Topic: Carb sync question 77cb-550f- now with more issues!

[benjamin550]

After watching the video on the SOHC4 homepage and doing some searching, I set off to adjust my carbs. Problem is I never came across anything that mentions leaving one adj. screw alone and tuning them all to that setting (until now of course).  I have adjusted all 4 screws and managed to make a "decent" running bike all messed up. I am using the blue carb synchronizer that the guy is using in the video. In the video he states that it doesn't matter where the needles read on the meter, as long as they read the same. But since i dont have apoint of reference, this is really difficult. Each time I try and adjust them even the slightest I end up making it worse. Now that I've successfully un-synced all of my carbs, what can i do to try and get them back in order. I would pick one and set it where it should be and then adjust the rest to match it, but I have no idea where to begin. Any help?

Thanks

[Nortstudio]

I just did this to my 550k. Are you saying you're it sure which one to choose, to match the rest to?

I actually chose the one 2nd highest, and then brought 2 up to meet it, and one slightly down to meet it too.

TwoTired corrected me, and explained it's probably best to bring the lowest 3 up to meet the highest one.

Does that answer your question? Or are you having a different issue altogether?

Someone more knowledgable will chime in I'm sure...

[benjamin550]

Nortstudio-

My problem is that I didn't chose one at all to match the others too. I attempted to adjust all 4 of them, which subsequently through them all a little off. I was wondering if there is a point on the gauge to set one too and match the others to it. I had al little luck though after some trial and error and at this point It seems as though i might have found a decent balance. It seems to run smoother and pull better through the gears. The problem now is that is burns a little rich and blows a little smoke where it didn't ever do that before. It also want to idle high. hmmmm, go figure. Fix one problem and create another.   

[Nortstudio]

Not sure about the smoke, but I think as long as they are all hitting the gauges equally, then you are doing pretty well.  it's more about getting them lined up the same on all 4 gauges.  I think that the needle/gauge measurement is arbitrary.

I forgot to mention that after setting my carbs to all read the same, the idle was through the roof.  But this can be common since you just adjusted you carbs to idle higher (if you moved them up at all).  Turn that down with the idle screw, and you should be good.

I also forgot to ask where you had your air mixture screws set on the individual carbs???

Is it blowing smoke after it's warm?

I'm sure you'll get it to come around soon.

[DYSKORD]

Nortstudio-

My problem is that I didn't chose one at all to match the others too. I attempted to adjust all 4 of them, which subsequently through them all a little off. I was wondering if there is a point on the gauge to set one too and match the others to it. I had al little luck though after some trial and error and at this point It seems as though i might have found a decent balance. It seems to run smoother and pull better through the gears. The problem now is that is burns a little rich and blows a little smoke where it didn't ever do that before. It also want to idle high. hmmmm, go figure. Fix one problem and create another.   

So you need to constantly adjust your idle screw (the large screw with spring on linkage) when you are doing the sync.. When you adjust them the idle will be directly effected. You MUST keep the idle between appr. 800-1300. Letting the idle get too high will negate the adjustments because your carbs will be operating outside of the idle circuit. Adjust one, wait a few seconds for the idle to differ, then adjust idle back up/down to range previously mentioned, then continue with syncing adjustments constantly bringing the idle speed into the appropriate range when necessary.
1. To continue from where you are now, I would go ahead and lean out your mixture screws first at 1/8 turns just until smoking stops.
2. set all nuts on the carbs where you were adjusting during the sync so that 2-3 threads of the screw are showing above the nut.
3. Adjust number #1 carb to #2. Make sure to adjust idle speed after back down/up
4. Adjust #4 carb to the same vacum as #3 carb. Adjust idle.
5. Adjust #3 to #2. Adjust idle.
Repeat sequence until they are all reading the same vacum. Adjusting in this sequence will keep you from going in circles since adjusting one will effect the others.
Once you have them synced you can fine tune your idle mixture (rich/lean)

Remeber, you must have valves in adjustment, cam chain tensioned and a clean air filter before you sync the carbs. It will do you no good to sync them if this hasnt been done FIRST.

Hope this helps

[Kong]

What year is your 550?  I ask because all years did not use the same carburators and they are not all adjusted the same way.  In fact when it comes to the "mixture screws" the way they operate on early carbs is exactly backwards from late model carbs; with early carbs they adjust fuel flow and they are indeed adjustable, but late model carbs are not actually adjustable (the screw acts as an On or Off valve, with no adjustment inbetween the two extremes).

At any rate from where you are now - presuming you do  have them all screwed up - I'd say your best bet is to just remove them, bench sync them, and then start again. 

[flybox1]

So you need to constantly adjust your idle screw (the large screw with spring on linkage) when you are doing the sync.. When you adjust them the idle will be directly effected. You MUST keep the idle between appr. 800-1300. Letting the idle get too high will negate the adjustments because your carbs will be operating outside of the idle circuit. Adjust one, wait a few seconds for the idle to differ, then adjust idle back up/down to range previously mentioned, then continue with syncing adjustments constantly bringing the idle speed into the appropriate range when necessary.
1. To continue from where you are now, I would go ahead and lean out your mixture screws first at 1/8 turns just until smoking stops.
2. set all nuts on the carbs where you were adjusting during the sync so that 2-3 threads of the screw are showing above the nut.
3. Adjust number #1 carb to #2. Make sure to adjust idle speed after back down/up
4. Adjust #4 carb to the same vacum as #3 carb. Adjust idle.
5. Adjust #3 to #2. Adjust idle.
Repeat sequence until they are all reading the same vacum. Adjusting in this sequence will keep you from going in circles since adjusting one will effect the others.
Once you have them synced you can fine tune your idle mixture (rich/lean)

Remeber, you must have valves in adjustment, cam chain tensioned and a clean air filter before you sync the carbs. It will do you no good to sync them if this hasnt been done FIRST.

Hope this helps

+1!

[benjamin550]

First off, thanks for the help so far. DYSKORD, your instructions were very helpful, thank you. I followed them and it helped a lot. I also followed the instructions on Lars website Honda Hobby, which is amazing BTW. He deserves a medal for for putting that site together.   http://www.hondahobby.no/website.aspx?displayid=1593

First, before I started this whole process, the bike started perfect, idled great, but it was sluggish in the in the low rpms on the first few gears when driving it. The engine was noisy as all hell. Lots of rattling and some knocking/ tapping noises. BUT It didn't smoke at all.

Here is where I am now after a couple days of tuning-

I replaced plugs, adjusted valves, set point gaps, manually checked timing, and synced carbs. Now, most of the noise is gone from the engine, the bike is much more responsive and 90% of the lack of power at low rpms is gone. There is still some rattling in the engine, but it seems smoother... cam chain maybe?  Whole bike feels better over all BUT now, it smokes now and smells rich. I have the idle screw all the way out so it is basically not in use, which i'm assuming i'snt good, and if i use the air/fuel screws to try and lean out the mixture the idle jumps way up to around 2-3k. So where do i go from here? I tried to incclude everything I did without being too wordy so ask questions if you can think of anything.

Also, my bike is a 550f and put a 4-1 Mac exhaust on it which is meant for the 550k. When I did this I rejetted to 550k jets (from 98 to 100 mains) to compensate. This obviously adds more fuel to the mixture. One thought I had was to just drop back down to the 98 jets. This might help, but I want to make sure im not just masking another problem i should fix. Thanks in advance for any help.

Kohl

[benjamin550]

Kong,

Its a 77. I fixed the title.

[thehammer]

keep a fan blowing on your motor while you are doing this, of course.

[DYSKORD]

First off, thanks for the help so far. DYSKORD, your instructions were very helpful, thank you. I followed them and it helped a lot. I also followed the instructions on Lars website Honda Hobby, which is amazing BTW. He deserves a medal for for putting that site together.   http://www.hondahobby.no/website.aspx?displayid=1593

First, before I started this whole process, the bike started perfect, idled great, but it was sluggish in the in the low rpms on the first few gears when driving it. The engine was noisy as all hell. Lots of rattling and some knocking/ tapping noises. BUT It didn't smoke at all.

Here is where I am now after a couple days of tuning-

I replaced plugs, adjusted valves, set point gaps, manually checked timing, and synced carbs. Now, most of the noise is gone from the engine, the bike is much more responsive and 90% of the lack of power at low rpms is gone. There is still some rattling in the engine, but it seems smoother... cam chain maybe?  Whole bike feels better over all BUT now, it smokes now and smells rich. I have the idle screw all the way out so it is basically not in use, which i'm assuming i'snt good, and if i use the air/fuel screws to try and lean out the mixture the idle jumps way up to around 2-3k. So where do i go from here? I tried to incclude everything I did without being too wordy so ask questions if you can think of anything.

Also, my bike is a 550f and put a 4-1 Mac exhaust on it which is meant for the 550k. When I did this I rejetted to 550k jets (from 98 to 100 mains) to compensate. This obviously adds more fuel to the mixture. One thought I had was to just drop back down to the 98 jets. This might help, but I want to make sure im not just masking another problem i should fix. Thanks in advance for any help.

Kohl

I noticed when I did my very first carb sync, without following the sequence mentioned previously, that I ended up chasing my tail during the syncing process, that I eventually ran out of adjustment on the idle screw (it was all the way out) and the bikes idle was around 2k. I eventually had to go back and set the nut you adjust for syncing to the minimum the manual calls for (on my 750, one thread showing) and re-do the sync. This might be your problem if you didnt already adjust them before the second attempt at syncing.

Check that your cam chain tensioner isn't stuck to address a possible/common sourceof the rattling. You can pull it off pretty quickly and check. My Honda twin was found to be stuck, I took two hammers and placed the wooden handle of one against the tensioner and then rapped a few times on the head. Made a world of a difference. If you find your tensioner was sticking you will need to resync though.

As far as the smoking I would think you should check the size of your slow jets. Unless you have changed the airbox out, the stock slow jets should be pretty close. Your mains arent operating in the range which you seem to be having problems and seem to be a reasonable size. The main jets operate between 3/4 and full throttle. Also double check your float heights as I believe they pour over into other circuits if set wrong. They also have a tendency to crack, fill with gas, and therefore not float like they should. 

Also note that if your mixture screws are on the airbox side they adjust the amount of air (turning in will richen/out will lean). If the jets are on the engine side turning in will lean/out will richen.

Seems like your problems are mostly carb related. There are a few other areas of concern like slide and needle condition and clip position. If it were me I would spend a saturday, pull the carbs and make sure everything is in order/spec per the shop manual, if you are only running an upgraded exhaust (I would think your main jet size is fine though). Just for peace of mind. If you didnt purchase the bike new in 77 then there is no telling what previous owners have swapped out or forgot to install.

[benjamin550]

DYSKORD-

Thanks for all the help, I think we're getting somewhere here. Couple of questions... When you say to back the nuts out on the adjustment screws to where 2-3 threads are showing do i then screw them down so all of the screws start from the same position? Otherwise, what effect would just loosening the nut have on anything unless I also changed the height of the screw? I hope that makes sense... Also, when I do this process, should I turn the idle screw back in to a certain point to begin with? Currently is is all the way out.

A couple on months ago I took the carbs off and cleaned them on the rack, replaced all visible 0-rings and float bowl gaskets and thoroughly cleaned out all my jets, needles...ect. Besides being dirty, everything looked up to spec. Up until I messed with the carb sync, it never blew smoke. Also, it only seems to blow smoke when I rev the engine, not really on idle (that i can see at least).

Also, when i took it for a 10 mile ride yesterday it died half way through as I was approaching a stop sign. The engine just cut out. It had plenty of gas in it. Being that my battery sucks right now, I gave it a kick and it fired right up and I rode a few miles home with no problems. Not sure if that helps, but it hasnt done it before.

Thanks,
kohl

[benjamin550]

bump-

[DYSKORD]

DYSKORD-

Thanks for all the help, I think we're getting somewhere here. Couple of questions... When you say to back the nuts out on the adjustment screws to where 2-3 threads are showing do i then screw them down so all of the screws start from the same position? Otherwise, what effect would just loosening the nut have on anything unless I also changed the height of the screw? I hope that makes sense... Also, when I do this process, should I turn the idle screw back in to a certain point to begin with? Currently is is all the way out.

A couple on months ago I took the carbs off and cleaned them on the rack, replaced all visible 0-rings and float bowl gaskets and thoroughly cleaned out all my jets, needles...ect. Besides being dirty, everything looked up to spec. Up until I messed with the carb sync, it never blew smoke. Also, it only seems to blow smoke when I rev the engine, not really on idle (that i can see at least).

Also, when i took it for a 10 mile ride yesterday it died half way through as I was approaching a stop sign. The engine just cut out. It had plenty of gas in it. Being that my battery sucks right now, I gave it a kick and it fired right up and I rode a few miles home with no problems. Not sure if that helps, but it hasnt done it before.

Thanks,
kohl

So when you do a sync, there should be a locknut that you must loosen first on each carb then adjust the screw that the locknut threads onto. Loosening the locknut isnt going to do anything. Adjust the threaded screw, with the locknut loosened, so that 1-3 threads are showing (error on the side of 1 thread showing) above this nut (I would suspect you have several more threads showing above the locknut). For my carbs on my 750, the manual states no less than one thread showing above this lock nut. After my first attempt at syncing, I had alot of threads showing above the lock-nut and no more adjustment at the idle screw (all the way out). I then started over by setting all the carbs so that only one thread was exposed above the lock nut. At this point, the bike wouldnt idle with the idle screw all the way backed out. I adjust the the idle screw so it would idle at stock RPM. Now I was back to a good starting point to start following the proper syncing sequence previously mentioned. So to answer one of your questions directly, you dont back the nuts out to expose 1-3 threads, you loosen these nuts so that you can (in your case I suspect?) screw in the adjusting screws on each carb so less is showing above said nut. Yes all carbs should have about the same amount of the treads showing above the locknut as a starting point, with the locknut just loose enough to make adjustments to the screws.

There isnt a specific starting point with the idle screw. I would turn it in about half way between bottomed out and backed out. See if the bike will idle and adjust as necessary form there to achieve stock idle speed. Then resync, keeping idle where it should be.

Blowing smoke is usualy only the result of two things, bad rings or badly adjusted carbs. In your case, it is most likely the carbs. Not to worry though, it will get sorted out with some practice.

The bike randomely dying could be anything and quite possibly unrelated to the carb issue. No way to diagnose that via forum without alot of speculation. However a voltmeter could quickly rule out charging system issues that may be the  culprit.

[benjamin550]

DYSKORD-

Thanks a lot man. I just finished up following these instructions and it seemed to come out perfectly. No more smoking, engine runs smooth, Idle screw is right where it should be and the whole bike feels much tighter. Best of all, it sounds great. Unfortunately I wasn't able to take it for a test drive because I was adjusting my cam chain and broke one of the tappet covers due to over torquing. I ordered some new ones from ebay and as soon as they get here I'll recheck the carb sync (since I adjusted the cam chain) and take it for a test run. Thanks again, I really would have been lost without all of your help!

Kohl

[Nortstudio]

Isn't that the BEST feeling!  And now that you have it under your belt - so much easier next time around.

Great explanation Dyskord.

[benjamin550]

Nortstudio-

Absolutely. I remember only a few months ago bringing my poor sick bike home from what must have been a lifetime of abuse and thinking, "what the hell have I done." Basically everything I touched or looked at needed to be fixed or replaced and everything the PO(s) fixed had been fixed the wrong way. I had no experience AT ALL working on motorcycles, and serious buyers remorse. It needed WAY more work that the PO told me. But after finding this website and a few months of hard work, it runs great, and I know almost every part on the bike. I don't think I'd trade it for anything. I might buy more bikes, but I'm not selling this one. 

On another note, reading about you working on your bike in NYC, on the sidewalk, in the winter definitely inspired me to get my ass out to the freezing garage this winter. So thanks for that.

[Nortstudio]

My pleasure!  Glad someone was following along with my pain . Seems like we are in the same boat.  Bad abuse by PO, turned over to eager new owners....

Well, I have found this wrenching thing is somewhat like dieting (sadly, not that I would know about that first hand).  Getting the first bunch done is easy, but then getting that last little bit is becoming harder...

I still have a ways to go, and a ton more to learn, but I am finding that these last 10% of the tweaks are taking more motivation than the whole first 90%

I was good up until it hit 30 degrees, and then retired for the winter, except for a few nice days.  Now I think I'm waiting for more than one day in a row to be sunny.  Damn, I need some sun!

[DYSKORD]

DYSKORD-

Thanks a lot man. I just finished up following these instructions and it seemed to come out perfectly. No more smoking, engine runs smooth, Idle screw is right where it should be and the whole bike feels much tighter. Best of all, it sounds great. Unfortunately I wasn't able to take it for a test drive because I was adjusting my cam chain and broke one of the tappet covers due to over torquing. I ordered some new ones from ebay and as soon as they get here I'll recheck the carb sync (since I adjusted the cam chain) and take it for a test run. Thanks again, I really would have been lost without all of your help!

Kohl

Kind of funny how when the advice you give works, it makes you almost as excited as the person with the problem. Glad I could help ya out.

Oh and remember you are going to have to dial in the idle mixture srews after the re-sync.

[Kong]

On your carbs the "idle mixture screws" aren't really adjustable.  They are simply On/off switches.  If you unscrew them 1.5 turns they will be opened, less and they are closed, more and they will vibrate loose and fall out - but in no position are they adjustable, they either allow the froth to pass or they do not.

This is not true for the pre-'77 carbs, they in fact do adjust the idle circuit, but yours don't.  It is very easy to tell if yours are adjustable or not.  Just remove the screw from the carburetor and look at its tip.  If it is of the adjustable sort it will have a tapered point on its end.  If it is not adjustable - like yours - then it will have two square-edged steps on the end of the screw.  So with yours when it is closed it is completely closed, and when it is open (at 1.5 turns) it is completely open but unlike its tapered sisters on older carbs there is no in-between.

[TwoTired]

I will have to correct some bad information given.

The 77 CB550 F carbs are not the PD style carbs as found on the Cb550K for 77 and 78.  All CB550F models had the same 069a carbs from the factory (at least in the U.S.).
Further, whether it be the early style Air bleed pilot screws or the PD style Idle Mixture Screws, they are most definitely adjustable in both cases.  The PD carbs do have a more restricted adjustment range, but it is still variable within that range.

The PD's IMS tips do have a shallower taper angle to them.  But, they fit into a hole rather than on a tapered seat like the earlier carb style.  The respective geometry of the two styles works as it should.
I can see how one could get a false impression if only looking at half the mated mechanism.

Heed other ill-advise at the risk of your own confusion.

Cheers,

[benjamin550]

Thanks everybody for the information. While we are on the subject, what is the best way to dial in the air/fuel screws from the point I'm at now? 

[DYSKORD]

Thanks everybody for the information. While we are on the subject, what is the best way to dial in the air/fuel screws from the point I'm at now? 

That is an aquired skill my friend

I will have to correct some bad information given.

The 77 CB550 F carbs are not the PD style carbs as found on the Cb550K for 77 and 78.  All CB550F models had the same 069a carbs from the factory (at least in the U.S.).
Further, whether it be the early style Air bleed pilot screws or the PD style Idle Mixture Screws, they are most definitely adjustable in both cases.  The PD carbs do have a more restricted adjustment range, but it is still variable within that range.

The PD's IMS tips do have a shallower taper angle to them.  But, they fit into a hole rather than on a tapered seat like the earlier carb style.  The respective geometry of the two styles works as it should.
I can see how one could get a false impression if only looking at half the mated mechanism.

Heed other ill-advise at the risk of your own confusion.

Cheers,

+1

Thanks everybody for the information. While we are on the subject, what is the best way to dial in the air/fuel screws from the point I'm at now? 

That is an aquired skill through trial and error. The manual should state what the intial setting should be. For mine 1 +/- 1/4 turns from slightly seated. Check the manual for this starting point. Beyond that, its up to you. You will need to be able to recognize rich/lean conditions. I would print the info TwoTired has in the FAQ section on carbs outlining some of these characteristics, put a copy by the #$%*ter and night stand, read it, alot. Thats what I did.

[benjamin550]

The manual should state what the intial setting should be. For mine 1 +/- 1/4 turns from slightly seated.

Right. The manual. I keep forgetting about that thing. This site is spoiling me.

Thanks.

[Nortstudio]

You will be in an even better place with the manual AND this forum. The parts list and shop manual round out the whole package!

Sounds like you're getting there.