• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

  • Beginning April 1st, and running through April 30th, there is a new 2024 BMW MOA Election discussion area within The Club section of the forum. Within this forum area is also a sticky post that provides the ground rules for participating in the Election forum area. Also, the candidates statements are provided. Please read before joining the conversation, because the rules are very specific to maintain civility.

    The Election forum is here: Election Forum

Running lean, getting awful mileage; not sure how to fix. 1994 K75

So tonight I did another one over of a couple things and when I had the spark plugs removed I did a compression test.

Cyl 1 = 180psi
Cyl 2 = 150psi
Cyl 3 = 160psi

Not sure what symptoms that would attribute to but I know that the separation is too much. Next i'll be checking the valves.
 
Last edited:
deilenberger said:
Sounds like a valve adjustment may be overdue then.
Click to expand...

When you say overdue, what is the recommended interval for checking/adjusting?

Mine were adjusted by the dealer less than 10,000 miles ago. I didn't think the 2-valves motors needed to be checked so soon.

Edit: Nevermind. Found a copy of the maintenance schedule and looks like 8-12k miles is the interval. (http://cdn-5.psndealer.com/e2/dealersite/images/bmw-ok/K75%20K100%20K1100%20K1.pdf)

Hopefully it is just the valves.
 
If one of the exhaust valves is tight (tighter than around .007") it will cause the exhaust to not fully close. That will put backpressure in the cylinder not allowing a full incoming air/fuel charge which results in a lean condition.

If you have to adjust any, set the intakes toward the tight side of tolerances and the exhaust at the loose end of the tolerance.





:dance:dance:dance
 
There is a great Youtube video on how to do the valves on a K75, if you have the two special tools (there are aftermarket versions on IBMWR and eBay in the $25 range) and are able to exchange the shims it looks pretty easy.

As for the dealers doing service, well, it never hurts to double check the work :)
 
Ted said:
There is a great Youtube video on how to do the valves on a K75, if you have the two special tools (there are aftermarket versions on IBMWR and eBay in the $25 range) and are able to exchange the shims it looks pretty easy.

As for the dealers doing service, well, it never hurts to double check the work :)
Click to expand...

Thanks Ted. I actually just paid for a set from Kenneth. Rather than take my bike in I intend to do it myself. It is entirely too easy to check the valves so I figured what's another 30mins to swap them out

98lee said:
From two years ago:

Hi Lee
Yes, I have BMW "K" engine Valve Adj tools available for the 2 valve "K" engine.
The 2 Pieces are made from 3/16” Laser cut steel. Working contours are identical to factory tools. Tools are new. Tools come w/ instruction sheet.
$27 S/H included.
Clutch pilots for K's are available also. New, from steel
$18 S/H included.
“Pay Pal” to Polepenhollow, Cashiers Checks, Money Orders and Personal Checks accepted.
I ship as soon as Pay Pal is posted or the check arrives.

Thanks, Good Luck and Good Riding.
Kenneth Lively
318 S Hart St
Palatine Il 60067

polepenhollow@yahoo.com
847-561-8555
Click to expand...

Thanks Lee!

roncooper said:
8-12,000 seems conservative. At what interval do they usually need adjustment?
Click to expand...

That's what I thought too but with my compression reading i'm really hoping that it is the valves needing adjusting. If not it's something worse.

My valves were adjusted by the dealer in 03/2009 (about 10-11,000 miles ago). Some people say that after they are adjusted the first time they an go 40-50,000 miles without needing adjustment again.

I guess i'll find out tomorrow when I check them.
 
Typically - 30-36,000 miles between "adjustments" is normal. I'd still check the clearances every 12k miles. It costs nothing (if you're careful with the profile gaskets) to do a check.

If you've never done it before - and the dealers receipt from the last time they did it doesn't indicate the gaskets were replaced, I'd want to have a new set on hand before starting. Also the rubber donuts that actually clamp the cover down (they are on the shoulder bolts that hold the cover.)
 
I still need to check my valves but I have minimal available free time :violin

Anyway, tonight I finally got 30 free-minutes to put on a fuel pressure gauge. As I had hoped I'm getting exactly 35psi at the rail.

Soooo...looks like my pump and filter are in fine shape. Since I was pulling the fuel rail anyway I decided to swap out the injectors with some newly refurbished ones. I'll be anxious to see if that makes a difference tomorrow. As of thi evening I was still having issues running lean. The bike also decided to stall again after I was going ~70mph in 5th and I put the clutch in in preparation of slowing down for an off ramp. Once the tach dropped to ~2000rpms the engine dies. The engine seems to stall like that a bunch when making quick transactions from high rpms (~5000+) to idle rpms.

Speaking of injectors...every time I pull there there is always a bunch of little stones sitting the the recessed areas underneath the injectors. This seems to be the case even after I run some compressed air. How do you guys prevent those stones and debris from getting into the engine?!?
 
toddlamp said:
Once the tach dropped to ~2000rpms the engine dies. The engine seems to stall like that a bunch when making quick transactions from high rpms (~5000+) to idle rpms.

How do you guys prevent those stones and debris from getting into the engine?!?
Click to expand...



Sounds consistent with a tight exhaust valve.




Compressed air.



:dance:dance:dance
 
Another possible piece of the puzzle.

On my way into work today, I tried the starter button trick however I did it at 5000rpms instead of idle. When I hit the starter button, with clutch in (cause I was on the road), the rpms dropped significantly (by ~1500 rpms). If the same is true at 5000rpms as it is at idle and lower rpms this would indicate that the bike was running rich.

Why would the bike be running lean at low rpms and rich at high rpms?
 
toddlamp said:
Another possible piece of the puzzle.

On my way into work today, I tried the starter button trick however I did it at 5000rpms instead of idle. When I hit the starter button, with clutch in (cause I was on the road), the rpms dropped significantly (by ~1500 rpms). If the same is true at 5000rpms as it is at idle and lower rpms this would indicate that the bike was running rich.

Why would the bike be running lean at low rpms and rich at high rpms?
Click to expand...

Valve adjustment affects both absolute opening area and valve timing. And if these are off air flow and mixtures can vary a bit all over the board. Get the valves dead-on correct first, and chase any remaining issues after that would be my advice.
 
PGlaves said:
Valve adjustment affects both absolute opening area and valve timing. And if these are off air flow and mixtures can vary a bit all over the board. Get the valves dead-on correct first, and chase any remaining issues after that would be my advice.
Click to expand...

You got it. Thanks
 
Just got back from checking the valve clearances.

-----Cyl1------Cyl2-----Cyl 3
I----.011"----.008"----.0095
E----.0065"---.0085"---xxxx

Cyl #3's exhaust valve didn't even have enough clearance to pass my .004" shim.
 
toddlamp said:
Just got back from checking the valve clearances.

-----Cyl1------Cyl2-----Cyl 3
I----.011"----.008"----.0095
E----.0065"---.0085"---xxxx

Cyl #3's exhaust valve didn't even have enough clearance to pass my .004" shim.
Click to expand...

Bingo! After two months and seventy something posts, you finally got down to basics (that's usually where the problems are). Valve adjustment was suggested two months ago (in post#5 and #12).

But it almost looks like you've got the exhaust and the intakes transposed. If not, those numbers are TERRIBLE! It's amazing that you didn't have noticeable problems MUCH earlier. I would suspect that the last time they were done (just before the trip) they were done wrong.

Now if you remember my earlier post, Set the intakes to the tight side of spec, (.006") and the exhausts to the loose side of spec. (.012").



:dance:dance:dance
 
98lee said:
Bingo! After two months and seventy something posts, you finally got down to basics (that's usually where the problems are). Valve adjustment was suggested two months ago (in post#5 and #12).

But it almost looks like you've got the exhaust and the intakes transposed. If not, those numbers are TERRIBLE! It's amazing that you didn't have noticeable problems MUCH earlier. I would suspect that the last time they were done (just before the trip) they were done wrong.

Now if you remember my earlier post, Set the intakes to the tight side of spec, (.006") and the exhausts to the loose side of spec. (.012").



:dance:dance:dance
Click to expand...

I know that the valves were suggested a while ago. Problem was, I had several other issues going on at the same time. I was going at the bike one thing at a time. My first problem was the severe intake leak. And unfortunately I work 7 days a week so I don't have really any free time to work on it. So little in fact that I succumbed and took it over to Bob's today to have the valves adjusted. They were the ones that did it last time and I will be sure to double check they're work when I get it back.

And no, the numbers are not transposed.

We shall see how it runs when I get it back. These bikes are crazy. They will run just fine with multiple issues and then that last one will take it over the top.
 
toddlamp said:
They were the ones that did it last time and I will be sure to double check they're work when I get it back.

And no, the numbers are not transposed.
Click to expand...

From the looks of the numbers, they adjusted them wrong (intake numbers for the exhaust and exhaust numbers for the intakes. I know nobody trains their mechanics on old K-bikes, but that is terrible. They SHOULD make them right for free. It could have caused a burnt valve.

If they are that bad at adjusting valves, you might want to specify loose side of tolerance on the exhausts and tight side of tolerance on the intakes. Otherwise they might just get them somewhere inside of the tolerance (but only a few thousand miles before they are out again).




:dance:dance:dance
 
98lee said:
From the looks of the numbers, they adjusted them wrong (intake numbers for the exhaust and exhaust numbers for the intakes. I know nobody trains their mechanics on old K-bikes, but that is terrible. They SHOULD make them right for free. It could have caused a burnt valve.

If they are that bad at adjusting valves, you might want to specify loose side of tolerance on the exhausts and tight side of tolerance on the intakes. Otherwise they might just get them somewhere inside of the tolerance (but only a few thousand miles before they are out again).

:dance:dance:dance
Click to expand...

That might be the issue. I had them done and the bike was running great for 99% of my trip. It was on the last day that I started to have issues. However, it's hard to narrow down my problems to just the valves since there were a few things that needed to be looked at. The bike is done and I'm just trying to get in touch with the service department to find out what their "recommendations" (as the voice message said) are.

The tech gave me the specs last time but I didn't think to look at them. I will ask for the same info this time and probably double check it myself. There is one tech at Bob's that primarily works on old K bikes. I have talked to him before and seems more than competent.

Lee: Just so I have it clear, tight = less valve clearance and loose = more valve clearance right?
 
You must log in or register to reply here.

Similar threads

E
No fuel to fuel rail?
Replies
12
Views
2K
98lee
98lee
S
Refurbishment of low mileage 1993 K75
Replies
7
Views
2K
beemerguru
beemerguru
A
1985 K100RS, rough running
Replies
2
Views
1K
pglaves
pglaves
J
87 k75s CONSTANTLY (every ride) cleaning the injectors - HELP
Replies
7
Views
2K
parked2long
P
N
2016 F800GT: acceleration flat spot 4K-5K rpms. Couple of questions...
Replies
1
Views
257
oldcamper
O
Back
Top