R27 Cold Start Nightmare

[Bob Allan]

Would the raging idle be due to air leaks?
Mine initially did things like that- engine speed going wild. I sprayed the joins with carb cleaner but couldn't find anything. I couldn't get to the bottom of it but it eventually came good.

[Seek]

Could be the ignition timing advancer being sticky. If it doesn’t return to rest position it will have too much advanced timing at idle and thus increasing the idle speed.

[Worleybird89]

Would the raging idle be due to air leaks?
Mine initially did things like that- engine speed going wild. I sprayed the joins with carb cleaner but couldn't find anything. I couldn't get to the bottom of it but it eventually came good.

Quite possibly so. And based on some video content I found on air bleed idle adjustments in general, I am probably too lean. When I initially cleaned the carb, I did not have new gaskets. They all looked okay, but looks might be deceiving and my eyesight is not what it used to be. The Bing carb rebuild kit just arrived today. Hopefully I can get to it this weekend, and will post an update with results.

[Worleybird89]

Could be the ignition timing advancer being sticky. If it doesn’t return to rest position it will have too much advanced timing at idle and thus increasing the idle speed.

I will certainly check that. The bike did a lot of sitting after the initial restoration, so I'm not sure it was ever really completely broken in.

[Bob Allan]

Seek's idea about the sticking advance is a good one. Thinking about it now, that may be why mine played up in a similar fashion. Though of course the 26 & 27 have different units.
Sorry to keep bringing this back to my bike, but the symptoms are so similar it's worth comparing ideas.

[Worleybird89]

Seek's idea about the sticking advance is a good one. Thinking about it now, that may be why mine played up in a similar fashion. Though of course the 26 & 27 have different units.
Sorry to keep bringing this back to my bike, but the symptoms are so similar it's worth comparing ideas.

No problem, Bob. There doesn't seem to be near as much info on the thumpers as there is on twins, so if this thread helps anyone with an R26 or R27, mission accomplished!

[Rodolfo850]

Hello

Its good to fit a brand new ignition points set (Noris or Bosch), don't use knockoffs, I found that this replicas has poor quality con central bushing that deforms to oval shape, causing ignition problems.

check your ignition coil and contact plate for clean and tight connections. You need to check what's happening when have new starting problems, if have wet spark plug can be a flooded carb or too high float level. Check or change wiring between ignition points and generator body, it tend to crack due too short bend angle near ignition points cover hole.

valve clearance also affects starting.

regards

Rodolfo

[Worleybird89]

Bing sent me a 7 gram float with the 1/26/68 rebuild kit. My carb currently has an 11 gram float. The float is fine, so I can complete the rebuild without replacing it, but curious if this was a mistake, or if there is some configuration of this carb that uses the 7 gram float? The Max BMW parts catalog shows 3 float options, (11 gram brass, 11 gram alcohol proof plastic, and 7 gram brass), but only lists the R27 on the 11 gram options (attached).

Would the 7 gram reduce leaking/flooding, or would it starve the engine?

[schrader7032]

The singles require an 11gr float...the twins got the 7gr float. I think if you used the lighter float, it's going to ride higher/quicker in the bowl and cut fuel off sooner.

[Worleybird89]

The carb rebuild seems to have fixed the leaks, but that's all so far. Could not get it to fire after putting everything back on, so back to electrical. That new plug I put in last week was jet black, so I was definitely running rich with the carb mixture. When I kick the motor over with the plug grounded, I am still getting an inconsistent weak spark. I got some new and used parts this past week, including points, coil, condenser, stator, rotor, etc. I'll start testing and swapping things out until I find something that works.