Topic: Ignition /firing problem

[martin.g.g]

I am at the end of my teather as regards to this CB550F2. I have spent so much time and money on it rebuilding it from a pile of scrap and it still won't run properly. I did have it running on all four at sort time but now it will only run on pot 1 & 4. I presume that it's a coil problem. I do get a spark from all the plugs all be it a bit on the weak side. I have swapped coils over and it ran with pot 1 and pot 2 missing and the others no life. One thing i did notice was that I was getting a lot of points arcing on points set 2&3 so I presume that its the condenser. However they have both just been replaced. My next step is swap the condensers over (may try one of the old confessors) and to change both the coils for new set of Dyna coils that I was going to use for my Suzuki GS1000G rebuild (which is due to happen one the Honda is sorted). In their installation instructions they talk about fitting a ballast resistor. I presume that the Honda has one fitted, but I cant find it. Does any one know where this is located and how to test it. And if not what type do I use were to I fix it and were do i get one from. Any advice on getting this stubborn bike living again would be appreciated.

[mrbreeze]

I'm all for the dyna. Make sure you are careful hooking it all up. Do you have proper instructions...wiring diagrams??? Make sure because I have heard of these units getting burned down beyond repair if improperly wired. I would imagine your problem is indeed ignition related if it effects only 1-4 and moves with the coil change. I have never regretted ditching the points and going Dyna. Good luck with your scoot.

[bryanj]

Hondas DO NOT have a ballast resistor (except for goldwings)

[SteveD CB500F]

Hondas DO NOT have a ballast resistor (except for goldwings)

However, they do have a big (usually green) resistor in the charging circuit (part of the voltage regulator). If your bike charges OK then this is nothing to do with the ignition.

[martin.g.g]

Cheers for the info guys.I have not had this bike running fully yet. It was salvaged from my brother in law who was moving and was going to scrap it. Its was an engine in a frame and two rotting tea chests of bits that had sat in the back garden for 10+ years. I thought I could get it up and running in 6 months, however 2 years on an a lot of time and an even greater pile of dosh its still refuses to coopperate. I will keep trying, the best will live. I would have posted a picture but get work out how to on this site yet.

[SteveD CB500F]

As these bikes run on a wasted spark system, there is two of everything so faultfinding is fairly simple.
1/4 fire together, as do 2/3, so swap bits around until the fault moves.

I usually start at the points and work towards the ignition coil, wires and caps.
Make sure you check all the wires for continuity as 90% of the problems on these bikes are down to 30-year-old connectors.

[TwoTired]

The stock CB550 Coils have 5 ohm primaries.  This is the bit that gets switched on and off by the points.  And, it needs no ballast resistor to soften the current draw for extended point life.

It sounds like your suzuki coils have lower ohm primaries.  These will draw more current through the points contacts and increase their heating.  A ballast resistor would reduce this current, and also lower the voltage developed by the coils.

A ballast resistor is usually used only during run conditions and bypassed during engine electric start.  This boosts the voltage developed while the battery is being sucked down by the large starter motor currents.  The CB550 is not normally equipped with this arrangement.

Dyna Coils can be found in 5 ohm rating, but most are of the 3 ohm primary variety.  These can develop higher spark in some circumstances, but do so with increased power draw through the points AND from your battery/charging system.  The 550 does NOT have a very powerful charging system and the battery is smaller than the what the CB750s have.

Back to troubleshooting your existing ignition...
 1. make sure your points contacts are clean and unoxidized.  They need to draw 2.4 amps when closed so any extra carbon or film between them can reduce spark output.  If they are old use a metal fingernail file if you can't find a point file.  If they are new, burnish the contact surface with some non-waxed or painted thin card board to wear away any surface oxidation. Avoid silica grit as it will embed into the points metal and partially insulate the points contacts.

2. ensure the wire and connections between points and coils are clean and low resistance.

3. Measure the voltage on the black wire to the coils, both static and while the engine is cranking.  Voltages below 10 V can be problematic for reliable spark.

4.  Check each spark plug cap unscrewed from the ignition wire and measure the resistance in the cap  Higher than 10 K is a problem and it is better if not less than 5K ohms.

5.  Look at the connection between wire and plug cap.  Clean and well made?  Maybe a wire trim before screwing it back on is an improvement?

6.  Check the entire length of the ignition wires for insulation cracks, particularly where the wire joins the coil body.  If you can see the wire core is still intact, you can clean the area and patch it with RTV.  (Allow to cure before service.)

7.  Are the spark plugs new?  Correct type?  Are the old ones clean?  Soot build up on the center electrode insulator can shunt some or all the spark energy away from the spark gap.  If you can't clean that porcelain insulator throughly, get new spark plugs.

As mentioned, the ignition fire 1&4, then 2&3 together.  If your cylinders are cold along those boundaries, ignition is suspect.  However,  non-firing plugs ought to be wet and/or smell of petrol after running with a malady.  Don't blind side yourself with ignition focus while a clogged jet or hung float in a carb contributes to your engine woes.

Cheers,

[HondaMan]

That "extra arcing on points 2&3" is a good clue: it could be that condensor (if it is open, there will be much arcing and very little high voltage spark). It can be a shorted coil primary: I have seen this on CB500 more than on any other Honda, don't really know why, and usually the 2&3 coil. I even have 2 sets of them (still) in my junkbox with bad 2&3 coil, just for testing stuff.

I have also seen, on several SOHC4 bikes, where the HV spark leads are arcing to the frame where they go near it. If either one of a coil's pair arcs like this, both will misfire. Usually a cracked wire (from age) is the culprit.

[martin.g.g]

Hello guys. Got that condenser from David Silver and now have spark on all four, but the gremlins have got into this bike. It started on on four with a little easy start, but then started missing on pots 3 & 4. Found to be fuel starvation. The fuel tap had one of the out lets partly clogged up with crap (this bike has a twin out let fuel tap). I had almost drooped the tank of the seat earlier and must have stirred up some crap. By the time I had cleaned the tap out and managed to shake most of the crap out I was time to pack up(hope this was enough as i had done this before but some always seems to stay behind). Does any one know a priest who can cast out the demons that seem to be residing in this bike,

Finally how do I get pictures upon this site.

[Einyodeler]

If you had rust in the tap, then you`ve got got dirt in carbs now. I`ll bet the idle jets are plugged on  3 & 4.

[Bob Wessner]

Can't help with the exorcism, but as to posting pictures, on either a new topic or a reply, in the lower left of the text input box you will see Additional Options. Click on that and it will display another input box for the file name of the pic. You then use the browse button to locate the file on your PC. Double click on the file name and it loads the name into the input box. Then hit post. If you have more than one pic, to the right of the Browse button is (more attachments). You can repeat the steps for them. Remember though, the pic file is limited to 80K which generally means you would need to compress the image using some utility.

[TwoTired]

Agree with Stephan.
If you fed your carbs crappy, chunky, crusty, fuel, something's likely clogged up in the carbs now.  It only takes a piece 0.016 inch in diameter to plug the slow jets.

You can try flushing them on the bike by opening the drain screw and squirting carb cleaner into the base of the bowl using those long red tubes.  Might get lucky and have the crud fall out the bottom.  Worth a shot, so to speak.  It's saved me pulling the carbs off before.

Cheers,

[martin.g.g]

Hi guys

Thanks for all the advice. I was aware of the crap in the tank and had spent a lot of time trying to shift it, but could not get it all out. So I fitted a couple of in line fuel filters so I could see if any crude managed to find its way down the fuel line as after 4 strip down and rebuilds of the carbs to try to find the fault I was not going to let the crap I could not shift dirty the carbs up ( all carbs were rebuilt using a rebuild kit, new jets & needles). I even managed to get them into my little ultra sonic cleaner, so they must be the cleanest Honda CB550 carbs around.

I have now fitted the replacement condenser and the Dyna 3ohm coils and have a good spark, but it does have a slight hic cup from time to time (hesitates for one beat), but its not fully set up yet. I have set the ignition timing, plug gaps, points gap, strobe the timing, balanced and colour tuned the carbs, but its still needs another going over. I have also set the valve clearances using the thread pitch method to take into account rocker wear and they run nice and quite, but not to the extent that valve burn could happen.

I do have two problems one a real head ache

The minor one is tick over. The bike will not tick over below 2000rpm and has a tendency to surge up to 3500rpm. This I believe is a slight sticky throttle cam, or I need to play with the height of the carb balance adjusters. I have checked for air leaks and can’t find any, but I will go over this area again. My reasoning is that it’s the carb cam is that if I push on it the rev’s drop back down. Thoughts on this matter would be appreciated

The real bug bear is the leaking carbs. No 2 & 4 carb’s have a persistent drip ( one drip every 2-3 seconds) and No 1 & 3 have a slight drip (one drip every 10 seconds or so). I have as I said had the carbs stripped down on more than one occasion and have replaced the needle valves and seats TWICE. I have swapped floats over all to no avail. The method I use is a couple of modified drain plugs fitted with a clear plastic tube and screw into the drain hole on the float bowl. This allows for the fuel height in the carb bowls to be seen. Adjustment was made on the float tang using a digital vernier so the amount of adjustment could be noted. However the float tang has to be adjusted so much to stop the overflow that the bowl is staved of fuel. So I have a dilemma the last set of needle valve and seats were Honda originals. Fuel can’t be getting past the needle valve seat seal or it would always flood.

So guys any thoughts as this is really getting on my nerves. I almost put it on eBay as a none runner because of this, and would have considered selling it for parts. I have worked on many bikes and car over the years, but never have I had such an obstinate vehicle.

[Bob Wessner]

The real bug bear is the leaking carbs. No 2 & 4 carb’s have a persistent drip ( one drip every 2-3 seconds) and No 1 & 3 have a slight drip (one drip every 10 seconds or so).

Dripping from where?

Your picture posted OK, but it is a very pixelated version. Was that deliberate, as in artsy??

[SteveD CB500F]

Martin - the size limit on pictures is 80K (not 8K !)

Dripping carb overflows must be because of dirt in the float valve if the float heights are OK. I read somewhere on this site that some of the replacement kits have useless float valves and needles (TT will confirm, I hope)

[SteveD CB500F]

Not much!   

[martin.g.g]

Cant be any dirt in the carbs, but I do suspect the needel valves. Any body have a good source for them. My last ones came from Dave Silver original Honda ones. As for the pictures I will try again, but higher resolution seems to time out.

[martin.g.g]

Oh the carbs leak from the brass overflow pipe at the bottom of the float bowl

I think I have the picture thing sorted

[Bob Wessner]

Picture is good. As to the leak from overflows, like Steve says, either a float height problem of float valve seat leak are the two most probable causes.

[TwoTired]

As a guess, maybe the overflow stand pipe in the float bowl is cracked.  No amount of float needle/ or float adjustment is gonna fix that.  I had one that drove me bonkers for a while. (I'm muuuuch better, now.)  The danged thing wouldn't leak unless the engine was running.  Apparently, the vibration would make crack open like a mouth.  Was still hard to find, too, as the crack was on the least visible side.  I've fixed them with gas tank sealer and even tubing slid over the crack.  But, it is best to replace bowls with cracked stand pipes.

In general, I find the aftermarket components are not made with the same attention to close tolerances, specifications, and quality control effort as the Honda approved parts.  (Though there is a lesser variability there, too.)  There's a good reason why many aftermarket parts are cheaper than Honda parts.

Cheers,

[750goes]

If you had to bend the TANG on the float assembly to such an extent, is it possible that your floats are in uoside down???

just a thought...

[martin.g.g]

That cracked over flow pipe souds intreasting I will delve into the further Cheers TT

As for the floats being upside down I don't belive they are. With the carbs fixed to the bike the floats are located in with the brass stop/tang pointing down so the float does not drop. but I will check whrn I goe back in cheers for that 750

Time for my bed got work tomorrow 6:30am start till 6:30pm (12 hours) so I will need some sleep. Will get back to you guys next week with the results when I have some more time to play wiht the Honda

Many thanks again for all you help.

[Bob Wessner]

A cracked overflow pipe would fit the description also, but with all four dripping various amounts, seems like it might be something else. 

[750goes]

Just to throw one out there....

the fuel delivery pipe joining pieces between 1-2 & 3-4 if the O-rings are cactus then they might leak from both sides and then drip on to the carb bowls ?

[martin.g.g]

The carb link 'T' piece 'O' rings were replaced when I ripped the carbs down so they should not be leaking and running down but i will check. Thanks for that one. I may try a desperate way and lap four of the spare seats and needle valves using auto solve to see if I can get a better seal as I suspect poor quality needle valves, but I may be looking at the wrong bit. So keep those sugestion comming and I will let you know as soon as i have a result