Author Topic: 91 K75 trying to get a tune out of her AGAIN (Read 4314 times)

Popinnlockin · « **on:** December 22, 2019, 01:06:08 PM »

Purchased a 91 K75 from a friend that's been stood for over 5 years. Where I'm at is found water in the oil so done the oil/water pump, checked compression on all 3 cylinders over 10 bar, checked for spark on all 3 OK ( cleaned and re gaped plugs) serviced fuel pump and changed fuel filter. Found injectors to be seized purchased reconditioned ones. So after this fired up and purred like a kitten, let it get up to temp fan kicked in but no reading on the gauge. So at this point ( for some reason ) decided to drop some engine flush in the crank, opened the oil filler cap and stalled ( i now know why) But since the engine has been running rich, checked pressure in fuel line 39psi which i believe is correct just wondering where to start next ? Thanks in advance.

Chaos · « **Reply #1 on:** December 22, 2019, 06:03:43 PM »

checked air filter?

Popinnlockin · « **Reply #2 on:** December 23, 2019, 01:07:58 AM »

Hi greetings, yep done the air filter. I've read that there is a flap on the air flow sensor that can occasionally get stuck. Does the crank case vent into the intake before or after the air flow sensor?

Laitch · « **Reply #3 on:** December 23, 2019, 09:35:56 AM »

Quote from: Popinnlockin on December 22, 2019, 01:06:08 PM

just wondering where to start next ?[quote

The engine was running. Are you having a problem getting it to start again?

Popinnlockin · « **Reply #4 on:** December 23, 2019, 10:58:23 AM »

Yes pal, after fitting the reconditioned injectors fired straight up ran sweet as a nut. Left it running for 15 minutes until up to temp and let fans kick in a couple of times, but then decided to put the engine flush in opened the filler cap and stalled it. Can this cause a problem?? I see that the crank case vents into the throttle bodys so shouldn't cause a problem at air flow meter.

alabrew · « **Reply #5 on:** December 23, 2019, 12:15:33 PM »

Whole thing has to be leak free. I assume it started up again after you put the filler cap back in?

I think I would next test the MAF, air temp. sensor and the coolant sensor to determine if they are actually in the correct range.

How do them plugs look?

Popinnlockin · « **Reply #6 on:** December 23, 2019, 12:59:40 PM »

No hasn't started since it stalled on cap removal.has to be leak free from which point, after the MAF ?

Popinnlockin · « **Reply #7 on:** December 23, 2019, 01:56:36 PM »

nancy.png (39.02 kB . 432x576 - viewed 454 times)

alabrew · « **Reply #8 on:** December 23, 2019, 02:09:31 PM »

I'm saying the oil fill cap has to be in and tight. Would have expected it to fire once you got it back in.

Lets's try again. You wrote "opened the oil filler cap and stalled ( i now know why) "

What do know why?

The crankcase z tube needs to be leak free. The throttle body rubbers need to be leak free. The throttle body rubber caps need to be leak free.

Only air getting in there has to come through the MAF.

Laitch · « **Reply #9 on:** December 23, 2019, 02:52:20 PM »

Quote from: Popinnlockin on December 23, 2019, 10:58:23 AM

then decided to put the engine flush in opened the filler cap and stalled it. Can this cause a problem??

Removing the oil filler cap from one of these engines while it's running causes a vacuum imbalance. Stalling can be one of the side effects. Add flush or oil when the engine is not running.

Remove the spark plugs. Clean them. Reinstall them. Recharge your moto's battery then try starting then engine again if there is clean fuel in the tank.

Popinnlockin · « **Reply #10 on:** December 23, 2019, 03:23:02 PM »

I've had cars where you could romove the filler cap while the car was running. Anyway this evening I've removed the MAF looks OK the flap wasn't stuck, removed the spark plugs there really damp. Noticed this before and removed plugs and dryed out but still wouldn't start.

With you saying recharge the battery is the fact that it's turning the engine over enough ? I'm asking because the time i got it going I'd jumped it from the car, but since I've been running it from a old car battery that's had no problem turning the engine over.

Ill try the car again tomorrow. I'm getting a horrible feeling I've been tail all week :(

johnny · « **Reply #11 on:** December 23, 2019, 03:31:49 PM »

greetings...

jumping it from a car... why didnt you say so in the 1st place...

is the gas cap on backwards...

what else are you not sharing...

j o

Martin · « **Reply #12 on:** December 23, 2019, 03:34:00 PM »

After trying to start and it doesn't, remove the plugs. Are they wet or dry??? Do not open the throttle while doing this.
Regards Martin.

Laitch · « **Reply #13 on:** December 23, 2019, 03:46:35 PM »

Quote from: Popinnlockin on December 23, 2019, 03:23:02 PM

With you saying recharge the battery is the fact that it's turning the engine over enough ?

No, it isn't. What's the voltage output of whichever battery you're using?

Popinnlockin · « **Reply #14 on:** December 23, 2019, 04:58:52 PM »

The voltage output from the battery is 12.35.

Regarding the plugs, when turning over with choke on no throttle, plugs are wet. Whenever its been left to dry out it does fire and try to go but when i go off the starter it dies.

Popinnlockin · « **Reply #15 on:** December 23, 2019, 05:07:41 PM »

Could it be possible the battery is enough to turn it over but not run, but with jump leads from the car is enough to get it running ? The jump leads shouldn't be a problem the bike will only pull what it needs, right ?

Martin · « **Reply #16 on:** December 23, 2019, 05:29:13 PM »

Wet plugs and failing to fire up can be a sign of a faulty temperature sensor or connection. Try removing the fuel pump fuse number 6 Kraffstoppe. Then try to start it, it should fire up on the residual fuel in the combustion chamber. It will run a bit ragged and you will have to manipulate the throttle. As the engine starts to die ram the fuse back in and with a bit of throttle manipulation you should be able to keep it running, albeit with throttle manipulation. An assistant helps. If this is the case cleaning the connection to the sensor sometimes works other times you will have to check the sensor values. The sensor is in a bad location and suffers from road spray and crap smearing silicon grease around the plug can help stopping the ingress of water and crap.
Merry Christmas regards Martin.

Popinnlockin · « **Reply #17 on:** December 23, 2019, 05:49:08 PM »

Just had a quick look and noticed the sensor is completely burried in crud so i guess this is my next port of call.

Thanks Martin and everyone else who took the time to advise and Merry Christmas.

alabrew · « **Reply #18 on:** December 26, 2019, 11:46:27 AM »

Don't have to take much apart to test several sensors. Go to page 25 of the Bert Vogel flow chart and test the values at the Jetronic female connector. You can test water temp., air temp., and the afm.

Popinnlockin · « **Reply #19 on:** December 27, 2019, 06:37:02 PM »

So tested the sensor at pin #10, at 0° it should be 5.5 K ohms and i was getting 4.5 at 8° so shouldn't be over feeding to flood. So went back to power and changed for new plugs and jockeyed the battery with jump leads from the car, fired straight up. So now on a full strip down, the bike is a ex police bike so there's a lot of wire on it that's redundant so thinking of fitting a Motogadget M unit and re wiring the bike so ill no doubt be back on. Thanks

The lesson is just because the battery is turning over the bike that it's enough to start it, it ain't.

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Author Topic: 91 K75 trying to get a tune out of her AGAIN (Read 4314 times)