Do you have an idle problem on your K brick? - K-Bikes.com - Excellence in Motion
 
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post #1 of 9 (permalink) Old Jul 19th, 2007, 2:45 pm Thread Starter
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Do you have an idle problem on your K brick?

I don't have an idle problem, but I do have a motor sitting on my garage floor nearly rebuilt and I'm looking straight down the inlet throat of the beast. This is a rare moment, you can't do this in the frame.

If you've had ECU's changed or the stealer has been tinkering with your bike this may not be for you. However, If your bike has been running fine then suddenly starts to develop idle problems this may be your problem:

Efi motors aren't magic. If your bike has been working fine and then starts giving idle problems, I always suggested the problem was physical - nothing to do with the ECU, although the ECU may have a response to try to correct a problem or find the problem puts its mixture calculation out of range.

So, I'm studying 4 ABS plastic manifold stubs which have O ring grooves 2mm deep and 2.4 mm O rings fitted and I'm thinking, they haven't left much to make a face seal. I torque down no.1 and have an idea. Wind the crank so the valves are shut, stick my pinky over the injector hole and blow down the stub. Wow there's an air leak at the base! Now this is the most critical area to not want an air leak, the same applies to the injector O ring when fitted with the rail. On idle the injection cycle is very short and fuel hangs around a long time waiting for induction.

I remove the stub, blue the face and put it on a surface plate: Wow, its like a banana (in machine thou terms) and the 2 ali bushes they set in the moulding are raised above the surface. I check the other 3 - all similar.

Solution - carefully re-face on 600 grit emery to take down the high spots (at the bolt flanges), replace and no more air leak. Now it's possible some of you may have 'fixed' an idle problem by powering down the ECU and doing a reset. What I think happens is the ECU re-learns the idle with the manifold air leak still there, but over time if the leak gets worse the ECU won't correct for the weak idle mixture.

Most probably poke around the airbox, but you probably wouldn't remove the manifold stubs and check the face seal. Even new O rings don't help if the bushes are proud. Let me know if this helps anybody.



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post #2 of 9 (permalink) Old Jul 19th, 2007, 4:58 pm
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mmmmmm...interesting..mine is getting a mind of its own....some mornings it starts and runs at idle just fine...other days i have to crank it 2 times to get it running...other days it starts but only comes up to 700 rpm.....im thinking throotle cable cause once in a while it feels like it wants to stick....what do you think about spraying some carb cleaner around the ports to see if its sucking air?..
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post #3 of 9 (permalink) Old Jul 20th, 2007, 2:37 am Thread Starter
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Your problem may be different, so try the simple things first.

If you think how small the air supply needs to be controlled by the throttle body butterflies and any by-pass air jetting at idle, any small air leaks can make a big difference.

You really need to get air down there like I did and perhaps spray soapy water around the body flange. There's another step that's more complicated but tells you even more. I think you could block off the emission return hole in the throttle body, leave the body in place, remove the airbox, and make up an airtight adaptor to fit a cycle pump/air line and plug it into the top of the body. Then when you spray soapy water around you get to see any air leaks including the throttle butterfly spindles. Since my motor isn't in the frame, I don't know how difficult this is. If you get massive leaks your valves are shot!

BMW haven't allowed a lot of rubber on the manifold O ring seals, given that aluminium expands a lot when hot (and ABS plastic doesn't) - I can see a possibility for intermittent idle problems. But as I said, each issue could be different and checking the obvious like throttle cable and sticking butterfies comes first. My emission return hoses were badly perished and split, but their condition hadn't caused any idle problems (they aren't connected after the butterflies).

I tried a K&N filter for a year. Now I've been inside and seen the mess around the throttle bodies, I shan't use them again. The brown sticky oil they put on the filter had migrated into the throttle bodies, allowing all sorts of muck to stick to them. It took me a couple of hours to remove the whole lot and clean everything up.

I have the large spec'd free play in my throttle cable, checked lock to lock, and I can actually hear a positive click as the body spindles hit their stops - and I've got the springs relaxed. Just by listening you should be able to hear the right sounds with the motor off.

There's some other interesting electronic things on the common butterfly spindle which could also be looked into. There's the TPS we know a bit about (DON'T remove it or mess with it!). It has 2 variable resistance ranges, a fine one for the first range of throttle to about 1/3, and a second resistor more coarse going 0 to 100% throttle. There's also another jobbie, which is just a switch, its one way when the throttle is on the stop, and the other when the throttle is moved off it. Although I've measured a few things on the wires, I haven't fully studied the purpose of the switch yet.

Sorry if this is a bit more complicated than squirting cleaner around your throttle bodies.



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Last edited by voxmagna; Jul 20th, 2007 at 2:44 am.
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post #4 of 9 (permalink) Old Aug 26th, 2007, 5:20 pm
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Quote:
Originally Posted by voxmagna
There's also another jobbie, which is just a switch, its one way when the throttle is on the stop, and the other when the throttle is moved off it. Although I've measured a few things on the wires, I haven't fully studied the purpose of the switch yet.

Sorry if this is a bit more complicated than squirting cleaner around your throttle bodies.
I haven't yet stripped down my K12RS that far (and I hope I won't actually need to..) but if the injection system is anything like the Bosch L or K systems, the switch that Voxmagna is referring to should be a simple idle set switch. It's purpose is to tell the system that throttle is fully closed, and the response is a 20-25% boost in fuel for smooth idle running.
I have come across many, many instances where garages have set the air-mass meter (on cars) after adjusting the idle bleed when the switch has been open while the throttle was already fully shut. This means that too lean a mixture occurs at mid to full power and long term will burn valves . If you ever setup an injection system.....start with this switch.....
1/ adjust venturi gap(s) 2/ set this switch 3/ set idle mixture 4/ set air mass meter


Assuming of course that like Voxmagna, you start off with a clean, leak free system..

Ideally you want a logical flow block diagram of an injection system before poking it too much
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post #5 of 9 (permalink) Old Aug 28th, 2007, 12:14 pm Thread Starter
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...........Assuming of course that like Voxmagna, you start off with a clean, leak free system..


AND when you get it all back and get a 3K idle with the throttle cable dropping out of the twist grip, you find the large hose clip clamping No.3 throttle body hose is stopping the throttle quadrant from returning fully to its stop!



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post #6 of 9 (permalink) Old Sep 9th, 2007, 11:16 pm
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New O-Rings were Too Expensive for the Dealer!

I've had idle problems and vibration that was uncharacteristic for a K since the dealer did the 24K service. Your post gave me hope that when we did the throttle body cleaning this weekend, I might find something simliar.

I found something, just not exactly what you described - I guess this is the way professionals work...







It only took a few extra hours to clean all that crap off! The new O-Rings were put in without whatever adhesive or sealant the dealer used when they had thing apart at about 34K.

It took too long to actually finish everything by the end of the day, so I haven't had a real test ride yet, but I'm expecting it'll be a much improved idle!

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post #7 of 9 (permalink) Old Sep 11th, 2007, 5:38 pm Thread Starter
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Strange there should be adhesive/sealer around there, unless somebody thought that was a good way to fix the type of air leak I had (?).

Alternatively, you might have a K&N air filter which puts loads of crap and gunge into the throttle bodies. Won't use them again.

Still, at least we don't have the new bikes with the complicated airbox 'we can fix it under warranty but haven't got any' problem.



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post #8 of 9 (permalink) Old Jan 14th, 2008, 3:17 pm
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No Vacuum

Is this my problem???

I dusted the K bike off to give it a tune up. I found next to no vacuum on # 2 cylinder - others were OK. Must be a stuck valve I assumed, but found the compression to be normal (about 150psi). Fitted new plugs - no improvement, pulled the fuel rail and injectors - all were spurting. Pulled the plug cap - the plug was firing energetically, but I was getting a mild shock through the metal cap.
Must be the intake manifold leaking - took a good look at it and sprayed WD40 all around to see if things would change - no such luck. Blocked vacuum take-off pipe maybe? - sprayed oil in there, it came belching out of the exhaust.
The bike is in good mechanical order, when used last, 3 months ago, all was well.
I am sure that this is a no-brainer (I have no brain) Please help.

Mark

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post #9 of 9 (permalink) Old Jan 17th, 2008, 3:33 am Thread Starter
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If you haven't got a hole in the piston, air must be getting in somehow.

What happens when you put your hand over the top of the inlet stub? If there's suck from somewhere else then you have a leak, if there's lots of suck, then is the throttle butterfly on #2 stuck open at idle when the others are closed?

You get highet vacuum when the butterflies are virtually closed as at idle, because the vac monitor port is engine side of the butterfly if I remember correctly. If you get high vacs at part open throttles you've got a blocked air filter!



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