1961 R27 difficulties...

[schrader7032]

A bike that starts cold but has a problem starting hot tends to point towards the coil. This is especially true on the /2 twins which have a magneto ignition system. I believe the singles have a battery ignition system. In the battery system, the battery is a key to the running of the ignition system, so I would also make sure the battery is fully charged and the wiring is good. You said you replaced the battery, so that would seem like that's not the problem.

There may also be a carburetion issue such that the mixture, etc., is fine for a cold start but it may be getting easily flooded when trying to start hot. I've been having the same problem on my R69S. It could be my coil, but I've been experimenting with how/when I tickle the carbs and the position of the throttle when I kick it.

You said it died while riding and the plug looked black. I'm wondering if maybe the coil is breaking down over time, resulting in a weak spark and thus a rich condition (unburned gas) in the combustion chamber making the plug dark. On the twins, there's a way to measure the resistance from one spark plug to the other as a way of assessing the health of the wiring and coils. I'm not sure how to do that on a single, but my guess is something like that might reveal that the coil is breaking down.

Kurt in S.A.

[Isettaman]

I have ordered a new coil from Vech. I'll post once I get it and swap out the old coil. I'll keep you posted. Thanks!

[Allan.Atherton]

I have ordered a new coil from Vech. I'll post once I get it and swap out the old coil...
I doubt if the coil is the problem. The /2 magneto ignition coil failed gradually as the insulation broke down, windings touched each other and reduced the number of effective turns, weakening the spark until a kick would not make enough spark to start. The touching of windings happened when hot.

But the R27 is battery ignition, the coil is not a magneto coil, and my experience is that the coil fails suddenly and with finality.

I think your hot starting problem is likely from flooding. If the bike starts well cold, and runs well, the battery, coil and state of tune are likely all OK, and the hot starting is just flooding from poor technique.

The gas in the float bowl can get too high and be carried over into the cylinder. This would be your doing and you can take steps to avoid it and get out of it if it happens. Turn off the petcock 15-30 seconds before turning off the engine, either while riding or by letting the engine idle. This is to run down the the fuel level so it has room to expend from the hot engine while stopped. When starting, turn on the petcock. Do not tickle but do open the throttle about 1/4 way. I like to use a double kick. This is two kicks given as one with no pause, not assuming or waiting to see of the first stroke started. If the engine does not start, the next kicks may only flood it. In that case open the throttle wide and give 3 kicks, then almost close the throttle and resume kicking.

Here's a couple of my R27 pages you might like:
http://home.insightbb.com/~aatherton/R27a/R27a.html
http://home.insightbb.com/~aatherton/R27/R27Rest.html

[c.d.iesel]

ALWAYS begin with:

valve adjustment

float level and remove float cover
and OBSERVE it's action

point gap & ignition timing

idle mixture, and idle speed

On hot starting - try holding throttle 3/4 to FULL open while
kicking over

[VBMWMO]

I recently picked up a 1961 BMW R27 motorcycle, bought off of ebay. I paid TOO MUCH for the condition, but whatever...it is now in my garage. The bike has me puzzled and perhaps some of you may know of a solution....

My routine...I turn on the fuel petcock and the bike starts on the 2nd or 3rd kick and it idles and runs well. Then, when I stopped for gas today it would not re-start. This has happened twice before. Any ideas?? I wound up walking the bike home (this makes the THIRD time I have had to walk it home...maybe it is a vintage XERCYCLE!!!). When I got home it still wouldn't start, so I let it sit for another 10 minutes. Then, I kicked it over and if fired right up! I've replaced the battery and the plug and this still happens... Could the replacement spark plug I am using might be the wrong heat range? According to the websites I am using one of several alternative proper plugs. Perhaps the coil is going?? I got spark when I checked it out by kicking it over and looking for spark at the plug... The bike being a 6 volt system is less than ideal, but still a very cool looking bike. (see the pix attached). By the way, while my headlight is on the horn won't honk unless I rev the engine.

I was riding a couple of days ago and the bike simply died while I was riding. I pulled off onto a sidewalk waited several minutes and it ultimately started. I've looked at the plug and at one point it looked black (rich). I cleaned it and it hasn't looked that way since that time. I even took a nice long ride into Chicago and the bike was just fine. It died on the way home though and after letting it sit for 5 minutes or so, it started right up. Any thoughts on what I should try next??
THANKS in advance for any and all suggestions.