BMW K bikes (Bricks)

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Fentible

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I converted my standard naked 84 K100 to k1100 throttle bodies and using the standard k100 TPS, I am also using an uprated injector that has the same flow rate as the original injectors but uses a multipoint flow head that allegedly improves atomisation and hence the burn rate. Everything else is standard K100.

The bike starts easily and needs choke when cold. It settles into a reasonablysteady 1000rpmtick-over however there is a tendencyto regularlyhunt between 950 - 1050. My nose tells me it smells rich and when I remove the plugs sure enough they are black. I can't tell if its my imagination but there alsoseems to bea momentary lag when revving up from tick-over. It may simply be a case of 'they all do that' but it isn't noticeable when revving up from 2000rpm.

I have balanced the TB's and I alsocan't detect any vacuum leaks, but I thought if anything that would cause lean running. I know you can adjust the idle mix on the MAF, clockwise or counter to lean off?? I don't have a sniffer so any adjustments would be seat of the pants.
Also when first turning on the ignition, should all the warning lamps light up?? My templamp doesn't.

Imust stress I haven't had the bike on the road yet as its not currently roadworthy. So all running is on the bench.

Ideas or suggestions gratefully received

    

RicK G

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What you are describing isn't at all uncommon, the LJetronic injection from Bosch was fairly rudimentary stuff and runs open loop all the time. It measures the air coming in then squirts about the right amount of fuel in and it idle is not exactly metering well but does a fairly good job in the mid range.
The throttle position has only 2 positions idle and wide open throttle. It may pay to check it by listening for a click just as the throttle starts to open and the finer adjustment there the better it will settle at low revs.
It's not at all uncommon to have a tiny lag of idle but as you say above 2000 it OK then I would not be concerned about it.
Playing with the mix adjustment at the MAF can be a dangerous thing without the right gear.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

Inge K.

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Have you checked/measured the water temp sensor?
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Measure the resistance between contact #10 and 13 at the injection ECU connector
(female side).
Count from the rear end, also the empty slots.
In the troubleshooting guide at the portal you find a table, resistance vs. temperature.
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CCW to lean out the idle mix.
The temp warning lamp comes on only when the temp is to high.


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Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

Fentible

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Thanks Rick G, I wouldn't normally be overly concerned by what the engine is doing but the sooty plugs do concern me. Ialso appreciate your concerns about playing with the MAF idle adjustment without proper gear

Inge K I measured 2.5K ohms at the EFI socket when cold and 0.0 after it had been idlingfor about 15 minutes, not sure if that is within spec. Thanks for the heads up on idle adjuster and temp lamp function.

I'll note my start point andtry a turn or soon the idle mixadjuster in thelean direction and see if it makes any difference.

    

Inge K.

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@Fentible wrote:Inge K I measured 2.5K ohms at the EFI socket when cold and 0.0 after it had been idlingfor about 15 minutes, not sure if that is within spec. Thanks for the heads up on idle adjuster and temp lamp function.

The resistance should go down as the temperature rises, but not down to 0,0.
Anyhow this is not the reason to your fat runnin problem, as it would have been
opposite way.....the resistance would have stayed to high.

But your temp sensor doesn't show normal values as it varms up................


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Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

Fentible

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Further to the above, I made some further checks on the resistance values for the water temp sensor. My previous post at 0.0 was incorrect, I wasusing a smallanalogue meterwith poor eyes. Using the digital shows a steady decrease from 2.5to between .3 and .4 after a prolonged idle. It was also nice to hear the fan kicking in.

I'm going to swap back to the original injectors to see if its the new ones causing the problem, I'll also try swapping the FPR for a known good one as I don't have a suitable pressure gauge.

One thing I wondered about, my original TB bank hada vacuum switch attached. I know this was dropped fromlater modelsand as mine was badly corroded I simply binned it and insulated the abandoned connector. Could this have any effect??

As said it starts easily and ticks over, its just the sooty plugs that are concerning me.I have now been able to run it up and down my road, only for a few hundred metres and can only get it into 3rd gear but it seems okay. Incidentally nicest gearbox I have ever had on a bike. How smooth are they??

I need to replace the fork seals after which it should pass the UK road test (MOT) and then I can get it out for a longer run to see how its behaving.

    

Inge K.

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@Fentible wrote:One thing I wondered about, my original TB bank hada vacuum switch attached. I know this was dropped fromlater modelsand as mine was badly corroded I simply binned it and insulated the abandoned connector. Could this have any effect??

No...........

The resistance through your water temp sensor should be around 250 ohms at operating temp.
Your is a bit higher (correspond to ~ 80oC) but I don't think it should cause sooty plugs.
But that combined with driving just a few hundred meters up and down the street,
I really don't know.......


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Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

Fentible

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I did a compression check yesterday (all4 cylinders reading between a 152-155 psi) when I looked a little more closely at the spark plugs, the gaps seemed a little on the narrow side. Sure enough I struggled to get a 15 thou (imperial)feeler gauge in. Opened them up to 25 and on starting the bike the tick over was noticeably smoother and rock steady at 1000 rpm. what should have been one of my basic checks, I missed totally Embarassed. I'll see if it makes any difference to the sootiness of the plugs which seems to be subsiding anyway since I backed of the idle mixture

On another note, the RH caliper has been weeping so I ordered a new seal kit. I really struggled to get the pistons out and resorted to the foot-pump method. On the plus side it looks like the pistons are unmarked, on the downside I am still hunting the depths of the garage for the piston that suddenlyblasted out Shocked. I have used this method loads of times but never seen a piston come out with such force. Just a cautionary note to take care.

    

RicK G

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When I was working for Honda an apprentice was using compressed air to do that and put his fingers in the space for the pads to catch the piston and got 3 months of work while the doctors fixed the fingers. One finger was almost severed and the other just pulp.
He wasn't a fool either but just a moment of brain fade.


__________________________________________________
If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

Fentible

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Sadly Rick it wasn't brain fade, if I can't get the pistons out from a caliper still connected to the hydraulics I've always used a foot-pump to supply sufficient pressureto just get the piston moving, then ease the pressure back on until the piston just pops out. I've done numerous brake calipers like this and as stated its the first timeany piston has come out with such force. I'll deffo take more care in future

FYI I've now retrieved the flying piston, thankfully unmarked.

Fent

    

duck

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I usually idle mine up above the 950-1050 spec idle (like 1100-1200) to get rid of the occasional lag when accelerating from idle. (and I adjust the TPS accordingly.)


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Current stable:
86 Custom K100 (K75C fairing, K75 Belly pan, Ceramic chromed engine covers, 32/10 final drive)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
93 K1100RS
94 K1100RS
93 K1100LT
91 K1
93 K75S
http://www.ClassicKBikes.com
    

Fentible

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Thanks Duck. Hopefully get the leaking caliper rebuilt today. Ordered the rebuild kit from Motorworks on Monday and it arrived yesterday. Then get the bike inspected (MOT) and out on the open road to see how it runs.

    

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