2 replies [Last post]
Bigsieuk
Bigsieuk's picture
 Offline
VBMWMO #8791
Joined: 02/27/2012
Posts: 96

Having had my first R12 (grey) for a 3 years now I finally managed to travel more than 100yds!

My second R12 (tan) has had its engine rebuilt by the most generous and enthusiastic BMW person I know, Peter Ardron (many thanks Peter) here in the UK, I was planning to attend the Pioneer Run here in the UK. This is a pre-1914 bike run but a great collection of old bikes turn up for the start in Epsom, Surrey.

I focussed my efforts on my tan R12, It would start, but as soon as I opened the throttle it spluttered and died. Also the front brake wasn't capable of stopping it even if I couldn't get it moving. So I pulled the cover off my grey R12 which also hasn't moved more than 100yds under its own power in 3 years because it too started, idled and ran on the choke but dies when I open the throttle, but at least stopped, and resigned myself to riding the 2-3 miles on the choke. (I'd cleaned both carbs out thoroughly and checked all the jets were clear).

Well the grey one got me to the event. The first time I've ridden an R12 - I know most of you ride your bikes regularly, but do you remember the first time and how it felt? Anyway time to leave the event and it started but died every 200yds. Each time it stopped I tickled the carb it started it ran for 200 yds then died. Same pattern until it got me home. Regardless I was on cloud 9 that I'd finally ridden one of my R12's, despite the constant stopping.

Now some of you may have already guessed the next part:

When I went back outside to put the bike back into the garage I noticed a faint hissing coming from the bike. Puncture ? No. The hissing was coming from the fuel tank cap. When I loosened the cap a vacuum was released! The cap was on too tight or (if it has one ) the breather was blocked and no air was getting into the fuel tank.

Having had that enlightened moment I loosened it slightly started the bike and it ran on the throttle! Helmet back on and finally a proper ride on an R12 using the throttle for at least 10 miles with no problems.

Happy days.

John

Darryl.Richman
Darryl.Richman's picture
 Offline
VBMWMO #6285
Surf City, USA (Santa Cruz, CA)
Joined: 10/27/2006
Posts: 2185
That's a great story of

That's a great story of perseverance! Yes, the cap should vent the tank. If I remember right, there should be a small pinhole in the middle of the top of the cap. Inside, there is a plate that is riveted on and prevents the fuel from sloshing directly on the hole. I would try spraying the hole through with brake or carb cleaner, but be sure to wear eye protection!

__________________

VBMWMO Webmaster,--Darryl Richman
http://darryl.crafty-fox.com

Bigsieuk
Bigsieuk's picture
 Offline
VBMWMO #8791
Joined: 02/27/2012
Posts: 96
Thanks

Thanks Darryl,

I'm hoping it will be the same solution for both bikes.

Now I can ride them I suppose I'll find out what else needs repairing/rebuilding!

Regards,

John

PS thanks to all the help I've had from all on this forum on my previous posts.

Comment viewing options

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