MOTOBRICK.COM
TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: surreybeemer on November 19, 2015, 09:17:22 PM
-
Hello Everyone!!
I am new to this site and this is my first post here. I just picked up my first 1987 BMW k75s with only 10000 miles on it. The bike is super clean and runs super nice. I was just doing some regular maintenance and when I opened up the valve cover to check the clearances, I noticed these pieces sitting next to exhaust timing chain sprocket. Two fell out when I removed the pan and one was still sitting in the shelf underneath the sprocket. There was another chewed up washer thingi that also fell out with this ring thing. Please take a look at the pictures and help ID the part.
Although I am familiar with airheads (have three in my garage) but this is my first K bike so not sure where this belongs too...might be from timing chain chest?
Thanks!!
-
Do you have a Contact Spring (#4) part #11121460811 stuck to either the engine block or engine cover?
-
Yes Tim...there is a spring there. It is attached to the middle journal.
-
greetings surreybeemer...
welcome to motobrick.com...
id be looking for some loonies in there too...
j o
-
Thanks Jo; I guess next is to open up the timing chain chest. Anything to watch out while opening the chain cover? Is there any possibility that this washer thingi could have came up from the sump area? I guess that will next in line if I don't see anything missing in the chain area.
-
I don't see how anything that big could get into the area in which you found it - are you sure it's not a loop of the spring that Tim referred to ... although that wouldn't account for the lump o swarf that accompanied mystery object ... intriguing!
Definitely not a loonie johnny ... they are more coppery coloured!
-
You write that the bike had been running well then you did maintenance and found these scraps, surreybeamer. How long had it been running well in your possession—hours, weeks, months, 10 miles or two thousand miles?
-
What is the part in question made of? In the photo it looks to me like a rubber o-ring. Is it actually broken in three parts, or is it pinched? Is the chewed up stuff the same material as the ring? Judging from the dime in the photo, we are looking at something that is about 20mm in diameter.
Looking at the parts fiches for the K75 engine, there is nothing like what you found used in that part of the engine(timing chain and valve train). There appears to be some sort of plug and what may be an o-ring used in the center of the timing chain cover, but there is no information on them in the parts lists that I have access to.
I am thinking that what you have are the remains of some o-rings that somehow got into one of the covers, got stuck to some oil and were not noticed when the covers were reinstalled. Being soft rubber, they were just chewed up without causing any internal damage and found a resting place out of the way of the moving parts.
-
Thanks for your help folks.
It is not a rubber o ring part. It is solid steel, ring structure, broken at three places. The other metal sheath thing has some sort of green coating on one side of it groove on the other. Looks like the broken steel pieces were riding in the groove of the metal sheath or covered by it.
I just bought the bike and have not ridden it (it is cold here now till spring). The PO was riding it around and bought it sitting in someone's garage for more than ten years. He did some maintenance to revive it, rode it for the summer and then decided to sell. He also owns one k100. The bike started fine and runs well. No abnormal noise or sounds from the engine.
I did the splines lube, front and rear brakes and was taking a look at the valve clearances when I noticed this stuff. I guess I should open the timing chest and then oil pan to see what else is lurking there. Here is a pic of the bike.
-
The fact that the ring is broken perfectly at 120 degree point I think is significant.
-
Update is that I ended up opening the timing chain cover, found another small piece of metal stuck to the cover. Looks like part from the chewed up washer.
Now my question is how do I remove the lower guide without disturbing the timing? It is under strong tension. Should I remove the two bolts holding the chain lifter and slide the rail out? I am also worried about loosing the original timing chain setting, don't want timing to be off. Any suggestions? Thanks!!
-
You must be very unlucky with your work if you gonna make the chain jumping of the sprockets.
You can secure the chain to the sprockets with zip ties or steel wire loops (metod used on 4V's, where
the camshafts have to come off when adjusting the valves).
When undoing the chain tensioner...hold it compressed using Your thumb and index when removing
the screws (ain't that much spring pressure w/o oil pressure).
When remounting you must twist and compress it, probably you must try several times...to get the
ratchet mechanism in correct position.....keep it compressed with a zip tie, snip off before thightning
the screws.
-
What kind of "maintenance" did the previous owner perform to get the bike running, or was it actually repair with replacement parts?
Any scuff marks on the metal surrounding the seal on the inside of the case cover? I'm tending to agree with Mighty Gryph that this debris may have migrated from somewhere else by carelessness in reassembly. I hope you're able to avoid following the March Hare down the rabbit hole.
As rbm notes, the ring's breaking in uniform sequence is interesting—almost like the Motobrick equivalent of a crop circle.
Dropping the oil pan would also seem essential to see if there are any corpses rotting in the goo.
-
Thanks for some good hints guys. I will use the zip tie to secure the chain before I remove the guides. Just want to see if there is anything broken there at the guide pivot.
What kind of "maintenance" did the previous owner perform to get the bike running, or was it actually repair with replacement parts?
The PO did replace the fuel pump and rubber internal parts coz those were deteriorated of age and ethanol. He also cleaned the injectors but nothing in the timing chain area.
Any scuff marks on the metal surrounding the seal on the inside of the case cover?
There are absolutely no marks anywhere in the case or sprockets or any where else. Looks like this was the first time someone opened the timing chest, even green marks on some of the bolts were still there. I am wondering if something from some tool got left behind stuck to something....no idea...so far it is a mystery. I will drop the oil pan tomorrow and will see if there is any new surprises.
-
+1 re rbm's thoughts on the 120 degrees ... almost like a collett of some sorts - although one of the edges looks a little rougher than the other two ?? There should be some kind of prize for best guess before all is revealed !
Nice looking bike btw.
Gio
-
The left piece almost looks like part of a broken nylock locking nut.
-
The prize is a good idea, Gio!
My guess is that it's a broken nose ring worn by the previous owner's Yorkshire terrier and was misplaced during maintenance when the PO was rifling through his pockets looking for the replacement contact spring.
-
EDIT.........about the chain tensioner.
Did miss that it was about a K75.....those have a bit different tensioner.
You have access to release the ratchet mechanism from the small hole in the front off the housing.
It's a stub guide at the rear, so you must pull the tensioner straight out.
If you can't compress the tensioner enough, you must pull it out together with the tensioner rail.
-
Took the little mystery part to the local BMW guru at Shails BMW and he said that he has never seen anything that matches to this mystery part. His guess was that it might be part of some power tool that some mechanic might have used. There were some other BMW enthusiasts who tried to id the part but no one thought it was anything from the bike.
I am going to open the oil sump and take a look at it tomorrow. Just ordered the Haynes manual as well.
You guys are right, there should be a Parts Master Trophy given to the person who ids this part. :bmwsmile
-
Or even the start of one of those collective-input compilations for the off-season ..?
"Daddy ... have you finished working on your bike yet? Half-cousin billy wants to know what you did with the engagement ring he bought for me at the pawn shop just before going back to jail ... you promised him you would keep it safe until the parole hearing"
-
Looks like the ring on the end of the square drive on my rattle gun.
Regards Martin
-
Looks like the ring on the end of the square drive on my rattle gun.
Regards Martin
+1
-
Thanks for your help and suggestions folks. Here is a quick update. I ended up opening the oil pan and there were some more bits from the same part but nothing as big in size as I found in the timing and valve cover area.
Still a mystery from where it all came. I have a hunch that it might have been from some tool used in the factory. The bike is in almost new conditions and inside the engine was super clean as well. I replaced all the fluids, replaced the cracked Z vent hose, cleaned the tank and fuel level sensor. Put everything back together and it runs like a new bike.
I do have some sort of mild rattle just off the idle which is more prominent on a sudden blip of the throttle but nothing if gradually increased. It is less when the bike is fully warmed up. Already checked the monkey nutz, those are as new. So not sure if the rattle is normal or not, experts can chime in. Thanks!!
-
Regarding the rattle you hear coming off idle. Mine does the same thing, but louder and doesn't go away when the bike is warmed up. Seems to peak between 1200 and 2000 rpm. Has done it for the 18,000 miles I've owned it, and probably before that. Doesn't seem To hurt anything, just sounds like crap.
I think it is caused by the anti-backlash gear on the output shaft flopping around because the spring that tensions it is bad. I might go into my engine this winter to see what it looks like.
-
Thanks for the update, surreybeemer! Your engine does a fair job of processing scrap metal.
My giving the bike a little more throttle on takeoff and shifting at slightly higher revs quieted that rattle.