New Carb Rebuild

Time to rebuild the carbs today, my carb rebuild came in the mail

• New Diaphrams
• New Gaskets
• New O-rings
  

I did noticed that the left carb ran much smoother, I did one at a time, between test rides.

Here is the kit visually

New Clutch Cable

I installed a new clutch cable today, boy what a difference the new bowden cable made, I adjusted to the proper feel, with no slippage, it made such a difference in shifting from first to second.

New Plugs Bosch W5DC Copper Core

I installed new spark plugs today, man bike started right up, first try with choke. The old NGK plugs did not look that bad, and I will save for emergency road trip parts, but at least I know they are new, and original Bosch plugs to boot.

Bing Carb Numbers

In preparing to order Bing rebuild kits, I came across conflicting information about my 1977 R100S. Some of the third party online parts suppliers have my carbs listed as 32mm carbs, others listed as 40mm carbs.

The Beemershop showed me where the numbers are, man they are hard to read. On mine they are located on the left webbing area right below the cover, they are stamped vertically, and mine were not stamped deep. The "/" slahes alomst look like 1's if your aware this is the format X/Y/Z.

Mine are 40mm carbs, like I thought, but it is worth checking, measure twice, buy once.


Left Carb
94/40/103

Right Carb
94/40/104

Reference:

Bing Link

Good Vibrations

Real Progress

A short 40 mins test ride, no stumbling, no lurching, no stalling, very slight popping on engine braking, but not load or consistent. I might have somewhat corrected the fuel issue. On the next ride, I will pull over at random times, and check fuel level in bowls just to see if the absense of screens is realing making a difference.

Next problem, is why the low vibration at all speeds. Idle is rough, Plug replacement, and check gap spacing is next test, of course one at a time to see if the new plugs will help.

Tranny Drink

Continuing my maintenance list, I had order some Redline Transmission fluid, not a difficult task, not necessary given the unknown maintenance this bike had.

While draining the old gear oil, I realized I forgot to get a new crush washer for the drain plug. I have a new filler plug crush washer, hopefully it will not leak much.

One quart of Redline 75W90 synthetic oil, and about 10 mins later were good to go.

Note
Old oil did not look bad at all. Magnet drain plug had a bit of black paste, and some small flakes.

Fuel Petcock Screens

Since my stumbling, lurching issue started, I want to test if this was a fuel flow issue.

The Test Ride
I went for a short ride, various speed, after about 10 mins, the bike lurched, and begin its usual crappy ride. I pulled over, gave it about 2 mins for carbs to fill back up and continued on. I rode another 10 mins, and the bike still was lurching, this time I had only one petcock on, the left, I quickly reached down turned it off, and pulled over.

The left carb bowl was about 1/3 full, and the right about half. I left the petcocks on, and it would not start, until I let the bowls fill back up. At this point the carbs are not synced, so it might be running lean or rich, but it did seem as though my issue is fuel flow.

Fuel gas cap is venting, so I decided to check the new petcock screens. I proceeded to let the bike cool off, and then drain the fuel, the left side seemed slower than the right as the fuel flowed out of the petcocks. I cleaned them out,, there was some red flakes coming out of the petcock tops, and reinstalled minus the small lower screens. I left the top straw screen on, since i know the tank is flaking a bit.



This tank is due for flush out, repair, and paint, but for now I will try riding without lower screens to see if this helps.