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svejkovat
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A few questions please? 1983 R65.
07/21/18 at 12:15:36
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First disassembly/cleaning of Bing Type I CVs in 45K.

Reason...  Left carb can't keep up with right carb vacuum on the manometer under any tuning conditions.  Eliminated any source of possible vacuum leaks. 

Test rides resulted in rough running, slow to return to idle, and idle revving to 4K rpm at stop lights.  Had to bump the clutch to get idle return to normal.

I recently removed the emissions tubes from filter box to cylinders.  Plugged the vacuum line in the box that leads to the T between carbs.  Plugged the holes left by the tubes removed from box itself. Plugged the cylinders with pair of crankcase drain bolts using high temp Loctite. But doing all this had no effect before/after regarding the above-said symptoms. 

Carbs are dismantled on the kitchen table presently.

First.. what do these symptoms suggest?  Sticking slide?
And.. anyone off hand know the exact dimensions of the O-rings within so that I can grab some pairs of nitrile or viton at the parts store?  Other gaskets in the carb are less than a year old and are fine.  The rubber diaphrams appear to be in excellent condition and will remain.

Lastly.. the 15mm "bungs" at the top of the carbs are rattling and loose. ???  I've read online that these ought to be sealed tight.  Makes sense.  Water could get in.  Visual close inspection inside both "domes", under these bungs, there is a loose piece of what looks like a round black rubber flake loosely moving around. About the same diameter as the bung and won't shake out.  Ought to just grab it/them with tweezers but was reluctant until I asked here.  Suspect it's simply the sealant that used to retain the bungs that has separated and is drifting about in there.  So... remove this rubber 'chit' and seal the bungs?  Epoxy them from the outside?  Jb weld?

The carbs are practically spotless within. I'm not going to have them parts-washed/dipped.  I intend to draw carb cleaner through passages using a shop vac in reverse of their natural aspiration. This method has done me very well in the past on many other carbs.   

Thanks for any input here Smiley
  
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Barry
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Re: A few questions please? 1983 R65.
Reply #1 - 07/21/18 at 14:24:33
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Sealing the dome tops is essential as leaks will reduce the vacuum above the diaphragms and prevent the slide lifting as they should.  Although the slides wouldn't be lifting anyway on a no load vacuum balance, leaks could still have an impact.

O rings sizes:

  

O_ring_sizes.PNG ( 7 KB | 4 Downloads )
O_ring_sizes.PNG

Barry Cheshire, England 79 R45
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svejkovat
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Re: A few questions please? 1983 R65.
Reply #2 - 07/21/18 at 18:26:24
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Thank you very much for that
  
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georgesgiralt
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Re: A few questions please? 1983 R65.
Reply #3 - 07/23/18 at 02:42:28
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I'm a bit late, but...
If you do not have replaced any brass on these carbs, I suggest you do.
Buy a new pair of needle jets and needles and put them on. This will change a lot of things. Returning the behavior to normal.
Just my 2cents...
  
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svejkovat
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Re: A few questions please? 1983 R65.
Reply #4 - 07/27/18 at 12:08:12
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Thank you here for the input.

Joy!  At last!

I've had this bike since '92.   Had a bout 10K on it.  Owner was a German citizen living in US who planned to ship it back to Ger but changed his mind.  It was/is in pretty mint condition.  I wasn't surprised to find the inside of the carbs looking pretty new.

I diss/reassembled the carbs on the kitchen table.  Diaphrams were fine.  Replaced orings with viton.  Vacuumed and compressed air all passageways with carb cleaner.  Deoxidized any/all internal alum corrosion with CLR and fully flushed with water.  Found some scoring on the left slide, the piston that mates with the dome.   I very lightly cleaned all four of these mating surfaces on the carbs with scotchbrite and lubed lightly with 30wt oil on reassembly.   

All brass looked perfect.  Dropped it all in a clear wine glass full of CLR and watched as the small amount of scum and impurities finely bubbled up to the surface.  Ten minutes later the bubbling ceased.  I swished all around well. Rinsed fully with water. Finished with compressed air.  Reassembled.

Buttoned everything back together.  Sealed the caps on the domes.  One full turn out on the idle mix screws.  Set idle stops with a manometer till perfect.  Half hour later on the road I brought the left idle mix out 1/8 turn.  Right out almost 1/4 turn.  Just done to satisfy my ear through the low rpm ranges.

Bliss.   Wow.    Perfection!   So far Smiley   

It never fails to impress me how smooth and vibrationless these bikes can be when in tune.
The minor little vibe between 4k and 4.25k is only "there" after all because the engine almost disappears beneath you at any other point on the tach. 

I remember the first month I had the bike my girlfriend and I took it from Ann Arbor to her home in Chicago.  Not fully used to the bike, at one point on the highway I panicked to see the tach redlined.  Over 80mph in 4th gear.  I literally had not noticed, for how many miles now?,  that I was redlining! That smooth.

I sit at red lights next to Harleys and watch their rear view mirrors shaking off of the stalks, worse yet when they accelerate.  Ah well... to each, his own.  All's good Wink
  
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svejkovat
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Re: A few questions please? 1983 R65.
Reply #5 - 07/27/18 at 12:21:15
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As a postscript.   The chaff that was rattling around under the domes turned out to be black gasket material discs, about nickel sized.  Finely crimped around the circumference suggests they were crimped in place along with the thin metal plugs at the top of the domes to seal.  Eventually falling out.  The metal plugs were loose in place but still within the crimp.  Just leaking air.  The round gaskets were just fluttering around at the top of the domes doing nothing but waiting to disintegrate and clog the carb.   I got them out with long tweezers and cleared away remaining junk beneath them with a tiny pad of scothbrite on the end of a stick.  Sealed the domes from without after replacing the carbs on the bike.
  
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Re: A few questions please? 1983 R65.
Reply #6 - 07/27/18 at 21:37:29
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So do you think it was the dome caps that were causing the problems you originally talked about?
  

1983 R65 w/ Velorex 562 Sidecar
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svejkovat
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Re: A few questions please? 1983 R65.
Reply #7 - 07/28/18 at 11:59:42
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So do you think it was the dome caps that were causing the problems you originally talked about?

I never did get a proper read on that.   
If one googles something on the order of "bumping the clutch to bring down the rpm" there are various explanations having to do with vacuum imbalance causing one carb to overcompensate while riding... when returned to idle the overcompensating carb is for a while too lean and overrunning the other.   Never quite understood it.   

I was not able to find an obvious vac leak.  The metal seals on top of the carb domes were equally loose, and precision enough in their "seats" that at vacuum they would not have leaked much really, or at least equally enough not to have been much problem. 

What I suspect was at issue is probably what plagues most of carburetors at some point.  "one little speck of debris can ruin your day".   In the process of rebuilding I likely never even noticed the removal of that speck/clog at some point and now all is fine until next time.

I do believe one vacuum slide was sticking.  Could that have caused what I described.  I'm not carb expert enough to guess.  On the chrome piston of the diaphragm holder there was scoring similar to what is seen sometimes on a main piston.  Maybe even a bit of aluminum build up.  I polished it bright with scotchbright as well as sweeping the inside of the cylinder of the dome where this piston slides with scotchbright and clr.  The smoothness of movement was very much improved and I reassembled it with a few drops of 30wt oil.

Might be that this piston/diaphragm was sticking, and blipping the clutch changed the vacuum suddenly enough to unstick it.   
  
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Re: A few questions please? 1983 R65.
Reply #8 - 07/28/18 at 18:42:57
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Very frustrating.  I almost like it better when I find something broken.  At least then I know what the problem is.

Hopefully all that you did fixed whatever it was.    Good luck.
  

1983 R65 w/ Velorex 562 Sidecar
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Re: A few questions please? 1983 R65.
Reply #9 - 09/09/18 at 02:24:45
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Barry wrote on 07/21/18 at 14:24:33:
Sealing the dome tops is essential as leaks will reduce the vacuum above the diaphragms and prevent the slide lifting as they should.  Although the slides wouldn't be lifting anyway on a no load vacuum balance, leaks could still have an impact.


My dome tops are bouncing around - one has been for a while (probably a few months) and can have a little fuel spilt on top after using at high revs and I just noticed the other side also has a small amount of movement of the dome top.  I haven't noticed any difference in performance but would like to seal these up before there is a problem. 

I haven't taken the tops off yet to inspect but would like some advice if possible - Svejkovat sealed his from the outside - has anyone resealed the domes from the inside?  Possibly replacing the gasket and re-peening?

Thanks in advance for any advice.
  

 1985 Black R65  -  1983 Ducati Pantah 500 - 2001 DRZ400 dirt only
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svejkovat
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Re: A few questions please? 1983 R65.
Reply #10 - 09/09/18 at 12:44:56
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I actually found an elegant solution to this.   I have a set of hole/hollow punches from harbor freight.

These have been indispensable over and over again. Very highly recommend.  Holes in gaskets,  small washers in any gasket material, perfect holes in any thin material.

Anyway, I took an appropriately sized punch and knocked out two round discs from a piece aluminum duct tape.  Peeled the backing off the tape and adhered the discs to the domes with just enough overlap to seal the edges.  Pressed really hard with the thumb the aluminum molds itself to contours, adheres well, and looks professional.  I expect it to stay... who knows how long?  Ill try to post a pic
  
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