Topic: CB500 problems carbs 4into1 / 4into4 experiment

[jonda500]

Experiment part 2:
Just temporarily to note the difference it made, without changing the carb settings I  fitted the 4 into 1 with straight through muffler to my 1st honda today. Its carbs are the originals that the bike came with and have, for the last ten years at least, never been vacuum synced or professionally rebuilt. I have cleaned them with petrol and brushes only several times and a few years ago replaced the float needle & seats and correctly set the float height when fuel started leaking out the overflow tubes. They are set up stock standard -pilot jets #40, idle screws 1 turn out, main jets #100, needle clips #4 from top. With the 4 into 4 fitted the bike has always been quite hard to start when cold but has always pulled smoothly throughout the rev range with the only problem being in the range from the last quarter of throttle to WOT. It seemed to pull better with the throttle not fully open, with full throttle slowing it down slightly.
   So now with the 4 into 1 fitted it started easier than normal, didn't take as long as normal to idle nice, and was running amazingly well when I took off. As it warmed up it ran less well and felt a bit laboured and rich in the mids. The top end however was cured of its problem - the last little bit of throttle doesn't slow it down any more!
   I wonder if for this bike, when the 4 into 4's are back on it, it might worth trying #98 mains and then possibly moving the needle clips to the bottom #5 slot...

[rb550four]

Wow. Just read this entire thread..... Powerful......Moving , what else is there to say, right? Could make a movie outta  something like this. There are no villains, only heroes ,focusing on an carburation issue as deep as a crevasse .Will they all be sucked in? Can any of them survive?.....
   Really? Here's what I got 3 pages of finger pointing from an owner who can change position of any item inside a carb , before any of his would be rescuers can fire off a solution.
  No, No.  It's a love story about 3 boxers who are thrown together in the same ring , they all love  the same girl, but  one is married to her and' is reluctant to see the light.  What a fight....What a battle...There's no understanding...and what becomes of this temptress that is anxiously waiting for the hand s with the right moves, the right touch, that can make her come alive!
   Screeeech!  Holy $hit guys, you are all right, but your timing is all off between the 3  of ya.
Jonda 500  needs to stop making changes to the carbs long enough to repair what was previously discussed as an issue, such as replacing the plug caps and why you are running 8's instead of 7 plugs,and the 2 and 1/8 turn instead of this 1 turn that you refer to(That's small Mikuni adjustments not these, book says 2-2 1/4)
   Johnda should also make up his mind on what filters and exhaust  he will be running so an accurate platform can be presented to other members  to discuss. And make 1 change at a time, discuss, make next move . Not 10 changes overnight and start with a different machine in the morning.
  CAN WE? IS IT AT ALL POSSIBLE to start with stock jets at stock settings on the carbs , new plugs , caps and sync gauges?
Take it all one step at a time, including a full description of what is on the bike now so we have a platform to work from
  Jonda if you would be interested in a  real group tune ,( how much better can it get?) and since this machine is one of three, this machine could actually be used as  a training thread  for new members joining this site that have no "f"ing idea what they are doing-but would like to learn. You would be the photographer and the leading man....Could do it stock first, then adjustments for optimum run , then maybe some jet changes and slide adjustment tricks later for the more involved ,which could involve  exhaust and intake changes and solutions..
 Hey , this could be a movie after all.

[TwoTired]

I tried to wait until the dust settled, after deciding that Jonda was more interested in spreading the confused/frustrated feelings he has among us, than actually learning to reduce the confusion/frustration he clings to.  Perhaps that sounds mean. But, it was taught to begin with a clear and concise problem statement before trying to solve any given problem.

I suppose when all you know is how to swap parts, that's what you do if you can't diagnose methodically.   I learned the latter is far more efficient and less frustrating/labor intensive. Most of use have no experience diagnosing 20 different configurations at one time, so now we are frustrated too, with nothing solid to point towards.

FYI, exhaust changes, induction changes, displacement changes all effect either engine mixture demand, or carb delivery capability.
For US models, the Cb500 came 627B carb set ups, CB550K came with 022a or 087a carb set ups (early 4 into 1) exhaust, and Cb550F came with 069a set up carbs and a 4 into 1 exhaust.  Simply swaping carb assemblies among these models is pretty much guaranteed to bring run issues the forefront.  Some of which will foul spark plugs, and that in itself will cause run issues, even if the carbs were perfectly adjusted.  Anyway, all these carbs look the same externally, but are different internally for specific reasons.

It would appear that Jonda's "experiments" have only verified that different engine/exhaust/induction configurations need different carb settings.  But, in no way rules out that he may still have a set of dodgy carbs with unknown internal components settings/sizes.

From my point of view it seems like some of these frustrations/problems are self inflicted.  ...With a few more variables added to make things nebulous.


Wish I could help.  But, I really don't know what needs fixing most in this thread.

[jonda500]

wow. I swap things around (one at a time) to satisfy my curiosity about what effect it would have and hopefully learn something as I often have weeks of saving up for parts followed by weeks of waiting for them to arrive and just can't stand having to keep cleaning the plugs just to be able to ride a bike that runs badly rather than trying doing something that will make it run different, maybe even better! I agree this thread has become far too complex and epic to easily follow and feel quite ashamed that I didn't have the foresight to not "finger point" here (I realise that clearly should have been done through emails!).

  Just to clear up confusion these carbs that I had rebuilt came with my 2nd honda cb500 and this is the bike I want to use them on.(I was so keen to try them out when I first got them back all beautifully restored that I put them on my nice 1st honda as this (2nd honda)bike already had the unrestored carbs fitted and was running well.) I am slowly collecting original pipes for it(I have the two outer ones), but I want to set it up to run with the 4 into 1 that it came with at the moment as it may well be years before I have a nice set of 4 into4's ready to bolt on. The bike like my other two has a completely original original honda air filter setup.
   Relavent work I've done so far on this bike:- valve clearances set, timing chain tensioned, inlet manifold to cyl head o rings replaced, new carb mounting boots fitted, new points plate/points/condensers fitted, new genuine honda coils fitted, replaced the D8EA plugs with new ones many, many times.
   Carb work I've done:- replaced the oem needles with new aftermarket ones, raised the needle clips to #2 slot to suit the 4 into 1, replaced the OEM #40 pilots and #100 mains with secondhand OEM items the same size (in case a PO messed with the originals), wound the air screws out to two and a half turns.

   My cb550Fss(built mainly from parts bought on ebay) has, in my spares collection for it, a set of cb750 carbs with pods - I have tried fitting these on the 2nd honda500 and the 550, but although they seem to work quite well on both bikes I don't want to use them because they can only fit with pods and the outer two fill up with water when it rains. So I purchased a set of carbs from carbkeith. My 550 was still incomplete when they arivved so to try them out I fitted them to my 2nd honda500. Keith made an excellent video to show me how to drop the needles down 2 positions to suit the 4 into 1:
  http://s888.photobucket.com/user/kpruyne/media/2013-05-08/MAH00651.mp4.html
With the needles dropped the bike ran fantastic at all but very small throttle openings(0 to 1/4). Next I swapped the #40 pilots for #38's that he sent me with the carbs and the misfire at small throttle openings all but dissappeared.
   Having proved to myself that my 2nd 500 is capable of running perfectly well, I now have the carburettorkeith carbs on my 550 and that is where they will be staying. With these carbs on the 550 the slight misfire at small throttle opening  is a little worse now and wot feels very flat. Waiting for new #35 pilots and #98 mains that I've ordered to arrive and meantime I want to test the 550's ignition coils which seem sus.   
   

[Don R]

the original honda plug caps have a resistance of (ohms):

#1 - 9000, #2 - 8600, #3 - 7000, #4 - 7000

Are cap readings of 1st and 2nd cyls high enough to cause problems?

Even with those readings, I wouldn't expect a spark issue, especially if the connections are solid.
In the US, the standard plug caps were 10K.  The original caps had no external markings for value.   Hard to believe that all four of yours are really that far off 10k.  Is their corrosion visible at the cap connection points?   
Do you have a local electrical supply that sells 10K ohm resistors?  Check your meter with one of those for calibration error.


Regarding the over rich mixture:
Have you checked the actual fuel level in each carb with the clear tube method?

Do all the spark plugs show the same deposit patterns across the bank?

What spark plugs and the numbers on them?

Do you know the numbers stamped on the slide needles?

Can you verify that the emulsion tubes are clean?  Has the needle jet been enlarged or the needles worn?

Check the air box inlet for restriction(s).

While a new air filter shouldn't cause restriction, try operating with out for a test period and note the effect.


I should ask about choke operation to verify that you know up is choke applied (on/cold start) and down is warmed up running position (off).

[jonda500]

Here's where my 2nd500's float bowl fuel levels are at today. Number 4 is a tad higher than 1 & 2, but number 3 fills right to the rim of the bowl. Looks like time to pull the carbs back out again to check the float levels. Meanwhile new plug caps is second from the top of my wish list below vacuum guages, and D7EA's is in third position but I've got 8 used but still ok D7EA's soaking in petrol.