Topic: CB550 Bad MPG and Skips / Running Rich

[INSANE REINDEER]

I have a cb550 that I bought a few weeks ago that had 7800 original miles on it. 4 into 2 pipes. I have put 600 on it since then and I have slowly been getting it back into good running condition. The last time the bike was registered was before I was born which was in 1989. I have put new Dyna 5 ohm coil, wires, caps, plugs, cleaned the carbs/rebuild, change the oil, adjusted everything besides the valves, new air filter (which is going to be done soon). The only thing that hasn't been done as been a carb sync *by me* and the valves adjusted. (which i was told was done before I bought it by a buddy who was in the process of restoring it but lost time). Carb sync will be done as soon as my gauges get here.

My problem is that it is running rich and I can see a tad of black smoke. I have take my carbs off many times and I know for sure that they are spotless and everything is adjusted right. I know that the air filter is good since I bought a new one (stock). The jets are stock as well. I have noticed though that if I look into the carbs the #1 cylinder slide is a tad bit more open than the rest which I thought would throw it out of since by I was told that they're not always going to be exact. I need some help on finding the final problem for this because I am running out of ideas. Smoke come out of both side pipes.

Another thing that is making me wonder is that when I stop giving it throttle and let it cruise at the same speed it want to gurgle out of both side exhaust pipes a bit. When I start to give it gas again the engine will sound like it is about the stall for a split second like it is being flooded and then catch up. When I go WOT is doesn't hesitate at all but only when I start to cruise and it doesn't matter what speed. When I used a timing light earlier I noticed that plug wires #1 & #3 would skip every now at any rpm and then when watching the light which I am guessing could be the problem of the gurgle but #2 and #4 don't miss. What could be the problem for this?

I'm only getting about 22 mpg and I know it can do better my 4runner gets that. I'm guessing after I solve these problem is should change but what MPG should I expect?

Thanks

[Bankerdanny]

Welcome ot the board. What year?

I'm a big believer of sticking with the original equipment as much as possible until the bike is up and running, then replacing as necessary to deal with problems. The 'if it ain't broke don't fix it school'.

I bought my '77 with very similar mileage and down time and the only part of the ignition system I replaced was the plugs. With new coils, wires and plug caps you have introduced a bunch of possible sources for your problems.

Did you retain the old coils and plug wires? Perhaps you might switch them back in and see what that does. What appears to be rich running could be a poorly working ignition which you compensate for by using more throttle.

When I had a problem with a loose wire between the 1-4 condensor and the points I misfired like mad and my fuel economy dropped like a stone. I would look in that direction before I did anything to the carbs.

When you say you rebuilt the carbs, what does that mean?

[INSANE REINDEER]

Well I do still have the original electrical equipment but I replaced because of this reason here. They were also arching really bad and I had them temp. taped up.  The boots were cracked pretty bad and the wires were split and arching in many places. The bike was still doing the same thing before the coil replacement so I know that they were not the problem. I have just replaced the coils, wires, boots in the past 30 miles since it could have been the problem. I did keep the original on as long as possible but since I thought it might be the problem I went ahead and replaced them.

Also what makes no sense to me is why the 1 and 3 cylinders are the only ones skipping with the timing light but 2-4 never miss. The old one were the same way.

By rebuild I mean like the floats, jets, o-rings, etc. Carb kit items.

Also it is a 1974

[TwoTired]

Many carb rebuilders fail to remove the mains emulsion tube in these carbs.  Simply overlooked because they are behind the main jet and have to be driven out from the slide side (carefully, as that is also the slide needle jet, too.)

"Skipping" with the timing light is probably a pulse polarity issue.  For each pair of the coil outputs one has a positive pulse and the other has a negative pulse.  So, you have to turn the timing probe over to make it consistent with the opposite polarity than what it likes to see.

The slides really should be near the same height/opening, assuming the mechanical bits of all cylinders are behaving well on each and every cylinder.
Don't bother vacuum syncing until the tappets are adjusted.

Cheers,

[Bankerdanny]

That is odd, since the 1-4 and 2-3 are the paired cyliders, not 1-3 2-4.

I'm surprised that your ignition compoenents were in such bad shape given the mileage. It must have lived outdoors for a long time. It definitely sounds like replacement was in order.

[INSANE REINDEER]

I did clean the emulsion tube. They were completely clogged when I cleaned them.

The timing light doesn't have a special way it skips or any kind of consistency though. It just misses every now and then at random intervals.

I was surprised they were too. The guy I received it from had it in a building but I bet before him it probably sat for a while outside.

[TwoTired]

I did clean the emulsion tube. They were completely clogged when I cleaned them.

OK, did you also verify that the passageway in the carb body between emulsion tube cavity and the air jet was clear?

The timing light doesn't have a special way it skips or any kind of consistency though. It just misses every now and then at random intervals.

Did you TRY inverting the probe polarity?