Hello again,

I managed to get my fuel pump working again - not too sure how. I'm glad it responded to my efforts.

I tried to start up the bike. It wouldn't! I reckon the fuel injectors may be to blame. I put them back with new o rings at the weekend. I gave them a clean but there had been water in the system and perhaps there's rust in them? I have added an injector cleaner to the fuel - maybe that will help.

There is an unidentified noise when the engine turns over. It's not a "knocking" sound and there was no rumble through the footrests when I had it running prior to the work I have started.

I would say it sounds a bit like an electric drill - when the bit is biting a hard wall. I don't think it's the bearings and am wondering if it could be to do with the timing chain?

Well, any thoughts on this would be welcome.

Cheers,
Neal

Neal,

I heard so many noisy engines (mine too), and most of them have a grinding sound coming from the back of the engine. My brother had a loud knocking coming from his engine too.
In most of the cases, the culprit is (or was) the alternator.
Just remove your alternator and try running the engine without it.
It's amazing how the noise can travel.

Hi Bert,
That sounds interesting - will check it out.
Regards,
Neal

What was the result of your experiment, Neal?

Hi,
I haven't been able to start the bike to really check it out yet. Little time to work on it of late too.
Anyhow, the problem seems to be the injectors. The fuel is arriving underpressure to the rail but the infectors are blocked - or some of them at least.
I'd like to faith heal them but to no avail as yet.
They cost £25 each second hand from Motorworks so that may be the next stop if my laying on of hands fails.
Cheers,
Neal

the ford injecters in the inbmwr tec were about half the price of new amasing difference

Hello,
Im new here,come from Poland. My K 100 bike is 1985 year, and about 125 000 km.First I would like to say hello.

I found this topic like my similiar problem.
My bike produce strange noise -rattling or sth like that - but only when i shift down gear - and no accelerate (slowing down=braking(?) using a gearbox-hope you know what i mean) When i drive for example on 3rd, and deaccelerate i hear this noise. Under 2000 rpm there is silence-no rattling. Im not sure where it comes from-front or rear of engine.
When i rev up engine on neutral is ok, and when its rev down, i can hear this rattling also but shorter and quietly.
What can it be ? Alternator bearing? Or sth with output shaft ? Or maby chain tensioner ? But im not so sure it comse from front, and on idle is quiet, and when accelerating-also quiet.

forgive me my english

Thanks
Cristoff

Neal Cooper wrote:Hi,
I haven't been able to start the bike to really check it out yet. Little time to work on it of late too.
Anyhow, the problem seems to be the injectors. The fuel is arriving underpressure to the rail but the infectors are blocked - or some of them at least.
I'd like to faith heal them but to no avail as yet.
They cost £25 each second hand from Motorworks so that may be the next stop if my laying on of hands fails.
Cheers,
Neal

Hi Neal

I bought and am using with no problem a set of 4 refurbished ford injectors ($85 +shipping). Seems they are same as the Bosch 280-150-210 /211

http://stores.shop.ebay.com/Mr-Injector__W0QQ_sidZ68034504?_nkw=k100


Roy

I use exactly the same without any issues.

Hi,
I take out alternator, start engine - and there is same noise.
When accelerating no rattle, but when deaccelerating (revs down) on any gear im hearing this strange noise. Im almost sure now that it comes from rear part of engine.

Any sugestion from where this rattle it is coming from ?

Thanks

Cristoff

Cristoff,

I had a problem of rattling noise on my bike too. I could only hear it when I was riding but it was difficult to pin point where it was coming from.

After a week I found that the rattling was coming from the one way valve on the return gas line in the tank. The ball is bouncing on the seat of the valve and the noise seems to travel all over the bike.

It could be your problem as when accelerating, less gas come back to the tank, and when decelerating, all the flow sent by the gas pump returns to the tank. The fact that you hear it when decelerating and only over 2000rpm may prove that this is gas related. Here is the clue:

When decelerating (shutting off the throttle), the idle switch (at the back of the fuel injector ramp) is contacted, and the FI computer shuts down the injectors until the engine reaches (down) 2000 rpm.

I doubt that the rattle comes from the injectors as they stop working when decelerating.

Do you hear the noise when decelerating and not totally shutting off the throttle? Maybe you should disconnect the idle switch to test it.

Just an idea.

Bert

Hi Cristoff, my bike had the same noise Bert mentioned and caused by the same non-return valve on the low pressure return fuel line. First time I noticed it was decelerating down a steep hill and previously no hint of a problem.

Mine was more noticeable when the bike was warm but long story short a new valve (minus the spring) fixed the problem. Definitely hard to track down where the noise was coming from but opening the tank made it louder so that was the clue.

Regards,

Phil

In fact in 1986 BMW modified the design of the gas tank to remove this noisy non-return valve. The return line is now internally going to the top of the tank preventing the gas to drip when you remove the return hose.
On my bike, I first removed the spring inside the valve but that didn't solve the problem. I then removed the ball too.

Hi again,
I made test - drive, deaccelerate, when i hear noise, i just turn off ignition system,(i hope fuel pump then also) and noise still was the same. So i think it is NOT valve in return fuel pipe.

I think noise comes from right side back of ongine(alternator/flywheel side). (Took a plastic pipe, puting many places on engine, and hearing.)

This what i read on forum, seems that alternator bearings is the problem, or sth in output shaft.
Is needed to take out crankshaft to take out output shaft ? Or same to change alternator bearings?
Or only required take out gearbox and driveshaft ?
Maby someone can give me clues what is needed to do, to check alternator bearings, and outputshaft bearings?

Thanks is advance

regards
Cristoff

Check this page and you will have plenty of information: K100 rebuild

Thanks a lot ! Ill wait till winter, and start disassembling.

Hi again! I decide not waiting till winter.
And i disassemble my bike right now.
Bearings on auxiliary drive shaft and starter clutch components looks fine on first sight (in my opinion). All splines are ok also.
Still dont know what producing that strange rattling noise when engine is revs down. That noise coming from alternator side.
I was surprised why there is no bearing on end of starter shaft in engine housing ? On alternator end shaft there is a bearing in engine housing.
I give up for today with disassembling into pieces the auxiliiiary drive shaft, but you can see it on video, like my gearbox.

Names of things by Haynes Manual

Any sugestion? What can make this ralling noise?

VIDEOS:

gearbox

auxiliary drive shaft

See also pictures:
Pictures of k100 rs disassemble gearbox/bellhousing
Regards
Cristoff

My K75 had a terrible rumbling noise. It seemed worse when cold and became less obtrusive as she warmed up. I got a large screwdriver with a ling blade and used it as a stethoscope. I helt the handle end to my ear and probed around the entire engine till I found where the rumbling was loudest. It was the alternator! As Bert says it's amazing how that alternator noise was being transmitted around the entire engine casing.

Anyways I successfully bid for a used alternator off e-bay for about £13. The intention was to fit it in the K75 whilst I re-built the original alternator. Once swapped the difference was amazing. I was now getting a noce whine from the engine rather than a loud rumbling.

I noticed on the faulty alternator that the shaft end was very lose in its bearing. I have since stripped it down and the bearing is very easy to replace. they are available from MotorWorks here in the UK for about £7.

http://www.motorworks.co.uk/bmw/products/product.php?f=i&code=BA_15_40_JA_10&shnew=New&model=K75%2F100%2F1100&shnewcode=15&part=Electrics&sub_part=Charging+(alternator)&modelcode=40&partcode=JA&source_code=BA_15_40_JA_10&header_text=&header_text_image=0

Good on you for diagnosing that, and getting an extremely good value replacement and now having a spare alternator.
Regards,
K-BIKE

At my bike it is NOT alternator, coz i was driving without it, and there was same strange noise sound.
I suppose auxiliary shaft bearings (which looks more or less ok) or the engine output shaft.
I think ill take it out today, then i can see sth. is vrong to outputshaft or not.
Dunno, maby gearbox is cheating me

Cheers

Hi there again ! Hope im not spaming this topic. After I change all bearings on auxiliary alternator shaft, there is no special change. Strange noise still coming, when deaccelerate.
I suppose that maby it is camshaft chain, tensioner or so, that giving me strange rattle noise when deaccelerate.
Soon, ill look on chain and see what about it. Hope there is nothing bad on auxiliary drive shaft goin to gearbox, and hope nothing bad on rod bearings.
Cristoff

How many miles or kms do you have on your bike?
The noise could come from the tensioner spring between the absorber and the idle gear (output shaft) or worst, the rivets on the output shaft being loose.
Normally, if the rivets are loose, people are replacing the output shaft and it is expensive. Somewhere, I have seen that you can buy replacement rivets. It maybe posted on this forum but I don't remember where.

In order to check the output shaft, the engine has to be removed from the bike.

Bert

Bike had about 122000 km, much for motobike, but not much for k100. I bought it with this distance, but it looks preety good, good serviced(every nut or bolt are lubricated cuprum, or loctite when necesery) no problem hot or cold whatever, except this strange noise coming i dont know now from where, but only when deaccelerate. Maby it had first timing chain, tensioners, and its wear- need to check it.
When i take out gearbox, and bell house, there was nice view to crankshaft coghwheel. There was NO play between crankshaft and outputshaft when i turning flywheel (with output shaft of course). So i hope rivets are ok.
You mean this spring ? Spring on idle gear.
Ill open camshaft case, look on timing chain, its tensioners, if this will not help me, ill took out the output shaft.
Thanks a lot