• The idle screws felt extremely touchy
• Small adjustments made big changes
• I couldn’t get it to settle consistently
• I’m not confident I properly “reset” the idle screws from a true baseline

At this point, I’m not sure I’m correctly identifying when the idle screw is actually making contact internally vs just free play, so I may be chasing my tail there.

Current issue:

Right now, unless I keep the idle set relatively high, the bike wants to stall when I try to bring it down near ~1,000 RPM.

Additional observation (possibly related):

Yesterday, after running the bike and shutting it down, I put it on the center stand and realized I had left both petcocks on.

About 10 minutes later:

• Left side looked normal
• On the right side, I could see what looked like continuous fuel bubbling in the small glass area above the carb

I shut the petcocks off immediately.

Appreciate any guidance. I’m trying to be methodical here and not make things worse by guessing.

Keeping it real, if there were a spectrum of folks who are experienced and knowledgeable airhead mechanics, if it's not obvious, I'm pretty low on that spectrum. I have the original service manual as well as a copy of both a Clymer's and Hayne's manual. AI is a great resource for finding what I'm looking for as well. I came here, because on my clutch repair, some kind fellas helped me dial right into what needed to happen.

***Additional observation.....when I turn the throttle it does not snap back....it usually makes it's way back eventually, but not immediately and consistently. Sometimes I have to turn it back myself***

Ive been having trouble syncing my carbs. The left cylinder pulls way more vacuum than the other, so the manometer won’t level at all. The carbs were just rebuilt by Bing. I did a compression test and it was strange. I saw online to remove the carbs first before testing, so I did both:

with carbs on, no filter: L=65 R=120

without carbs on: L=130 R=125

what on earth is going on??

thanks!

My first thought was to pick up Rick Jones Classic Boxer Charging to see if it would lend some insight. In reading through his book, it seemed like my Voltage Regulator may have been the issue. But, I swapped out, what I believe to be a functional, used voltage regulator, and it did the same thing.

In full disclosure, I had one of the moments when putting the bike back together, that makes me feel a little less than bright. Fairly recently, I replaced the battery with a MotoBat. They seem highly regarded and I've been really pleased with it. However, these batteries have 4 connection points rather than 2. And I found out the hard way then the connections aren't symetrical.  Obviously, I wasn't paying close enough attention when reinstalling the battery and had it sitting in the cradle backwards. I attached the positive terminal first and then when attempting to hook up the negative terminal, I was treated to an impressive sparks show. It took me a minute to figure out what I had done. I then swapped the terminals, turned on the ignition switch and everything seemed to work as it should. 

This past weekend is when I finally had the bike ready for its first spin. It started just fine and seems to run with no apparent issues, other than the generator light burning brightly as I motor down the road. I'm wondering if I have fried the diode board or maybe something else. Any sagely advice would be greatly appreciated. 

Much appreciated. 

Bombadil

Longtime lurker, I just joined the community today.  My 1988 R100GSPD Bumblebee has remained stock for 27 years of ownership, but I never took the beast too far off road.  Pick it up 4x in sand or mud and you will start looking for weight savings...

DURABOOST lithium ion battery shows 13.3V at the terminals.  Rev to 3000 and the voltage spikes all over the place.  28V 30V?  Scrambled numbers hard to read on multimeter.  Collective wisdom here says it's the VR.

Yesterday, my AIRHEAD friend emailed this same question to you experts, and the team answered the call!  "BP", Dave F. and others responded to my pal via AIRMAIL, and steered me in the right direction.

Thank you for the quick responses and suggestions for a solution.  Voltage Regulator replacement in the mail.

-Chris "Big Bird" Ryan

Yes, valves have been adjusted.  Yes, timing is correct.  Carbs have had a “sub total” rebuild with cleaning soak and new o-rings.  Diaphragms are either new or fully intact.  Fuel/air mixture screws are new.  The rich condition seems to be true for both cylinders. The “choke” levers close fully.

Main jet, needle jet and needle all are at factory settings for sea level where I ride.  I can’t, however, tell if the needle or needle jet are worn enough to alter the air mixture or not.  

Without buying new main jets in multiple sizes, new needle jets in multiple sizes and new needles, where should I start in trying to alter the fuel air mixture?

I hope that I have conveyed that I’m aware this is a complex system and there may be other factors at play but I’m specifically asking if renewing or changing main jet size, needle jet size or needle height is something I should consider.  

 trying to fix my /5 but am having trouble with the carbs. I’m used to Japanese bikes and these are a bit different. I had no good top end performance and the left cylinder was running rich. I could smell gas on the plug. I noticed fuel leaking from the throttle shaft so decided to rebuild. All going ok until I tried to remove the shaft. I couldn’t get those two screws loose on the valve. Folks on Facebook said to grind down the back sides because it’s crimped but they still won’t budge. Now the head is starting to strip and I’m afraid that if I keep trying it will strip completely. I’ve used plenty of PB blaster with no movement. How do I get these screws out?? I’m almost to the point of replacing the carbs with Mikunis! Many thanks!