Topic: Why Won't My 76 550F Start?

[MandEms]

It's been running great and then last weekend I went to ride it and it wouldn't start.  It is not firing at all.  It sounds like it does when the kill switch is in KILL position, but the switch is in RUN.

The basics:

1.  Good spark
2.  Plugs have fuel on them when I pull them out
3.  Good compression (thumb on sparkplug hole test)
4.  I haven't done anything to the bike since I last rode it
5.  The points aren't loose and haven't rotated from their original position
7.  There's plenty of gas in the tank and I have clear fuel tubes so I know it is reaching the carbs.

Other info:
1.  Starting fluid was no help (sprayed through the air box without the filter and also into the vacuum synch ports next to the head)
2.  Like I said, it sounds like the Kill switch is in Kill position but it's not and I have really good spark.

[oldhatt45]

Mark,

In your description, you have 2 items that appear to me to contradict each other.
1.  Good Spark
2.  Plugs have fuel on them when I pull them out.

How did you check for Spark?
Is the choke on or off?
Is the engine ground nice and clean?  (yeah, that's a bit off the wall.    )

Charlie

[MandEms]

Well, now.  You know what, Charlie?  I hadn't thought about it that way.  When I put the plugs on the engine case and crank the engine there is bright blue sparkage on all the plugs.  But I see what you are saying about how can there be fuel on them.

I mentioned the fuel on the plugs because I was thinking that was a sign I was getting fuel to the cylinders.

The only thing I can think of at this point is the timing is off, but I don't know how that can suddenly happen.

[MandEms]

Also, I have tried it with and without the choke.

[oldhatt45]

Mark,

OK.  So, you have spark.  To me that would rule out the kill switch.
It would also seem to rule out points being welded shut. 

You said that the plugs were wet.  Can you post a picture of what they look like?
Also, have you checked the Valve tappet clearance?  (I'm not sure about the 550 adjustment procedure since I have a 750)
Timing is also a possibility, guess you need to check that as well.
Does your 550 have one of the starter safety modules?  I don't know if that might cause the bike not to start if it failed if yours has one.

Hope one of the 550 experts will chime in and give you some good info.

Charlie

[MandEms]

Thanks for the replies Charlie and Cal.

You have hit everything on my list to try.  I am battling the flu right now so I won't get back to it immediately, but I will let you know as I go through it.

I will also get pics of the plugs.

Thanks again!

[Dino]

Try draining the float bowls, then turn the petcock on for a count of ten, then turn it to off. Try starting it. You might have a stuck float, or two. Based on what you say about having a spark at the plug but it's wet makes me think it's flooded with to much gas.

[MandEms]

Thanks, Dino.  That is also on my list.

It just seems weird that it all of a sudden wouldn't start so I'm arguing with myself about how in depth I need to go.

I'm mostly afraid that I'm going to get the thing half way torn apart and then see something obvious.

[Dino]

It is almost ALWAYS something simple.
Here's an example.

I recently worked on an 85 BMW 535is for a friend. It wouldn't idle correctly. He took it to a shop and they replaced the fuel pump, fuel filter, fuel pressure regulator, idle speed control motor even the air flow meter. It still had an intermittent rough idle and stall out. He brought it to me to check out. It took me about 15 minutes to discover that the o-rings that seal up the the oil dip stick were missing. These cars pull intake manifold vaccum on the crankcase to vent pressure and the missing o-rings were the equivalent of a vacuum leak. Two $.59 o-rings later and it idled rock solid.

Simple.

[MandEms]

So, I finally got around to taking a closer look at why my bike suddenly wouldn't start.  I didn't want to tear into it too far since, like I said, it just didn't start one day.

After pulling the carbs and making sure nothing was clogged up, and checking the spark by pulling the plugs and cranking it over, I decided today to take a look at the timing.

I pulled the points plates off and got to the advancer and found the advancer was very slow to return to the idle position and in fact it never actually returns all the way to the idle position.

Here is a video of it:

Before I get too excited, is this significant enough to cause the bike to not start?

Thanks.

[Mr Freeze]

You can grease that advancer shaft that it pivots on so it moves smoothly. It's not the likely cause of your issues though. Those sprung weights spin out from centrifugal force as the RPM's increase to advance the timing.

Since you have the points plate off, make sure the #1 cylinder is back at TDC before you reinstall it.

[harisuluv]

pictures pictures pictures pictures.  pictures of the bike, the carbs, the plugs.  the only media we have to go off is a video of your spark advancer.

With spark, fuel/air and compression the bike will run.  Establish you have those first, then move onto the electrical stuff.

Just because fuel is in the carb bowls, does not mean that the fuel gets to the cylinder correctly, that is an assumption and it doesn't follow. 

What changed before the bike suddenly stopped?  Do any work to it?  What you are positing is that the spark advancer either was in its current state and was running fine, or the springs suddenly wouldn't retract and quit running.  Doesn't sound right to me.

If I were you I would take the spark plugs out, photo them, show us, spray starter fluid directly into the cylinder while you got the plugs out, then see if there is any different in the engine when you try and start it.  Then go from there.

[MandEms]

From my original post:

It's been running great and then last weekend I went to ride it and it wouldn't start.  It is not firing at all.  It sounds like it does when the kill switch is in KILL position, but the switch is in RUN.

The basics:

1.  Good spark
2.  Plugs have fuel on them when I pull them out
3.  Good compression (thumb on sparkplug hole test)
4.  I haven't done anything to the bike since I last rode it
5.  The points aren't loose and haven't rotated from their original position
7.  There's plenty of gas in the tank and I have clear fuel tubes so I know it is reaching the carbs.

Other info:
1.  Starting fluid was no help (sprayed through the air box without the filter and also into the vacuum synch ports next to the head)
2.  Like I said, it sounds like the Kill switch is in Kill position but it's not and I have really good spark.

------

The bike was running great.  I just went out one morning and it wouldn't start.

[harisuluv]

When the kill switch is on, basically nothing happens.  What do you mean by "sounds like" the kill switch is on.  In other words, there is no sound that would come from the bike with the kill switch on.  How can the bike "sound like" something that has an absence of sound?

I am aware of your points in your original post, however, with those things which you think you have, the bike should run.

[MandEms]

When the kill switch is on, basically nothing happens.  What do you mean by "sounds like" the kill switch is on.  In other words, there is no sound that would come from the bike with the kill switch on.  How can the bike "sound like" something that has an absence of sound?

I am aware of your points in your original post, however, with those things which you think you have, the bike should run.

Well, the bike, even with the Kill Switch in the Kill position, the bike starter cranks the engine.  That is what the bike "sounds" like.  Cranks, but no fire.

I agree, it seems like I've got everything.  Obviously, I don't.  But this issue suddenly developed so I didn't want to change too much from the set up I had since that set up was working fine.

[harisuluv]

I think that you're right and the starter will turn with the kill switch on.  However there shouldn't be spark.  Sorry, I was thinking "ignition switch" instead of kill switch.

I would still advise you pull the plugs, take pictures of them, and then squirt starter fluid in the cylinder.  If nothing changes, it would seem that it's not a fuel issue.

[Deltarider]

Maybe, I have missed it, but did you check the timing yet? Can be done statically in this stage.
Did you have the advancer apart and possibly have assembled it wrongly? There is a tiny carve in the rim of the cam of the advance unit. Make sure that after reassembling the tiny carve (it is very small indeed) faces the little hole in the advancer unit. There is only one such hole and it's located where it says "TEC". That's the correct way for assembly. Indicated with a white circle in the picture below.

[Restoration Fan]

Do a simple test: use a multimeter and confirm you have 12v at the coils (measure the BLK/WHT wire with the key ON, and KILL set to RUN). If your bike is cranking and you have fuel, and this happened "suddenly" I'm betting the KILL switch has flaked on you or the coil power wire (BLK/WHT) is detached.

Please post the exact voltage reading at the coils. And the exact voltage at the battery from a meter.

This. If that connection has gone bad (either at the switch or at the coils), you're not going to get juice to the coils and there will be no spark.

I suppose it could theoretically be timing but the timing would have to gotten way off "all of sudden" as the OP stated and that seems unlikely to me.  If it was only off by a smidge you'd still get ignition, it just would run rough or would only fire intermittently.  He says he isn't getting ignition at all.

FWIW, my money is on the connection at the coil wires first and then the kill switch second.

[Deltarider]

He says he isn't getting ignition at all.

Didn't he say he had blue spark at all four?

[hedfurst]

Spark/Fire
Fuel
Compression
If you have all three it should run.
If it's flooded with too much fuel it won't crank, but if it was working well before and you haven't altered carburetor adjustments in any way then this is unlikely. If floats are sticking usually results in fuel leaking from the overflow tubes.
My bet is the timing, adjust the valves first and then set the timing. Culprit may be the plate the points are mounted on. I've had that problem before.
Fred

[Dino]

Check that the little brass sync port plugs in the carb barrel near the head are still there. One or more may have fallen out. Also check that all the throttle mechanisms are working properly. I think it's a fuel delivery problem.

[MandEms]

Maybe, I have missed it, but did you check the timing yet? Can be done statically in this stage.
Did you have the advancer apart and possibly have assembled it wrongly? There is a tiny carve in the rim of the cam of the advance unit. Make sure that after reassembling the tiny carve (it is very small indeed) faces the little hole in the advancer unit. There is only one such hole and it's located where it says "TEC". That's the correct way for assembly. Indicated with a white circle in the picture below.

Thanks for the feedback everyone.  I'm just now getting back to this and I don't have a lot of time to work on it.

Deltarider, thanks for the pic on the spark advancer.  I have cleaned it up and assembled it according to your pic.  Sorry, forgot to check the position before I disassembled.  Should I shorten the springs while I'm at this point?  The advancer returns fully to the idle position now with the springs as I removed them.  After I cleaned everything up.

Like I said, I don't have a lot of spare time to work on this, but when I get things back together I will make some videos and try to cover everyone's questions above.