Sunday, March 31, 2013

Happy Easter and Balancing Carbs

It seems like I was just here. I returned from Barrow on Friday evening and after spending the weekend in Fairbanks, I again find myself in the deserted terminal at the Fairbanks International Airport (FAI). I am on my way to the Polar Technology Conference being held in Annapolis, MD, at the Naval Academy. Should be interesting. It turned out to be another warm day (well above freezing) but not as nice as it was yesterday.

Yesterday morning, I got a call from the local Airheads Air Marshal letting me know that it may be a good day to balance my carbs. That afternoon, the same fellow Airhead who helped me overhaul the Bing carburators had me bring the rig by his home and he balanced the carburators. He had a nice quad Hg manometer set up of which we only needed two. They weren't too far off at idle but pretty far off at higher RPM. By adjusting the idle stop screw and the throttle cables he got them balanced pretty quickly. He also had a ColorTune set up which allowed you a peek into the combustion chamber to see the color of the flame while the engine is running. He adjusted the idle mixture (it was only off 1/8th of a turn on one of the carbs) to get the orange color that he was looking for and ran the engine at higher RPM. He said the it was as perfect as you can get with a nice blue.

On the test ride back home, I was pleasantly surprised by the huge difference in performance. There was none of the roughness that was there before and a whole lot more power. With the sidecar, I had resigned myself to never use fifth but now it not only pulled fifth just fine but I was easily able to accelerate in fifth. I had always been concerned about having to restart the bike as it seemed like the battery had just enough charge to turn over the engine but during the balancing process, we probably started the bike a dozen times with never an opportunity for the battery to get charged. No problems at all.

14 comments:

Martha said...

That's a good looking airport!

I had to hesitate when I read "balance my carbs"...potatoes and rice? Should have known it was mechanical... : ^ )

RichardM said...

That's pretty good. That kind of carbs never even occurred to me. Though with all the sugar flying around the house today...

Black Inazuma said...

Bing carbs on the RS or RT?

A couple of 1/4" polythene tubes in the ears and carb intakes to get the sounds roughly the same with the throttle stops, twiddle mixture screws until the tickover is rough, but not very rough - the two options are 'rough' or 'very rough', repeat process to improve tickover if possible until you're bored and then just hope that the bike doesn't conk out when you pull in the lorry-rated clutch to put into it 1st gear.

A Colortune can help but repeatability is normally the issue after snapping the throttle open and shut a few times. Normal tickover on 80's Boxer BMW's can vary from stationary to 1500 rpm! The most important thing is that if the tickover sounds awful then you've probably got it about right. A common problem was sticky throttle cables invalidating all careful adjustments at the carb end.

Aren't you sad that someone else had all the fun for you?!

Black Inazuma said...

PS: You have to re-adjust BMW Bings about every 3 months because they tend to go out of adjustment.

redlegsrides said...

Good stuff getting your carbs balanced by a Guru! I am curious about this colortune method....must find out more next time I am at an airhead tech day.

I used the shorting sticks method, seems to work OK for me so far. We compared my settings against a harmonizer and they were pretty much dead on....

dom

Redleg's Rides

Erik R said...

Richard, I'm glad you got it running better. Now, if the weather would just cooperate.

Trobairitz said...

Another trip? You sure do get around, but at least we get to follow along.

I am glad you carbs are balanced - a smooth ride is a good ride.....

Unknown said...

Richard:

amazing how just a little turn of the set screw can create such a difference in power. I'm glad you're now "balanced" and your cylinders are now working together, rather than against each other.

Another trip ? (echo) Sounds glamorous to us but you are probably tired of all this traveling

bob
Riding the Wet Coast

RichardM said...

I appreciate the expertise since he had a lot of experience with airheads. In the five years I've owned the bike, I've never balanced the carbs since it seemed to run okay. Last summer, during the latter half of my road trip, it seemed like the carbs needed some attention. After cleaning and replacing the diaphragms and gaskets, I adjusted the idle by ear and roughly adjusted the throttle cables. Bob had a nice setup and offered to help.

RichardM said...

As I mentioned in my reply above, this is the first time I've bothered with balancing. It was my intent to just make the $5 version of the manometer but Bob had a much nicer setup.

The ColorTune was something new, I hadn't seen it used before.

RichardM said...

I thought that the weather cooperated pretty well on Saturday. It was a beautiful day and above freezing!

RichardM said...

Yes, another trip. I was getting antsy sitting around Fairbanks for so long. I've never been to Annapolis before and it looks like a very interesting town.

RichardM said...

Not very glamorous but I'm not complaining either. It was a long flight last night as I left Fairbanks at 8:30pm and arrived here at 12:30pm without much of a layover in Anchorage of Chicago.

I didn't think that balancing the carbs would make such a huge change.

BeemerGirl said...

Exciting to notice such a big difference with the slight work. I'm wondering how it will behave in warmer weather.

Have fun in Annapolis. I'm positive there will be some great things to see, all allowing you to walk. Have fun!