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Old 08-23-2010, 09:01 AM   #16
drooartz OP
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Quote:
Originally Posted by Renner
64/32/13 & 14: those are the right carbs.

Concerning the fuel delivery issue and resultant stumbling: I would suggest you try a few miles without the "VW" style paper inline filters as the added restriction, though minimal, can result in the symptoms you describe.

Really good to hear you've had a chance to take it out for an extended ride, except for the part where it's slower than your not-so-old Bonnie.
Thanks for the confirmation on the carbs -- good to know what I have. In general this bike, though tired, appears to be generally unmolested and original, which really helps with troubleshooting. I'm going to play a bit tonight with draining the tank and checking the petcocks and fuel lines at least. Will try running without the filters to see if that makes a difference.

As for the slower part, this bike is probably sitting well over 100k in miles (hard to tell, as the speedo/odo/tach is broken). So it's down a bit from where it should be. I expect that by the time I'm done I'll have it back in tip-top shape.
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Old 08-23-2010, 07:49 PM   #17
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Both speedo and tach are broken? Are the cables disconnected?
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Old 08-23-2010, 07:59 PM   #18
drooartz OP
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Quote:
Originally Posted by Wirespokes
Both speedo and tach are broken? Are the cables disconnected?
Yes to all questions, and the needles on both have broken off. PO told me that they both stopped working, so he then disconnected the cables.

It's a winter project for me to pull the gauge and find a good refurb shop.
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Old 08-23-2010, 09:09 PM   #19
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Quote:
Originally Posted by drooartz
Yes to all questions, and the needles on both have broken off. PO told me that they both stopped working, so he then disconnected the cables.

It's a winter project for me to pull the gauge and find a good refurb shop.

Well, when youre ready for a fix, talk to wirespokes about your gauges.

I needed the faces on mine converted to /6 style and a little general maintenance and not only did he do an outstanding job but he got them back to me in time to make the MOA National Rally.

Good guy, good prices and great service!
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Old 08-24-2010, 02:08 PM   #20
drooartz OP
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Quote:
Originally Posted by mymindsok
Well, when youre ready for a fix, talk to wirespokes about your gauges.
Good to know. That's one of my top priority winter projects. Just need to do a few more gigs to raise some more bike cash.
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Old 08-25-2010, 04:16 AM   #21
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Quote:
Originally Posted by drooartz
Good to know. That's one of my top priority winter projects. Just need to do a few more gigs to raise some more bike cash.
With both petcocks open, you are getting plenty gas to the carbs, no matter what.

Pop the float bowls, insomuch as it takes 2 seconds and have a look. Fine sediment or water globs indicate a tank flush and need to fit filters. I always run filters...and watch them fill up with crap too. The stuff in a lot of gas pumps is crummy and you never know what the last guy got in the end of the hose. Never buy gas if there is a tanker filling the gas station tanks.

If the diaphragms are bad it is bad all the time. un-mistakeable. If the jetting is off it wwill be gutless and run hot---but smooth. Air leaks at the carb or the carb-to-head rubbers will lean it out too. But simply examining the plugs will reveal this. The next time it is stumbling kill it and cheeck the plugs.

I would most suspect an ignition issue---weak sparks from old coils or bad wires or old /dirty plugs. This shows up most under load and it is a stumbly sort of effect, not smooth but gutless.

I'd give it a basic tuneup, plugs points, check the plug wires and also the coils before I messed with the carbs. And then don't mess with the carbs unless you have balancing issues (idle air screw does nothing for example) or plug chops reveal a mixture problem.



Beware the front brake if it is damp inside and your speed is low.
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Old 08-25-2010, 06:36 AM   #22
drooartz OP
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I drained and pulled the tank last night. Blew out the petcocks and they seem to be working fine. I'll replace the in-tank screens. Inside of the tank doesn't look too bad at all. There was a bit of gunk on the internal screens, but not too much.

Before I pulled the tank, I did a quick test run with the external inline filters removed and still got the issue (not surprising). I've got a carb rebuild kit coming from Hucky. I'll pull the float bowls after work tonight and see what's in there. Carbs look pretty grungy from the outside, so I don't mind digging in an cleaning them up.

Plugs and plug wires are new, points were set by a known good BMW mechanic (ie not me ). Coils were not replaced.
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Old 08-25-2010, 09:45 AM   #23
Bill Harris
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Quote:
points were set by a known good BMW mechanic
Check the point gap anyway. Sometime's they'll wear in after a few hundred miles and close up. 0.016" or 0.4mm. Make sure a dab of distributor cam grease is rubbed into the felt pad on the breaker plate.

Remember, you have a new-to-you bike and although it's been well-maintained, assume nothing. You're zeroing out the maintenance history.
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Old 08-25-2010, 04:12 PM   #24
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Quote:
Originally Posted by drooartz
Bike definitely has a fueling issue (PO did tell me about it). Quite a few times the bike would feel like it was out of gas -- tank was full and both petcocks were on. Sputtered and hesitated. Carb rebuild, as well as cleaning out the tank and petcocks probably in order.
I had the same issue when I picked up my /5. Turned out one of the floats was set just slightly too low. The bike would starve a bit when on the throttle. Raised the float a smidge, problem solved.
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Old 09-05-2010, 07:02 AM   #25
drooartz OP
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Got it running!

To wrap this thread up, I put some time in over the last week and rebuilt the carbs (new gaskets/o-rings, throttle shafts, jets, cleaned everything carefully) and cleaned out the petcocks. New in-tank screens and new inline filters (from Bing).

Got the bike reassembled yesterday and took it for a quick spin. Acceleration is much improved, and the stumble is gone. Woohoo
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Old 09-05-2010, 07:57 AM   #26
Bill Harris
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Yep. Even though carbs can "look good", unless you know it's been done recently and correctly, it's a good idea to re-do the carbs. Eliminates one area of questions.
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Old 09-05-2010, 08:52 AM   #27
lkchris
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Quote:
Originally Posted by Frank06
At 9,000 feet altitude your bike will be running fairly rich I would think... maybe float levels are a bit high? Go down one size on main jets?
Nah, Bings self-adjust for altitude--thinner air means less diaphragm deflection.
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Old 09-05-2010, 09:06 AM   #28
Renner
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Quote:
Originally Posted by drooartz
Acceleration is much improved, and the stumble is gone. Woohoo
Most excellent, dude.
Ride on.
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Old 09-05-2010, 09:34 AM   #29
fishkens
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Quote:
Originally Posted by lkchris
Nah, Bings self-adjust for altitude--thinner air means less diaphragm deflection.
Kent, I'm surprised to hear you say that. My Bing manual clearly addresses the possible need to reduce main jet size for higher elevations. Granted, you don't need to change jets for a two week tour through Colorado but when I moved from sea level to Santa Fe (and another time to Ft. Collins) I went to a smaller main jet and dropped my needles.

Depending on where the bike was tuned for previously, if he's going to regularly ride at > 5K - 10K feet adjustments may be in order.
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Old 09-05-2010, 10:49 AM   #30
drooartz OP
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Quote:
Originally Posted by fishkens
Depending on where the bike was tuned for previously, if he's going to regularly ride at > 5K - 10K feet adjustments may be in order.
Once I get used to the bike I figure I'll need to dig in a bit and see if it is running too rich. Easy enough to tweak once I know what needs to be done.
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