One pot wonder

[peteremc]

OK, so I did get a tip earlier today not to concern myself with playing with head bolts while checking valve clearances. The reason I was checking valve clearances was the bike will only fire on one cylinder (the left one) and I was starting with the basics.

The backstory is that I tried to run with pod filters, and the bike ran beautifully until we got to operating temperature and then it was all over the place. (Please be kind because right here, and right now, I really don't need tirade of "I told you so's" that could come).

So, I reinstalled the entire original air intake system and from that point on it magically reverted to running on one pot and I have no idea whether the two things are related - I suspect not, but it's part of the recent story.

The general rule seems to be to not try to tune carbies until valve clearances are checked. The valve clearances were all very tight. I understand they tighten up over time and its about 700klms (approx 450 miles) since they were last done while pushrod rubbers were replaced. I'm happy that they're now set at 0.1mm inlet and 0.2mm for exhaust. Still only one pot.

I then set both mixture screws at what I believe is the factory setting of about half turn back from screwed gently all the way up. Still only one pot.

Dropped both carbies bowls. Both have fuel, both nice and clean, gaskets and floats in good condition. Still only one pot.

I pulled the plugs and checked their condition and spark. Both have what looks like good strong spark. Still only one pot.

I then swapped the plug leads to find that I still had only one pot, but this swapped which pot was firing i.e. seems to be good lead on the left. But, I can see good strong spark from both plugs when I pull them (I've also swapped which plugs are on the end of each lead) but can't get the pot I hook up to the right plug lead to fire.

Any ideas please?

[wilcom]

Could be a bad wire or cap. If you don't have a spare wire I'd grab a wire off the car and and see if it fires, if so, you have a bad wire or cap. If the spare spark plug wire doesn't fix it,  you're down to the coil.........

I had a bad cap on the road and grabbed a used wire out of the trash at the local auto store and it got me to the next shop to make a proper repair with the proper cap.

[peteremc]

Pulled the coil from the bike with plug leads intact. Having fun separating the suspect plug lead from the coil. Seems like a really tight fit. Should it just pull out of the coil?

Also, My car is a diesel so no swapping leads from there.

[mrclubike]

I had the same symptoms and it was a bad coil
If all else check good
(No real good test for a coil)
"Replace with known good part"

[peteremc]

OK, so finally got the leads out of the coil - damn, they were tight. Then I swapped the leads over at the coil and think this has given me a final diagnosis of one bad lead because the problem moved with the lead. The right pot finally ran beautifully - without the left one. So it appears that the coil is OK and I just need new leads. Will get some first thing tomorrow and see how things go.

[wilcom]

If you have electronic ignition(1981+) the cap is 5K ohms.... if the cap has gone bad it will have to be replaced with like kind.

[peteremc]

Thanks Wilcom. It's an '82 model. Thinking of getting to the local auto parts store in the morning. Is there anything I should be specifically looking for in terms of specs for leads? From what I can see online it seems like there's a bunch of generic leads that will do the job in most applications - although there's not a lot of detail online.
Thanks

[mrclubike]

You will have to go to a old school Motor cycle shop to get the 5000 ohm caps like this one

http://www.ebay.com/itm/TRIUMPH-NORTON-BSA-NGK-5K-5000-OHM-SPARK-PLUG-CAP-BOYER-SPARX-PN-TBS-38-1001-/360608436871

Then go to a auto parts store and find a older counter person and ask for a "4 cylinder universal plug wire set with copper core "
Or an Farm tractor  dealer may have them

http://www.ebay.com/itm/9994-OMNISPARK-IGNITION-WIRE-SET-/301867688395?hash=item4648b761cb:g:U6cAAOSwUuFWuAKg&vxp=mtr

Then build your own set and you will have plenty of extra wire to replace the leads when they get ugly

Don't be surprised if you still only have one cyl running at a time
You still may have a bad coil
If it is the original it needs replacing any way

[Barry]

One method for checking ignition leads is to run the engine in complete darkness and look for arcing that might be bleeding off the HT energy.

The replacement leads I have are solid copper cored HT cable sold of a drum and the commonly used NGK LB05F spark plug caps which incorporate a 5K resistor.

[mrclubike]

The green or orange Dyna coil works just fine
I prefer the green because it will work with the older systems
The blue Dyna only works with the newest ignition modules with dwell limiting 

[mrclubike]

One method for checking ignition leads is to run the engine in complete darkness and look for arcing that might be bleeding off the HT energy.

The replacement leads I have are solid copper cored HT cable sold off of a drum and the commonly used NGK LB05F spark plug caps which incorporate a 5K resistor.

If the Local auto parts store has it in bulks that's  good
but it is just as cheap to buy the universal set and then you get the ends and enough to do 2 sets

[Tony Smith]

The backstory is that I tried to run with pod filters, and the bike ran beautifully until we got to operating temperature and then it was all over the place. (Please be kind because right here, and right now, I really don't need tirade of "I told you so's" that could come).

I didn't once say "I told you so Peter" when you dropped in yesterday, and i am certainly not going to now. It is perfectly possible to build a custom induction system, that will leave your airhead every bit as tractable as standard and will not suck in water.

The first thing is the intake induction tubes which form part of a "tuned length" system, it's not hard to measure the BMW ones and the appropriate sized tubing is available in both alloy and structural resin. Small problem though, the ends of the tubes will be about where your ankles want to be, and you haven't yet fitted an air-cleaner. The secret is of course to bend the intake tubes upwards (you could bend them downwards of course, but then they would pick up road grime and heat from the exhaust.

Now that your "velocity stacks" are all nicely curved in order to get the right length in a confined space you need to organize some air filtration.

You could of course fit the accused pod "filters" (in fact they do bugger all filtering but K&N have a very effective marketing arm) but you would the have a small problem in wet weather, or if you need to cross a flooded gutter, or gasp, a small creek crossing.

So you get to build a waterproof housing to contain your filtering system and keep the elements at bay.


And when you finish, your bike will run perfectly. now along the way you will probably design the air-filter carrier so that it is as large as possible, and if you are really clever, it will be cunningly made so that a stock, readily available filter slips right in.

As you finish your design and start cutting metal (or plastic) you could give some thought to a system to allow the engine itself to dispose of nasty crank case gasses and the small amount of oil that comes with them.

The last step will be to use a good dyno and give the air intakes into your air filtration system a good tune up as there is horsepower and economy both to had by careful design in this area.

And, when you have finished all that, it will probably look like the first picture below.

There are alternatives like the one in the 2nd photo, for an alleged gain of a whole 2 horsepower (on an R80) you get one of those egregious waste of money pretend filters from K&N and guaranteed induction howl to keep you awake on the bike.
http://www.bmwr65.org/htdocs/yabb2.612files/yabbfiles//Templates/Forum/default/grin.gif


P.S I hope you have two pots running by now.

[peteremc]

You're a funny man Tony, but you also have too much time on your hands, obviously. I'm on the learning curve alright, and I was warned, but had to give it a go. Now if you didn't live so close and weren't such an amiable bloke who was so prepared to lend me parts and advice when I need them .....

On another matter, after setting valve clearances I'd be interested to know what is the go with the valve cover cap nut? No torque setting available in either of the manuals I have. One says to "tighten firmly".

OK but when I try to do this, on one side it feels like the threaded stud is turning and on the other side I'm pretty sure it is because there is not enough thread exposed to even start the nut. How does that work?

As always, any and all advice appreciated. Thanks

[Barry]

On another matter, after setting valve clearances I'd be interested to know what is the go with the valve cover cap nut? No torque setting available in either of the manuals I have. One says to "tighten firmly".

This thread is known for stripping in the head not least because the stud is a little too short and often isn't engaging all of the threads in the head so that's the first thing to correct if necessary. The steel nut can cope with far less threads engaged but the alloy head can't. As for a torque setting, I've never used a torque wrench on it. Barely above finger tight is all I've ever used and never had a leak. At a guess no more than 5ftlbs.

[Tony Smith]

On another matter, after setting valve clearances I'd be interested to know what is the go with the valve cover cap nut? No torque setting available in either of the manuals I have. One says to "tighten firmly".

The merest whisker above finger tight is about right. If the nut unwinds and you lose it - it was too loose, if it doesn't unwind and jump ship it is probably too tight. Don't panic about losing the central nut, most of the work in holding the tappet cover seal is done by the two M6 studs. I usually put a smear of "Aviation form-a-gasket" onto the exposed stud threads - it isn't loctite but it provides enough "drag' to prevent casual unwinding - same logic as causes bicycle wheel builders (including me) to dip spokes in linseed oil when building a wheel - when the linseed dries out it provides just a little resistance to undoing.

OK but when I try to do this, on one side it feels like the threaded stud is turning and on the other side I'm pretty sure it is because there is not enough thread exposed to even start the nut. How does that work?

The first thing is to verify whether you do have a loose stud of not - if it is merely loose then lock a couple of nuts on it, wind it out and put it back in with some stud lock on it (making sure that there is enough thread exposed for the central nut.

Your other stud has probably simply wound in a bit - two locknuts, wind it out and stud lock it.
 
If the thread is buggered i have helicoils. If the stud is broken I can easily spot you one until your parts order arrives.

To briefly refer to your earlier comments which I didn't quote. I didn't say "I told you so" the other day when you visited and I certainly don't say it now. I've been playing with boxers a while now and I reckon I have done all the usual misguided things people do - remove stock aircleaner, aggressive cams, higher compression, lightened flywheels etc. People with knowledge told me that some of the things I wanted to do would not work - I did them anyway. So far be it for me to say "I told you so" when I have a long time ago done exactly the same things.

However, now that you have tried running pod air cleaners and discovered the truth, I do feel it is my duty to take the piss.