Surging/stalling

[Ed Miller]

I picked the above title because many people seem to describe what I'm experiencing as surging.  

To me, it feels more like I'm riding along, the motor is running as it should be, and it sporadically stalls, for very short periods of time, then resumes running normally.  When it's at its peak, and I have the rpms just wrong, it seems to happen every several seconds, not quite in any real rhythm.  I can't tell if it's one side or the other.

It only happens on warm days, when the temperature is over about 45 to 50 degrees, though I think it's becoming worse (happening at cooler temperatures).  Since the R65 has mostly been my winter bike, it hasn't been a huge problem, but it still bugs me.  The problem happens worse in the lower gears, like if I tried to maintain a steady 4,000 rpms in third gear, the bike will buck like crazy.  In 5th gear it's not so bad, but is noticeable, until I get over 5,000 rpms or so, when it SEEMS to run smoothly.  It feels like, if you are going down a long slope, and try to maintain a steady speed, like what the bike does as it can't decide if it should accelerate or decelerate for the conditions.  If it only happened on downhills I could live with it, but it happens any time I try to maintain a steady speed, if the ambient temperature is warm enough.

Here's a boring list of stuff I've done over the past several years and tens of thousands of miles, to try ineffectually to deal with it.

Purchased 3/21/03 with 27,637 miles
  Rebuilt carbs, except throttle shaft O-rings, including diaphrams
6/26/03  Heat sink compound on I.C.U.
8/31/04, 31,917 miles first record in my book of surging problem, but that doesn't mean it's the first time it happened to me
10/17/04    New coil, BMW replacement for my bike.  The old one tested very high resistance between the wire towers, two orders of magnitude more than the spec.  Also new plug wires and caps, NGK 5K caps and 8mm Taylor wire.
5/18/05, heat sink compound on the I.C.U.
5/14/06  New I.C.U. from Rocky Point, just as a cheap test.  No change in symptoms, so I have a spare I.C.U. now.
7/10/06  Even when bike is surging, the timing marks flash smoothly.
...up to this point, had been 3 sets of spark plugs, W5DC, WR7DC (by mistake), W7DC, and W6DC, with no change in symptoms.  
3/27/07   49,400 miles, new needles and jets
6/20/07 51,500 checked and adjusted float level, new floats
7/1/07  52,100  Replaced the rubber hoses for the carb intakes
7/4/07  52.300 New carb diaphragms, even though they had been changed with the rebuild.
7/15/07  52,400  New air idle jets
7/26/07  Removed the vacuum sampling tubes from the fresh air pulsed injection system, capped the spigots, at the carbs, but had no change
8/6/07  New throttle shaft O-rings
9/9/07  52,600  New New choke gaskets and O-rings though these had been changed before I ran the bike at all
9/10/07  Swapped out ignition canister for a known good one, still does the surging/stalling thing

At some point I put clear silicone rtv on the carb top buttons, in case they were leaking.

I guess I could try to clean out the carb little holes again, but for right now, I'm facing a pretty big gumption trap, and I think I'll try to see if it's alcohol soluble.  I'm glad I have a '70 Triumph Bonneville who's biggest problem seems to be that it leaks oil if I rev it over say 5500 rpms for a good (fun) period of time.

I mostly posted all this (except the previous paragraph) so I could send it to AskOak.whatever, and see what he has to say.  But obviously I'm open to suggestions.  Except to just wait another couple of months, so that it will be cold again and the bike will run fine.  

[Bob_Roller]

Ed could you give me the carb numbers that you have on the bike, so I can check it against what Bing says should be in your carbs ? The numbers are on the vertical flange on the front of the carb, seeing as you have an '81, I would assume you have 64/32/325, and 326 .

[Ed Miller]

Those are the numbers I have, stamped on the inside boss.  I do have Bing's book, and it's a good one.

[Bob_Roller]

The numbers for the internal parts are as follows, though I doubt that some of these parts have any numbers on them, the slide is 906-1 , main jet 145, needle jet 2.66 , jet needle 241, atomizer 591, and idle jet 40. The jet needle is set at position 3 , that is counted from the top. So if you have any receipts that may have part numbers on them, you can confirm that you have the correct parts. Hope this may help out some !

[tagordon]

Did not see you mention carb diaphrams or the peculiar little tops of the Bing carbs. I know I need to to address those little button thingies on mine. But I only have the stutter @ extended periods of 5000+ rpm. And I just don't do that often enough to worry about it. Even then if I vary throttle a few hundred rpm it never happens. I know the buttons on the tops of the Bings are prone to loosen & cause probs. I can watch the button on the top of my right carb spin. It is on my list for this winter. Also the diaphrams not working properly is a symptom of the wrong atmospheric condition in the carb.
That diaphram only works properly when the parameters are correct. Will always work though unless its completely trashed.
Not being an engineer I have no idea why the tops aren't a solid casting. Gotta be a reason though. I understand the dome vs the flat top. But that button ...

[Ed Miller]

I've edited the original post to indicate that I did seal the carb tops with silicone, though I don't think mine were leaking yet.

All the parts I've put in have been correct per the Bing book.  I don't think I changed the main jets, just cleaned them, but they are the correct number.

Tagordon, you don't go over 5 grand for very long?  "But Mama, that's where the fun is!"    

[Bob_Roller]

Ed, have you ever changed the rubber tubes that go between the carbs and the head, are the worm gear clamps still in good condition ? When you rebuilt the carbs, did you shoot carb cleaner or similar fluid through all of the passageways in the carb body ? A generic search on the inter-net for surging in motorcycles, always seems to point towards a lean mixture situation, or vacuum leak. Have any exhaust modifications been performed ?

[Ed Miller]

Ed, have you ever changed the rubber tubes that go between the carbs and the head, are the worm gear clamps still in good condition ? When you rebuilt the carbs, did you shoot carb cleaner or similar fluid through all of the passageways in the carb body ? A generic search on the inter-net for surging in motorcycles, always seems to point towards a lean mixture situation, or vacuum leak. Have any exhaust modifications been performed ?

Yep, and I've now added it to the list above.  No exhaust modifications, at least I believe Epcos mufflers should flow about the same as original.  Thanks,

[nhmaf]

All the people with oilheads tell me that surging on their bikes means time for a valve adjustment and
careful throttle body injector synch afternoon project, though apparently there is also a software update
involved to fix an earlier production line problem.....     Somehow I don't think that your issue is
related to valve lash adjustment and carb synching at this point, but when was the last time you did it ?

[Ed Miller]

Weird, my "edit" button seems to be missing in the original post.  I wanted to add that I check the valves every 3 - 5,000 miles.  Only rarely do I have to adjust them; so far no valve deformation.  So the problem has persisted through probably 8 valve checks.  I synch the carbs every time I try a new adjustment, most recently a few days ago.  Oddly the idle is OK.  I couldn't find any air leaks by spraying the carb and the head joint with carb cleaner.  Prior to replacing the throttle shaft O-rings and the choke gaskets, I could get the idle to speed up if I really hosed the backside of the carbs down, but not now.

[Semper Gumby]

Hi ED,

Try this.  Put in a new set of plugs.  Run it up to where it "surges" and when it starts, Shut off the ignition and look at the plugs to see if too rich or lean.  The one thing you havn't done is replace the needle and the needle jet in each carb which is where you be on the throttle in this situation.  Your needle postion could be wrong as well.

My BSA Firebird had a miss when I came up on on about mid throttle (4000 rpm) .  The plugs showed rich.  I moved the the needle clip up one notch to drop the needle and make the mid range mixture leaner and the miss went away.  

If anything verify the needle position with the stock setting.

Good luck.

[Ed Miller]

I did replace the needles and needle jets 3/27/07; position number 3 from the top.  I forgot to add that I replaced the floats and float needles that day too and set the float levels.

Replacing the original air intake didn't make any difference.  Hey, I can hope!

I think the left cylinder is lean; if I pull on the cable whilst' surging, it pings, but doesn't if I pull the cable on the right carb.  I think I'll clean out the left carb again, as I have a set of O-rings and stuff anyway.  

Does anybody know of a diagram of the air and fuel passages for Bing CV carbs?  Google didn't find one for me.  I've seen them for Amals.  They would give me a good idea of where, when I spray Berrymans into some hole, it should spray out, so that I can be sure to direct it toward my face.  There are sure a lot of teeny holes in those things.

[Bob_Roller]

Ed , it's a long shot, you might want to try emailing the Bing Agency at : bing@bingcarburetor.com , they may have some not so available diagrams that may help you out. All I know is if you put the nozzle extender into an opening, and nothing comes out else where, you may have a problem . I thought I was the only one that got sprayed by toxic chemicals while cleaning a carb out !!

[Ed Miller]

Shoot, I was just on the phone with Bing a couple of weeks ago, too.  

Yeah, Berryman's makes crummy in situ contact lens cleaner.  Actually it may work well but is painful.  I always remember to wear safety goggles after that.   :-/

[Bob_Roller]

Ed , if you contact the Bing Agency, could you ask them how much main jets are ? I'd like to try a different set for the hot weather season here in Phoenix, just want to see if they are more cost effective than the dealer.