The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: tsal on January 31, 2010, 03:00:59 PM
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1979 R65
Heres the scoop. Start the bike up cold, and it will run only on right cylinder. After a about 60 seconds running, the left cylinder will kick in, and the bike seems to run fine after that. Getting good spark both sides. If I squirt some gas in the spark plug hole left side before starting, she will fire right up on both cylinders. So I am assuming it is a fuel problem.
I dropped the float bowl and checked the float, which seems to be working ok. The left carb is now off, and on the bench. Have any ideas what I should be looking for?
Thanks,
Tony
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Tsal, if you just went thru a clean and rebuild I would double check the "choke" on that side. It may be that the cable is not adjusted quite right or perhaps it was reinstalled backwards. The plates inside are "handed" and can be sensitive. I've had that problem myself that is what I found. Of course it could also be the butterfly plates or the idle mixture screw. Try one thing at a time to isolate the problem.
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Maybe a good cleaning, spraying carb cleaner through the drilled passageways, jets and such .
There's a paper gasket under the 'choke' assembly, check condition .
Also there are 4 or 5 small holes in the brass disc that is inside the 'choke' cover, make sure these are clear as well .
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The jet in the bowl for the choke could be stopped up. I had this on my R90 when I first bought it but didnot know this until cold weather came.
Don
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I have only had the bike about a month now, and the problem has been since day one. I do not have any service history information on the bike so I don't know if the carbs were messed with before I got it.
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Simple fix. My '81 did exactly the same thing. Drop the float bowl on the afflicted carb and use a needle or a very small numbered drill bit to open up the fuel passage at the bottom of the enrichener circuit fuel "well". It'll fix your start issue and won't cost you a red cent. Monte
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fi196.photobucket.com%2Falbums%2Faa1%2Fmontmil%2FBMW%2520R65%2Fbowlvent.jpg&hash=65c063b41f1a9c7ccb68da1b4a6641bd6d3e8e37)
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Thanks Monte,
Took it all apart, and blew out all jets and passage ways i could find with the air compressor. If i get time during the week, i'll throw the carb back on and see if that fixed it. Thanks everybody for your help
one last thing, there is a hole in the slide, that I "think" was facing the back (air box side) but cant remember for sure. I had the diaphragm off, so i couldn't use the tab on it as a guide. does it matter which way it gos in?
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Feel free to re-size your photos to make it easier to view.
This is 400 x 300 pixels:
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It appears you have not removed the diaphragm from the slide. If that's the case then the small tab on the diaphragm will fit into a corresponding indention in the carb body.
It does matter, but since I can't remember which way just now that should get it back together. No doubt one of the more experienced mavens can chime in.
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There's a small indentation in either the carb body, or carb top, where the tab is supposed to reside .
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one last thing, there is a hole in the slide, that I "think" was facing the back (air box side) but cant remember for sure. I had the diaphragm off, so i couldn't use the tab on it as a guide. does it matter which way it gos in?
Tony
The way I read your question - you are unsure if you put the diaphragm back on the slide 180 Deg out so that although the diaphragm tab would fit in the carb body indentation the slide could be back to front.
If that is the question the answer is the vent hole in the bottom of the slide faces towards the engine. I've never had my diaphragm off so I'm having to assume mine are correct. I don't know for sure if it even matters.
Just checked around to be sure I was correct and as ever the 'Bum'
has every bit of detail covered. The hole does face towards the engine.
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There are two locating tabs on the diaphragm. There's one on the inside that locates it properly onto the slide, and a tab on the outside (which you can see in your photo) which locates the whole assembly to the carb body. If you didn't see the inner one when you installed the diaphragm, you should take it off and reinstall it.
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Flash got it! BINGO!
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Thanks Monte,
Took it all apart, and blew out all jets and passage ways i could find with the air compressor...
I doubt air alone will clean out the bonded sediment that is clogging the fuel passage between the main float bowl and the enrichment fuel well. Poke it. Monte
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I doubt air alone will clean out the bonded sediment that is clogging the fuel passage between the main float bowl and the enrichment fuel well. Poke it. Monte
That particular passageway is probably safe from overindulgence with a poker, but on any of the others in the carb body, you want to use a soft wire, like a single strand of copper from a lamp cord. You don't want to scratch them.
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one last thing, there is a hole in the slide, that I "think" was facing the back (air box side) but cant remember for sure. I had the diaphragm off, so i couldn't use the tab on it as a guide. does it matter which way it gos in?
Tony
The way I read your question - you are unsure if you put the diaphragm back on the slide 180 Deg out so that although the diaphragm tab would fit in the carb body indentation the slide could be back to front.
If that is the question the answer is the vent hole in the bottom of the slide faces towards the engine. I've never had my diaphragm off so I'm having to assume mine are correct. I don't know for sure if it even matters.
Just checked around to be sure I was correct and as ever the 'Bum'
has every bit of detail covered. The hole does face towards the engine.
Barry,
Thanks! Yes, that's exactly what happen. When I reinstalled the diaphragm, I was unable to find the notch on the slide that the inside tab on the diagram fits into as it is under the plastic ring. The only other reference point on the slide was the hole that runs through it. Without knowing which way that hole faced, I had a 50/50 shot of getting diaphragm on it correctly. I was indeed 180 deg out.
Tony
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When I reinstalled the diaphragm, I was unable to find the notch on the slide that the inside tab on the diagram fits into as it is under the plastic ring.
Don't you look for the notch before pressing on the white ring?
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Don't you look for the notch before pressing on the white ring?
Pressing on the white ring???...........
:-[
Boy, do I feel like a complete idiot!! I did not realize that ring came off! When I fist took out the slide. The diagram just about fell off it. This being my first time, I figured it just sat in the grove between the slide and ring.
I now realize the diagram had come out of its proper grove on the slide and was not seated properly. (maybe what was causing that carb to act up?) It must have been like that for awhile because the inside of the diaphragm is deformed to the point it will no longer fit in the proper grove.
Ordering new diagrams from Bing.
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Order two new white rings, also, and ask them for their advice on heating the rings up prior to installation.
Also ask which side is supposed to be UP. I put the flat side UP. (see gallery, below)
New rings are a VERY snug fit.
You want to be careful to have the diaphragm lined up when you snap it on.
The rings are not meant to be re-used (too many times!), and until just a few years ago, they were not available as a separate item. Bing wanted you to buy a whole new slide when you wanted a new diaphragm for the flat-top carbs.
You are correct in your assumption that a loose diaphragm, or one with a hole (even pin-sized) or tear will affect performance. Usually, keeping the engine from revving beyond 4000 RPM.
Here is my tale of woe. One of mine kept coming loose, but there was a rally a few States away that I really wanted to try for. So I bought some silicone sealer. Nah......
click on the picture for gallery:
(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.pbase.com%2Ftomfarr%2Fimage%2F80793380%2Fsmall.jpg&hash=ac27787198f741e7e855c1a01b2a35d7547a87c5) (http://www.pbase.com/tomfarr/attemped_fix)
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Order two new white rings, also, and ask them for their advice on heating the rings up prior to installation.
Also ask which side is supposed to be UP.I put the flat side UP.(see gallery, below)
Rob, Thanks for the pics, and especially the tip on getting new rings with the diaphragms. You must have read my mind because the next question was going to be which way the ring should face. My ring was with the lip facing up and was a very loose fit. Thought for sure the lip should face down like you have yours. It seem to fit much better that way. But when I spoke with the Bing Agency today to order the diaphragms and rings, they told me the lip should face up and smooth side down.
Tony
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Yes, always ask folks like Bing. Don't trust even people like me who take pretty pictures and appear to know what we are talking about! [smiley=bmw_smiley.gif]
Did you see in the gallery where I measured the inside of the old and new rings?
Old Ring - 36.25 mm
New ring - 36 mm
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Just wanted to thank everybody here for your help. Finally got the new diaphragms and clips in, and the bike starts and runs 100% better now.
Temp is going to get up to the freezing mark today, so going for a ride :D
Tony