Author Topic: I think I've confused myself (carbs)  (Read 2806 times)

0 Members and 3 Guests are viewing this topic.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
I think I've confused myself (carbs)
« on: July 26, 2012, 10:21:43 PM »
First, I'm confused on the jet needle, and it's clip positions.

According to dansmc (Dan's Motorcycle Course), "... you can move the little clip on the end up or down to lean (down) or richen (up) the mixture."

According to everything I've read here (unless I've confused myself, because some people refer to it as raising the needle or lowering the clip, and vice versa), moving the clip downwards, thus raising the needle, enriches the mixture.

Which is true?
____

My second issue is my real-world experience. It was suggested to me to raise the needle/lower the clip to help with the bogging from idle. I did so and it helped noticeably "in the shop" (just sitting there and twisting the throttle, not riding). Once I got out on the road, opening the throttle (either from a dead stop or rolling), I noticed that I had a period of nearly NO pull, then a sudden rush (going from none to normal suddenly) pull. No pull seemed to happen from closed to about 1/4 throttle, then the sudden pull after that. Another point is that when I checked my plugs after that ride, they were really white/lean. That's understandable, but I've never been able to read my plugs because the bike burns oil and always fouls the plugs.

Will only raising the needle one notch really make that much of a difference?
____

Third thing is more of seeking approval of my course of action. Because my plugs read lean in the pilot circuit, I was going to go up one size pilot jet, or should I go up two, considering how lean they read? I was thinking of staying with my current main jet because it felt like it had adequate pull once it got on the power.
____

Current setup [Planned changes]

Bike: 1974 CB550K
Intake: Velocity stacks (Steel Dragon).
Exhaust: MAC 4 into 1 with cut baffle.
Main jet: 110 [110]
Idle jet: 38 [40 or 42]
Needle clip: 5th from top
Pilot screw: 1.5 turns out.

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #1 on: July 26, 2012, 10:49:38 PM »
raising the needle by lowering the clip will enrichen,and visa versa,how much effect this has is determined by the taper of the needle,one slot can have a big result,you wouldnt do it otherwise,you have your clip on the bottom slot= max rich for that needle,did you jump a few slots and go straight to max rich?if so try going one leaner with the slot,if it feels better go another slot.

Online HondaMan

  • Someone took this pic of me before I became a
  • Really Old Timer ...
  • *******
  • Posts: 13,801
  • ...not my choice, I was nicknamed...
    • Getting 'em Back on the Road
Re: I think I've confused myself (carbs)
« Reply #2 on: July 26, 2012, 10:52:09 PM »
Rule #1: if the bike burns oil, fix that first. Otherwise, the uneven compression between the cylinders will defy all attempts to make a smooth-pulling engine.

Rule #2: Millions of miles with the stock pilot jets can't be wrong. Leave those stock. You can adjust the air screw to accommodate 40% change richer (out 1/2 turn from stock setting) or leaner (1/2 turn in from stock setting). If you need to go further than this with a stock cam, see rule #1.

Rule #3: The clips on the needles adjust the mixture about 1% of the mainjet per notch, richer or leaner. Moving the needle upward makes it richer. Open velocity stacks will usually require a richer mainjet (about 5%) and the idle air screw be turned outward about 1/8 to 1/4 turn from stock settings. Be sure to provide dead air to those stacks above 30 MPH, as the turbulence of the air around your legs will strongly affect the airflow into the outer 2 carbs, causing them to act strangely. In other words, build a still-air box around the openings of those stacks for best results.

Or, just use the stock airbox, which does all this for you...

 ;)
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline cgswss

  • Enthusiast
  • **
  • Posts: 221
Re: I think I've confused myself (carbs)
« Reply #3 on: July 26, 2012, 10:52:53 PM »
You are right.  the needle slightly restricts the fuel coming in thru the main jet.  The lower the needle (higher clip) the more restriction, leaned flow from main jet.  It sounds like you have a lean surge, and I would think raising the needle should richen the mixture and reduce the lean surge.

one step should not have a big effect.

When you have pods AND after market pipes, tuning the carbs can be a real chore.  You might try turning your pilot screws in a little to see if that helps.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: I think I've confused myself (carbs)
« Reply #4 on: July 26, 2012, 11:06:52 PM »
Dave: Thanks for the clarification, but how do I explain the extremely lean condition my plugs showed (the carbs were recently cleaned very thoroughly)? I only moved the clip down one. Fourth from the top is stock position.

HM:
#1: It burns oil, but I've wet and dry compression tested and all the cylinders are within 10% of each other. I know I should be fixing it, but I'm saving up for a full rebuild (being unemployed sucks).
#2: I actually tried adjusting the pilot screw 1/2 in and out while sitting and opening the throttle and both were not better than the stock position. And is 1/2 turn each way the maximum you'd recommend for adjustment?
#3: I'm assuming this is basically suggesting I use the stock airbox :P But I have to ask, are the side covers not enough to "still" the air around the openings?

I still can't think of anything that would cause the extremely lean plugs, despite all the oil fouling.

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #5 on: July 26, 2012, 11:37:12 PM »
the air in that triangle will be going all over the place,this is what happens when the factory airbox isnt used on this type of carb,youll have to fiddle around with things,dont concern yourself too much with the colour,if its too lean youll be melting the electrodes.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: I think I've confused myself (carbs)
« Reply #6 on: July 26, 2012, 11:43:28 PM »
Well, I'll be fiddling with it some more I guess.

Another thing I'm just curious about: what is the reason(s?) of needing to use the stock airbox? I know it needs still air sucked in through specific taper of the stock boots, but WHY? Is it the carbs, manifold, cam profile, something else?

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #7 on: July 26, 2012, 11:52:44 PM »
two tired has gone over and over with this "phenomenon",,the carb entry likes the air to come in straight not all turbulent more or less,the washing machine air flow with out the airbox goes all over those brass bleed jets you see in the carbs entry mouth,it even makes its way deeper and above where the main needle jet dischages,,its a bit like trying to drink a shaken up beer can,it still tastes ok but its not as satisfying.
« Last Edit: July 26, 2012, 11:54:30 PM by dave500 »

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: I think I've confused myself (carbs)
« Reply #8 on: July 27, 2012, 01:12:32 AM »
its a bit like trying to drink a shaken up beer can,it still tastes ok but its not as satisfying.

Well that's just about the best damn bike analogy I've heard in a while.

So it's basically the carbs themselves that don't like the turbulent air? Switching to different carbs, say CR29s or RS34s would remedy that? (Obviously going with a more aggressive cam or big bore to go with that)

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #9 on: July 27, 2012, 01:49:02 AM »
umm?now your complicating things further!these bikes stock run with the pack on rides together etc,my smokey 550 out drags three rebuilt norton 850s that the owners arent really thrashing,but they comment how well my little 550 goes,everyone does,,one guy we ride with has an early 80s suzi gs 450 twin cafe thing that is nothing to look at,,all stock,,i easily out run him but come the twisties im hard pressed staying on his arse,,unless its uphill,if your truly after real grunt just buy a newer and cheaper bike,just have fun with these old things,if you rode mine ill bet youll say thats how i want mine to run?try and go stock intake dimitri,,i can lug 5th down to 2500 and cruise,then slowly open to say 4000 then crack it open,no bog or #$%*,,or just down shift a couple and power on,youll be happier with the feel of torque than peak power,,its more usable.

Offline lucky

  • Really Old Timer ...
  • *******
  • Posts: 6,717
Re: I think I've confused myself (carbs)
« Reply #10 on: July 27, 2012, 01:58:26 AM »
Dimitri13 left out THE most important fact!!!

EDIT MISTAKE. Dimitri did give all the facts.

Bike: 1974 CB550K
Intake: Velocity stacks (Steel Dragon).
Exhaust: MAC 4 into 1 with cut baffle.
Main jet: 110 [110]
Idle jet: 38 [40 or 42]
Needle clip: 5th from top
Pilot screw: 1.5 turns out.

First I heard about the cut baffle though.

Raising the needle by lowering the clip is correct and it got the results I would expect!!
Richer and running better. Now he can fix that idle leaness by increasing the jet size.

His plugs do not lie they were running lean just as you would expect with STACKS.

Now with the needle raised and the clip on the very bottom groove it will start to run right with stacks.


QUOTE:

"First, I'm confused on the jet needle, and it's clip positions.

According to dansmc (Dan's Motorcycle Course), "... you can move the little clip on the end up or down to lean (down) or richen (up) the mixture."

According to everything I've read here (unless I've confused myself, because some people refer to it as raising the needle or lowering the clip, and vice versa), moving the clip downwards, thus raising the needle, enriches the mixture.

Which is true?" That is correct. LUCKY




QUOTE:

"My second issue is my real-world experience. It was suggested to me to raise the needle/lower the clip to help with the bogging from idle. I did so and it helped noticeably "in the shop" (just sitting there and twisting the throttle, not riding). Once I got out on the road, opening the throttle (either from a...."

It is not READY to go out on the road until it runs well in the shop at idle. That must get corrected first.

Did you even adjust the mixture screws at all?


Does it still idle?
« Last Edit: July 27, 2012, 02:12:43 AM by lucky »

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #11 on: July 27, 2012, 02:00:32 AM »
thats not the most important fact at all lucky!the most important fact is the airbox etc has gone awol!!#$%*?

Offline lucky

  • Really Old Timer ...
  • *******
  • Posts: 6,717
Re: I think I've confused myself (carbs)
« Reply #12 on: July 27, 2012, 02:05:55 AM »
That is what I said, He is running stacks.

With velocity stacks it will need to be tuned differently.

Offline lucky

  • Really Old Timer ...
  • *******
  • Posts: 6,717
Re: I think I've confused myself (carbs)
« Reply #13 on: July 27, 2012, 02:07:17 AM »
You got what you asked for Dimitri13.

A online argument about stacks and OEM filters.

Happy???

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: I think I've confused myself (carbs)
« Reply #14 on: July 27, 2012, 02:09:08 AM »
Well, I am having fun with it; all this messing with it trying to make it run decently. I'm one of those guys can't leave well enough alone. It may not be as good as stock, but it was fun tinkering with it.

I had stock intake with the MAC 4-1 with an in tact baffle. It was nice and smooth, but a little too boring for my tastes. I'm still young, not ready to settle down with a 'nice' bike :P A little bogging down (not a lot) in exchange for some cool looking stacks and intake noise to me gives it a bit more character.

I ride mainly with a bunch of Ninja 250 guys (I had one as my first bike. Fun as hell, cornered like a beast), and a couple of vintage/mod guys, but that's just cruising, nothing fast.

I know I'm being hard-headed wanting to keep the stacks, but I do appreciate the advice and help :) Maybe I'll go back to the airbox one day, but I'm having too much fun with these things. All the downtime saves me gas too haha.

Lucky: I did try messing with the pilot screw, both half a turn in and out from 1.5, one way made the idle hang more, the other gave a bit more hesitation... I think.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: I think I've confused myself (carbs)
« Reply #15 on: July 27, 2012, 02:09:23 AM »
You got what you asked for Dimitri13.

A online argument about stacks and OEM filters.

Happy???

 :'(

At least it's a little better than airbox vs. ebay pods
« Last Edit: July 27, 2012, 02:15:11 AM by Dimitri13 »

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #16 on: July 27, 2012, 02:11:35 AM »
i run a 4-1 and boyer micro power ignition,,thats all,100/38 jets,,i forget where the needle clip is,,pretty slack ill admit!

Offline lucky

  • Really Old Timer ...
  • *******
  • Posts: 6,717
Re: I think I've confused myself (carbs)
« Reply #17 on: July 27, 2012, 02:17:22 AM »
Well Dimitri I like your attitude.

You really need to get rid of that stock pilot jet with this set up.
I would go with  #40 idle jet considering that you moved the needle clip position.

I would have said #42 idle jet.
 But It could over do it.
 I am being cautious.

Late night cats too  huh??  LOL...lol Friday 2:19
« Last Edit: July 27, 2012, 02:20:36 AM by lucky »

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #18 on: July 27, 2012, 02:28:26 AM »
if your idle jet is too rich youll blubber a lot on cruise around 35/40 miles per hour,itll be a pain to ride and foul plugs,,everyone thinks they need more rich on the slow jets and read too much into these "plug chops",,less can be more!its always more of every #$%*ing thing,,i need more air and more fuel etc,,you dont,,if your not porting the head right out and using a super cam and all the rest of the stuff the stock #$%* works fine,,the biggest thing is all these improvements to induction rarely include an ignition upgrade,so many run points with all this #$%*,you cant even buy decent points now anyway,,plus the lobes on the advancers will have to be worn by now,,#$%*,,check the camshaft lobe wear but not the advancer lobes and still swear by points?ive never seen any specs for the points cam,,ill bet more than a few have less lift than they should,,if you want to soup up and havent considered electronic?sort your ignition first,,i always stress this.
« Last Edit: July 27, 2012, 02:42:24 AM by dave500 »

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: I think I've confused myself (carbs)
« Reply #19 on: July 27, 2012, 02:58:48 AM »
I understand what you're saying, and I understand how well the bike performs with stock intake/exhaust, but I'm not looking for a perfect runner daily driver. I would've kept my brand new ninja 250 if I wanted that. I'm not exactly looking to rip up the streets either, I could've gotten a late-model supersport for the amount of money I've put into this. I just want something that's a little bit different from the norm (even though a vintage bike around these parts IS the definition of different), even if it doesn't run as well as it should.

I do appreciate the advice about the ignition system. I hadn't even thought of that. I treat my points like the Showtime Rotisserie, just set it and forget it. HondaMan's ignition system was next on my list though, after replacing my shocks and fork springs (nothing matters if your worn out shocks bounce you into a ditch).

If I can't get it to run decently after the next few jetting changes, I'll just end up going back to the airbox. Until I do my complete rebuild of course; big bore, port, cam, carbs. Then I'll be opening up a whole new can of worms and even more headache and fun :D

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #20 on: July 27, 2012, 03:25:22 AM »
with all due repect to anyone,,if your thinking power and high performance,,ditch the points full stop and use a proper electronic ignition system of your choice,a "little bit different from the norm" when its a pain to ride is far from the norm,especially when youve lost power and tracability from stock for the sake of looks,youll have more fun on a standard honda of this vintage,,thats what they where built for,you still meet the nicest people on a honda,,at least thats what the last person i ruffed up said before he died.

Offline Dimitri13

  • Not a
  • Master
  • *****
  • Posts: 1,603
  • 1974 CB550K
Re: I think I've confused myself (carbs)
« Reply #21 on: July 27, 2012, 03:29:28 AM »
It's not particularly hard to ride, I just have to give it a bit more gas when taking off. I rarely ride in traffic so that's not much of a problem.

Dave: For electronic ignition, is there any particular one you'd recommend? I know HondaMan's is backed by all his expertise and the forum, but it still uses the points(?). You have a Boyer, but would you recommend it to someone else?

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,000
  • WHAT?no gravy?
Re: I think I've confused myself (carbs)
« Reply #22 on: July 27, 2012, 04:08:25 AM »
i recomend the boyer units as ive used them a lot,,i like them,the boyer unit replaces the mechanical advance as its all in the box ,hondamans excellent system isnt an electronic ignition system,it switches the stock coils via the stock weight and spring advance system you can modify,if you know how and like to tinker,most of the true elecronic after market systems use the honda advance system(mechanical)and also the 5 ohm coils,boyer offer two systems,one runs the stock coils with a good enough spark ,the other(micro power)runs a pair of .6 ohm wired series coils that also release a good amount of usable battery charge current,the pamco unit also has a great reputation however ive heard about many dyna failures but only through this forum.

Offline cgswss

  • Enthusiast
  • **
  • Posts: 221
Re: I think I've confused myself (carbs)
« Reply #23 on: July 27, 2012, 05:03:42 AM »
NO NO NO!  Your all wrong!  All you need is a big bore kit.  It will solve all your problems.  More displacement, 10.5 to 1 compression, It will solve ALL your problems!


OK not really, but I'm dying to  hear how one works (big bore kit) and I can't afford to get one so next best thing is talk someone else into it  (BMFG)

Offline MattFreeman

  • Hot Shot
  • ***
  • Posts: 331
  • What Have I Done?
Re: I think I've confused myself (carbs)
« Reply #24 on: July 27, 2012, 07:11:18 AM »
sub