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jchen
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I've had my r75/5 inspected by the local BMW dealership since the last post but it continues to "cough"
0r "stutter" a lot intermittently with acceleration. It has a bit of the feel of a scooter bog. Do r75/5s bog?

Dan McCarthy
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I failed to get my R75/5

I failed to get my R75/5 running acceptably too... and judging by the paperwork that came with the bike, the two previous owners had spent money on sorting out the carburation with no appreciable success either.

My confusion was largely based on the assumption that the CV Bings were the same tried and tested design I've had on my /6, /7 and mono bikes - not so. The R75/5 was the first bike to be fitted with these carbs, and, according to Snowbum, they were poorly suited to the bike. He goes into detail about various modifications that can be made to improve matters here: http://bmwmotorcycletech.info/earlybingR75CV.htm

My solution was to fit a pair of carbs from a mono R80 - virtually a plug & play fix and the difference in performance is literally astounding with easy starting, regular tickover hot or cold and plenty of power on acceleration with no flat spots or coughing. I've got the original Bings in a box if a future owner is concerned about originality, but for real-world riding fitting the mono carbs has transformed the bike.

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jchen
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Many thanks! Interesting

Many thanks! Interesting thought (although I hope I don't have to replace them!). I'll ask the mechanics. JMC

fishtown boy
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Joined: 01/29/2014
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My 1972 R75/5 does a bit of

My 1972 R75/5 does a bit of that Bog thing as well.
I had carbs adjusted, and also ,it seemed that the throttle cable was pulling on one side more than the other.
It runs much better,now.
I was told by a local BMW Mechanic ,this coming spring I should look into getting a newer carb set up.
That Mono R80 carb sounds like the thing. I love original, but, if it works better...

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Dan McCarthy
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Bing thing...

fishtown boy wrote:

My 1972 R75/5 does a bit of that Bog thing as well.
I had carbs adjusted, and also ,it seemed that the throttle cable was pulling on one side more than the other.
It runs much better,now.
I was told by a local BMW Mechanic ,this coming spring I should look into getting a newer carb set up.
That Mono R80 carb sounds like the thing. I love original, but, if it works better...

Hi Bernie!

I thought long and hard about changing my bike's appearance but the visible difference is so subtle that only a "rivet counter" as we call them over here would notice. As mentioned in my post, the two previous owners had paid for service kits, new diaphragms and professional tuning etc. before I ever got the bike and I know that the continued poor running was one of the reasons the guy sold the bike to me. He probably thought all BMWs were gutless and ran badly but I knew a 750, even an early one, should fly. I went to three "experts" and all they did was take my money and chase the problems around. I ended up speaking to a true BMW guru at Motorworks in Yorkshire. He supplied a very nice pair of used 32mm Mono Bings and had them fully serviced before sending them out. They did need the choke actuating arms swapping over to allow the original choke lever system to work, but that was the extent of modification required. The total cost for the "new" carbs was around £350, which I agree is a big chunk of small change but is not a lot more than I'd already spent on service parts and labour charges in my attempt to get the bike running right. Add in the money already spent by the two previous owners and it seems like a small price to pay for a proper fix.

Dan

fishtown boy
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Joined: 01/29/2014
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Hello Dan, Glad that worked

Hello Dan,
Glad that worked out for you.
I think in the early part of next season, I will try something like that.
Thanks for the info!

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Warren Zevon

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