Hello all, new here, need help!!!

[jetmechmarty]

Some meter leads make good replacement wire.

[der verge]

Well, more bad news. Need more help. I traced the harness for the pick up coils back up to near the battery, where there was a connector. Instead of searching for broken leads all over the place, I decided to rebuild the harness. So I cut the existing wires with in 1" of both the coils, and the connector, and soldered in new wire. NO CHANGE. Still missing on 2,3, and 4. Are there any other frequently encountered problems with these type of symptoms? I will go through and ohm the coils tomorrow, but I seriously doubt the coils themselves are bad.

[motoman]

Well, more bad news. Need more help. I traced the harness for the pick up coils back up to near the battery, where there was a connector. Instead of searching for broken leads all over the place, I decided to rebuild the harness. So I cut the existing wires with in 1" of both the coils, and the connector, and soldered in new wire. NO CHANGE. Still missing on 2,3, and 4. Are there any other frequently encountered problems with these type of symptoms? I will go through and ohm the coils tomorrow, but I seriously doubt the coils themselves are bad.

Low voltages through ignition switch and kill switch(dirty contacts) is notorious for low voltages to coils. I'd suggest going thru cleaning every electrical plug-in, cleaning and dialectric grease. Ballast resistor can cause issues also on the older models like you have.

[Gallaecus]

Where to look guys? could this be a bad coil? I know 1 and 4 run together, as 2 and 3 do. Never seen a bad coil cause back fire at low speed, just flat dead miss.... HELP!!

Thanks from snow covered MI!

I could be wrong, but i think back firing is more common to carb problems.
take all the plugs out. and one by one check them for spark as you hold it to the engine and crank. get a service book if you dont have one. ohm out the coils per FSM. with caps off, (caps and ballast have their own resistance. )
cut a quarter inch off the plug wires before you screw the caps back on.
then totally disassemble your carbs and clean them (3 times)

I would check compression. check valve clearances, adjust your cam chain tensioner (if you can) then get an automatic CCT.

[motoman]

I could be wrong, but i think back firing is more common to carb problems.
take all the plugs out. and one by one check them for spark as you hold it to the engine and crank. get a service book if you dont have one. ohm out the coils per FSM. with caps off, (caps and ballast have their own resistance. )
cut a quarter inch off the plug wires before you screw the caps back on.
then totally disassemble your carbs and clean them (3 times)

I would check compression. check valve clearances, adjust your cam chain tensioner (if you can) then get an automatic CCT.

Again, since Marty stated you already know that carb issues are electrical, you would also know that includes both primary and secondary ignition gremlins.

[MaximPhil]

So, broke out some wire and the old solder rifle. Bike used to misfire on 2 and 3. Now it misfires on 2,3, and 4!

I guess I will be rebuilding that entire wire harness.......

To the my new, local friends. I will meet up with you all in the near future I am sure. I am VP of one of the local BMW clubs, and therefor spend most of my time on two wheels. We will have to meet for breakfast sometime....

Welcome der verge,
I don't know how many BMWs you have to own to be Vice President at that club BUT here at XS11.com owning just one XS11 qualifies you as a Vice President
Those who relinquish their VP status by selling their XS but continue to hang here with us are known as FOXS ( Former Owner)
Maxim Phil

[bikerphil]

Check the 4 wires going to the primary side of the coils, the wire can break inside the insulation at the bullet connectors. The 78-79's are more prone to break there from tugging those type of connectors apart. I found one like that that last week, no spark on 2 and 3, and it stretched just like a broken pick up coil wire would.

[der verge]

Welcome der verge,
I don't know how many BMWs you have to own to be Vice President at that club BUT here at XS11.com owning just one XS11 qualifies you as a Vice President
Those who relinquish their VP status by selling their XS but continue to hang here with us are known as FOXS ( Former Owner)
Maxim Phil

Funny. Actually, it was not the number of BMWs I had owned that got me the position. I made the mistake of missing the meeting when nominations for office were held. I guess punishment for missing a meeting is a year of service! It is surprising when you are elected to an office you did not know you were running for....

Bikerphil, thanks for the tip. I hate wiring issues, so any pointers where to look are very, very appreciated. I have a go at it tonight when I get home.

[TopCatGr58]

Hey Verge and Gallaceous,

You have to be careful when checking for spark on the plugs when you remove ALL of them from the engine at the same time, because these coils are wasted spark design, they fire both plugs for each coil at the same time, running through one plug, then the engine, and then back up thru the other plug.

So....when you try to test them, you need to be sure to have a plug in the coil wires for both plugs on the same coil and laying against the engine. The spark has to have a complete path to travel through to be able to see and test for spark. IF the other plug isn't properly grounded, then you won't be able to see any spark, and some coils can actually be damaged if the spark energy can't pass thru the circuit.

T.C.

[Gallaecus]

well, i did start off by saying "i could be wrong"
I was thinking...by taking all the plugs out, the engine would spin easier and not kill your battery, but then again it may blow all the gas out the plug holes and light your bike on fire when checking for spark. I probably would have just got a fifth plug and checked them one by one and not removing any plugs.
what do I know?
I did google wasted spark and it talked about spark on the exhaust stroke being wasted. no mention of spark traveling back up to the coil. I cant say Im convinced on that one, but if you say so. I dont want to fry a coil either so Ill take your word for it.

[TopCatGr58]

Hey again Gallaecus,

No aspersions intended, just some FYI for others that may also be reading this to prevent them from either making wrong diagnosis as well possibly damaging their coils. Yep, the wasted spark is where it fires during the exhaust stroke, but that's because the 1 coil is firing both plugs at the same time, and the paired cylinders are timed so that when 1 is on compression/power stroke the other is on exhaust. And unlike auto coils that disharge into the engine, our paired coils require the spark energy to travel from the main plug wire, thru the plug, then thru the engine, and then back up thru the other plug and back to the coil to complete the circuit. And so that's why if either wire is not connected to the engine/frame/ground then a person won't see a spark on the other one they are watching/testing and may make an incorrect assumption that they have no spark and a bad coil.

The idea of all plugs out of the cylinders IS a good idea, similar to when performing a compression test, lets the engine crank easier and faster, less stress on the battery/starter, and as long as the fuel is not turned on, you shouldn't get much/any thru the carbs and out the cylinders.

T.C.

[MarkD]

TC- your 'wasted spark' explanation makes sense to me now. A few years ago, when I had my first XS, the infamous spark advance weak wire problem caused a break-up at 4500 rpm. I checked the coils, replaced them, as they seemed to have no spark, and of course, still had the 4500 rpm break-up afterwards. I was not a member of the forum, so after 2 ' mechanics' couldn't figure the problem out, I found one who knew exactly what the problem was, had it fixed in a very short time. Glad I'm now a member.

[Crusty Snippets]

Missing

Phil. Thanks for posting that.
My Yami has a misfire at idle after being riden in the rain for a while.
Runs on 3 at idle and stutters a bit when taking off, then runs on all four.
I will replace all the plug caps and check the wyres you described. Will study the coils next time I have the tank off.
Unkle Crusty