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chuckr
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hi, I have a 72 R75/5 - just swapped US bars for low Euro bars, was fairly straightforward, but I find that my throttle is somewhat sticky - that is won't return...I checked the screw under the assembly but it's turned out. Did I miss something on re-assembly?

Or - a different question - is the throttle designed to 'snap' back to idle? I am a returning BMW owner (had a Guzzi Eldorado for a few years, and 14 years ago - an R75/5) so don't quite remember how the throttle should feel...

thanks, Chuck

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Chuck R
1972 R75/5, '69 2002, '82 528e
NY

tonyhutchinson
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Durham England
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Are the throttle cables

Are the throttle cables trapped under the tank or do they have tight bends in them that could cause the cable to stick. Did you dismantle the handlebar throttle assembly when you changed the handlebars?

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Tony

chuckr
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Hi Tony, I don't have the

Hi Tony, I don't have the tank on now and the cables are loose and not kinked...I didn't open the assembly, just pushed it on the new bar - so it could have been like that before - didn't really notice if it was like that before the bar swap. But with the assembly OFF the bar it's the same 'sticky'.

I read somewhere that these weren't designed to snap back to idle?

thanks Chuck

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Chuck R
1972 R75/5, '69 2002, '82 528e
NY

schrader7032
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San Antonio, TX
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Yes, the throttle should

Yes, the throttle should automatically go back to idle. The slide carbs have an internal spring while the CV carbs have an external spring. Something must be binding...you said the screw is out. Is there a cruise control? If the assembly is off the bar, then either the cables inside the assembly are not positioned correctly or the throttle tube needs some lubricant.

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

chuckr
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Yup the 'cruise' control

Yup the 'cruise' control screw is not engaged. I'll check the cables for kinks again and will pop the assemble open to check for lubrication...here's another Q, there's a largish rubber block under the tank (and frame) that locates the plug wires to the coils, with a few other openings - is that where the throttle cable is supposed to go? The middle opening is a perfect fit for them...seems logical, as it would make a soft bend and have the cables be practically vertical as they enter the carb...

thank you, Chuck

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Chuck R
1972 R75/5, '69 2002, '82 528e
NY

khittner
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My bet would be that the

My bet would be that the throttle gear and chain assembly on the handlebar hasn't been opened and greased in a long time.

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Konrad

chuckr
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I dismantled the throttle

I dismantled the throttle housing and cleaned and lubed the gears, it was not bad but not perfect either (used white grease, but may re-do with moly lube). I think I had a kink in the cables as well - but it does return now, just doesn't 'snap' shut. I'll take another crack - I pulled on the cables and they do snap open and closed, so something is hanging it up...thanks for all the input.

Chuck

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Chuck R
1972 R75/5, '69 2002, '82 528e
NY

schrader7032
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San Antonio, TX
Joined: 10/27/2006
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Personally, I wouldn't want

Personally, I wouldn't want it to snap back, assuming we're talking about a hard pull back to idle. You're hand will be fighting that all the time. Of course, it should return, but not so hard. The R69S has a built-in cruise control inside the throttle tube. Unfortunately, the PO on my bike had defeated that feature. I was forever having to fight to keep the throttle from going back to idle...I couldn't take my hand off the throttle otherwise it would slam back to idle. I'd reach over with my left hand to hold throttle if I need to use my right hand...kind of dangerous. Then I was able to purchase a NOS throttle tube with the built-in cruise control. Much, much better.

My point is, you need to find the reason it's hanging up, but I would want something to reduce the tendency to return to idle. I believe the small screw under the throttle housing is not really as a crude cruise control...I was always figured it was a way for you to lock the throttle when performing maintenance in the garage. There are springs sold for the CV carbs that have half the pull of the stock ones...that would reduce the snap back to idle feature.

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

chuckr
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thanks for the thoughts - I

thanks for the thoughts - I see why 'fighting' it would be tiresome for sure. I think it's working properly now, it goes back to idle smoothly, but doesn't snap back in a flash. I think the lube and a massage of the cables solved it.

thanks Chuck

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Chuck R
1972 R75/5, '69 2002, '82 528e
NY

Snakeoil
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Upstate NY
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I would suggest that on a

I would suggest that on a bike with some age to it, the cables could be contributing to this. Since you have the tank off, I would remove the cables and soak them in mineral spirits. The pump the cores relative to the housings and watch how much black gook comes out of the cable. Keep pumping until the black stops coming out or the min spirits become opaque with crud. If it goes black, replace with clean min spirits and continue until both cables are squeaky clean inside. Blow them out with compressed air. They should dry very quickly inside with air. Now lube them by holding vertical in a vise (don't crush) and drizzle motor oil or your favorite cable lube down the cores and past the housings. Do this until it starts to drip out the other end. Now blow thru with compressed air to remove excess and reinstall.

You might find the difference is significant.

regards,
Rob

chuckr
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Hi Rob - thanks for response

Hi Rob - thanks for response - you know, I think you are right - I was switching to low bars, I was going to roll with the old cables, but just bought new cables (and clutch cable) and it's perfect now. However, next issue is replacing the pushrod seals...

Chuck

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Chuck R
1972 R75/5, '69 2002, '82 528e
NY

sminn560sl
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Central Kentucky
Joined: 04/13/2011
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Throttle Sticking

If you've changed to euro bars from the U.S. bars I would suspect that your cables are now too long (if you used the original U.S. spec cables). If you didn't re-route them they will have a much sharper bend somewhere between the throttle and the tank due to the excess length. No matter how you route them they will have a sharper bend somewhere than they had with the U.S. bars.

I would suggest buying the proper length cables for euro bars (shorter). I think this will solve your problem.

Edit: ...and yes, the throttle should self-return. A throttle that won't self-return is a hazard in the event of the bike going down.

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Steve in Kentucky
91 BMW K1 (caretaking); 87 BMW R80 (RS); 61 BMW R60/2; 66 BMW R27; 74 R90/6; 59 NSU Maxi; 71 Norton Commando; 71 BSA 250 GP; 66 Triumph TR6R; 61 Norton Manx; 59/61 Triton; 14 Triumph Thruxton

chuckr
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Hi - yes - I realized that

Hi - yes - I realized that the US - longer - cables were not routing correctly. I did get the shorter low bar cables, and the throttle returns now...all looks a lot better and is working fantastic. We had a super nice + warm morning here in NY so did a ride and the low bars feel much better for me and all controls worked great. thanks for input.

regards,
Chuck

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Chuck R
1972 R75/5, '69 2002, '82 528e
NY

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