'84 K100RT loud engine knock

[tomhughes209]

Hi there

Picked up the bike a week ago. Passed MOT no problems. Made several trips to London and back to Oxford - no problems. Lovely bike.

However at low speeds there is an intermittant knock which feels like it is in the lower right portion of the engine. The 'knock' can be considerable and can defintely be felt. It tends to occur most whe the bike is cold and in low revs. A couple of knocks will be felt, then perhaps a couple more and then it dissapears. It also seems to occur after the bike has been into a corner, over a speed bump or pot hole.

When it first happened I was really alarmed, this is quite a physical knock sound (no griding noise) and cad truely be felt.

I would appreciate any help. I have never owned an engine like this and have onl had it for less than a week.

Thanks in advance.

tom

[JohnL]

Hi Tom

Probably best post on the K series Q & A - this is the airhead section

Hope the knock isn't too expensive!

Regards

John

[nmag]

Sounds like a worn universal joint in the driveshaft.

[steptoe]

is it just the engine that's knocking ? i.e. does it knock when started from cold and then goes away as the engine warms up .....

Most likely to be a worn engine output shaft, the rivets that hold it together are loose. In the end they fail, leaving you with an engine that's next to useless.
Fairly common problem, rectified by BMW on the later 16V models by increasing the amount of rivets. And why if you're buying a K100 (K75 models have a different one piece output shaft) you must hear the engine start from cold, if it's been warmed up beforehand walk away.

[Jaythro]

it's not the end of the world tho

http://www.facebook.com/album.php?aid=1 ... e3cbc6eb62

[RustyGT]

Most likely to be a worn engine output shaft

Is that what it is?
I was starting to think the crank was trying to get out of my high mile K4.
It's horrid at startup.

In the end they fail

With a bang or a whimper?

I'm curious, i'm sure the bike is close to its end.
Now at 185K kms.
I've belted it for the last 50K and it will still do 230KM/H.
But the rattle is getting worse.

[HanMaki47]

Hi Tom,

There can be a little problem between CHAIN TENSIONERS, parts 11 and 20 in picture (link under). Oil pressure is too low, when low rounds in engine. You have to maybe buy new part(s). I had same kind of problems. K100 1983 180k in clock.

http://www.realoem.com/bmw/showparts.do ... g=11&fg=30

Check also parts 10, 17 and 18 (link under). They can be dirty and and 17 can be too worn-out.

http://www.realoem.com/bmw/showparts.do ... g=11&fg=10

HannuM
Finland
Helsinki

[electric_monk]

In the end they fail

With a bang or a whimper?

If it is the output shaft then it will go out with a whimper.You'll just put it into gear one day, and when you let the clutch out you will hear the last rivet snap and you will have no drive.
Hopefully you won't be banked over at low speed when it happens.
The one featured in Jaythro's facebook page is mine, and I have had no trouble with it since the rebuild.