• Welcome Guest! If you are already a member of the BMW MOA, please log in to the forum in the upper right hand corner of this page. Check "Remember Me?" if you wish to stay logged in.

    We hope you enjoy the excellent technical knowledge, event information and discussions that the BMWMOA forum provides. Why not take the time to join the club, so you can enjoy posting on the forum, the club magazine, and all of the discounts and benefits the BMWMOA offers?

    Want to read the MOA monthly magazine for free? Take a 3-month test ride of the magazine; check here for details.

  • NOTE. Some content will be hidden from you. If you want to view all content, you must register for the forum if you are not a member, or if a member, you must be logged in.

1994 K75S High-pitched chirping noise when hot?

Update

Just got back from the BMW dealer where I managed to get a meter of the correct 8x13 fuel hose which I will cut to length and begin installing this afternoon. I also got the two fuel injector nipple caps (one of the old ones was split, btw---probably wasn't helping my situation) and two more BMW hose clamps to replace the ear clamps that were on the FPR side of things.

Unfortunately, the vacuum line and crankcase breather hose were out of stock so they are now ordered. Hope to have in hand either this Friday or else next Monday so the earliest I'll be back on the road is about a week from now.
 
Last edited:
FPR good but further airbox woes

I took the FPR off (by removing the nut and washer holding it in the bracket; much easier than trying to rmove the whole shebang) and conducted a simple test as outlined in my Haynes Manual.

By sucking on the vacuum hose I am now fairly confident that the FPR is still good as there were no leaks evident.:whistle

So if the ordered items arrive tomorrow I hope to have it all put back together by sundown. I'll use plenty of Back To Black or Armour All to lubricate the air filter and housing so my struggle might be alleviated somewhat.

One strange thing about the airbox, though. When I removed the two screws on top that hold the airflow meter inside I later realized that that wasn't necessary and probably only made the situation worse. No matter how many times I line up the screws and holes in the airflow meter the screws only go in partially now. They come to a dead stop about halfway in which creates a small gap between the screw heads and the plastic airbox top. Didn't strip the screws at all so am really confounded by this. I don't suppose anyone has any ideas on this but it never hurts to inquire.

If that tiny gap is going to create a problem I might have to put some sort of sealant
(hot glue would be easy) on the top to prevent airflow bypassing the air filter.
 
If that tiny gap is going to create a problem I might have to put some sort of sealant
(hot glue would be easy) on the top to prevent airflow bypassing the air filter.



DO NOT PUT ANY SEALANT ON THOSE SCREWS!!

Figure out what the problem is and fix it correctly. I've got to go out for a few hours, but when I get back this afternoon, I'll look at one of my spare airboxes and see what the problem could be.




:dance:dance:dance
 
One strange thing about the airbox, though. When I removed the two screws on top that hold the airflow meter inside I later realized that that wasn't necessary and probably only made the situation worse. No matter how many times I line up the screws and holes in the airflow meter the screws only go in partially now. They come to a dead stop about halfway in which creates a small gap between the screw heads and the plastic airbox top. Didn't strip the screws at all so am really confounded by this. I don't suppose anyone has any ideas on this but it never hurts to inquire.

If that tiny gap is going to create a problem I might have to put some sort of sealant
(hot glue would be easy) on the top to prevent airflow bypassing the air filter.

Those screws are threaded their entire length. The holes that they screw into on the air flow meter are through holes. The only other explanation than Don's for them not tightening up all the way, is that you cross threaded them or they are the wrong length bolts.:dunno


air box bolt.jpg





:dance:dance:dance
 
Last edited:
See: http://www.realoem.com/bmw/showparts.do?model=0572&mospid=51745&btnr=13_0518&hg=13&fg=71 - Under Fuel-System, Intake Muffler. There are bushings in the rubber grommets that go through the plastic cover. Bet'cha your bushings are sitting on top of the AFM, or have scurried like rats to the darkest corner of your garage.

Without them the screws will never tighten up.. PN 11 - X2.

Trouble is, those bushings are there right there where they should be. Rubber grommets that they fit into, too. I didn't change anything from when I took the airbox off to when I tried to put those two screws back in place. I tried about a dozen times alteady but they're still not 100% right, only about 90 or 95% IMO. I do have to wrestle with the boxtop and the airflow sensor at the same time to get all the holes to line up, though.

I'll take them out and try again and again and take photos if I can't get them in properly. They shouldn't be sticking out at all; that airbox top will be hard enough to get back in place even if they were all in! Thanks for coming to the rescue once again, guys (bad event# K75S 00024,334,284,560,063,018,456,977);)
 
Trouble is, those bushings are there right there where they should be. Rubber grommets that they fit into, too. I didn't change anything from when I took the airbox off to when I tried to put those two screws back in place. I tried about a dozen times alteady but they're still not 100% right, only about 90 or 95% IMO. I do have to wrestle with the boxtop and the airflow sensor at the same time to get all the holes to line up, though.

I'll take them out and try again and again and take photos if I can't get them in properly. They shouldn't be sticking out at all; that airbox top will be hard enough to get back in place even if they were all in! Thanks for coming to the rescue once again, guys (bad event# K75S 00024,334,284,560,063,018,456,977);)

Chase the holes in the air flow meter with a tap and clean up the threads on the screws with a wire brush. Use just a bare hint of anti-seize on the screws when you reassemble it.
 
And screw them in all the way with your fingers while holding the air flow meter up against the inside of the air box. If you don't hold the meter up and try to put the bolts in with a wrench,with the meter hanging at an angle, you WILL cross thread it.


:dance:dance:dance
 
What size tap?

Guess I must need a tap to clean up the threads as suggested. Are those M5 screws or something different?

They look OK but it's entirely possible that I messed up the threads on the airflow meter side.

Ironically, the parts on back order qrrived this morning so I am on my way to pick them up soon. I'll stop at Harbor Freight or Ace Hardware on the way back and try to get the right size tap if I can find one. Never used one before so if there's anything I should know first please repond as soon as possible.

I'll try to hold off on reinstalling the airbox until the last minute so I can figure out how to best accomplish the tapping out.

I'll also pick up two new filister head screws at BMW, too (can't hurt).

Thanks again, ---Jeff
 
Got everything including two new airflow meter screws as well as an M6 by 1.0 pitch tap bit.

Will start work after lunch and see if I can remedy any cross-threading that occured.
 
Airbox problem sorted

Thanks to 42906 and Lee's suggestions the airbox screws are now correctly in place;

I had cross-threaded them earlier---if I ever have to undo them again I will make sure they are perfectly perpendicular to the holes before screwing them in. Some Alu-Slip on the threads helped out nicely, too.

I took great pains to carefully clean any bits of Alu-Slip residue inside and outside the box, too (don't want any anti-sieze running around inside, do we?).

Got the FPR with new vacuum hose and fuel rail line installed along with the new OEM crankcase breather hose (with the clamp screws facing portside so I can change it out easily whenever need be) now it's on to install the two fuel tank hoses and reinstall the air filter before a storm whips up here (the bike is parked outside and the winds are beginning to kick up).

More updates later.
 
No more chirping from now on

After a couple other brief but intense rides over the last day or two I am confident that my screeching fuel pump situation is now over.

When I filled the tank with Chevron unleaded today there was no "whoosh" from the previous vacuum condition that was probably indicative of the blocked vent---for the very first time in my memory---it had become so commonplace I just assumed that it was standard behavior for fuel-injected systems!

With all new fuel and vacuum hoses, new crankcase breather hose, new FI nipple caps, new ABS relay and a new Westco battery my bike is running better and smoother than I've ever experienced. I suppose that when I bought it in Georgia in October of 2008 some of these problems were already underway (two cracked rubber pieces at least).

I am personally amazed that I failed to detect these simple problems despite my fairly extensive renovation about three years ago---which only goes to show one that it often pays to seek out the advice of the many generous experts here.

Unless I am extremely unlucky or inept I now consider this annoying and noisy problem solved. A sincere "thank you!" to all that responded.

What a joy to ride such a smooth Beemer now!:dance:dance:dance:
 
I spoke a bit too soon

After a couple other brief but intense rides over the last day or two I am confident that my screeching fuel pump situation is now over.

Unless I am extremely unlucky or inept I now consider this annoying and noisy problem solved.

Ah, well, the screeching is back once again. Two different BMW mechanics have also confirmed my suspicions that the fuel pressure regulator is going bad and making all the racket. While not nearly as often or as bad as before it still screeches and chirps when the bike gets hot in traffic or idling along on a hot day.

At least the fuel return vent is no longer blocked so that is no longer the cause. Apparently bikes that have sat for a long time with fuel inside the FPR and or fuel pump get gunked up and that is probably why the FPR is acting up.

So now my question is:

Has anyone here actually used one of those Napa (or equivalent) FPRs that look just like the OEM FPR but are $72 instead of $152?

Very curious to hear of others experiences in regards to replacing their FPR on an early K.
 
Ah, well, the screeching is back once again. Two different BMW mechanics have also confirmed my suspicions that the fuel pressure regulator is going bad and making all the racket. While not nearly as often or as bad as before it still screeches and chirps when the bike gets hot in traffic or idling along on a hot day.

At least the fuel return vent is no longer blocked so that is no longer the cause. Apparently bikes that have sat for a long time with fuel inside the FPR and or fuel pump get gunked up and that is probably why the FPR is acting up.

So now my question is:

Has anyone here actually used one of those Napa (or equivalent) FPRs that look just like the OEM FPR but are $72 instead of $152?

Very curious to hear of others experiences in regards to replacing their FPR on an early K.

Given the challenges you've had lately, why would you want to add variables to an already complex issue with a "jobber" part replacement? I like to keep the unknown variables to a minimum and I do that by using OEM replacement parts as much as possible. This habit of mine keeps my K75S as close to stock as BMW intented it to be and my beamer bike retains its reputation and value. :beer
 
Valid enough point there, Ghyber and a path I would normally take as I am a fan of OEM parts more and more these days. It's just that I've spent so much in the last couple of weeks on getting new wheel bearings in, fork seals replaced, new fork boots and other work done by real BMW mechanics that I'm considering a generic version to tide me over.

The generics that I have seen look identical to BMWs and have nearly identical specs (37psi instead of 36psi) and are slightly less than half the cost.
This is what I find tempting hence my query. But if I can round up enough funds soon I may play it safe and buy the $152 model after all; at least it's something that I can replace myself.

Since it is now screeching whenever the bike gets warmed up and I'm riding in slow traffic I think I will make a decision and get to work on it pretty soon (that's why someone invented credit cards).

Thanks for your input and while I may very well go your suggested route I would still like to hear from anyone who has used a generic FPR at one point or another just to get an idea of how well they work in a K bike.
 
Hello Zagando,

Knowledge is power and you are right to seek for alternatives for many different reasons: availability, quality and costs are but a few that come to mind.

You should see the cost of BMW motorcycle parts up here in Canada. Most riders here have large slits in their back, that's where take gave up one of their kidneys to pay for the cost of the OEM part + 30% - 40% for the dealer plus the provincial and federal taxes on top to pay for the collusion and corrupt elected officials.

Take care,

Ghyber
 
Informal survey; Use a non-OEM fuel pressure regulator?

I can well imagine; I will consider myself lucky in light of that, Ghyber. Thanks again.

Whichever way I go I'll certainly follow up here with an installation report; hoping to rustle up a review or two of the generic FPR substitution soon in case anyone following this has used one.
 
Chances are - BMW didn't make the FPR, and it was designed by Bosch to use with their injectors and their L-Jetronic ECU. And I'd be willing to bet it was an off-the-shelf part that was used on a car of that era.. I doubt very much if Bosch saw enough volume in K bikes to design a specific part for the FI system.

The 36PSI vs 37PSI probably means different people rounding up or down from the "Bar" measurement used in the metric measuring system.. I doubt very much if it's significant.

Right now we have people running Ford - Bosch injectors on their K bikes, Ford fuel pumps, and on some K's Ford O2 sensors. I'd bet that like the sparkplugs, if you dig around enough in BMWs car models of that era, you'll find the same identical FPR being used (like the K75 sparkplugs - used on the E30/M3 engine, or the airhead voltage regulator - used on the 2002 car, or the airhead oil pressure sender - same source..)

Sounds to me like an interesting experiment. Worst that could happen is it doesn't work and you're out the cost of the generic FPR. I can't see the FPR blowing up or causing other leaks if it's physically identical to the one on the bike.

Let us know how it works out..
 
Progress of sorts

Lots of good points there, Don and in my search for a replacement I heard that a VW Super Beetle 2.5 bar FPR should work. I also searched through pages and pages of Bosch FPRs on ebay but 98% of them were different enough with threaded fittings and the tops fitted with large O-rings and vents that I was wary of trying any of those.

I did run accross a Bosch FPR for Jaguars that looked the part but at around $90 I began to think why take the chance in the first place?

Now I have a line of a couple of used K75 FPRs and I'll know soon if they'll be available and of good working order. Will follow up soon.
 
Back
Top