R75/5 choke stopped working

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Wobbly
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Re: R75/5 choke stopped working

Post by Wobbly » Thu Mar 01, 2018 7:20 pm

Additionally, the cable housings screw into the holding cups at the lever AND at the carb end. When you reassemble the carbs onto the bike you must insure that the cable housings fully engage the cups or you will not be able to PUSH with the cable to turn the chokes OFF. You'll be able to pull them to the ON position, but that will be it.

Hope this gets you on your way.
After 20 years as a professional bike mechanic and 30 years as an engineer I know just enough to be dangerous !

barryh
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Re: R75/5 choke stopped working

Post by barryh » Fri Mar 02, 2018 5:19 am

Wobbly wrote:
Thu Mar 01, 2018 7:20 pm
Additionally, the cable housings screw into the holding cups at th elever AND at the carb end
This was a puzzle to me when I first got an airhead. When you attempt to use the cable adjuster at the carb end in the normal way you can only use the lock nuts as turning the adjust cup itself will unscrew it off the end of the cable. It eventually clicked that the spiral wound cable outer was acting as a thread in the adjuster cup and for the good reason said.
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hal
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Re: R75/5 choke stopped working

Post by hal » Mon Mar 12, 2018 7:57 am

I converted my left carb to something like this, took away the cable on the rhs. Find it starts well with only one side enriched.

Image
choke conversion.jpg
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Hal

'74 R90/6
'97 R850R

Rob
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Re: R75/5 choke stopped working

Post by Rob » Mon Mar 12, 2018 1:46 pm

hal wrote:
Mon Mar 12, 2018 7:57 am
I converted my left carb to something like this, took away the cable on the rhs. Find it starts well with only one side enriched.
+1

Best mod to any CV Bing-equipped airhead.
Rob V

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Zombie Master
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Re: R75/5 choke stopped working

Post by Zombie Master » Mon Mar 12, 2018 7:09 pm

Very interesting!
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enigmaT120
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Re: R75/5 choke stopped working

Post by enigmaT120 » Mon Mar 12, 2018 8:52 pm

I like that but I would still do both carbs. No point making the poor engine run on one cylinder until the other one decides to fire up too.
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melville
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Re: R75/5 choke stopped working

Post by melville » Tue Mar 13, 2018 12:56 am

I did both carbs, making ringtopped pulls out of old bicycle spokes. The right one I usually turn off before I even move--maybe 10 seconds on that side. The left one gets turned off right after I hit second gear.
Call me Mel. Some years ago- never mind how long precisely- having little or no money in my purse, and nothing particular to interest me at home, I thought I would ride about a little and see the other parts of the world.

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Ken in Oklahoma
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Re: R75/5 choke stopped working

Post by Ken in Oklahoma » Tue Mar 20, 2018 1:38 pm

MikeGeee wrote:
Mon Feb 26, 2018 9:04 pm
Ahhh, thanks. I haven't taken these carbs off the bike yet, so had no idea what the reverse side looked like.

I don't know if I'll have time to get to it tonight, but I'll post an update when I know more.

Thanks again everyone!
Mike I don't have any specific advice for you, but I would like to amplify on what ZM said. When I have something strange going on, other than some obvious, I will 'clean' the carbs. But I never ever simply dunk the carbs in some cleaner. What I do do is to check out the fuel and air passageways. Often there is a passageway, air or fuel, that has an obstruction. My weapon of choice is spray carb cleaner to clean out the passageways. Pardon me if I'm talking down to you. When you hold a carb in your hand you will see some 'lumps' on the outside of the carbs. Those lumps have to do with drilled passageways, will usually have some capped off areas associated with the lumps. These are passage ways for fuel or air. When carbs don't operate right, a plugged passageway is often the culprit.

My weapon of choice is carb cleaner in a spray can, with the ubiquitous red tube plugged into the nozzle. The idea is to verify that the passageways are open by shooting the cleaner in one end and seeing spray exiting somewhere else. There are some very small orifices, most notably in front of and behind of the throttle butterfly. You will see the spray exiting, telling you that that passageway is clean.

You may find an orifice that doesn't spray, and more carb cleaner doesn't clear the problem. What I have done in the past is to use a small length of a guitar's little (steel) E string to unblock the passageway. Now just snipping the guitar string in two will likely leave a sharp edge. That is BAD and could screw up the passage way! What I have done in the past is to take the end of the the steel string and do my best job of rounding the end on a bench grinder, even though I can't actually see that it has been rounded. As I touch the end of the string to the grinder I will twirl' the end of the steel string by rolling it between thumb and finger. If in doubt about how successful you were, poke the end of the string at an angle to your skin, as you rotate the wire. If the wire digs into your skin you have to try again until it doesn't.

My thoughts.

Ken
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There's no such thing as too many airheads

Beemerboff
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Re: R75/5 choke stopped working

Post by Beemerboff » Tue Mar 20, 2018 6:01 pm

The choke draws fuel from the float bowls through the hole on the bottom corner, so easy to slip the bowls off and check that they are clear first.
Might want to check that the end of the small brass pick up tube is clear too, but easier with the carb off.
FWIW ,with the choke on a pressure pack sprayed up that tube should exit through one of the pin pricks in the inlet if all the choke passageways are clear.
The two other pin pricks can be checked by blowing into the idle jet hole and the smaller of the two passageways which run parallel to the inlet tract.
Last edited by Beemerboff on Mon Apr 16, 2018 5:49 am, edited 1 time in total.

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MikeGeee
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Re: R75/5 choke stopped working

Post by MikeGeee » Thu Apr 12, 2018 4:19 pm

Hey guys, thanks again for all the good info. I took the carbs off, cleaned what I could and checked all the possible culprits. I found absolutely nothing out of place. Yet, after reassembling and reinstalling the carbs, the choke works fine.

I'm guessing I just had a loose screw that contributed to a bad seal someplace.

Anyhow, this problem seems to be solved. On to the next one!

Oh, the joys of having a 45-year old machine as your daily rider...
1972 BMW R75/5 Toaster
1976 Honda CB200t
1948 Harley Davidson WL45

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