'after the fix' so the rest of us can appreciate the K music?

I'll post a video next week. Off to the Snowy Run and then back up North for a few days. Won't be back to end of next week.
Your theory sounds interesting Rawdon. Poorly seating valves might explain a few things possibly, like a slight revving at idle and a tendency to run a little hot. What do you think? That's been bugging me for quite a while and I've not been able to put my finger on it.
Will post fuel consumption figures (with new chain) after this weekend and do a compression test.
Cheers

K75cster wrote:Would there be any advantage in having that bridge hole an interference fit? Perhaps help keep the bridge thread together. If you put the cap in the fridge and the Ali strip in the sun then it will slip over the cap and shrink onto it. Anyone see an issue with that???

Another potential issue is the operating temperature of the engine. Depending on the composition of the iron/steel and the aluminium alloy, the aluminium thermal expansion is at least 50% greater than the iron/steel.
At operating temperature, I think the interference wouldn't do too much interfering. 

Bill

I think the cam bearing cap is an aluminum die casting alloy and will have a similar thermal expansion to a strip of aluminum.

Point-Seven-five wrote:I think the cam bearing cap is an aluminum die casting alloy and will have a similar thermal expansion to a strip of aluminum.

Brain fade - too used to thinking of all the cast iron engines I've worked on.

Thanks for the correction.

Bill