Topic: 78 CB550 running on #2and#4 only

[anthonywiley]

Hello everyone, Just registered here to maybe find some help with our 1978 Honda CB550K.

The bike was backed into while parked on the street in 1999. Dented tank and carbs started leaking really bad. Bike sat and sat for a few years. Carbs were really bad by then and float valves were not working correctly. I bought some nicely redone carbs off ebay that were really nice, clean, and bench synched. Old carbs were PD 460 PF. New carbs are PD 46A 0J. Everything sat while I repaired the tank. First I used acid about 3 years ago, worked good, but sat around and rusted again. This time I used electrolysis. Worked great!

Once tank was all cleaned I filled with gas and keep it filled with new gas. I get gas from it to cut grass and keep it filled with new gas. I put new clear fuel lines and a small clear new fuel filter on the bike.

I did a valve adjustment, I set intake to 0.05mm and exhaust to 0.08mm. Turned crank to 1-4T and adjusted valves with loose arms (#1). Rotated 360 degrees did the other (#4) that now had loose rocker arms. Then turned crank to 2-3T and adjusted the cylinder with loose arms (#3), rotated again and did the last one (#2), again making sure it was the right one.

I used a static timing light to check the timing. When I turn the crank to 1-4F light comes on hooked up on that side with blue wire.  Other side hooked up to yellow wire line up 2-3F, light comes on. I cut a little off spark plug wires and installed new NGK caps. Along with NGK plugs. When I take the plugs out of the bike and lay them on top of the motor they all fire with a blue spark.

I changed oil in the bike, I put in Gn4 Honda oil.

Umm… I cleaned the points and adjusted them to .4mm when fully opened. I have a new sealed scorpion battery that I keep on a genius wicked G1100 tender.

I am using the stock air box with a clean stock filter. Bike has a 4 into 1 exhaust with the spark arrester/baffle installed. I see small pieces of birdseed come out of pipe every once and a while. Guess I should probably take the pipes off and have a look inside to make sure it’s all clear. I’ve never taken them off before… I checked the compression:

 (#1 = 135psi)  (#2 = 129psi)   (#3 = 125psi)   (#4 = 129psi)

Added a little squirt of oil into each cylinder from a small oil can and checked again.

(#1 = 160psi)  (#2 = 150psi)   (#3 = 150psi)   (#4 = 160psi)

Oh, and the way I did the compression test: I took all the spark plugs out, tightened the compression gauge by hand in the cylinder, I pulled the choke out all the way, and gave it full throttle. Is the choke supposed to be pulled out or pushed in?  Hmmm, maybe I did that wrong now that I think about it. Pulled out would close the choke. Now that I think about it, I would think it should need to be opened all the way. Which is it, opened or closed, Pulled out or pushed in all the way?

Bike only starts with choke off, pushed all the way in.  It’s very hard to start.

The PROBLEM right now is she only runs on cylinders #2 and #4. 

I probably give it too much throttle to get it cranked and might be flooding the cylinders. Maybe I should check the plugs to see if they are wet. I think they might have been when I took them out for the compression test. Plug in #4 was brown and is the hottest pipe. #2 is hot too, but rest are cold.

By the way one of the carbs was leaking some gas out the air intake before, I think it was just a stuck float valve or clogged something, whatever it was I think I fixed that. I made sure all the main jets were clear and blew air through the fuel intake and main jets. Carbs are still really clean and shiny inside. I also set the floats to 14.5mm. The carb boots seem okay and are tight.

I have a Clymer manual which I’ve learned not to trust in most cases, so I use a SHOP manual mostly. I usually look in both and online for info.

I have not adjusted the cam chain yet. Could this be a problem with cylinders not firing?

Any ideas in what I should be focusing on or looking into would be appreciated.

Thanks in advance, and thanks for taking the time to read my long post.

Anthony

[Rgconner]

Common part is the coil, it goes 1-4 and 2-3 respectively.

So check it with a timing light to see if strobes, then trace it back till you find the fault. Might be a bad condenser if you are lucky.

[harisuluv]

Thanks for the detailed post. You will get more/better help this way. I didn't see you mention anythisee about your spark plugs though. See if the coil is working before you check the plugs.

Also very odd that the bike only starts without choke. Sounds like you have some mixture ratio problems. Any idea what your air screws are set to?

[anthonywiley]

I used a static timing light to check the timing. When I turn the crank to 1-4F light comes on hooked up on that side with blue wire.  Other side hooked up to yellow wire line up 2-3F, light comes on.

 I cut a little off spark plug wires and installed new NGK caps. Along with NGK plugs. When I take the plugs out of the bike and lay them on top of the motor they all fire with a blue spark.

All the plugs are firing. I have no idea about the air screws or any mixture screws, so that may very well be the problem. I know on other things i've worked on there are stock settings for screws as a base to start with, like 1 1/2 turn out or 2 turns out. Guess I should see if I can find these screws on the carbs and what the settings should be to start with. I'm pretty sure the coils are good since I have a good blue spark on all plugs.

[anthonywiley]

I know there are screws on the bottom of the bowls besides the drain screws. I was planning on learning about mixture screws when I do a carburetor synchronization. I have a set of vacuum gauges. I have never messed with the any screws on the carbs as of yet, except for the drain screws.
Figured I needed to get the bike running first, but maybe screws need adjustment to get it running in the first place?

[luap]

compression numbers will be lower without using a small displacment tester,  do you have gas in 1/3 bowls,
Im my clymer arms should be set at .02 an .03

[anthonywiley]

Yes there is fuel in the bowls, it will drip out of a couple of them eventually while trying to start it. My manuals have 0.002in 0.003in. Earlier I mentioned .05mm and .08mm.  All my feeler gauges are metric because my other bike is a '99 carbed Ducati.

[cavi]

A couple of logical points, you are sure you have fire from all four plugs, so you either do not have gas in those cylinders or the timing on those cylinders is off or the valve adjustment.   with what you are stating you have done I would really revisit the timing and vavle adjustments you did.  Someone mentioned coils, that would not jive with the two cylinders you are sayinga are firing....

[grachman]

Yep, doesn't sound like the coils, if #2 AND #4 are firing.

IF timing and valves are within spec, THEN check carbs on 1 & 3.  Sounds like it could possibly some clogged idle jets, but start on 1st base.

[anthonywiley]

When I did the valve adjustment I made it so that one size larger feeler gauge would not fit in, so the correct size was tight but would still get in there. Could that be too tight? Maybe I should check them again. 

Also when I use the timing light as I rotate the crank, the light comes on when it's supposed to, I guess, but stays on for a while after as I rotate it. How long is it supposed to stay on when rotating it with the wrench. Is it supposed to come on and then go out fairly quickly? I turn it pretty slow. As I look at the marks through the little window, light seems on more than off. But is on when the F marks pass. Light turns on right as I'm getting to it, maybe a hair before.

I should probably check to make sure TDC is in the right place too with a screwdriver in the spark plug hole. I should stop assuming things are right and check them myself. I want to check everything I can before I take the carbs off again. I figured TDC was correct because the rocker arms were loose.

Also I was wondering, and this may be a stupid question, but if the points plate needed to be moved, would you move it line up with T and piston TDC or the fire mark and the light coming on? Is there a priority or is it a case where if one is right then so is the other? Sorry I'm kinda new at doing some of these things.

Seems logical that if I can somehow determine it's not the timing or valves then it has to be a carb issue.

Thanks for your help, I kinda just hope it's timing or valves so I don't have to get those carbs off and on again.

[Spanner 1]

Do #1 and 3 plugs get wet with fuel when you try to start the bike ?? If not maybe your floats are upside down in carb 1 and 3 

[TrueSpin]

Had a similar issue where #4 only was not firing. Removed the sync port screw, shot some starting fluid in it, and it fired on the next crank.
Removed the bowl and gave the carb a quick sprits with carb cleaner, then put maybe a couple MM of starting fluid in the bowl, and snugged it back up. No more issues with non-firing.

[anthonywiley]

I cleaned the points and set the gaps again today. Rechecked the timing with a static light and it is dead on. I hooked up a spark plug and when the timing mark reached F it would fire exactly on the mark. Same as when the light would come on. So I know points and timing is good. I rechecked all the valves again and they are just right.

All spark plugs are firing.

I think it must be a carb problem.

Tried cranking it again and now only #4 pipe is getting warm.

Other three carbs are dripping gas now out overflows.  #4 is not leaking and is firing.

Gas is getting through the carbs and into the cylinders, plugs are getting wet. It seems to be flooding.
I’ve pulled the carbs off again, when I took them out the rubber boots had gas on them, engine side. It seems like gas is going through, just maybe too much?
These carbs are very clean, I think something is just not adjusted correctly or maybe something inside is not tight enough and letting too much gas through?

What should I check on the carbs?

I set the float height to 14.5mm exactly when it started touching the float needle valve last time.

Also what’s the best way to bench test carbs? I bought a Mityvac recently, any tips or links on how to do it?

Thanks again for all the help!

[harisuluv]

Hmm well it sounds like you are running rich.  Only starting with the choke off is not normal.

Do you have any idea what kind of jets you have in there?

Did you rebuild the carbs yourself?  I know you have the floats set to the correct height but did you replace the float valves?

You definitely need to take a look at those air screws.  They should be 1.5 out.  So you can find out roughly where you are pretty quickly.

[anthonywiley]

I have no idea what jets are in there, do they usually have numbers written on them?

Someone else rebuilt the carbs.

The float valves are new and in working order.

I have my old carbs still too, maybe I will compare jets, and see what I can find out.

I will definitely check out those air screws tomorrow. Thanks again.

[Spanner 1]

Forget about jets and airscrews, if your carb boots have fuel in them then your float valves are not closing/sealing and the bowls are overfilling. Are you sure about the float level being correct for your carbs ?Also are all bowl/ body vents free to outside air ?

[bollingball]

Forget about jets and airscrews, if your carb boots have fuel in them then your float valves are not closing/sealing and the bowls are overfilling. Are you sure about the float level being correct for your carbs ?Also are all bowl/ body vents free to outside air ?

Spanner is looking correct
Anthony You can through this 2x4 stand easy the board the rack is mounted to has only one screw at the end so the carbs can be tilted to what ever position you need the in then locked down those two black things at the bottom are c-clamps to lock that jig to the table this will free up both hands. Then you fill the carbs with fuel then you can see what level the fuel is with the clear tube method.
Do the drain screws on your bike work  like my 78 750? Can you put clear tube on your drains and test fuel level?
click on photo to get a larger one

Ken

[anthonywiley]

I just went through the carbs, the pilot jets (slow jets) are completely clogged up. I can’t even blow any air through them. They are soaking in a jar now. I threw the main jets in there too.
Checked all the numbers today, all stock jets.
Readjusted and rechecked float heights too.
Took all the float valves out and cleaned related areas.
Air screws were a little over 2.5, more like 2.75 out, now 1.5. With clogged pilot jets, guess it was like having them closed all the way.

[grachman]

Thought so.    Soaking carbs might make them look nice, but it almost always clogs the jets.  Sounds like it should be up and running in no time.

[anthonywiley]

Still had to use a tiny guitar string help clear those pilot jets after soaking all night. 
Just put it all back together.
She's RUNNING!
Now on to synchronizing those carburetors.
Thanks again for all the advice and insight,
It is very much appreciated!

-Anthony