Author Topic: running really rough, desperate need of advice--- *Problem SOLVED!!*  (Read 17292 times)

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Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #50 on: December 17, 2013, 02:17:34 AM »
sheesh, never thought of that Dave. Which way is the cut away supposed to be facing? currently it is facing the filter side. the filter removed makes no difference with the over-fueling issue..

do you think the intakes are also at fault here? But it doesnt make sense, surely an performance mods would demand more fuel, not less??..

maybe do the ignition advance mod with the springs that Hondaman recommends? cutting a coil off etc...
« Last Edit: December 17, 2013, 02:22:52 AM by Bru-tom »

Offline fdbrat

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #51 on: December 17, 2013, 02:51:03 AM »
What made you rebuild the carbs in the first place? How did it run before.

Are you sure you cleaned the emulsifier tubes? They would make you run rich.

Was the smoke your pal described black or white?

I love a good mystery novel.
1975 CB750F
4-4, Dyna S and box
5 ohm coils / 5k ohm caps
In- .05 / Ex- .08

San Luis Obispo

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #52 on: December 17, 2013, 03:11:03 AM »
they were stuck from varnish and slides would not move a bit.

She ran okay, its my first bike and i never really knew what was supposed be good running or not.

i just checked the emulsifier tubes and they are clean and clear.

the smoke was black

im glad you do, i need all the help i can get ;)

Offline fdbrat

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #53 on: December 17, 2013, 10:02:36 AM »
Are you still running the Ristorante plugs and the resistor caps?

I'm only running the 5 K ohm caps, with normal plugs.

Have you made sure the plug wires a firmly screwed in to the caps?
1975 CB750F
4-4, Dyna S and box
5 ohm coils / 5k ohm caps
In- .05 / Ex- .08

San Luis Obispo

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #54 on: December 17, 2013, 10:06:44 AM »
im not so sure what the ristorante plugs are but id have to say no. I bought new NGK 5k plug caps. they are all working 100%.

After my reassembly today, i did screw the air-screws out a further half turn, now at 3 out from bottom and i noticed a difference. Im not sure if its that or the ignition advancer that i oiled? But there is a change for the better :D

Offline fdbrat

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #55 on: December 17, 2013, 10:21:47 AM »
I fat fingered. Ristorante. Hahaha. It was supposed to be resistor. Ha.

Hmmm. Just a thought. You said you put in O rings that weren't stock and that they were tighter than stock.

Now that I think about it, I bet because they are smaller it is allowing the AFR screws to go in deeper. Thus they need to back it out even further.

Go ahead and turn it out further yet even more and see if it improves.
1975 CB750F
4-4, Dyna S and box
5 ohm coils / 5k ohm caps
In- .05 / Ex- .08

San Luis Obispo

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #56 on: December 17, 2013, 10:25:44 AM »
oh hahahaha, excuse your french! ;D

but which o-rings are you referring to? the main jets ones are the only funny sized ones i had to use that were smaller and had to be stretched over...

there are no o-rings on the air screws, only main jet, needle and seat, float bowl etc...

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #57 on: December 17, 2013, 10:26:51 AM »
Well it would appear that you have stock jetting for a modified air and aftermarket exhaust.

You have black smoke and hesitation on idle, correct?  Runs fine after 1/4 and does it still have black smoke then too?  Or is the rich condition isolated to idle?

I'm thinking that your air mixture screw is at a point where it's not actually going to be able to "adjust" much.  You may find that either way you turn it there isn't really much of an affect.  Once you start getting around 2-2.5 turns out you will have limited success with adjustment.

That hesitation at idle can be addressed with stepping up the idle jet to say a 40 but you are running rich at idle.

As Hondaman states in his book:  Contrary to popular belief in "pulse type" carburetors such as ours an air leak or more air can actually cause a RICH condition.

Like if you had a leak in #1 or whatever cylinder it was.

Did you replace the manifold o-rings? 

Also, I noticed from your picture of setting the float height that the main jet appears to be the original one.  Which is fine, but wondering if you replaced the o-rings or if you did got the right size one.

Offline fdbrat

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #58 on: December 17, 2013, 10:32:35 AM »
I'm I missing something here...

Do main jets have rubber o rings?
The air screws should have an O ring.
1975 CB750F
4-4, Dyna S and box
5 ohm coils / 5k ohm caps
In- .05 / Ex- .08

San Luis Obispo

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #59 on: December 17, 2013, 10:34:08 AM »
Also, I'm not sure if I like your band clamps.  Are those OEM?  They look too wide to me.  There is a groove for the clamp to go in and if your clamp were too wide it would be totally out of that groove and much less effective at tightening.

Just another thing you might want to eliminate with a leak test, spray something around the boots..

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #60 on: December 17, 2013, 10:35:40 AM »
There is no o-ring on the air screw.  If you looked at the screw it almost looks like there is a groove for it but there is not one on there. 

The main jets, though do have an o-ring.

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #61 on: December 17, 2013, 10:36:52 AM »
thanks for the input. Yes, i replace all the o-rings throughout the entire motor and carbs. Not all stock sizes, but they are definitely ones that work.

The black smoke is limited to idle and beginning after 1/4 throttle, i assume the after is caused by the excess fuel that the carbs had at and before a 1/4 Throttle. but most certainly clears up after a 1/4.

So if my airbox mod were to be more restrictive it may help in other words?  I cant understand why im running rich, especially if jets are stock.

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #62 on: December 17, 2013, 10:37:25 AM »
With a misfire on that one cylinder, you might want to swap plug caps or even swap the idle jet and see if the problem follows it so we can actually start eliminating things.

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #63 on: December 17, 2013, 10:38:52 AM »
Also, I'm not sure if I like your band clamps.  Are those OEM?  They look too wide to me.  There is a groove for the clamp to go in and if your clamp were too wide it would be totally out of that groove and much less effective at tightening.

Just another thing you might want to eliminate with a leak test, spray something around the boots..

they are not stock,my stock ones are all rusted and and. These are wider, but i have made sure they do seal nicely. I will spray some soapy water there and see if there are any leaks though. just to confirm.

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #64 on: December 17, 2013, 10:44:02 AM »
Yes.  I once helped out a guy with a 75 cb750 with all stock jetting. 

He had totally open pipes, K&N filters, you would think he would need to do some rejetting and at least rejet, but the bike seemed to run ok, except the idle would runaway at times and not come back down.

Fiddling with the air screws seemed to have little affect.

He did notice that when he pushed down on the linkage for the carbs, the idle would come back down, he thought they weren't closing all the way.  I however, noticed that if you pushed down on the carbs anywhere, not the linkage, if you just even grabbed a float bowl drain and pulled it down, the same thing would happen.

He had air leaks on his manifolds and pushing on the entire assembly would seal it up.  I think those air leaks were making him run richer to the point where the bike was ridable.

I don't know if he ever got new boots though.

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #65 on: December 17, 2013, 10:45:12 AM »
you should spray something flammable so you see if the rpms climb, you don't want soapy water to get sucked into your engine.

Just watch out for the paint on that nice blue tank.

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #66 on: December 17, 2013, 10:50:37 AM »
With a misfire on that one cylinder, you might want to swap plug caps or even swap the idle jet and see if the problem follows it so we can actually start eliminating things.

well, my carb sync yesterday showed that the miss could have been the carb being way out on vacuum. she started fine today on all four. I have done some swapping of plugs and caps since this problem started. so far so good.

Could the ignition advancer have had something to do with it?

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #67 on: December 17, 2013, 10:52:08 AM »
Yes.  I once helped out a guy with a 75 cb750 with all stock jetting. 

He had totally open pipes, K&N filters, you would think he would need to do some rejetting and at least rejet, but the bike seemed to run ok, except the idle would runaway at times and not come back down.

Fiddling with the air screws seemed to have little affect.

He did notice that when he pushed down on the linkage for the carbs, the idle would come back down, he thought they weren't closing all the way.  I however, noticed that if you pushed down on the carbs anywhere, not the linkage, if you just even grabbed a float bowl drain and pulled it down, the same thing would happen.

He had air leaks on his manifolds and pushing on the entire assembly would seal it up.  I think those air leaks were making him run richer to the point where the bike was ridable.

I don't know if he ever got new boots though.

will give that a try and see what happens, not sure what to use as a flammable substance thats safe hahaha

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #68 on: December 17, 2013, 10:54:53 AM »
Like someone mentioned the coils and the advancer work in pairs, so it wouldnt' be isolated to just one cylinder.

Did you adjust the vacuum so that they were all the same now?

You should now swap the idle jet on your problem cylinder and see if that changes things. 

Offline harisuluv

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #69 on: December 17, 2013, 10:56:18 AM »


will give that a try and see what happens, not sure what to use as a flammable substance thats safe hahaha
[/quote]

You can use brake clean but..  be sensible about where you're spraying it.

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #70 on: December 17, 2013, 11:00:51 AM »


You can use brake clean but..  be sensible about where you're spraying it.


yeah, i dont know about that, all my paint is fresh and new, i will try the older clamps out and see how they fit compared to the new wider ones...and if it changes anything



well, the problem cylinder has kind of gone away now. Its more of a jerk at below 1/4 throttle. and the richness. i did find that when it did run on 3 cylinders, that the one needle was stuck closed after standing for a bit, that was one instance though...

so my issue is with the blubber now, and rich condition at low rpm while in gear.. but seems better after the lubing of the advancer and airscrews 3 turns out

i may just take some fuel and pour it on the mating surfaces and see what happens after that...

I never knew that an air leak could cause such problems!
« Last Edit: December 17, 2013, 11:05:51 AM by Bru-tom »

Offline Duanob

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #71 on: December 17, 2013, 11:16:22 AM »
FWIW anytime I've ever had hesitation just off idle is was always clogged pilot jets (all things being adjusted correctly). Have you removed your carbs since you first posted this thread? You can remove the bowls without removing the carbs and remove the pilot jets and make sure they are clean. They have the tiniest holes and will cause what you're describing if they get clogged. It's not uncommon to clean the carbs 2 or three times to get it right.

I am surprised you can get the bike to start with your air screws out that far.
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Offline dave500

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #72 on: December 17, 2013, 11:35:24 AM »
the slides are correct if the cut away faces away from the engine

Offline Bru-tom

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #73 on: December 17, 2013, 11:38:06 AM »
I stripped the carbs today to see whats potting. They are as i left them, super clean and clear. I removed all the jets, emulsion tubes etc and found nothing. Thats whats confusing me, why am i getting this absurdly rich condition?!?! but only at under 1/4 throttle... which again does not make sense with my nearly free flowing exhaust and less restrictive than stock, airbox mod...

the slides are correct if the cut away faces away from the engine

Thanks Dave ;)

Offline LesterPiglet

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Re: running really rough, desperate need of advice--- *pulled carbs off*
« Reply #74 on: December 17, 2013, 11:39:30 AM »
Just a quick off-topic while I remember.
The last time I came off a bike was a Yamaha TY80. I installed the slide backwards and it started with full throttle after I bumped it. I was wearing my house slippers. The bike tore towards a brand new car so I pulled it to the ground, ripped the knees out of my trousers and my slippers went about 20 feet in the air. Lesson learned.   ::)

Carry on.   :D
'Then' and 'than' are completely different words and have completely different meanings. Same with 'of' and 'have'. Set and sit. There, their and they're. Draw and drawer. Could care less/couldn't care less. Bought/brought FFS.


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