Topic: 75 CB550K #3 cylinder not firing. HELP? (*UPDATED*-Timing Issue?)

[Sprocket75]

Last night, I got everything buttoned back up and ready for her maiden voyage this weekend. (even bought my very first helmet!) So, I fired her up, and noticed that she sounded a little "rough". I let her warm up, blipped the throttle a little, and noticed that it was sluggish as it came back down. The revs went up just fine, but sort of took their time coming back down to a nice smooth idle. So, I checked the temp on each of the header pipes where they exit the engine, and #1, #2, and #4 were hot, but #3 was barely warm. So, thinking that maybe it wasn't getting any spark, I pulled the plug (new NGK's by the way) and took a look. It was a little wet and blackish/brown. I then checked the spark (new plugs and boots by the way) by grounding it against the engine block...spark looked good. I also (just to be thorough) installed an in-line spark tester (see photo) and it showed a clean, strong spark. I then swapped the #2 and #3 wires just to see if the problem moved...it didn't. The#2 ran fine w #3 wire on it, and #3 was still cold with #2 wire on it. So, swapped the spark plug to see if it followed the plug...still cold on #3. On a side note, I noticed that when I have the engine running, and I hold the throttle at around 3000 to 3500 RPM's, there sounds like a "popping" noise (not quite a backfire) coming from the right side exhaust. (#3 and #4 cylinders are on right side as I have 2 into 1 headers) The popping noise is intermittent, but noticeable when the throttle is held there. My rookie thoughts are that #3 is only getting fuel at high RPM's and thus fires quickly and dies thus making the popping noise? Which would mean that the #3 carb has an issue? I have read through several posts here and see that my issue is not uncommon, which is comforting. There are some great troubleshooting processes here that are very detailed which gives me confidence. I just need to get a feel for what you all think here. Maybe a direction to start in. My next step I am thinking on taking is to pull the airbox, and check the vacuum (suction) with the engine running, especially on #3. I read an idea here to spray a little starting fluid into the carb intake while it is running to see if that cylinder fires. My next step (speculation) is to pull the bowl on that #3 carb and check there. (float etc.) as well as that the fuel line going to #3 is not clogged. (obvious, but possible) Could it be a sticky valve? Any way to easily check that possibility with the engine still on the bike? I suppose that I will go ahead and pull the carbs off and clean them if the fix is not something "average". I am going to order the Carb Sync Vacuum Gauge set online today, as I'm sure it is a tool that I will need again anyway. So, anyone out there wanna help a rookie out and see if I can take her on her maiden voyage this weekend? Thanks in advance...

**Update**  Bought a compression tester on my lunch break. I will test the compression in all of the cylinders tonight as well, just to see if there is an issue there. I also forgot to mention that I added a little Seafoam to the tank last night to help clean the fuel system too. (It really helped my Mercury Tracker on my boat, so I figured it would help here as well) No change really. Is it possible that I may have made the #3 plug wire a little too long when I replaced them with the Accel wires and that is affecting it? Anyone?

[Vinhead1957]

Think you are heading in the right direction. The compression test will tell if it is a cylinder problem but odds would put the problem in the carb.

[ONEdownFOURup]

Having the same issue with cylinder 3 and 4

[ANDY W]

Sound like you getting to much fuel in #3. First thing I would check is the fuel level in the bowl and make sure the air screw is set to spec

[Sprocket75]

Back at it again last night. Ran a compression test on all four cylinders last night. I honestly couldn't be happier with the results...all cylinders read 150 to 151psi. So, reinstalled spark plugs and then checked the tappet clearance on #3 cylinder...all good. Adjusted the air screw on the #3 cylinder, fired her up and voila! All 4 pipes were hot! Now, she was idling rough, so that tells me that the carbs definitely need to come off for a good cleaning and sync. I played with the air screw a little more, but never could seem to find the sweet spot. I decided to take her for her first ride, and she ran really well all things considered. I noticed some popping/backfiring on deceleration, but again, nothing has really been adjusted properly. I took the points cover off and let her idle. Seems odd to me, but the contact points are barely moving at all. There is barely ANY travel (movement) in them. Shouldn't you be able to SEE them opening and closing? I took a video and will try to post it here if I can reduce the size small enough to fit this way you can see what I mean. Not sure how well you can see it in the video, but might shed some light. The task of pulling those carbs seems somewhat daunting to me, but I feel like you guys will help me find my way if I get stuck... I hope.     Also,  she blew a fuse twice last night (the main) while the rectifier was connected. I disconnected it, and no more blown fuses. Assuming it needs replacement, how do you feel about the regulator/rectifier combos? Seems like they would be a solid replacement? Thoughts?

https://www.youtube.com/watch?v=nwZLENCoYII&feature=youtube_gdata

[Sprocket75]

I should have NEVER touched the #3 air screw. She will not idle without the choke being on now. Pulling the carbs this weekend... Carb adjusting tool, Carb sync gauge set, and carb cleaning tool all on their way from Amazon. Should be delivered Saturday, I hope. That gives me Friday night to pull the carbs and start cleaning. Saturday to reinstall and sync, then set the timing and work the bugs out. I can see that the #1 bowl is leaking now as well. I have opened a Can-O-Worms now...lol.

[Adam_F]

I have opened a Can-O-Worms now...lol.

Sounds like progress! 

[Sprocket75]

Wondering if I should go ahead and buy this: 
and replace these parts...or just clean everything???

[TwoTired]

Wondering if I should go ahead and buy this: 
and replace these parts...or just clean everything???

Don't replace the metal parts, clean them.  The part dimensions can be slightly different than what you have, or not.  But, it's pretty certain it ran well at one time with the part you now have, right?
Do replace the rubber parts.

[TwoTired]

The bike in your avatar is not an F model.  It is a Cb550 Four,  K model.  If truly a 75, it is a K1.  The vin number would determine that, though.

The designation matters when replacing parts.

[Sprocket75]

TwoTired, you are the MASTER! My mistake on the designation, I am so new to all of this. Yes, mine is a K model indeed as the VIN starts with CB550E-105... Will order the replacement rubber parts today then.  **Notice the gap between the seat and tank? I ordered the seat through Ebay, seller said it was for a K model. Guess it wasn't. Either that or the tank is not the original tank?

[TwoTired]

You have an F model seat in those pictures.  The F model tanks are longer than the 71-76 Cb500/550 K models.
You have a K model tank.

[Sprocket75]

Got her running earlier, but rough. Decided to adjust the points and timing...but man am I really stuck on setting the timing. I am reading step by step from the manual, and the process seems to go fine, but now she will not run. Anyone awake feel like walking me through this?

**I'm doing something wrong. Now my test lamp lights up on both points 2 & 3 when 1 and 4 fire...ugh. There has to be a better way than this. Have started over 4 times now...manual is beside me.

*** Set points gap first, then static timing? When the number 1&4 points are open the light should turn on and the mark should be at F...correct? And at the same time, the 2&3 point should be closed and there should be no power to them...correct? Then rotating the crankshaft, the F mark for 2&3 should roll into site...the 1&4 points should be closed and 2&3 should be open, light should come on...1&4 point should have no power on them... Help??

[Sprocket75]

Looking at the above photos, my test light comes on just at or right before the "F" mark. When I rotate the crank, do I need to go 180 degrees or 360 degrees beyond that to check the next set of cylinders? Maybe I am confused as to how far to rotate the crank and that is my issue? What I have been doing is starting at 1-4, rotate crank slowly until "F" mark lines up with timing mark and test light comes on, then slightly and carefully rotating plate until test light goes out, then tightening plate. Then, slowly continue to rotate crank until 2-3 "F" mark shows inside of the timing window hole and lines up to timing mark and test light comes on, then moving 2-3 plate carefully until light goes out, then tightening plate. Should I be rotating it more from the 1-4 to 2-3? Seems like I can get the F marks on both sets to line up correctly, but then it throws my points gap off.
If I start with the points first, which I have also tried, seems like I cant get the F marks to fire correctly. (line up) Is there a beginning (start from) position on both plates and points that is easy to reference and start from scratch? Maybe a mark on the points cam shaft? I can visually see the lobe, (sort of) but cannot eyeball it enough to see the highest point of travel. I just want to start all over from the beginning and go 1 step at a time to see where I am making the mistake(s). Any suggestions?

[ANDY W]

OK first u need to find the points max gap. I do this by opening both points to a large gap, to where they wont contact, and lock them down. also make sure the base plate screws are locked down. now rotate the crank back and forth, much easier to do this without the plugs in, until u find where the 1-4 point is at its maximum gap. now set 1-4 gap. next do the same for the 2-3 point. OK now that the points gap is set u can set the timing. rotate the crank till the 1-4 F line lines up with the notch. with the test light installed across the points, loosen only the 3 base plate screws (labled 6 in the manual)and rotate the base plate until the light goes from off to on, when u get it set to where the light first turns on lock the base plates screws down. now rotate the crank clockwise until the 2-3 F line lines up with the notch and set the right base plate the same way. only loosen the 2 right base plate screws ( labled 8 in the manual)

[Sprocket75]

Thank you Award! This is by far one of the best explanations/process I have seen for doing this yet! This makes sense and seems to simplify what I have made complicated...lol.    I am going to ask a few questions for clarification though, ok?

..."also make sure the base plate screws are locked down"- What position should the base plate be in? Middle way on all 3 screws?

..."now rotate the crank back and forth, much easier to do this without the plugs in, until u find where the 1-4 point is at its maximum gap"- I guess that I just eyeball this as I move the crank? Or am I looking for something that delineates the widest point like a marking on the shaft? (sorry, I just don't want to overlook anything)

..."with the test light installed across the points"- I have one end grounded, the other end clipped to one point, is this the same as across the points?

..."rotate the base plate until the light goes from off to on"- Does it matter which direction I rotate the plate?

..."now rotate the crank clockwise until the 2-3 F line lines up with the notch"- From the 1-4 mark that we are currently at, I rotate clockwise until I see the 2-3F line as in don't go a FULL revolution, correct? Because the 2-3 will come up BEFORE the 1-4F does again, but I've gotten conflicting info. Some say go past the 1-4F again to the 2-3F and others say no, just rotate to the 2-3F mark. Again, sorry, I just want to be certain.

I honestly can't thank you enough for taking the time to post this information for me. I really appreciate it. You have no idea what a HUGE help this will be tonight. Fingers crossed...and eyeballs too! 

[Sprocket75]

Been at it 2 1/2 hours... I am clearly doing something wrong. Tried w a meter...test light...LED test light. I keep messing up on the gap...somehow. It can't be this hard. Seriously.

[TwoTired]

Have you looked in the FAQ about shimming the points base plate?

I think they have relaxed the acceptance standard for that plate's diameter dimension over the years.  Some of them are too small to fit within the bosses without lateral movement.  When the screws are loosened, the springs on the points push the plate about when the cam rotates, and this changes the gap setting, which also changes the timing point.  Some method needs to be used to hold the plate firmly that allows rotation but not lateral movement.  I find it easy to stuff some shims (feeler gauge blades) between plate and containment boss so the plate can be rotated but not move about.  Other methods are possible.

Once this is done you can rotate the crank to find the high point on the cam for each set of points, set the gap(s), and not have to worry about the gaps changing later.
Then you want to mimic what the engine does while running, which is moving the crank to watch for the light to occur at the F mark for 1.4, moving the adjusting plate, if needed, an then rotate the crank again to watch for the light to come on as the F mark passes the index point  The large plate can then be tightened and the shims removed.  The 2.3 points has its own sub plate, and there is a separate F mark on the crank labeled 2.3.  The light is attached across the 2.3 points and the crank rotated to see where the light comes on in relation to the F2.3 mark aligned with the index mark.  The 2.3 sub plate is nudged a bit, and again the crank is moved to determine where the light comes on.  When the light comes on as the F2.3 aligns with the index mark while the crank is turned, the timing is set and the sub plate is tightened down to prevent further movement.

You will note on the plate there are two raised dots and and notch in the point mount.  When the months screws for the points are loosened slightly, a flat blade screwdriver turned while in the notch and raised dots will move the points to set the gap for each set of points.  There is another separate screwdriver type adjustment for setting the timing of the 2.3 points which does NOT involve moving the big base plate.

[Sprocket75]

She is running...on all 4 cylinders! Persistence is priceless...Its 2:30am... thanks gentlemen, for sticking with me. 

[Duanob]

TwoTired, you are the MASTER! My mistake on the designation, I am so new to all of this. Yes, mine is a K model indeed as the VIN starts with CB550E-105... Will order the replacement rubber parts today then.  **Notice the gap between the seat and tank? I ordered the seat through Ebay, seller said it was for a K model. Guess it wasn't. Either that or the tank is not the original tank?

That's an F model seat from a 75 - 76. I wish I hadn't bought one I already i would buy that from you.

It sounds like some of your problems could be from crap in the tank making its way into the carbs. the leaky overflows the mis-firing carbs. It does not take much to clog float jets or pilot jets and make your bike run like shyte. If you take the carbs off for cleaning I would do the same with the tank, fuel tap, and fuel lines as well. Other wise you will be right back where you started. Also when you re-intall your clean carbs I always leave the over flow rubber tubes off until I know my carbs are good to go with no more leaks. Its way easier to find the offending carb leak.

[Sprocket75]

..."That's an F model seat from a 75 - 76. I wish I hadn't bought one I already I would buy that from you. ..."  I  will trade you for the correct seat for mine if you have one?

Yes, I plan to remove the carbs this weekend now that I have the timing set properly. Supposed to storm on Saturday anyway. I have my work table cleaned completely off, numerous pages and photos and videos of the process, brand new bottle of carb cleaner and simple green, carb cleaning tool, small parts containers etc. Gaskets are on the way as well as vacuum gauge sync set. At least I know it WILL run on all four cylinders as it is right now, despite being grumpy about it.  I purchased new fuel lines as well. Did not purchase fuel filter, how do you feel about those on these bikes?

[Sprocket75]

Have you looked in the FAQ about shimming the points base plate?

I think they have relaxed the acceptance standard for that plate's diameter dimension over the years.  Some of them are too small to fit within the bosses without lateral movement.  When the screws are loosened, the springs on the points push the plate about when the cam rotates, and this changes the gap setting, which also changes the timing point.  Some method needs to be used to hold the plate firmly that allows rotation but not lateral movement.  I find it easy to stuff some shims (feeler gauge blades) between plate and containment boss so the plate can be rotated but not move about.  Other methods are possible.

Once this is done you can rotate the crank to find the high point on the cam for each set of points, set the gap(s), and not have to worry about the gaps changing later.
Then you want to mimic what the engine does while running, which is moving the crank to watch for the light to occur at the F mark for 1.4, moving the adjusting plate, if needed, an then rotate the crank again to watch for the light to come on as the F mark passes the index point  The large plate can then be tightened and the shims removed.  The 2.3 points has its own sub plate, and there is a separate F mark on the crank labeled 2.3.  The light is attached across the 2.3 points and the crank rotated to see where the light comes on in relation to the F2.3 mark aligned with the index mark.  The 2.3 sub plate is nudged a bit, and again the crank is moved to determine where the light comes on.  When the light comes on as the F2.3 aligns with the index mark while the crank is turned, the timing is set and the sub plate is tightened down to prevent further movement.

You will note on the plate there are two raised dots and and notch in the point mount.  When the months screws for the points are loosened slightly, a flat blade screwdriver turned while in the notch and raised dots will move the points to set the gap for each set of points.  There is another separate screwdriver type adjustment for setting the timing of the 2.3 points which does NOT involve moving the big base plate.

Thanks TwoTired! You are correct about the plate shims. That helped tremendously. I have a TEC plate, is that a good quality plate? I noticed a small amount of arcing on the 2-3 points with the engine running...how much is acceptable? After the engine ran for a bit, I connected my timing gun, and checked the advance. The 1-4 looked perfect! Movement was smooth and accurate. The 2-3 however, was a bit "jittery" and it almost seemed like (and I was very tired at this point) I could see the 1-4 numbers jumping in there with the 2-3 number movement. Does that make sense?

**On a side note, while I was setting the points/timing for the 168th time, I used all three devices (LED test light, incandescent test light, and digital VOM) Honestly I could not tell a difference between any of them, but then, it was 2A.M. by this time and I was exhausted. They all seemed to notify at about the same time. Just my 2 cents worth.

[Duanob]

..."That's an F model seat from a 75 - 76. I wish I hadn't bought one I already I would buy that from you. ..."  I  will trade you for the correct seat for mine if you have one?

I don't have an extra one or I would. You have a pretty rare seat actually. They only made them for 2 years and the F model is a lot rarer than the K models in production. If you don't do anything with the seat cover I know a guy over in Viet Nam that will make a nice reproduction quality seat cover with the pattern. In fact he will give you a free seat cover for the pattern. You could turn around and make some bank with a recovered seat and the rest of us will have access to a good seat cover. Pit-replica is his EBAY handle. pitreplica2@gmail.com is his email. He goes by TC. I've been trying to find an old cover to send him but haven't had any luck. There is only one company that makes the 550F seat cover and I their qulaity is not reproduction at all. See pic below for a pic of my 550K seat with pit-replica cover.

Did not purchase fuel filter, how do you feel about those on these bikes?

You can pull it out of the tank and clean it, its just a sock filter held in place by an o-ring. I don't think they are good enough to filter everything out. My thoughts are to put an inline filters on but other people on here have a different opinion. I get tired of crap finding its way into my carbs. I think the gas stations don't filter their gas and tiny dirt particles find their way in. Empty your bowls into a white or clear container sometime and you will see it. I use different gas stations all the time but any time I empty the carb bowls there is always crap in them. I clean my fuel tank set up every winter too.

[TwoTired]

You should have a fuel filter.  Honda supplied one with the bike.  It is located above the fuel tank valve, but is easily damaged by unknowledgeable invaders.  I see no need to double filter the gas.  You only need one good filter.

Clean carbs seldom remain so without a functioning fuel filter.  But, if you are confident, the gas, the tank, and the filter are in proper condition, forge ahead.

Did you get the simple green that is safe for aluminum use?  They make several varieties of the product.

[Sprocket75]

Okay, I will take the fuel valve out tonight and check/clean/replace the filter. Anything I need to be aware of while removing the assembly?
As for the Simple Green, I am certain that I did not get the aluminum safe type...because it there was a 50/50 chance of grabbing the correct one from the shelf, the universe dictates that I am 102% wrong.  Thanks for the tip, I did not realize they made different types. Back to the auto parts supplier on my way home then. While I am there, is there a particular brand of carb cleaner that you recommend?