Monday, August 11, 2008

Today's Wrenching Theme: Carburetors

I gotta tell ya, you really have to have a willingness to tinker and learn wrenching concepts when buying a motorcycle that's over 22 years old and has over 60k miles on the odometer!

Today's wrenching theme was Carburetion and my discovering how sensitive the carburetor floats are on Brigitta's left carburetor. Yep, the carburetor which has the broken float pin mount, and the subject of many of my recent postings.

After experiencing no issues on the ride in to work, I had some power loss near the end of my commute home. It felt like I was not getting gas and I even switched to reserve to see if perhaps that was it. Nope. I thought then that the new ICM which had been causing tachometer needle twitchiness was the culprit. Got home, swapped it with the old one which did not cause tachometer twitchiness and after after a few miles...experienced power loss again!

This power loss usually occurred above 60 mph which was kind of weird, then Brigitta would just run like there was no power, and I'd barely be able to ride along at 50mph on the straightaways, on the hills she'd just steadily lose way.

Returned home to dinner, thought about it some more and since it was not the ICM, figured perhaps the left cylinder was not getting fuel when at the higher speeds. Figured perhaps gas was being drawn up by the carb faster than the fuel was being resupplied into the float bowl.

So, finished dinner, took the left side carburetor floats out and bent them to be as straight as possible as I believed previous tweaking on my part had not helped things. Put it all back together, checked for leakage then geared up for another test ride.

I rode her out to Quincy Road as before and as before, experienced power loss symptoms at damn near the same mile marker! Damn. Stopped her on a side road, killed the engine and without using the sidestand, got off the motorcycle and put her on the centerstand.

I took off both carburetor float bowls and noticed that the left side bowl's fuel level was significantly lower than the right side float bowl's fuel level! Hmmm.

I "tweaked" the floats some more so that they were a bit more angled upwards as they hang on the mounting pin. This way, I thought, the fuel level would go up higher before the floats actuated the pin that shut off further fuel from the tank.

Once again, put everything back together and went off eastward on Quincy. Things were much better this time and I was able to sustaing speeds in the 70-80 mph range with the usual great performance I'd come to expect from my R80. I went all the way till Quincy Rd/CR30 became dirt, and turned around to do another high speed run westward in the direction of home.

Brigitta's floats must be at the right angle now since she did not complain or lose power through lack of gas to the left cylinder! I was a happy camper once again. Sensitive buggers these floats!


Today was also the day the replacement carburetor body I got from arrived. $75 was the cost and the part is in very good shape! Here's some photos of the part which I'll be swapping out with the damaged one come the end of the month.

Existing Carburetor: Bottom view, note the broken mount where the float mounting pin is exposed.

Replacement Carburetor Body: Bottom View

Looking down into the replacement carburetor body

Existing Carburetor, Inboard side

Replacement Carburetor: Inboard Side, not the unbroken float pin mounts!

Existing Carburetor: Air Intake Side, you can see the jet needle inside

Replacement Carburetor: Air Intake side

Existing Carburetor: Fuel/Air Mixture Output Side, note the Throttle Plate

Replacement Carburetor: Fuel/Air Mixture Output side

So why wait till the end of the month you ask? Well, one of the recognized Gurus within the Airhead Beemer community, Matt Parkhouse, in Colorado Springs has agreed to help me transfer the innards under his guidance; and he's ok with me taking pics throughout the process for the blog! The airhead beemer community is really full of helpful and experienced folks like Matt and I am very fortunate in that respect.

I've also received the BING Carburetor Manual, very handy reference and only $10.50. Today I also ordered new screws that hold the throttle plate to its mounting rod. I'll most likely have to dremel off the existing ones since they're peened to prevent their coming loose within the carburetor. I am thinking perhaps of ordering a replacement cork gasket for the float bowl as well. Maybe tomorrow.

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