Topic: '75 CB550 - HELP NEEDED

[sniper1]

I have been chasing gremlins on '75 550. Here is the problem:

I recently rebuilt this bike, just finished (or so I thought...) two weeks ago. Bike ran good for about a week or so. Last weekend it started having issues.

It seems to run fine when cold. When it warms up a bit (after about 5-10 minutes of riding) it suddenly starts to bog down. It feels like its starving for fuel. It won't go over 4000 rpm or 40 mph. The tone of muffler is really low and "bassy." Sometimes it will surge forward like its getting gas again, but quickly bogs down again. Today, I checked valve clearance again (.05 intake, .08 exhaust) all good. Made sure cam chain adjustment done, good. rechecked timing and breaker point gap, all good. I only checked 1 and 4 spark plugs, they were a little black, nothing major, so a little rich, maybe. I didn't pull 2 or 3.

I did recently rebuild the carbs with all new inards: 100 mains, 38 slow, air mixture screw out 1 turn. Bench Synched them and then vaccum synched. It ran good for about a week after doing this. Now all this.

Bike has 12k miles on it. 4-1 MAC exhaust, stock airbox w/new filter, everything else stock.

WHAT COULD POSSIBLY BE THE PROBLEM??

Fuel?
Electrical?
Spark?
Air?

Soichiro's curse???

WTF??

[Mo]

hmm. Could be out of sync carbs. The fact that you have new jets installed hints at that. Have you tried to re-sync them?

[luap]

.05 an .08 isnt stock but I think hondaman recommend that. .02 an .03 is stock from book
Fuel? wheres your needle clip?"It feels like its starving for fuel" you set the floats correct 22mm
Electrical?have you tested battery?
Spark? pull the plugs an rest them on the head
Air?so a little rich", maybe- not enough air. you turn your air screw out more

[Frostyboy]

You could try releasing the cap on the gas tank, if it's not venting properly it will hold the fuel back due to low pressure in the tank. I say low pressure because vacuum seems too strong a word.
Of course don't forget that the nylon sock on the petcock might be gunked up after all these years with such low mileage as well.
Turn the petcock off, place a container below the outlet, turn the fuel on & see what sort of flow is there perhaps.

[mronegear]

sounds like a fuel problem to me.
How is the inside of your tank? clogged petcock or breating vent?
Do you run the bike with inline filters?
Does the bike rev over the 4000 when its not boggin down? If no its set up way to rich,
turn the air-mixture screws out more (max. 2 turns) Where is your neddle cliip position at?
nedds to be at 2nd grove from top at the f model and 4th groove from top at the k model.
Does it run on all 4 cylinders? check temp of the headers.
good luck!

[sniper1]

OK, I got around to pulling the plugs. Here are some pics. Its 1,2,3,4 from right to left in both pics.

One thing I did notice was that I only had the air mixture screw out on the carbs 3/4 turn. I was playing around with it and thought it seemed to run better like that than 1 1/2 turns out. Maybe I was wrong.

Could that have caused the rich mixture and bogging/surging issues?

Can I still use these plugs? or should I replace?

[luap]

Could clean those plugs ride it see where you at an when your good put new plugs in

[luap]

MRRON
nedds to be at 2nd grove from top at the f model and 4th groove from top at the k model
where did you get that info from?

[DJ_AX]

...
One thing I did notice was that I only had the air mixture screw out on the carbs 3/4 turn. I was playing around with it and thought it seemed to run better like that than 1 1/2 turns out. Maybe I was wrong.

Could that have caused the rich mixture and bogging/surging issues?
...

yes .... could have

[Killer Canary]

Did you determine which cylinder(s) isn't functioning? that would tell us a lot.

[LesterPiglet]

My plugs are like that after idling if not sootier. Clean them and reuse. I don't understand people throwing away perfectly usable plugs. I shouldn't think your engine will run properly with the air screws turned in that much. 1.5 turns give or take should be close.

[sniper1]

Did you determine which cylinder(s) isn't functioning? that would tell us a lot.

I haven't yet. I will clean these plugs, back out the air mixture screw again and see what happens.
I really don't want to have to pull the carbs and take them apart again if I don't have to.

[sniper1]

My plugs are like that after idling if not sootier. Clean them and reuse. I don't understand people throwing away perfectly usable plugs. I shouldn't think your engine will run properly with the air screws turned in that much. 1.5 turns give or take should be close.

Ok, thanks. I'll give it a shot.

[seanbarney41]

that pic with the plugs in your hand?...are they displayed in order l to r  cylinders 1, 2, 3, 4?,...if so, 1 and 4 look alright, 2 and 3 look bad...I'd be lookin' at your ignition system...

[sniper1]

that pic with the plugs in your hand?...are they displayed in order l to r  cylinders 1, 2, 3, 4?,...if so, 1 and 4 look alright, 2 and 3 look bad...I'd be lookin' at your ignition system...

Anything in particular? I did check timing and made sure it was correct. Points were gapped correctly and timing was right.

[seanbarney41]

Are you sure that all four cylinders are even firing?  I've seen when sparkplugs get that sooted up, the spark don't jump at the electrode, it will go somewhere else...so even if you got spark, it won't fire the cylinder.  I'd start by checking for 12 volts at the coil, maybe a dirty black/w white stripe connector for the 2/3 coil?  Check coil primary and secondary resistance, spark plug cap resistance?  Two Tired has excellent instructions for this in the FAQ.

[LesterPiglet]

If they weren't sparking they would be wet not sooty tho looking again I do see a bit of a shine off them.

[sniper1]

The plugs arent wet. They are just sooty.

[LesterPiglet]

In that case my four plugs are like your 2 and 3.

[mronegear]

MRRON
nedds to be at 2nd grove from top at the f model and 4th groove from top at the k model
where did you get that info from?

2nd from Top is stock for the Supersport and 4th from Top is stock for the k Models. My manual tells
me that and i'm pretty sure that is correct.

[sniper1]

OK, I installed new spark plugs and fired it up. It does not appear to be firing on cylinders #2 and #3. When it started it was running very rough, had a very low tone, and when I felt the header pipes, #1 and #4 were hot, but #2 and #3 were cold.

Any thoughts on where to start checking. I am now thinking electrical. The points are gapped correctly, and I used a static method to set/check ignition timing. That went good for both 1 & 4, and 2 & 3. Plugs are new and gapped correctly. Tappet valves good.

What else could it be??
- ignition coil?
- plug wires?
- condensor?
- points?
- anything else?

This phenomenon came on relatively slowly but now seems permanant. What would cause this?

ANY HELP IS GREATLY APPRECIATED!!

[luap]

pull 2 plug out an lay it on the head kick it over look for spark
check the blk/wht wire off coils make sure getting a soilid connection from power

[windwalker]

methanol is playing havoc with our motorcycles. if you have fuel filters remove them. the alcohol is dissolving the glues that hold them together or fuel tank liner gelling? good luck

[sniper1]

methanol is playing havoc with our motorcycles. if you have fuel filters remove them. the alcohol is dissolving the glues that hold them together or fuel tank liner gelling? good luck

The only fuel filter is the sleeve on the petcock. I agree, stupid ethanol. Politicians are not only screwing up the whole country,,,,,they're screwing up our bikes!!!!

[sniper1]

Is there any way of testing by putting #1 and #4 wires on #2 & #3 to see if they go. I think the timing would be off, but would it work just to see if they fire?

[sniper1]

I just pulled the #2 plug, wired it up and fired the engine. No spark whatsoever. Now what?

Is it possible that the condensor is bad?

Could it be bad ignition coil?

Tank rubbing against wiring harness causing problems?

Where should I start to check? and how?

[TwoTired]

Plugs sooting up are almost certainly the air screws in too far.  Especially if you have the 069a carb with the solid tipped needle.
I don't care if you have and F model, unless you have the stock 4 into one muffler, you should have the carbs set up like a K model for the same year.  Replacement mufflers wer expected to replace the 4 into 4.

What is the condition of the condensers?  If you you swap them from side to side does the spark problem follow them?

I still don't get why you would adjust the tappets to anything besides Honda factory spec.  All mine have run well with those settings.  Maybe if you are racing or have a special cam, the clearance should be different.  But, Honda knew how to build a pretty stout engine.  But, if you must experiment, good luck!

Cheers,

[sniper1]

What is the condition of the condensers?  If you you swap them from side to side does the spark problem follow them?

That's a good idea, i will try that and see what happens.

I still don't get why you would adjust the tappets to anything besides Honda factory spec.  All mine have run well with those settings.  Maybe if you are racing or have a special cam, the clearance should be different.  But, Honda knew how to build a pretty stout engine.  But, if you must experiment, good luck!

I did adjust to factory settings. Everything according to the three different manuals I have.

[luap]

I just pulled the #2 plug, wired it up and fired the engine. No spark whatsoever. Now what?

Is it possible that the condensor is bad? swap 1-4 point condensor to 2-3 points see if that works

Could it be bad ignition coil? do a search to see how to test coils, http://forums.sohc4.net/index.php?topic=5752.msg8383#msg8383

Tank rubbing against wiring harness causing problems? do you have worn wires, an why is the tank rubbing

Where should I start to check? and how? get tank off of harness.

[Bailgang]

I just pulled the #2 plug, wired it up and fired the engine. No spark whatsoever. Now what?

Is it possible that the condensor is bad? swap 1-4 point condensor to 2-3 points see if that works

Could it be bad ignition coil? do a search to see how to test coils, http://forums.sohc4.net/index.php?topic=5752.msg8383#msg8383

Tank rubbing against wiring harness causing problems? do you have worn wires, an why is the tank rubbing

Where should I start to check? and how? get tank off of harness.

I'm the one that gave him the idea of the tank/harness issue. I just purchased a seat from him so we were PMing back and forth about this subject last night. I had issues with one of my coils on my 550 getting knocked out and running on only 2 cyls and I knew it had to do with the tank because it would always do it after I'd pull the tank and put it back on. Not sure how it was doing it because none of the wires were bare and all the connections for the coils were shielded/insulated but none the less that clump of connectors was getting pinched by the tank some how. I ended up make sure all connections were clean and made sure they stayed away from the tank and the problem went away. It's a long shot as to whether that's the problem sniper is having but it's worth looking into because many of the issues I had with my 550 when I first got it running ended up being simple stuff that I had assumed was OK and didn't dbl check.