I have one of those frustrating problems, I replaced my spark plugs with new ones, same sort. My bike has been running beautifully, clean exhaust etc, but idling high, around 1,200 rpm. I want to do a compression check but needed to put a new air filter and plugs in first.
Doing the right thing I decided to check my plugs. They were a bit brown in colour but otherwise ok, except they did not have the small caps on the top end. Checking the ignition lead plug, it was full of white carbon stuff, so I presume I have had a spark jumping across the gap at the top of my plugs.
New plugs, gapped as per Clymer using a size 25 (presume 0.25 ) gapper. Then the bike was missing every now and then. Thanks to Charlie99's advice I checked all the ignition leads fro resistance. No.4 was non existent, and when I checked that new plug, it was black with carbon.
No problem, checked my spares bike, resistance ok on that lead, swapped them over. Damnation, still missing at idle.
Finally have some dry weather here so about to go for a run then check the plugs again.

Am I missing something sinister here?, we were so happy together until I touched her.

RT

Don't be off put, the sense of accomplishment when you get it sorted will be well worth the small frustrations. I believe most of us here have had the 'it was fine till I messed with it' feeling.

Tks beanoldboy, as I am preparing for my test run, the clouds have rolled in looking threatening again. I must have used all my luck up on my last trips. Just want it to be in good shape for the Qld saga in May. Her goes.
RT

Could be that you got two different issues here.........if it misses only at idle,
have you checked for intake leak(s) below the TB`s?

Inge K.

rt ...do the check again .....just by removing the old lead from the spares bike might have been enough to ...ummm make it open circuit .... but please check number 1 again also (they go in pairs 1and 4 ,, 2and 3

also make sure the lead is definatly pushed home properly on the ignition coil....

measure the lead from 1 to the lead from 4 and you should get .....5000 + 5000 + 10000(coil) = 20000 around about set your meter for 200,000 ohms

Yep, Inge's right on about making certain you've taken care of all the possible leaks... hang in there Rt and keep us posted?

OG

Ok tks guys
the story so far

The plug on the left is no.2, and the right is no.4. There seems to be a wet deposit around the thread ( I may not have had the plugs in tight enough) but the carbon around the electrode is not good. Plugs 1 and 3 are similar to No.2, wet thread and minimal carbon.
Looking at Clymer they seem to suggest a blocked Air Filter (I put a new one in last month, perhaps backwards?) Inge's suggestion has merit, just cannot understand why this has gone wrong after changing plugs. New plugs were DPR8EA-9 same as old ones, Too cold for summer? got me beat.
I'll try Charlies suggestion, and have a look at Inge's theory , I renewed the bent air hose some time ago ,I'll do a spray around the rubbers on throttle bodies
Thanks for the help
RT

hmmm.... intersting pic rt ....what inge suggests is spot on ....we need to get the same vacume and mixture hitting the cylinder ,,,for explosion when it comes around ...

i might suggest that if it was sucking air ...it should be more to the white scale of look ....ie:... running lean

if the electrical test prove correct ...might i suggest having a look at the injectors ....seems to me that its running rich in number 4 ....could this be a bad atomisation (spray pattern) of the injector at that cylinder ....or the valve seal has gone bad causing a miss (poor compression ) on that particular pot ? i would love to see if number one ( the ignition mate ) is the same way ....

if the bike was suffering from lots of blowback (read poor compression ) there might be a chance that the manifold to crankcase might be carrying more oil in the vapour ....then causing more oily deposits in the closest cylinder to the breather

chin up rt ...well find it

A DPR8EA is not the right plug the D denoted the thread. the p is a projected electrode, the R is a resistor plug, the 8 is heat range and E is the length of the thread.
The projected electrode is not right and the resistor you dont need as the leads have a resistance of 5000 ohms the heat range should be 7 so all in all Bob you have plugs that are not really suitable a D7EA is the correct plug summer and winter and especially in Australia.
Now all that over if one plug is black then it says to me the problem is either that plug or the cylinder itself. Put the right plugs in it then if no good swap the plugs around and give it another run and see if it goes with the plug or stays at that cylinder.
Test the compression on all cylinders, 130 is what I would expect and maybe as low as 110. If they are very uneven more than 10 put some oil in each cylinder (3 squirts from an oil can) and test again to see if the low cylinders come up to close to the others, if it is still uneven then you have some leaking valves if they come up to all much the same then you have rings on the way out. Low compression will give a miss at idlebut will usually go away when the revs are up.
This summer and winter bit with hot and cold plugs is a load of crap the heat range of the plug determines how fast it can get rid of the heat from combustion and the engine should always run at the same temp +- a few deg summer or winter thats why they have a thermostat. Its the engine design that determines the plug heat range.
I seem to recall that it was you that posted about 95 in each cylinder is that right?

HI K Freak
no I havent even got that far yet, compression test was coming after plug and airfilter change, so will do that asap, after I get new plugs, and do everything everyone else said. I am more mellow about it just now, desert wine and home brew beer will do that to you. Tomorrow I will be an anxious wreck again. I know we will solve it though.
Cheers and adieu.
RT

Just my thoughts about this new info.....
A to cold plug(s) would become sooty.............the other three looking kind of normal.
Then with the correct heat range........could give three cylinders running to lean.
Then again..........air leak?

Inge K.

good thinking inge

I may have missed it but you must have the little bobbins on the spark plug tops in place and as K FREAK says the resistor plug is wrong for your bike they are only used on the 16 Valve which have no resistors in the ignition leads.
Regards,
K-BIKE

K-BIKE wrote:I may have missed it but you must have the little bobbins on the spark plug tops in place

They was missing earlier, but correction mentioned in the first post.

Inge K.

Thanks for that, have you cleaned out the insides of the caps and measured the resistance of the leads to see if they are approximately even? I do go along with the check to see if there are vacuum leaks, I use gas (butane) but carb cleaner is fine.
Regards,
K-BIKE

Not your valve stem seals?? I have seen this.

Update
new plugs ordered ( I live in the boondocks here), rechecked all
leads, all within a whisker of each other.
Charlie s suggestion to check leads 1 against 4 makes sense, but I'm afraid I can't really figure out how to do that. I took 1 off plug, and 4 off coil and checked with trusty meter and got 1. Not doing it right.
Whilst here just to check, lead 1 connects at the front of left hand coil, and lead 4 connects at the rear of left hand coil? just to make sure we are wired up right to start with.
Ans can I DeoXit all the connectors on the coils?
Thanks again
RT

yes rt ...indeed ...deoxit would be a good thing to use in the caps that got all corroded from the lack of the thimbles attached to the spark plugs .... and it certainly wouldnt hurt on the ...high voltage output of the coils .... if you can try and have a sqiz in there at the terminals (with a torch and your glasses ) the terminals should be bright and shiney brass looking sockets

when i got my coils from "blighty" ...(mutter mutter) ...at least one end of the coil was really corroded ....and i hope this hasnt hapened to you ...... if your saying you got a "1" .......thats kinda interesting ...it means that you have an open circuit coil ....the "1" is no reading at all = nada ...nothing on that range ...try turning it up to a higher range like 2meg = 2,000,000 ohms

what turned out to be working coils ....and im sure they do work... was an open circuit ...i guess the spark jumps the gap (internaly) anyhow ...but makes a mess of trying to electrically check the coils ...

ok heres the connection ....put black lead on the plugtop from number 1 spark plug lead......put the red lead on the plugtop of number 4 spark plug lead whilst they are still connected to the coils . you should get 20,000 ohms or so with your meter set to 200,000 ohms or more ....

i thought to just mention this process to eliminate any other information that we (collectivily ) didnt know already

i'm just suggesting to redo the mesurement rt ....so we can discount the high voltage electrics and move on to other things that could contribute to "missing as its idles "

all the above comments carry good and thought out recomendations to things we have noticed in many experiences and reading in here ....

as kfreak suggests ...could be rings ...valves and all that ...inge suggests vacume leaks in the rubbers and 1 bad heat range plug ... i had thought of a bad injector spray or possibly stuck partialy open



and i guess they are all contributing factors to the miss ....

not being there sorta denies us that "hands on feel" for the sound that you hear and the things that you see immediatly and what changes when you do this or that .

certainly a compression test would be adviseable .....all plugs out ...presure tester connected and wide open throttle as you crank the motor about 3-4 times and again with 3 or 4 squirts of oil in the cylinder under test .....wait about 15 minutes before doing the next one ....so the battery recovers some what (and cranks at the same speed ) write down the results of both tests as you do them ....

there are writings about the vacume leaks in the forum and how to test it ...but basically ...plugs in ...leads attached get the bike started and warmed up ...then get some cabi cleaner and spray around the rubbers that connect between the throttle bodies and the engine ...both sides (right hand side covers off ...sorry ) if you hear a change ...write it down

Excellent Charles, I knew I could count on you to dumb it down for me.
I might need to borrow a better multi meter though.
Compression tests today and clean everything. I haven't had a ride for 3 days now, cabin fever setting in.
:suspect:

heres the right setting for this test (not the 20k...as you would have used to measure the leads ...but 200k is the right one ) for leads and coils

your meter is fine ...just have to work on the settings part huh ?

Bingo thanks
reading was 21.9 (21,900 ?) from 1 to 4 lead so that alleviates one problem. 2 to 3 was 22.00 as an aside. Moving down the list tomorrow
compression test.
Cheers RT

Back to the BMWikipedia for me.
Compression tested today, 150,152,152,155 1-4 readings. Happy with that, but now I need to find the problem still. Whilst I had the bike up on the table I can now see that the rubber over Carby 4 has got an oily residue sort of around the top. I have to get some carby cleaner and squirt around but I guess that is my next move anyway?. That looks like a big job but not as bad as piston rings I guess.
These lifting tables are a great idea, except that I could see that the coolant reservoir return hose is leaking, had to fix that, then saw the dreaded oil smear under the bell housing. That will have to wait.
Rickmeister sent me a fabulous battery isolator gizmo to use an external battery to crank the compression up. Many thanks to him and everybody else who has helped me in this.

Also going to buy a non going Suzuki gs500 this w/e for the missus, I must be crazy.
Cheers Geezers
RT

you havent been out in the sun have you rt

RT wrote:Whilst I had the bike up on the table I can now see that the rubber over Carby 4 has got an oily residue sort of around the top.

Could possibly be related to the crankcase ventilation is connected to the rear end of the plenum chamber.

Inge K.

No Col, not a sign of sun all summer here, just going loopy I think.
Thanks Inge K, I did replace that breather hose a while ago but better
check it and anything else that might be leaking. It's dragging on a bit.
RT

RT wrote:Thanks Inge K, I did replace that breather hose a while ago but better
check it and anything else that might be leaking.

What I more have in mind is that cylinder #4 is the one that is closest to crankcase breather,
and the reason to that you see the most oil residue at this place.

On the other hand I don`t know how the velocity stacks inside the plenum is fitted, if it`s
just a press fit and not glued, oil would seek it`s way out first at this spot.

Inge K.

Cannot find any air leaks, this is getting to be serious now. Idling whilst cold is really rough, warm not so bad but can still detect a miss.
To recap
New correct plugs
all ignition leads resistance fine
compressions checked, fine.
Sprayed carby cleaner around rubber tubes from airbox, no difference
No.4 plug still fouling, it runs and burns but gets black carbon quickly around the gap
Opened oil filler cap whilst running, surge in revs.
The coil must be ok as No.1 burns really well.

Now I'm at a loss, I don't have access to a manometre, maybe I should bite the bullet and go see BMW?
RT

Maybe it would be a idea to check the spray pattern on the injector(s).
Could be that #4 have a damaged seat/uneven spray pattern...and minor leak.


..........and all this started with changing a set of spark plugs...........
..........gonna be a long time untill I change mine.........

Inge K.

i think alby has a few spares ....oh dang he sent them back to kfreak well hes has some at least ...im sure we could do an exchange thingy rt ...

im thinking after all your work ...possibly 2 things .....the idle adjuster could be partially blocked (air bypass jet thingy (brass screw)) maybe you could turn it in ...to the right and count the turns till closed ...then remove it completely ....you may see ...as i have lots of crud arround the needle ...and jet that it fitts into ...carby clean the needle and seat and try and get some upp the tube that feeds it from above the butterfly valves (tb) could be that its picked up some oil and crap from the breather and now partially blocked .....

else as inge suggested (2) the spray pattern of the injector ... swap it out rt ...in the process you will be putting new rubbers on the injector seals and an new filter in the fuel rail side of the injector ...and a good clean spray pattern as well

just some thoughts

The air bypass is a good suggestion Charlie....if available...
compressed air could also be used ...in addition to carby cleaner.

Inge K.

Thanks men, I have some spares that have been cleaned earlier maybe I can swap that one over.
You are right Inge, I was riding thousands of Kilometers happily ignoring the high idle revs, then I decided to go by the book to do an idle adjustment, starting with checking the plugs. Man I'm sorry at the moment.
Back to the shed.
RT

RT, at least it keeps you busy while it rains and stops us riding. Just started pelting down here.

Yeah Dave it's been a bummer of a summer
now I have a battery playing up, trickle charger broken and can't get my wife's suzuki to fire up.
I should've gone to midnight mass at xmas, I knew it.
RT

dang dontcha hate that rt ....good luck !!

Murphy been on a visit?.......he didn`t show up at the midnight mass either.

Inge K.

Went for a ride yesterday, earplugs in so I could not hear the idle miss,
had a good high speed run and when I came home, it was purring.
I am not game to pull the plugs and have a look.
RT

RT wrote:I am not game to pull the plugs and have a look.

Don`t even touch them, never ever........Murphy is just around the corner....waiting for you.

Inge K.

Let a sleeping dog lie.

rt
you must have been holding your tongue in the right position this time
good luck with the wifes new bike

RT wrote:Went for a ride yesterday, earplugs in so I could not hear the idle miss,
had a good high speed run and when I came home, it was purring.
I am not game to pull the plugs and have a look.
RT

See you gotta treat them like a child and give them a damn good flogging every now and then to keep them in line.

Well I have spark probs with her Suzuki, no spark. Now if only I could find the fuel rail and injectors and coils. Trying to find a good forum for it but they seem very unfriendly (GS500), so waiting for a manual.
The wiring and carbys make everything look soooo simple.
By the way K Freak the Department of Community Services is heading your way.

Have a look on this site RT, I downloaded a Suzuki 500GS manual last year.

http://www.repairmanualclub.com/motomanuals/index.php?cid=10

Tanks Avenger GT
it will help a lot, been flying blind so far.

This is an old recurring thread for me but there is progress.
After coming back from my 7 day trip and having Charlie 99 complaining about my oil burning smell I thought I better sort some stuff out.
I found I had cross threaded the oil filler cap and it wasn't sealed properly, letting a fine oil mist come out, and because I had painted the crankcase black, couldn't see it. Didin't use any more oil after I fixed that up somewhere in Qld.
Anyhoo, was reading the forum and saw mention of spark plug gap and thought maybe I should check mine again as was running very rough.
I had set all my plugs waaay to small, around 0.45 mm, cannot figure this out as I purchased a gauge from
Munich Motorcycles and used it. Beats me, so I have reset to 0.65mm and guess what, rough idle has disappeared . It still idling too high but starts and runs as smooth as it ever has. The gauge I bought was marked as 0.25 (assumed an inch thing don't know why). So all I have now is high idling, just like it has been since I first started her up. Back to the drawing board, thinking air leak but can't find it yet.
Waiting for it to get really cold so I can take her off the road for a few weeks.
Cheers RT

good find rt ....that should help your old girl run a bit cooler as well

i wasnt really complaining ....but i did notice the effect mate and was hoping that things would get better for you ..

cheers

Hi Charlie
the other thing is , the manual says not recommend to use a plug that has been regapped. I'm thinking load of crap, then my neighbour, out of the blue tells me his mate lost the electrode end of a plug in his lawn mower and crunch time, $1,000 damage. I'm ordering new ones tomorrow.

wow thats a new one rt ...

yes it does depend on how you made the gap bigger ....it isnt recomended to use the centre electrode to force the gap opening ...usually a pair of needle nose pliers applied directly to the prong for the opening event is the way to go .....levering the centre electrode is not cocher to get the gap ... it stesses the ceramic sometimes too much .

if you have done so ...yes.... get new plugs

You say that you had a leaking filler plug which you have now closed proper. Did you notice a difference in the running of the bike? Opening the filler plug with a running engine is a simulation of an air leak. If no difference I would have a good look at your crankcase breather hose and test for airleaks in the usual way.

I knew you would ask that, no I didn't notice any change. I put a new air hose on 1 1/2 years ago, maybe I should check it. I also have sprayed carby cleaner around the intake rubbers and no change.
It seems to me that when the "choke"lever is not in use, that the cable doe not release the little knurled nut all the
way back to normal, if I push on it (down near the fuel rail I'm talking about) then the revs drop a bit.
Spooky.