The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Mender on March 29, 2016, 04:12:16 PM
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Hi, I recently bought an R65 which ran really rough and leaked oil from the base gaskets and pushrod tube seals. I replaced the gaskets and seals and cleaned the carbs with compressed air and carb cleaner, replaced the diaphragms, and spark plugs and set up the carbs. It now starts and runs lovely. However! when running at about 6000rpm in fifth it is fine when on the power but if I roll off the throttle a tiny bit it feels really rough back on the power is fine. Secondly after a bit of a thrash today I returned home and it would only tick over on one cylinder, as I got off to investigate it slowly chimed back in on both. I reckon a jet is clogged or a passageway in one of the carbs, but where? Any ideas would be thankfully received.
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Could be partly clogged jet or sediment from the tank obstructing things, but another thing to consider - are you still running the original coil and plug wires? How about the condensor & points?
When these bikes seem to run out of steam, it is sometimes an airleak around the diaphragm, or maybe between the carb and the head.
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Cheers, will take the carbs apart first.
I visited your neck of the woods courtesy of the Royal Navy HMS Minerva back in 1971, I remember a pretty lady in a Mk1 white Mustang took me for a ride to the White Mountains.
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I had a similar problem on my 80 r65. It was the float level in one of the carbs. After cooling down, I turned on the fuel valve for a couple minutes, then carefully removed float bowls. One has gas about 1/4 inch from top, the other was over a half inch from top. Adjusted the "tang" under the needle, checked again and both were about 1/4 inch from top. Problem went away.
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Check the Idle Air screws and jets first. That air/fuel circuit is in play when the bike is, well, idling. A stoppage of fire on one cylinder might be traced to that side's circuit. Carefully count the turns required to remove the needle screw. You'll want to return it to its last position to check for proper idle on both cylinders.
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Mender,
Your symptoms at 6000 RPM sound like the classic roll off test for selection of the correct main jet. When the throttle is rolled off a touch at 6000 RPM it momentarily richens the mixture. If the engine runs rough when you do this that usually indicates the carb is set up too rich. If the engine pulls better when you roll off then it's set up too weak.
On the float levels it is important that they both be the same but it's not normal to set float levels to have a removed bowl full to 1/4" from the top as the level will rise substantially when fuel is displaced by the floats and carb body castings. 1/4" from the top is very close to flooding and will cause a rich mixture particularly at idle. 1/2" is closer to correct.
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Respectfully Barry if I set mine at 1/2'' below the rim I don't think it would run at all. After I made the adjustment everything improved. Starting , idle, higher speed, everything. Not saying where I set my carbs is right for all carbs but works for me. I had read on this forum that someone had a stumbling problem at higher speeds and that the float height was very critical. My carbs have the floats that just sit in the bowl over a rod that sticks up. Are all the Bings like that?
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Barry I re read your post and I see just what you are saying. When I said 1/4'' from top of rim, that was with the floats still in the bowl. And certainly if not in the bowl then that level would be much too high.
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...My carbs have the floats that just sit in the bowl over a rod that sticks up. Are all the Bings like that?
You may have the Bing accessory Alcohol Resistant Independent Float & Bowl Kit. This item has been a bit problematic for owners. Expensive to purchase as the kit requires entirely different float bowls. "...over a rod that sticks up" is what caught my attention.
Some owners have eventually bitten the bullet and converted back to OEM bowls n' floats to cure their fueling problems. I have the OEM Bing floats in all three of my Airheads and have never had an alcohol-related issue.
http://bingcarburetor.com/bmw/cvaccessories.html
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JBwell,
1/4" from the top makes much more sense now. The Bing independent float kit is relatively rare due to it's very high cost. With stock floats when the bowl is removed the floats stay connected to the carb via the hinge.
If you haven't already seen this, Snowbum has some very specific advice for setting up the Bing independent floats. http://bmwmotorcycletech.info/bingindependent.htm
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...Snowbum has some very specific advice for setting up the Bing independent floats...
on top of the trash can.
[smiley=whistling.gif]
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I've got them on my R100, and I still haven't got the thing running right yet. The R65 (knock wood) has the old originals and still runs like a top up to redline
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Whilst we are on Bings, I need pointing in the right direction to fix a running problem.
I have recently replaced the needles and seats on the 1985 R65 so readjusted the relatively new float bowls as per the parallel eyeball method and cross checked with the Snowbum 24mm depth method. The bike exhausts now pop during deceleration when the throttle is closed. What is this an indication of- mixture too rich?, too lean? Float bowl levels too high? too low? :-/
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The bike exhausts now pop during deceleration when the throttle is closed. What is this an indication of- mixture too rich?...
Yes. A bit too rich.
Usually, when a new problem pops up, it's best to readdress your last change. Are the needles the same taper size as previous and are they in the same needle grooves? Plus the float level alteration.
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he bike exhausts now pop during deceleration when the throttle is closed.What is this an indication of- mixture too rich?, too lean? Float bowl levels too high? too low?Undecided
It depends because it can be caused by air leaks but I would normally say it's usually caused by a weak idle mixture. How does the engine behave with regards to it's need for cold start enrichment ? Is it very cold blooded indicating weak or starts and runs with little or no choke indicating rich.
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Thanks Montmil and Barry. Needles and seats were purchased from Motobins and I was careful to ensure correct specification and to fit them to the right notch. There was visible wear on the old needles and the seats and a massive amount of fine crud blocking up the seats. With new needles and seats I would expect the bike to run leaner at unchanged mixture screw settings. It is all quite confusing. Bike has always and still requires limited choke to start and run indicating a rich mix. Just to further complicate the evidence, the left plug is the perfect colour and the right plug is sooty.
I will lean up both idle mixture screws about an 8th as the first experiment and see what happens.
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Mender,
Your symptoms at 6000 RPM sound like the classic roll off test for selection of the correct main jet. When the throttle is rolled off a touch at 6000 RPM it momentarily richens the mixture. If the engine runs rough when you do this that usually indicates the carb is set up too rich. If the engine pulls better when you roll off then it's set up too weak.
Thanks Barry, sorry for the delay in replying needed to check and clean!
After much cleaning and checking float levels it is still behaving exactly as your description re the roll off test. does this mean I may have too large main jets? or can I lower the needle as per the old Brit Amals?
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Got to be worth trying a change in needle position first - it's free !
These carbs run on the needle anyway except for close to full throttle.
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Barry,
May i respectfully disagree ?
These carbs have a procedure to be properly set up.
First install the correct main jet giving the strongest pull at full throttle and no problem rolling off.
Then play with the needle position and jet size.
After that adjust idle jet size if needed as it will contribute (a few percent but contribute) to mixture richness going off from idle and even at full throttle.
Of course, any of this has to be done on a sound engine : compression good, valve lash properly set, ignition set properly and perfectly timed.
And most of all clean and leak proof carburetors...
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I agree that's the correct methodology Georges but if he hasn't got different sizes of main jet to hand changing the needle position is worth a try although at full lift one needle position only makes approx. 5% difference which might not be enough given that one main jet size is more like 10%.
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Does the problem under throttle rolloff appear with the bike just sitting on the sidestand versus actually running on the road? Under road conditions, the decel of the bike causes the float bowls' fuel level to pitch forward, momentarily enrichening things by a significant amount.
Doing this with the bike on the centerstand of course doesn't create this effect - the evidence may help point in the right direction.
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The float levels are correct, and are unaffected by the very slight roll off at 6000rpm in any gear. I suspect that after 75000 miles the needles are worn so I will drop them a notch or two to see what happens. It has been getting progressively better as I rack up more miles since replacing the push rod rubbers.
I reckon it is running a bit rich but that in my opinion is more desireable than too lean.
I'll update as soon as I've tried it. Thanks guys.
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As any Airhead & Bing fettler knows, those needles are not rigidly fitted into the slide body. They wiggle a bit and this does permit them to "center" in the jet opening. Eventually, that continual wiggle of a steel needle wears the brass jet.
These small bits are economical enough to replace if you suspect a concern in that part of the carburetor. After a full carb rebuild on my '81 R65, I found the mid-range engine ops to be much improved with a one-notch needle clip change. Sure, there could have been other factors involved but tinkering with the needles is easy enough to try.
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For what it's worth dropping the needles one notch will compensate for approx. 0.004" of wear on the needle although I guess the needles wouldn't wear evenly.
Needle jets are reckoned to wear more than the needles and a 2.66 needle jet only has to wear by 0.0008" for it to be the same as the next size up 2.68 jet. That's less than 1 thou wear so it's no wonder that needle jets are recommended to be replaced every 30,000 miles or so.
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Feel I should report back to you on the results of a series of small experiments to try and eliminate the trailing throttle popping on the 1985 R65 after replacing the needles and jets.
1. Check for air intake and manifold leaks
2. reset float bowl levels to precisely 24mm
3. reset idle mixture screws to a leaner optimum
4. adjust warmed up tickover to around 1100
5 check and adjust carburettor balance.
Result: After 200kms, both spark plugs looking good and no popping under trailing throttle. Thanks all for your comments and observations. Memo to self. Now leave it alone.
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Hi !
I would be delighted to read how you managed to :
"2. reset float bowl levels to precisely 24mm"
Because I can't do it myself and my left boot ask for it. :(
Thanks in advance !
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Ok George here goes-
1. Take a narrow flat stick (trimmed emery board stolen from swmbo and also useful for cleaning electrical contacts) and mark off at exactly 24mm.
2. Remove left hand float bowl, empty (back into tank if no water globules) and cleanout any crap and circular central well of the floatbowl.
3. Refit the float bowl and turn on petrol.
4. Turn off petrol when translucent inline filter indicates no further petrol flow.
5. Carefully remove float bowl (no spillage) and place on a level surface.
6. Place measuring stick upright in central well and check petrol level against 24mm mark. (Leaning stick backwards and forwards can indicate how far off the petrol level is and compensate for the miniscus curve.)
7.1 If petrol level is above 24mm, open up the hinge angle on the float body by inserting a screw driver and gently twisting. (ie needle valve will close sooner)
7.2 If petrol level is below 24mm close the hinge angle on the float body by inserting fine long nose pliers and gently squeezing.(ie needle valve will close later)
8. Empty float bowl and refit. Repeat steps 3-7 as needed.
9. Repeat steps 2-9 on the right hand float bowl.
The same measurement process can be undertaken after returning from a ride. Close off the petrol, put the the bike on the centre stand, whip off a float bowl and check the level with your custom measuring stick.
It is probable that the above method (adapted from guru Snowbum a.k.a, Rob Fleischer) only really works with relatively new floats (with the same standard flotation values, ie not variable sinkers), good needles, springs and unworn float pins. I think several doctoral theses have been written on this stuff.
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So you do the same as I do.
But, when you turn the petcock off, there is still some petrol in the fuel line and when you remove the bowl, how do you prevent this to flow into the bowl ?
I am unable to do this, especially on right hand Bing, because the tubing is very long and hold a lot of petrol. So my measuring is always false.
This is why I asked.
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I agree Georges that the fuel in the lines will potentially cause an error. I don't think there is a perfect solution other than pulling the fuel hose off the carb before removing the bowl but that's something I wouldn't want to do often.
How big is the error ?
I calculated the volume of the fuel hose at 9.6cc per carb. which is an average because it won't be the same for each carb.
Th float bowls contain 46cc or 2.1 cc/mm of height.
9.6 cc is therefore potentially going to cause an error of over 4 mm in fuel height which frankly is hopelessly inaccurate.
I know this is far from perfect but in an attempt to reduce the error one thing I have done in the past is to shut off the fuel tap some short distance from home in order to use up the fuel in the hose. I calculated it as approx. 0.3 miles and considered it better to aim for using most of the fuel rather than all of it because there is no chance it will use the fuel evenly for both carbs.
Because you can't easily infer operational fuel levels accurately using the remove the bowl method, it becomes even more important that the floats weigh the same as each other, so that when set parallel, at least they will produce the same operational fuel levels.
In the end the only real way to do it accurately is to modify the bowl to fit a sight tube. It's been on my to do list now for several years !
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"In the end though the only real way to do it accurately is to modify the bowl to fit a sight tube. It's been on my to do list now for several years. "
That's a good idea !
I own a badly rusted bowl with the overflow tube broken. It makes a good candidate for modification !
If I remove the right bowl with the petcock closed, the bowl is at the overflowing limit... Maybe my line is too long or I start with the level too high ?
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If I'd had a spare bowl I would have done it by now.
Wirespokes did it I think by driving the overflow tube out the bottom of the bowl a short distance so he could attach a thin flexible tube..
In the absence of a spare bowl I've thought about drilling and tapping the bottom of the bowls to fit a short nipple but the metal is not very thick so I'm not sure how well it would work.
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I don't know - I think those bowls are made out of some largely Zinc alloy - easy enough to drill but prone to thread stripping unless you've got a thick section to tap
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- I think those bowls are made out of some largely Zinc alloy - easy enough to drill but prone to thread stripping unless you've got a thick section to tap
That's the reason I haven't done it yet, that and not wishing to modify original bowls. I need to find a spare bowl.
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I've played with my extra bowl.
It was decommissioned because a drop of water had seized hard the choke jet and on removing it the threads where destroyed.
I first planned to extract the overflow tube and put a plastic tube on it. Bad idea. The tube broke and I was obliged to smash it hard in order to plug the leak it has caused.
As I had found a very small nipple I though I could use it and I only had to drill, thread and voila !
But this is not so easy. The bowl walls are thin and in the center the hole for the main jet make this worse.
Fortunately, there are a couple of leftover from pouring the hot metal which are more suitable for threading.
Done. The nipple is on. Now, remove the plug on the "wrong" hole (opposite the choke jet) in order to put the bowl on left or right carb..
Last but not least, and I'm stuck here, how would I hold the plastic tubing in order to compare properly the level on the carb bowl ?
Any idea ?
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Last but not least, and I'm stuck here, how would I hold the plastic tubing in order to compare properly thelevel on the carb bowl ?
Any idea ?
Given the carbs are inclined forward the level check needs to be made in the same place for both carbs. I would position the tube at the side of the bowl in the centre aligned with the main jet. I expect the fuel level will be only a few mm below the top of the bowl.
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So I've to devise two ways of fixing the tube as the bolw has to be reversed for each carb....
Maybe this night will bring an idea ?
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Weak idle mixture and leaky exhaust flange did it for my B50.
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Hello !
I had an idea ! I made a spring with some iron chicken wire, on a 5 mm mandrel (an M5 screw...) which I "threaded" onto the plastic tube. The end of this spring serves to attach the tube to the bowl retaining clip on the carb.
The measuring is that the level stops at the carbs jointing end between the bowl and the body. On both sides.
I bet this is the reason the mixture tube protrudes from the body in the gas passage chamber otherwise the gas will flow into it...
Measuring the level on the bowl after removing it gives me 21 mm measured from the bottom of the center dip (but not from the bottom of it, my measuring device s too large to go that dip).
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The measuring is that the level stops at the carbs jointing end between the bowl and the body. On both sides.
So due to the floats and a substantial part of the casting causing displacement the operational fuel level is right at the top of the bowl.
To be honest I thought the level would be up to the top of the bowl at the front edge due to the downwards inclination of the carbs. If it's up to the top of the bowl in the middle then it would overflow at the front and might be flooding the pilot circuit. My test has been that if the idle mixture screw is removed and fuel drips out the pilot circuit is flooded and the level is too high.
Not quite sure what to make of your 21mm measurement. How about measuring the fuel level down from the top of the bowl and subtracting that from the overall bowl depth which I make to be 33.65mm.
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I never said my fuel level was perfect :D
I gave you the measure I've got this afternoon. As the bike runs very well but has a not so good mileage I suspect there is something to tweak on the carbs...