The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: beemer on April 11, 2011, 07:06:30 PM
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I recently changed my carb diaphrams on my R65LS 83 model and now she just won't go past 60mph!!!feels almost like fuel starvation,plenty of fuel flow,checked valves clearance,plugs,ignition coil seems fine,i have a spare coil so changed over just incase,bike starts and idles fine,help and advice please,thanks.
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Take your finger and lift each slide and feel the suction/vacuum. Do they feel the same? May have a leak on one of them. I had one tear on a trip and she wouldn't run at all, idled like a champ but wouldn't take any throttle at all.
Good luck
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By chance did you purchase 'pattern' parts from Motobins ?
A few of the UK members on this forum installed them and the thickness of the diaphragm caused problems, can't quite remember what they were .
I'm sure they'll post a response tomorrow .
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Yes, there are "non-Bing" replacement diaphragms that are the same overall shape but the rubber is definitely thicker and stiffer - these have caused issues with a number of folks. Also, be sure that you have them properly oriented/seated with the small tab going into the indented are on the inside edge.
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Yes these are the "non bing"type,can anything be done?or do i have to replace them?thanks. :(
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Yes these are the "non bing"type,can anything be done?or do i have to replace them?thanks. :(
Perhaps ask Motobins for a full or partial credit with an exchange for the "real" Bing diaphragms. The thicker rubbers will likely be problematic for, oh, forever. Sometimes pattern parts work just fine.
Monte
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Yes these are the "non bing"type,can anything be done?or do i have to replace them?thanks. :(
I was one of the folk with trouble with these only fit Bing originals the generic ones are cr*p especially troublesome if you have the flat top carbs. Also check the rubber connector to the heads have been properly refitted.
Lou
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On the one hand you have to wonder why Motobins and others continue to sell the generic diaphragms if they are so bad.
On the other hand you have to wonder why the thicker rubber makes so much difference when the old Stromberg and SU type CV carbs used to deliberately add damping with an oil dashpot.
Thankfully I've not had to replace mine yet.
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The Bing CV carbs works on substantially lower vacuum (pressure? or rather suction) than other CV designs from Mikuni, Keihin, etc. The thicker rubber is certainly stiffer/ less pliable as has been demonstrated with testing deflection while applying specific weights. The relative differences in overall carb vacuum is especially apparent when I am working on my Japanese motorbikes and my BMW airheads with my Morgan Carbtune (rotameter). One has to stand the carbtune upside down and let gravity assist the steel slides' movement when working with the bings - this makes the rotameter's full scale reading approximately 20 mm/HG, whereas in its normal position full scale is closer to 200 mm/HG units, which is what I use with the Kawasaki's carbs.
Just get the bona-fide Bing rubbers and you'll be happier!
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Dome-tops also may or may not have a return-assist spring (#7).
If you have these in your carbs, try removing them and see what effect that has.
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.realoem.com%2Fbmw%2Fdiagrams%2Fh%2Fm%2F4.png&hash=81db93213b54c173a118a24083657c8566ffbbe2)
http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=13_0462&hg=13&fg=05
I saw a pair of R100 dome-tops just this last weekend taken apart, and there were no springs in them.
The bike ran fine. (Bing diaphragms)
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On the one hand you have to wonder why Motobins and others continue to sell the generic diaphragms if they are so bad.
An old saying from P.T. Barnum, of circus promotion fame; "There's a sucker born every minute."
Prior to rebuilding the Bings on my 1981 R65, I did a lot –and I mean A LOT– of internet research on how to do it and how not to do it. The knock-off Bing diaphragms were noted as to be avoided like the plague.
Monte
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Well according to them these are fine and they haven't had any problems with them!!so you have to take their word for it i guess,why doesn't it show up being hesitant when you just rev the bike?i guess it has to be under load,ie,when your on the move.
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Dome-tops also may or may not have a return-assist spring (#7).
If you have these in your carbs, try removing them and see what effect that has.
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.realoem.com%2Fbmw%2Fdiagrams%2Fh%2Fm%2F4.png&hash=81db93213b54c173a118a24083657c8566ffbbe2)
http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=13_0462&hg=13&fg=05
I saw a pair of R100 dome-tops just this last weekend taken apart, and there were no springs in them.
The bike ran fine. (Bing diaphragms)
Thanks,i will try this.
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Yes these are the "non bing"type,can anything be done?or do i have to replace them?thanks. :(
I was one of the folk with trouble with these only fit Bing originals the generic ones are cr*p especially troublesome if you have the flat top carbs. Also check the rubber connector to the heads have been properly refitted.
Lou
which rubber connector Lou?
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which rubber connector Lou?
#3
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.realoem.com%2Fbmw%2Fdiagrams%2Fh%2Fm%2F1.png&hash=5d00a219fc6970ed3e98e7dff09c0f05a1e6aa86)
http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=13_0455&hg=13&fg=05
That HAS to be an air-tight seal. It can be checked by spraying carb cleaner on them while the engine is running. If the RPM's rise, you know you have a leak.
The rubber gets hard over time and can even crack. Best to replace them every 10 years or so.
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Well according to them these are fine and they haven't had any problems with them!!so you have to take their word for it i guess,why doesn't it show up being hesitant when you just rev the bike?i guess it has to be under load,ie,when your on the move.
I live and sometimes work near Motorworks so i used to call in for my parts during my rebuild forming a good relationship with the guys on the trade counter after less than fifty miles i was struggling with diaphragm issues especially when using fuel additives i did post some pictures of the impact on the rubber.
At first i phoned them and got the boss who said bring them back and we will swap them which i did, same problem with the replacement, so i called in (again) and the guy on the counter exchanged them for bing origonals (no charge) saying i dont know why we bother with "Those" they are a pain !! ive done 5k miles without a problem since.
Lou
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he guy on the counter exchanged them for bing originals (no charge) saying i don't know why we bother with "Those" they are a pain !!
That was exactly my point. If a reputable dealer refused to sell the generic ones it would flag up to everyone that they are no good.
A better solution all round might be for the dealers to say to the generic part supplier "your diaphragms keep coming back sell me ones that work or I ain't buying anymore"
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which rubber connector Lou?
#3
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.realoem.com%2Fbmw%2Fdiagrams%2Fh%2Fm%2F1.png&hash=5d00a219fc6970ed3e98e7dff09c0f05a1e6aa86)
http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=13_0455&hg=13&fg=05
That HAS to be an air-tight seal. It can be checked by spraying carb cleaner on them while the engine is running. If the RPM's rise, you know you have a leak.
The rubber gets hard over time and can even crack. Best to replace them every 10 years or so.
Thankyou,i will check them.
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Well according to them these are fine and they haven't had any problems with them!!so you have to take their word for it i guess,why doesn't it show up being hesitant when you just rev the bike?i guess it has to be under load,ie,when your on the move.
I live and sometimes work near Motorworks so i used to call in for my parts during my rebuild forming a good relationship with the guys on the trade counter after less than fifty miles i was struggling with diaphragm issues especially when using fuel additives i did post some pictures of the impact on the rubber.
At first i phoned them and got the boss who said bring them back and we will swap them which i did, same problem with the replacement, so i called in (again) and the guy on the counter exchanged them for bing origonals (no charge) saying i dont know why we bother with "Those" they are a pain !! ive done 5k miles without a problem since.
Lou
Iv'e just spoken to motorbins regarding these diaphrams,they say they have sold these to hundreds of people and also used them themselves and never had a problem with them!!ever!!!SO,i will check other things and then will have to buy some Bing ones i guess,strange that they say this though!.I also spoke to the other independent bmw spares company,they sell nothing but the Hydrin diaphrams and again say they have no problems with them,and say they work better with today's fuel then the original type!!.
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Yes these are the "non bing"type,can anything be done?or do i have to replace them?thanks. :(
I was one of the folk with trouble with these only fit Bing originals the generic ones are cr*p especially troublesome if you have the flat top carbs. Also check the rubber connector to the heads have been properly refitted.
Lou
Do the rubber connectors need to be really tight?or will they get damaged if you should overtighten them?
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Do the rubber connectors need to be really tight?or will they get damaged if you should overtighten them?
Before you really crank down on the clamps, pull the short hose connectors -the ones between the carb and cylinder head- and check for any cracks that may be discovered within the interior of the hoses. These rubber bits can look fairly OK with an exterior visual inspection, but I found one of mine badly decomposed, and leaking air, due to a bad sealing to the cylinder head stub from the poor I.D. condition of the hose.
Monte
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If you don't know the history of the rubber connectors, I would replace them so you have a baseline.
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If you don't know the history of the rubber connectors, I would replace them so you have a baseline.
Yes i think i will replace them,thanks for the advice guys.