Author Topic: 1977 Honda CB550K (Read 15240 times)

MgMt CB550K · « **Reply #50 on:** May 21, 2008, 07:44:53 PM »

well my carbs are off of a 77. The chart shows a carb setup number of X46A and also a carb type of PD. So looking at the column it has a 38 in there. Is that the correct column CB550K3 -77. Am I on the right track here?

TwoTired · « **Reply #51 on:** May 21, 2008, 10:25:54 PM »

Yes, I compiled that chart from Honda Sources. I rechecked the Honda booklet and what's on the chart is what Honda repair techs used to service the bikes; #38 for 77 PD X46A. You'll note that the 78 models used larger slow jets and such carbs "should" have been stamped with a different setup number.
I don't know. Maybe the proper jet bin was empty when they made your carbs and the newer model jet supplies arrived early, or the carbs were replaced by the dealer under warranty, or the published Honda data is wrong. Feel free to choose which problem to investigate.
I have only seen PD 46C carbs and they both had #42 slows. Consider your bike "modernized".

I just rebuilt my 78 550 carbs PD 46C and when checking the float height, it was 16.5 mm. Sure looks like it came from the factory that way. But, Honda printed material says they should be 12.5mm. I set them to 14.5mm and the bike runs well.

What do you think we should do?

MgMt CB550K · « **Reply #52 on:** May 22, 2008, 04:23:22 AM »

Well since the bike is running pretty rich especially in the low throttle range I don't think it would hurt to try the #38 and see if there is a difference in performance. My old man had this bike running for a little bit probably almost a decade ago and said that he always had problems with the bike running to rich and fowling plugs. I have gone over pretty much everything else so I might as well give it a try. Thanks again for all of your input TwoTired. Hopefully I am getting close to resolving this.

MgMt CB550K · « **Reply #53 on:** May 22, 2008, 05:29:41 AM »

So I am trying to order some #38 slow jets but I can't find them. Anyone have a good place to buy slow jets? I can't even find it in the microfiche to get a part number.

MgMt CB550K · « **Reply #54 on:** May 22, 2008, 07:07:28 AM »

I according to someone at the local Honda shop around here since the slow or "pilot" jets are pressed in they decided not to provide them as separate parts. So I checked here http://www.siriusconinc.com/carb/parts.asp# for some parts.

What is bothering me is that the rebuild kit for my 77 CB550K does not come with a slow jet but the kits for '74 - '76 come with the #38 slow jet. Do you guys think the right move is to try and obtain #38 slow jets?

I could buy the '74 - '76 kits for $27 plus shipping but I would only be using the slow jets in them.

It just bothers me that I am split so much on what size is the correct size. Since I am running so rich especially around idle and below it would seem that replacing my #42 jet with a #38 would help that problem.

I'm gona try to check Ebay and post something in the wanted section to see if I get luck and find just the slow jets. Any input is appreciated.

TwoTired · « **Reply #55 on:** May 22, 2008, 08:27:13 AM »

I think you're fretting over a non-issue. Take a look at how the idle circuit works.

The fuel is drawn from the bowl up the slow jet tube where it passes through the orifice and feeds that small emulsion tube at the exit. Here it combines with air from the slow air jet (emulsion), and then travels via carb passageway to the Idle Mixture Screw (IMS), where total flow is regulated. After that screw it is passed directly to the carb throat.

If your idle is too rich, you can completely stop all flow from that jet from being delivered to carb throat/engine cylinder by the IMS.

Look at the IMS setting on the chart. The one with #38 is adjusted at two turns. The one with the #42 is adjusted to 1 1/2 turns. The #42 is going to give you a larger adjustment range, that's it!

If the bike ever runs using a non-stock air filter or non-stock exhaust, you will want that extra adjustment range, as the #42 will allow a for greater adaptation than the #38.

Clean, install, move on.

You say it always ran rich. Was the air filter clean? What were the IMS settings when you took it apart? Where was the Jet needle clipped?

Good luck with your decision!

MgMt CB550K · « **Reply #56 on:** May 22, 2008, 09:19:11 AM »

Quote

Look at the IMS setting on the chart. The one with #38 is adjusted at two turns. The one with the #42 is adjusted to 1 1/2 turns. The #42 is going to give you a larger adjustment range, that's it!

I'm pretty sure it was around 2 when i first started taking the carbs apart but I have tried setting it to 1 1/2 as well. I read that with the airscrew on the cylinder side of the cards turning it out will make the mixture richer and turning it in will lean the mixture. Is that correct?

If that is the case I am pretty sure that I have tried to turn the screws in to a little over a half a turn out and I didn't see much. I also saw that one turn of the screw is like changing your slow jet a 1/2 a size.

If I were going to keep the #42 slow jet I would need to turn the screw in to lean the mixture correct? I'm afraid you might have to spell this one out for me $:-\$

TwoTired · « **Reply #57 on:** May 22, 2008, 09:31:08 AM »

Quote from: MgMt CB550K on May 22, 2008, 09:19:11 AM

If I were going to keep the #42 slow jet I would need to turn the screw in to lean the mixture correct? I'm afraid you might have to spell this one out for me $:-\$

I thought I did. However, if you refuse to learn how the system works... Then turn the screw in to make the idle leaner and out to make it richer.

MgMt CB550K · « **Reply #58 on:** May 22, 2008, 09:35:12 AM »

Well thats my issue when I had the screw only turned out 3/4 of a turn it still did not seem any better. I guess I can experiment with it almost all the way in but I just though that seemed a little extreme.

MgMt CB550K · « **Reply #59 on:** May 23, 2008, 10:31:28 AM »

Quote

I thought I did. However, if you refuse to learn how the system works...

I don't think I am refusing the learn the system. I understand that the idle mixture screw can slightly change the air fule mixture. What I don't know is if the 1 1/2 to 2 turns that I have to work with is enough to lean my mixture if i have to screw it in to accomplish that. But like I said I will try move extreme settings like 1/2 turn out of the seated position. I am also still trying to find a #38 jet.

TwoTired · « **Reply #60 on:** May 23, 2008, 10:49:33 AM »

If the slow jet is plugged, it won't matter what setting the IMS is at.
If the fuel level is high in the bowl, the engine is fed excess fuel from the throttle valve.

I simply don't believe a #38 jet change is going to fix the issue.

Were the carbs known clean when you had the adjustment problem?

You should also know that the idle mixture setting is going to effect the throttle response from idle under load. Since you don't have an accelerator pump, it will starve for gas when you crack the throttle if you set it too lean.

It's very odd you having a too rich problem on the lean burn carbs of the 77 and 78, especially at idle. Have you checked to see if the jets have been drilled? Something is wrong besides the jet number stamp.

rbirkhan · « **Reply #61 on:** May 23, 2008, 12:38:43 PM »

I used muriatic acid to remove rust it works great. I would not leave it in there any longer than necessary or it will eat a hole through. I used it full strenth to remove rust from a headlight ear. It was shiny clean when done. I would recomend killing the acid with some baking soda when done or it will continue to disolve metal in the edges of the tank. And of course I would coat it with some wd40 when done or it will just start rusting almost imediately after cleaning. Good luck. It should look like new when done right.

MgMt CB550K · « **Reply #62 on:** May 26, 2008, 02:53:08 PM »

I cleaned the slow jets out put them back in. I pulled the plugs again and number one and 2 were really black and 3 was pretty black as well but not as bad. 4 was really clean however which confuses me and leads to me think that there has to be something else that I am missing.

TwoTired · « **Reply #63 on:** May 26, 2008, 03:20:22 PM »

I agree.

edbikerii · « **Reply #64 on:** May 26, 2008, 08:51:05 PM »

Did you clean the holes that run ACROSS the slow jets? Those are the holes in the "emulsion tube". Mine were so clogged up that I didn't even know they were there the first time. Do you know the ones I'm talking about? If not, then you need to pull them again and clean those holes out.

Has anyone possibly overtightened the IMSs? Perhaps they broke off part of the tip? Are the o-rings still on the IMSs? Are they in good shape? Be careful checking as there is a spring and a very tiny washer in there with the IMS (or should be). The IMSs should only ever be "lightly seated", never forced closed.

I agree with TT, changing to a 38 slow won't solve the problem, unless your existing 42s are clogged or somebody who "meant well" drilled them out for some reason.

Sounds to me like your slows are still clogged up, or you float is too high (less than 14mm from base of carb).

My PD46C carbs on my 77 CB550K have 42 slows, and they work beautifully.

Quote from: MgMt CB550K on May 26, 2008, 02:53:08 PM

I cleaned the slow jets out put them back in. I pulled the plugs again and number one and 2 were really black and 3 was pretty black as well but not as bad. 4 was really clean however which confuses me and leads to me think that there has to be something else that I am missing.

MgMt CB550K · « **Reply #65 on:** May 27, 2008, 04:14:09 AM »

Quote

Has anyone possibly overtightened the IMSs? Perhaps they broke off part of the tip? Are the o-rings still on the IMSs? Are they in good shape? Be careful checking as there is a spring and a very tiny washer in there with the IMS (or should be). The IMSs should only ever be "lightly seated", never forced closed.

The tips were all still on the IMSs when I checked them the last time. I have also been careful not to overtighten these. When I removed them the first time I remember the spring but I don't really remeber any tiny o-rings or washers. Should the o-ring and washer have come out with the screw and spring? If so maybe that I am missing them. I will take a careful look at these tonight when I get home from work. Thanks

edbikerii · « **Reply #66 on:** May 27, 2008, 04:37:06 AM »

O-rings probably won't come out, but you might be able to see them in there with an inspection (dental) mirror. Yes, if you remove the IMSs there should be springs and washers behind them.

Look at assembly #7 in this parts diagram:

Quote from: MgMt CB550K on May 27, 2008, 04:14:09 AM

Quote
Has anyone possibly overtightened the IMSs? Perhaps they broke off part of the tip? Are the o-rings still on the IMSs? Are they in good shape? Be careful checking as there is a spring and a very tiny washer in there with the IMS (or should be). The IMSs should only ever be "lightly seated", never forced closed.

The tips were all still on the IMSs when I checked them the last time. I have also been careful not to overtighten these. When I removed them the first time I remember the spring but I don't really remeber any tiny o-rings or washers. Should the o-ring and washer have come out with the screw and spring? If so maybe that I am missing them. I will take a careful look at these tonight when I get home from work. Thanks

MgMt CB550K · « **Reply #67 on:** May 27, 2008, 05:25:14 AM »

Alright I will check for that washer tonight. I don't remember it coming out with the spring and screw but hopefully they are just pressed up against the o-ring.

TwoTired · « **Reply #68 on:** May 27, 2008, 08:58:25 AM »

Do check for that oring and washer. But, these are there to keep the the screws from weeping fuel And to keep air from leaking in when the engine is tunning. Air infiltration would make the idle mixture leaner.

If indeed you have a rich condition. (I'd like to know how you know the bike has this problem.)
And, if you can't solve the problem with IMS adjustment, and/or throttle valve jet needle position changes, I doubt the IMS orings are the issue.

Are you still fouling plugs? Post a picture of them.

How does the bike respond to sudden opening of the throttle? How much throttle will it take before you get the wheeze thing?

I recently took my 78 K 550 carbs apart to clean the slow jets. Of course, I checked float height while I was in there. The book called for a 12.5 mm float height. Which places the fuel level higher than the 77's 14.5mm. To my surprise, the float height was 16.5mm or 17mm. This would make the fuel level lower than any spec I'd yet seen for the PD carbs. Although I can't guarantee it, I saw no evidence that the carbs had been tampered with by anyone. They appeared to be factory set.
The effect of low fuel level in the carbs would be to lean the mixture across the operating range. I reset them to 14.5mm (not 12.mm) because the bike ran well, even with the low fuel levels, but seemed anemic in the power dept. I had previously thought it was the restrictive pipes. I drove this bike quite a few miles with the low setting. (Maybe the bike originally was operated in a high altitude area?)

I have not done extensive testing since the change due to a back injury shortly after doing this work, and it still doesn't have a headlight to make it legal for street use. But, a quick spin around the block and it seemed to run pretty good with power similar to the older 550s. Buy, honestly the jury is still out.

Anyway, if your throttle twist test shows that the idle mixture is indeed still too rich, as well as the mid range throttle operation, perhaps you'll want to lower the float bowl fuel levels.

Another adjustment you can do is the change the paper filter to a UNI NU-4055 foam type. This should also slightly lean the fuel mixtures.

Cheers,

MgMt CB550K · « **Reply #69 on:** May 27, 2008, 10:15:43 AM »

Since I fouled the set of plugs last week I really haven't gotten to ride much. I rode to work a couple times but thats about it. However when I pulled the plugs plugs 1 and 2 were really dark, 3 was pretty dark, and 4 was really clean. I can post a picture of them tonight.

Quote

How does the bike respond to sudden opening of the throttle? How much throttle will it take before you get the wheeze thing?

Wheeze thing? The throttle response isn't terrible and I haven't really thought to myself that it was really bad. I know at around 4,000 to 5,000 RMPs it is pretty responsive and gets up and goes.

As far as the throttle test I have yet to really do miltiple tests with my throttle in different possitions and killing the bike. I just know that any time I pull the plugs they are black, except for 4.

TwoTired · « **Reply #70 on:** May 27, 2008, 11:01:56 AM »

Put it in 1st gear and slow down where the tach reads about 1500. A well tuned bike will accelerate predictably when twisting the throttle up to half of the total throttle travel range (Temporarily mark the throttle). A 550 with the idle set too rich will take all the throttle and pick up predictably, or if extremely rich, will sputter and spit while picking up RPMs. A 550 with the idle mixture set too lean with wheeze, falter and not pick up at all untill the throttle is backed down again.

This is a valid test when all the carbs and cylinders are behaving the same. If your spark plugs are showing different deposit patterns, either your cylinders aren't breathing equally, or your carbs aren't providing the same mixtures across the bank. Or...
It it possible the exhaust on some cylinders is partially blocked or some more open than others? Nests of mice? Nests of mud daubers? Collapsed baffles?

Are you certain all the carbs have been assembled the same and have equal parts and adjustments?

Cheers,

edbikerii · « **Reply #71 on:** May 27, 2008, 11:21:13 AM »

I remember another issue I've had with my 77 CB550K:

Have you checked that all of the choke butterflies are actually opening when you push the choke knob down?

The choke plates are on two different shafts, one that links 1&2 carbs, and another that links 3&4. Depending upon the breather tube (hose from the top of the cylinder head to the bottom of the airbox) routing, the hose can rub on one of the shafts, causing the chokes on 2 of the carbs to either remain open or shut. Either re-route the hose or lube it with something like silicone or ArmorAll.

Right now, I'm not even sure if there is a direct connection between the cable actuator and any of the choke plates, or if they might all be operated by a spring loaded cam. Could be that the shaft(s) is binding up.

MgMt CB550K · « **Reply #72 on:** May 27, 2008, 05:09:34 PM »

So I feel like an idiot here but it turned out that when I first pulled the IMS I lost the o-ring and the washer. I had no idea that they were in there. The thing funny thing is that one day a while ago I noticed a tiny little washer on the floor of my shed and had no idea what it went to so I put it in a bin and then today when i was looking into the holes I thought "hey maybe that washer goes in here" So I found it and what do ya know it did. So Then I needed to find the rest of them. I still had the bin where I soaked the carbs in simple green and I stuck a magnet in there and what do ya know I caught some washers! So then I felt around the bottom for the o-rings. I ended up finding 3 of the 4. The one missing o-ring must have fallen out when the washer fell out that I found on the floor and I never saw that o-ring.

SO

I put the washers and o-rings in the 1,2, and 3 carbs and got her back together backing the IMSs out 1 1/2 turns. I started her up and the she was running pretty well. The exhaust smelt a lot better (not like lots of gas). I road her down the road a couple times and she was returning to idle and idling A LOT better. I did not pull the plugs and I didn't get a picture of them to post. But I am going to ride to work tomorrow and then pull the plugs to see if there is an improvement.

Does this all seem to good to be true? Could those missing o-rings have been my entire problem? I am hoping so. I'm gona order some other parts as well as the missing o-ring for #4. I guess I will find out tomorrow if this really solved my issues. Thanks TwoTired for sticking with me on this one and thanks edbikerii for your input as well.

Oh yeah I did the throttle test also and the bike seemed to take it pretty well. No sputtering and it picked it up without letting off the throttle.

edbikerii · « **Reply #73 on:** May 27, 2008, 09:09:54 PM »

Well it is consistent that if the mixture gets richer when the screws are turned counterclockwise, then it would pull more air AND fuel through the idle if the o-rings and washers were missing, and also letting more air in. At least that was my gut feeling.

I'll keep my fingers crossed for you!

Ed

Quote from: MgMt CB550K on May 27, 2008, 05:09:34 PM

So I feel like an idiot here but it turned out that when I first pulled the IMS I lost the o-ring and the washer. I had no idea that they were in there. The thing funny thing is that one day a while ago I noticed a tiny little washer on the floor of my shed and had no idea what it went to so I put it in a bin and then today when i was looking into the holes I thought "hey maybe that washer goes in here" So I found it and what do ya know it did. So Then I needed to find the rest of them. I still had the bin where I soaked the carbs in simple green and I stuck a magnet in there and what do ya know I caught some washers! So then I felt around the bottom for the o-rings. I ended up finding 3 of the 4. The one missing o-ring must have fallen out when the washer fell out that I found on the floor and I never saw that o-ring.

SO

I put the washers and o-rings in the 1,2, and 3 carbs and got her back together backing the IMSs out 1 1/2 turns. I started her up and the she was running pretty well. The exhaust smelt a lot better (not like lots of gas). I road her down the road a couple times and she was returning to idle and idling A LOT better. I did not pull the plugs and I didn't get a picture of them to post. But I am going to ride to work tomorrow and then pull the plugs to see if there is an improvement.

Does this all seem to good to be true? Could those missing o-rings have been my entire problem? I am hoping so. I'm gona order some other parts as well as the missing o-ring for #4. I guess I will find out tomorrow if this really solved my issues. Thanks TwoTired for sticking with me on this one and thanks edbikerii for your input as well.

Oh yeah I did the throttle test also and the bike seemed to take it pretty well. No sputtering and it picked it up without letting off the throttle.

News:

Author Topic: 1977 Honda CB550K (Read 15240 times)