Topic: Stumbling when roll on throttle- only when engine hot- fouling plugs?? 76 cb550

[kippstakes]

Since I can remember my bike has ran fairly well (except for the infamous cb550 flat spot), but only until it gets hot, so maybe around ten miles. At that point it will begin to stumble when I roll on the throttle. At first I thought the carbs were flooding, but now I'm pretty sure she's fouling plugs.
I have pod filters and 4/2 exhaust, so I have be jetting under the assumption of lean running. I have the needles set to the richest notch (and the bike needs it, on notch leaner and it runs like flat crap), the idles 1.5 out, standard slow jets (48s?), and 105 mains- which I think are most important in this case.
I'm thinking about switching to 100s, but it seems a little lean for the setup.
I've considered advancing the timing 2 degrees to even out the flat spot- could this help with the fouling?
Thank you

[harisuluv]

Start with actually verifying the status of the plugs.  It would be a real shame to start jetting going off "pretty sure she's fouling plugs."

Come back with pictures of plugs 1-4 and let's go from there.

[Grinnin]

How are your intake boots?

As engines heat up parts expand and you can get a little air leak.  If it's running on the edge of lean now then a tiny air leak can lean it further and cause rough running.

Air leak correlates with 2 symptoms:  only when it warms up and mostly when you roll on throttle.

[kippstakes]

...And standard slow jets should be #40, NOT 48s. If you are indeed running 48s, I have no doubt you're fouling plugs promptly.

I'm not entire sure what's in there, the slow jets aren't marked so I don't think it's possible to verify. The main was stock, so I assumed the idle would be too, which would make it a 40 (I was thinking 38 actually, which still would have been incorrect haha).
Thanks

[kippstakes]

The boots should be solid. I had the carbs off about a week ago and actually pressure tested each boot, and they are all air-tight. So hopefully that's not the issue. These symptoms have transcended two boot sets anyway, so that further leads me away from a boot issue.
Thanks

[kippstakes]

Start with actually verifying the status of the plugs.  It would be a real shame to start jetting going off "pretty sure she's fouling plugs."

Come back with pictures of plugs 1-4 and let's go from there.

I'll pop them out and have a look, with pics.

[harisuluv]

That would be great and very helpful

[kippstakes]

Okay, I finally got around to popping the 1/4 plugs out. Here's what we have (1 on left, 4 on right). Both look a bit black.

[flybox1]

The insulator color difference indicates your air/fuel mixtures are inconsistent across cylinders.
If you didnt do a plug chop for a specific throttle position, its tough to say whats really going on here as we are getting a picture of deposits throughout your whole throttle range....

Are the threads on #4 oily?

[Trad]

those are not fouled plugs, your issue is something else.

[harisuluv]

so..  what about #2 and #3.  did you interpret "1-4" as #1 and #4 only?

We need to see all plugs I said "1-4" cause we need to know which plug is which, i.e. placed on a piece of paper with writing 1, 2, 3, 4, with corresponding plug next/above it.

[kippstakes]

so..  what about #2 and #3.  did you interpret "1-4" as #1 and #4 only?

We need to see all plugs I said "1-4" cause we need to know which plug is which, i.e. placed on a piece of paper with writing 1, 2, 3, 4, with corresponding plug next/above it.

Wow sorry. For some reason I interpreted 1-4 as 1 and 4 (I was wondering why only those two would need to be seen). 
2 on left, 3 on right. These appear to be more chocolate in color, which seems strange. I would assume the outer 1/4 cyls would get more air with pods and run leaner. 

(the pics aren't the greatest, I did the best I could with the lighting I have here)

[flybox1]

If you didnt do a plug chop for a specific throttle position, its tough to say whats really going on here as we are getting a picture of deposits throughout your whole throttle range....

You need to first complete an accurate plug chop @ WOT with new plugs to determine main jet size changes.

[harisuluv]

Ok well, doesn't look like any of those are fouled, really.

How about some pics of the bike all around (with focus on carb/engine area) so we know more.

Have you done the basic stuff recently?

3k mile tune up checklist
ever vac synced the carbs?
checked for air leaks?  (how do you pressure test a boot??)

It's a good thing you made this thread, just about every hypotheses you had so far was dead wrong.
- Plugs are fouling (all four plugs not fouled, #4 in fact looks lean.)
- Carbs are "flooding" (nothing coming out of the overflow?)
-"I'm thinking about switching to 100s, but it seems a little lean for the setup." (not running lean overall, only possibly lean in certain ranges--unverified)
- Almost advanced the timing which wouldn't have helped at all

Don't take it the wrong way, pointing out the systematic troubleshooting and then taking the data and coming to real conclusions based on what we observe--this is going to be how you learn to troubleshoot correctly.  Also, anyone else who comes along and looks at this thread is going to learn something from your post--so that's a great service to the community.

Most people ride their 550's around all the time with no real problem with some big bad "flat spot."  It's unnoticeable or just not really a problem usually.  You need to understand you have drastically modified your intake and some people never really get it right.  If you're looking for the smoothest possible power band and want your bike to work as best as possible, get an airbox.

To go any further I think we need some pictures of your bike.  Just recently a guy was asking for help and we get to the second page and finally see that his "all stock" has pods and 4-1, so he was just wasting people's time.

[kippstakes]

No worries, I always welcome constructive criticism.
Here are a few snaps of the bike. 4/2 exhaust, pod filters- as she came.
I think one of the reasons I thought it might be running rich is because there seems to be a direct correlation with the distance I drive/engine heat, and how badly is runs. The longer I ride, the worse it gets.
I will try to get out this next week and do a WOT plug chop, just in case.
 
I'm beginning to think that something might be binding in the drive train. If I give it moderate gas off the line it will make a grinding sound from the crankcase for an instant, and the revs will go down- like something clamped down on the crankshaft for a split sec. Also, the bike just seems under-powered. The engine revs up and sounds like it's producing power that should be pulling like crazy, but the bike just doesn't want to go. Compression is 125+ on all four, so I don't think that'd be the issue.

There is occasional gas flow thru the overflow carb tubes, but nothing major. 

[harisuluv]

I don't see any pictures

[Zaipai]

So back when I had this sort of issue I went up 1 size on the Jets (Godffrey actually did the work) and it turned out the grinding noise was the clutch needing to be adjusted. The boots also had leaks how I checked that was with the bike idling I took a spray bottle of water and sprayed some on each boot and if the idle changed then it was likely leaking. In my case the band were just loose.. After all that the carbs stopped overflowing the bike idles like a champ despite having a 4 into 1 and pods (except when its cold, after about 2min it will idle just fine). Not saying any of that is what you have going on just thought I would mention it as more info.

GL I am sure you will hammer it out.

.: Scott :.

[kippstakes]

Let's see if this works...  there seems to be some kind of glitch, or I am screwing something up. I have tried to post pics four times and it keeps taking me to a 'start new topic' page
It seems to be working for text but not mult. pics. Ill try one at a time..

[kippstakes]

one

[kippstakes]

two

[kippstakes]

three

[kippstakes]

Let's see if this works...  there seems to be some kind of glitch, or I am screwing something up. I have tried to post pics four times and it keeps taking me to a 'start new topic' page
It seems to be working for text but not mult. pics. Ill try one at a time..

use a photo bucket account. much easier.

Thanks for the tip. Bc this is not easly  :/

[kippstakes]

Four

[kippstakes]

So back when I had this sort of issue I went up 1 size on the Jets (Godffrey actually did the work) and it turned out the grinding noise was the clutch needing to be adjusted. The boots also had leaks how I checked that was with the bike idling I took a spray bottle of water and sprayed some on each boot and if the idle changed then it was likely leaking. In my case the band were just loose.. After all that the carbs stopped overflowing the bike idles like a champ despite having a 4 into 1 and pods (except when its cold, after about 2min it will idle just fine). Not saying any of that is what you have going on just thought I would mention it as more info.

GL I am sure you will hammer it out.

.: Scott :.

Thank you. I've been considering ripping the clutch out again and having a look at it-- it seems like the most likely culprit. The boot were tested under pressure while off the bike/carbs (still attached to manifold). They seemed to have no cracks, which was encouraging, but I haven't tested them on the bike. I'll give the h2o trick a shot. I think I did about the same with carb cleaner a while ago... but that was a while ago.

[harisuluv]

Kipp can you elaborate on this pressure testing of boots?  I don't understand at all how you did this, can you explain what you did exactly?

I think I would probably not use water, just seems like if there was a leak why use water when you could use something else. 

[Zaipai]

Yea, I used water but any non-flamable liquid would work however a mild spray of water does no harm you get more water hitting those things during a ride in the rain. I have seen bike builders do it I am sure its not a problem. But do what makes you feel comfortable.

If of course you did the test off the bike then no need to do it at all.

.: Scott :.

[kippstakes]

Kipp can you elaborate on this pressure testing of boots?  I don't understand at all how you did this, can you explain what you did exactly?

I think I would probably not use water, just seems like if there was a leak why use water when you could use something else.

My 'pressure test' was really only to see if the boots' rubber was intact- no cracks, holes, etc. I removed the boots/manifold assembly, sprayed some soapy h2o on them, and put pressurized air thru the cylinder-side opening on the mainfold while plugging the carb-side opening on the boot- then looked for bubbles. From what I could see there was no bubbling, and no sound of leaking air either. This doesn't test for a true seal at the boot/carb junction, however. 
Maybe it's crackpot idea, but the theory seemed sound enough.

[DaveBarbier]

I'm beginning to think that something might be binding in the drive train.

Do you have an o-ring chain? You might be aware but o-ring chains eat up 550 cases eventually producing an oil leak which involves splitting the cases to fix properly.

Also, the bike just seems under-powered. The engine revs up and sounds like it's producing power that should be pulling like crazy, but the bike just doesn't want to go.

Sounds like a slipping clutch to me.

[kippstakes]

I'm beginning to think that something might be binding in the drive train.

Do you have an o-ring chain? You might be aware but o-ring chains eat up 550 cases eventually producing an oil leak which involves splitting the cases to fix properly.

Also, the bike just seems under-powered. The engine revs up and sounds like it's producing power that should be pulling like crazy, but the bike just doesn't want to go.

Sounds like a slipping clutch to me.

I think I will start with the clutch then- it's an easy starting point at the least.

I didn't realize o-ring chains caused problems. How do they cause the damage?

[flybox1]

They can wear a hole into the case & shaft seal causing oil leaks because they are too wide.
Put on a standard chain before its too late.

[DaveBarbier]

I didn't realize o-ring chains caused problems. How do they cause the damage?

https://www.google.com/search?q=cb550+o+ring+chain+case+damage&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari#q=cb550+o+ring+chain+case+damage+site:forums.sohc4.net&hl=en-us&prmd=sivn

[kippstakes]

Ah I see. Wow I had no idea- I'll have to have a look behind my counter sprocket and see if I'm in any trouble. Thank you for the heads up, guys.

[DaveBarbier]

Ah I see. Wow I had no idea- I'll have to have a look behind my counter sprocket and see if I'm in any trouble. Thank you for the heads up, guys.

Since you're not complaining of oil leakage I'd bet (hope) you're ok! Mine was close but not leaking yet.

[Redline it]

Kipp can you elaborate on this pressure testing of boots?  I don't understand at all how you did this, can you explain what you did exactly?

I think I would probably not use water, just seems like if there was a leak why use water when you could use something else.

My 'pressure test' was really only to see if the boots' rubber was intact- no cracks, holes, etc. I removed the boots/manifold assembly, sprayed some soapy h2o on them, and put pressurized air thru the cylinder-side opening on the mainfold while plugging the carb-side opening on the boot- then looked for bubbles. From what I could see there was no bubbling, and no sound of leaking air either. This doesn't test for a true seal at the boot/carb junction, however. 
Maybe it's crackpot idea, but the theory seemed sound enough.

That's a bad ass idea. If you have bubbles, you might have leaks.

[kippstakes]

Kipp can you elaborate on this pressure testing of boots?  I don't understand at all how you did this, can you explain what you did exactly?

I think I would probably not use water, just seems like if there was a leak why use water when you could use something else.

My 'pressure test' was really only to see if the boots' rubber was intact- no cracks, holes, etc. I removed the boots/manifold assembly, sprayed some soapy h2o on them, and put pressurized air thru the cylinder-side opening on the mainfold while plugging the carb-side opening on the boot- then looked for bubbles. From what I could see there was no bubbling, and no sound of leaking air either. This doesn't test for a true seal at the boot/carb junction, however. 
Maybe it's crackpot idea, but the theory seemed sound enough.

That's a bad ass idea. If you have bubbles, you might have leaks.

Thank you. Theoretically it seems like an effective diagnostic procedure, I can't see why not.I have heard of people doing the same with mildly-punctured tires to trace the hole down, the practice seems like it would apply about the same with boots.  Evidently it works to confirm a positive valve seal as well, as a leak-down test. There are a few youtube vids on it.