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Old 08-26-2012, 08:32 PM   #16
photomd
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IMHO, don't rely on the floats being parallel with the base. I did and chased my tail with a stumble at around 75mph. Follow Snowbums fuel heights: http://bmwmotorcycletech.info/bingcv-2.htm. There very easy to check on our bikes. Mine was 17mm by the parrallel method. I moved it to 24mm for the 32mm Bings and it's much better: no stumble.
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Old 08-26-2012, 09:14 PM   #17
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Originally Posted by photomd View Post
IMHO, don't rely on the floats being parallel with the base. I did and chased my tail with a stumble at around 75mph. Follow Snowbums fuel heights: http://bmwmotorcycletech.info/bingcv-2.htm. There very easy to check on our bikes. Mine was 17mm by the parrallel method. I moved it to 24mm for the 32mm Bings and it's much better: no stumble.
thanks for the link ... much easier than turning carb upside down
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Old 08-26-2012, 09:35 PM   #18
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cool, that makes sense - tune for the actual buoyancy of the floats, not just the geometry of where it 'should be'.

so if I understand his method correctly, you just deal with that extra bit that dribbles from the fuel hoses when you take the bowls off? It's factored-in? Or doesn't make a big difference?
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Old 08-26-2012, 10:24 PM   #19
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I didn't worry about it. I just pulled the bowl, emptied it, filled the bowls using the petcock, turned off the petcock and removed the bowl. I immediately set the bowl in the level concrete in my garage, took my venier caliper and measured it. I think I just held the bowl in place while filling it...just make sure it's full seated so you get a good reading. I think it took 20 minutes to do both carbs.
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Old 09-03-2012, 12:38 PM   #20
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same deal here

Any progress? I developed the same problem recently with my '76 R90/6. The problem started the same day my rotor went bad, which is weird. I replaced the rotor the other day and still have the stumble, at least I'm charging! Stumbles around 80mph, loses power, recovers. Feels like a fuel issue. I'm going to clean the tank, check the coils, plug wires, timing and points. Carbs have been rebuilt within the past 8K miles and balanced within the past 1000 miles. Petcocks rebuilt recently also. No crap was found in the float bowls.
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Old 09-03-2012, 01:22 PM   #21
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Well Chobro. You might have to start another thread because this one is really veeeery long. And you can't have the same things happening, can you? Stumbles at speed? They were working on carb float level when it died so maybe that means that was it? Check carb float levels.

Points ignition can have high speed misses from too little dwell. The points set too wide do not stay together (dwell) long enough at higher speed.

What do your plugs look like?
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Old 09-03-2012, 03:04 PM   #22
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Quote:
Originally Posted by photomd View Post
I didn't worry about it. I just pulled the bowl, emptied it, filled the bowls using the petcock, turned off the petcock and removed the bowl. I immediately set the bowl in the level concrete in my garage, took my venier caliper and measured it. I think I just held the bowl in place while filling it...just make sure it's full seated so you get a good reading. I think it took 20 minutes to do both carbs.
The "floats parallel" is an initial adjustment. It's correct most of the time. The fuel level in the removed float bowl is a good "as built" fuel measurement. On my /5, I used a spring-loaded center punch to put a small "ding" mark on the back corner of my float bowl at the correct distance down from the lip. Now all I have to do to check is remove the bowl and set it on a level surface to check.
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Old 09-03-2012, 08:37 PM   #23
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no updates yet - waiting for new points/condenser from BMW of Grand Rapids. I'm going to solve the weird ignition issue before moving onto other things.

when I was inspecting the bike when I first got it I checked the float levels with the fuel level-in-bowl method, and both of my carbs were low at around 18mm if I recall correctly. Snowbum says they should be 24mm from bottom for 32mm carbs. This even when they were parallel to the carb base.

on my first trip I had similar issues to what I described in the OP, and in doing damage control I raised the fuel level to 24mm among other things like retarding the ignition.. something seemed to solve the issue, but when I took it to the mechanic he set the floats parallel again, and all was fine for many miles.

I think I'll try raising the level to 24mm once I get the ignition functioning again.

chobro, please let us know when you solve your issue..
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Old 09-03-2012, 08:55 PM   #24
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You don't have to have the carb upside down to check the floats parallelism. Just adjust so the gas shuts off when the float is parallel to the carb body while the carb is on the bike. That adjustment gets you real close the same height gas in the bowl every time. After all, it all depends on how you look at the gas wicking up your measuring stick. I have double checked a LOT of 32mm carbs. I think 24mm is a bit deep but, again, that all depends on how you look at it. Maybe that accounts for not disconnecting or pinching off the the fuel lines right above the carbs? I always do.

Checking float bowl level without the floats in the bowl doesn't check their buoyancy very accurately at all. You have to check the fuel height WITH the float in the bowl for that. Lots of carbs you do just that.
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Old 09-04-2012, 01:34 PM   #25
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Well, my plugs look gray. They have 8k on them and the right one looked like it had gotten hotter than the left at some point, kinda rough looking texture on the tip. I checked my coil connections, cleaned them and put on some newer plug wires. I discovered my points had closed up a bit, to around .008, I regapped them and ran out of time to work. I'll check the timing tonight. I'm hoping that resetting the points helps my high speed stutter/stumble/sputter. I'll keep posting my findings and keep an eye out for other developments.
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Old 09-04-2012, 02:28 PM   #26
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At an .008 point gap, the dwell ("coil magnetic saturation") was way low and the timing retarded. It should oughta run betterer by just opening the points up...

You did use a points cam lubricant, yes?
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Old 09-04-2012, 10:27 PM   #27
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When I am working on a bike with points that isn't running right, the first thing I look into is the points because chances are that's the problem.
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Old 09-05-2012, 09:31 AM   #28
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UPDATE: New points and condenser did not fix the double/weird timing issue. Thinking of going to an electronic ignition, which one isn't sensitive to bent camshaft nose/mechanical advance?

Does anyone know someone in SE Michigan with some airhead coils I could try? I'd like to eliminate every variable first. In a related note, does anyone want a new condenser and points?
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Old 09-05-2012, 12:08 PM   #29
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I'll try asking in this thread: I have heard that BMW points are now junk? What brand is everybody using? Maybe BMW points aren't junk? I rarely work on bikes that still have them so I am a bit out of the loop.

Right now I have two RD350s in the shop. On of them already has the inevitable aftermarket electronic ignition. Guess which one runs WAY better? Points on a two stroke is twice the trouble! Per points set!
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Old 09-05-2012, 01:30 PM   #30
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The problem with BMW over the counter points sets was two years ago. Supposedly the problem is gone, has been gone for some time. What happened was the rubbing block on the points that rides on the advance cam was too large. When installed these points could not be adjusted. Some riders got around the problem by filling down the rubbing block.

The solution was that after market suppliers had the Norris brand of points and we all got them they worked fine. Eventually the dealers started selling Norris points. As far as I know the dealers and everybody now sell Norris points.

Blame was placed on the Chinese for making inferior parts. Somebody had to get blamed. The Chinese don't seem to mind, they lowered the price and cornered the market in inferior ignition points.

That's how I remember it.
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