Vw points set fr r90/6?

[Captdan]

This weekend while doing some maintenance on the r90/6 she started running really rough. The long and short of it is the right side was not firing all the time and after taking the carb off for a cleaning with no results I'm thinking the coils may be bad. I located two replements via a local parts dealer that should be here tomorrow. ( these are 6 volt vw coils).


Does anyone know of a cross over part number for a set of points? I am try that tomorrow if the coils don't solve the issue.

Thanks,,.

[disston]

The problem is very seldom the coils on a /6 machine. The VW coils will work only if they have the correct resistance. Not all do I'm told.

Right side not firing? Check the plug wires, plug caps and spark plugs. Spark plugs are non-resister. Wires are non-resister. Plug caps should have about 1000 Ohms rsistance.

Ignition points are a maintenance item. You need the BMW part.

Condensers go bad.

When you get it running check for uneven firing. The tip of the cam can be bent and causes one side to fire way later than the other side. You have to look at the timing window with a timing light while engine is running to see if both sides fire evenly. If it appears there are two firings or a ghost image you have found the problem.

[disston]

Erratic firing can be caused by a worn out advance unit. The tiny springs have to be in good shape to work. The advance unit gets cleaned and greased. The points cam gets a tiny amount of special grease.

[DoktorT]

There is no equivalent by anyone, not even Bosch, for those points. They are a one off design from the first /5 through the 78 model year /7's. It means low volume therefor high price. One thing that can be done is to add the Dyna Booster. It drops the amps load on the points to triple or better their life.

Oh, and the Bosch Blue coils designed for the 6v VW's are a perfect replacement. Very rare that stock coils fail. The only reason to replace them is if you see any corrosion inside the towers. They cannot be fully cleaned and it will come back to haunt you.

[Captdan]

Originally Posted by disston

Erratic firing can be caused by a worn out advance unit. The tiny springs have to be in good shape to work. The advance unit gets cleaned and greased. The points cam gets a tiny amount of special grease.

Thanks, good things to check. I'm hoping to locate the failure by going item by item. It's really odd to say the least; this morning head down the road to warm up the bike in order to replace the pan gasket. Ran like a bat. Then when the pan gasket ( also replaced the gaskets in the oil sump pick up) all got bolted together I noticed the rough running on the test run... I'm sure I did nothing to cause it working at the bottom of the bike.

[Captdan]

I should also mention that this rough running consist of backfires, spitting and rough running. Almost like the timing is out of calibration. The search for the problem continues.

[disston]

Originally Posted by Captdan

I should also mention that this rough running consist of backfires, spitting and rough running. Almost like the timing is out of calibration. The search for the problem continues.

So, tell us, have you checked the timing with a timing light?

Have you adjusted the valves yet? Most new owners of Airheads do not get the part about valves and tuning the machine. Once you have been at this for awhile it will make more sense. Right now you need to learn how to adjust the valves. Directions are in all the manuals. You do have a manual?

[Captdan]

Ok, so this morning I swapped the plug leads from right to left, same issues..... Right side sputters at mid rmp. ( yesterday was backfiring out of the right side, not today). So the coil may be ok. I did not include the points on my fact finding yesterday as I thought if the points were the issue then both right and left would sputter and pop.. Well, I popped off the front cover and inspected the points. Seems to be a "pit" on the lower side so not having a new set I sanded down both side with some 400 grit sand paper ( very lightly). The bike runs much better now, still not up to snuff and tends to miss in middle range rpm ( slow speeds in 2nd 3rd). Question: could indeed the point be the problem? Could bad points seem to make one side run bad and not the other? I can't see any other problems and a pitting of the points can't be good anyway so I'm going to order a set first thing Monday morning, along with a condenser.

[disston]

You need to adjust the valves. Set the dwell and timing on a new set of points and then you can adjust the carbs.

Use .006" for the intake and .008 for the exhaust.

Each year and model Airhead has a different starting point for the idle mixture screw. Tell us what the numbers are on the side of the carbs. They should be 64/32/11 & 12

[Captdan]

Originally Posted by disston

You need to adjust the valves. Set the dwell and timing on a new set of points and then you can adjust the carbs.

Use .006" for the intake and .008 for the exhaust.

Each year and model Airhead has a different starting point for the idle mixture screw. Tell us what the numbers are on the side of the carbs. They should be 64/32/11 & 12

Looks like 64/32/11 on the left and 64/32/12 on the right.

[disston]

As mentioned earlier. The Bing carbs all have a different start position on the mix screw. From this position the bike can be riden enough to warm up and then a final adjustment of the carbs performed. Also mentioned earlier the tune up should include a valve adjustment first, then points dwell and timing (new plugs often are helpful. Then the carbs can be adjusted.

Those carbs are the stock crabs for all R90/6 machines. The start setting for the mixture screw is One (1) full turn out. BTW this is a fuel adjustment, not an air adjustment like in many carbs. Counter clockwise is richer.

[Captdan]

Originally Posted by disston

As mentioned earlier. The Bing carbs all have a different start position on the mix screw. From this position the bike can be riden enough to warm up and then a final adjustment of the carbs performed. Also mentioned earlier the tune up should include a valve adjustment first, then points dwell and timing (new plugs often are helpful. Then the carbs can be adjusted.

Those carbs are the stock crabs for all R90/6 machines. The start setting for the mixture screw is One (1) full turn out. BTW this is a fuel adjustment, not an air adjustment like in many carbs. Counter clockwise is richer.

Thanks for the notes. I'm awaiting delivy of the points and condenser. Did the valves tonight ( were a bit tight). Also obtained coils, plug wires, and new spark plugs. This weekend I'll install all the new parts and see if I can get it back to running like it was. ( also ordered a new nutral switch and will install it too due to leaks). Another few years of r90/6 ownership and I may know something about working on one. :)

Ps: yes, have an old shop manual that came with the bike.

[disston]

Setting the valves and the other stuff you mention should have you purring along soon.

It is possible to put a neutral switch in the trans with the trans in the bike. Remove the rear cross engine mounting stud. The switches that are from dealers these days all leak I think I've read recently. Riders are sealing the switch with epoxy around the area where the wire terminals are. It was discussed sometime in the last week or two. Maybe I can find it.

[disston]

Here is the story and the fix for leaky neutral switches.

http://advrider.com/forums/showthread.php?t=465741

[Biebs]

I have seen this type in problem in an old point ignition car specalation was blown head gasket, bad cam
turned out to be a bad condensor causes all kind of misfiring points do not break clean leaves a spark traveling across the point. Condensor is there to make the spark take the least path of resistance and clean break on the points- no arc.