13 replies [Last post]
Johnwrightphoto
Johnwrightphoto's picture
 Offline
London
Joined: 02/01/2017
Posts: 18

Hi everyone

In need of a little guidance before I embark on the wrong road...

Took my R51/3 for a long run (60 miles round trip) six days ago. First 30 she was good as gold. On the way back she started choking, spluttering and trying to die at low revs. Keeping the revs up higher and higher at corners and junctions I got us both home in one piece Smile

I’ve left her all week in the hope she might heal herself (she does that you know! Smile ) but having come out on her this morning she started, as always, at first kick and idled beautifully. Half a mile out she’s back to wanting to cut out/die at low revs.

At speed she’s fine, if a tiny bit back firing, but all in all she seems happy to cruise all day. Come to a traffic light and I have to rev her like an over zealous pizza delivery guy just to get off the lights and roundabouts are like Russian roulette Smile

I think (and I’ not in any way qualified to be ‘thinking’) that I have a timing issue. Before I head off to the shop to buy a timing gun and try to make sense of the S- OT, F- TDC code book, I just wanted to reach out and ask if you think this sounds like a worthwhile approach.

Things to note. She has the 12V alternator conversion fitted. Are the various YouTube videos on timing solutions applicable to the 12V conversion? I’ve never removed the engine face cover and I don’t want to apply 6V magneto methods if they’re not applicable.

Any help or guidance appreciated. Links to any ‘how to’ pages or vids much needed too Smile

J

__________________

.

808Airhead
808Airhead's picture
 Offline
VBMWMO #7677
Joined: 08/05/2009
Posts: 1025
Clean the carbs.

Clean the carbs.

__________________

Thomas M.
R69s - R60/2 - R67/2 - R51/3

schrader7032
schrader7032's picture
 Offline
VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6901
Yes, you probably should

Yes, you probably should check the timing with a timing light...be sure it's the inductive kind and don't pay for the bells and whistles of a fancy light, you just want a timing light function. Timing is timing...shouldn't matter if it's 12v conversion or not. Suggest you use a off-the-bike 12v battery to power the timing light...there can be interference if you use the bike's battery.

Consider that the condenser might be failing. Also, check the valve clearances. You might want to do that before doing anything...it's free!

__________________

Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Johnwrightphoto
Johnwrightphoto's picture
 Offline
London
Joined: 02/01/2017
Posts: 18
You make that sound so simple

You make that sound so simple Thomas Smile

__________________

.

Johnwrightphoto
Johnwrightphoto's picture
 Offline
London
Joined: 02/01/2017
Posts: 18
Thanks Kurt! Valve clearances

Thanks Kurt! Valve clearances I can do! I’ll check that first...it’s just strange that the issue only showed itself during one ride out.

__________________

.

312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 436
Look at the plugs

Look at the plugs FIRST...plugs make a good diagnosis tool. In this high tech world we often forget the basics. Icarus

Johnwrightphoto
Johnwrightphoto's picture
 Offline
London
Joined: 02/01/2017
Posts: 18
Thanks Icarus. Did just that

Thanks Icarus. Did just that and they are kinda black and coked. Gonna pick some up and swap out...

__________________

.

312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 436
Black is a symptom of too

Black is a symptom of too rich a mixture obviously. Could also be due to wrong heat range plugs, retarded timing, partially blocked air filter, or low compression, or incorrect plug gap

In this order, I would change the plugs with known good ones of the proper spec, I would check the air filter, and then go for a ride, at cruising speeds, come home and look at the plugs. Then I would adjust the valves, and finally, give the carbs a good clean. Sticking floats, especially if you have OEM brass flats that may be leaking would leave too low a float position, causing over rich mixture. That is easy to check (assuming your /3 carb float tops are like the /2 ones.

Take the float tops off, and pull the floats out and see if they are flooded. If so, replace the floats.

Good luck and keep in touch,

Icarus

Johnwrightphoto
Johnwrightphoto's picture
 Offline
London
Joined: 02/01/2017
Posts: 18
Icarus! I changed the plugs.

Icarus! I changed the plugs. She’s good as gold again. I’ve redone the valve clearances just cos I can too.

Thank you so much for your advice.

I have to say I’ve personally never touched the Bing carbs due to having no idea of what’s in there. Can you recommend a ‘how to’ or ‘beginners guide’ link?

I really want to get on top of maintaining this old girl but I’m a little concerned that I may cause more harm than good. Smile

Thanks again

J

__________________

.

FL54
FL54's picture
 Offline
Joined: 08/12/2018
Posts: 76
The '66 owners manual gives a

The '66 owners manual gives a good overview of the Bing carburetors

https://bmwdean.com/1966-owners-manual.htm

312Icarus
312Icarus's picture
 Offline
Joined: 07/15/2016
Posts: 436
Consider why the plugs got

Consider why the plugs got fouled. Age and time count, but I would ride a bit and check thier condition again. I would also check the point gap. If the point gap is good (and the points are clean) you probably haven’t changed the timing enough to worry about.

The Bings are dead nuts simple. That said, you have to be careful as the castings and brass parts are delicate, and cross threading or over tightening can creat a nightmare. Suggest a new gasket set, take them off over the winter and give them a good cleaning. Remember the settings of the mixture screws so you can put them back where they were, although after a cleaning you will most likely need to tweak them a bit.

Good luck, glad it worked out.

Icarus

Johnwrightphoto
Johnwrightphoto's picture
 Offline
London
Joined: 02/01/2017
Posts: 18
Great advice Icarus and a

Great advice Icarus and a perfect winter project!

Thanks for all your help!

__________________

.

Johnwrightphoto
Johnwrightphoto's picture
 Offline
London
Joined: 02/01/2017
Posts: 18
Thanks FL. I’ll check it

Thanks FL. I’ll check it out!

J

__________________

.

FL54
FL54's picture
 Offline
Joined: 08/12/2018
Posts: 76
Icarus's statement about the

Icarus's statement about the Bing is spot on. So easy to strip the soft, pot metal castings.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.