Spark-check...Compression-check...Fuel-oh Yes...no ignition on #3/4

[BigD_83]

It runs again!

I pulled the carbs off this weekend and the float bowls were not totally clean of crud. In fact, there was an odd green/white residue in there that looked a bit like oxidized copper. Someone on another forum (or another thread?) had previously pointed to Seafoam as the cause...not sure about that, but I DID have Seafoam in the gas over the winter along with a bit of Stabil. Maybe a little bit of additive overkill.

After cleaning up the carbs again and making sure I had carb spray coming through every orifice, I bench synched them again and put them back in tonight. Of course, in my enthusiasm and surprise that they just popped right in I forgot to get the throttle cable hooked up. They have to come off again for the new throttle and choke cable on order, so I'm going to worry about it later.

With a freshly recharged battery I primed it, took the electric start through 3 cycles, and it fired up. I turned it off, let it sit for a while, and it started up again.

The new issues that have arisen are:

1. a hanging idle. A first for this bike, but I think the middle two airbox boots aren't quite seated

2. Backfiring on decel. Also (sort of) new. This could be related to #1 and/or #3

3. I wasn't getting any fire on #1 cylinder. This was evidenced by a cold header pipe and removing the plug resulted in no change in the firing pattern. The plug had previously given spark when grounded to the cooling fins. I swapped the lead with #4 cylinder and presto chango...ignition on all four cylinders. This also seemed to quell the backfiring. At least the one burble I got wasn't as violent as the first series when I didn't have fire in #1 cylinder. My diagnosis is that the plug cap is cracked, as it is a trifle shocky when touched while one's knee is grounded to the footpeg . I have new ones in the garage waiting to go on to test that theory.

The current battery numbers are:

Key OFF: 12.86V
Key ON: 12.70V but steadily dropping
~ 1500 RPM: 12.84V
2500 RPM: 13.79V

didn't dare go higher than that with the backfiring/hanging idle.

The new petcock MAY have issues, but I'm going to hold off on saying that is definitive until I get a full tank of gas in there.

When the bike was running for awhile with the petcock ON, it would eventually die (vacuum line to #2 is hooked up) and not restart. Turned it to PRIME again and it would start right away. This is a brand new Suzuki Genuine Parts petcock from Boulevard! It would be a shame if something is wrong with it.

I now have to pop rivet the baffle into the cone, and I'll be ready to vacuum synch it, and give it a road test.

[TheCafeKid]

So were you doing this without the baffle in the pipe? That'll certainly cause some popping and such...

[BigD_83]

So were you doing this without the baffle in the pipe? That'll certainly cause some popping and such...

Sorry. That wasn't what I meant, but I get why you read it that way.

To be clear, the baffle is in place, just a friction fit for the moment as I do not have the tools to pop in the rivet. One backfire had enough pressure to pop the cone out of the megaphone. but not strong enough to shoot it onto the floor. There is less friction and more pressure than I thought

[BigD_83]

Aargh!

2 hours later and it wouldn't start again. Cranking voltage across the battery terminals starts at 11.07 but quickly drops off to 7.77.

Looks like this battery may not make the cut.

[BigD_83]

I tried another fresh charge and got a couple of chuffs out of the engine but nothing after that. Switched batteries by pulling a good one out of another bike and no firing at all. I'm now less convinced the battery is the issue.

Next up will be a car battery (without the car running of course) and then I'll start exploring other potential problems.

Any suggestions as to what path to go down considering all of the information I've doled out already? Coil tests? Last time the resistances checked out fine and I've done nothing to them since.

[tom203]

Yeah, try another battery or non running car- you likely need 9 + volts at ignitor to keep it happy ( this is what I measured at my ignitor plug during cranking with weak battery), so voltage at battery better not drop below 10.
I know it's redundant but after you recleaned the carbs, did you poke and blow out that liitle hole in bottom of each fuel bowl ? I don't understand why it's failing to restart after a few hours off- should fire up asap with "choke" applied.

[BigD_83]

I did clean out the pickup from the bottom of each bowl and blew them out with carb cleaner and compressed air. The carbs did not warrant a full strip and dip.

If I can't get it to start off a car battery, then it's time to pull out the multimeter yet again and look at what is happening at the coils. The spark looks great when it is grounded on the head, but, you know the thing about assumptions...If it is just a really weak spark despite the blueness of it, then I'm draining the battery by cranking the engine over repeatedly, and there we go through the revolving door...

It does "huff" the first time and if it catches will run. Once I get it running I can determine if I am getting fuel flow out of this new petcock.

[BigD_83]

One more thing I just thought of...

One of the mounting bolts on the 1/4 coil is loose, with a stripped head. My understanding is those bolts also serve as grounds for the coils. Is that correct?

That is the only "new" thing in the ignition system since it was last starting easily and running well.

[tom203]

One more thing I just thought of...

One of the mounting bolts on the 1/4 coil is loose, with a stripped head. My understanding is those bolts also serve as grounds for the coils. Is that correct?

That is the only "new" thing in the ignition system since it was last starting easily and running well.

What is "new" thing ? Anyways, no, coils are grounded thru igniter (primary) and engine via plugs.
After a start attempt, are your plugs dry? I looked at my spare carb set closely and discovered that the copper pipe that sticks down into fuel bowl for enrichment system has a tiny hole ( .020 inch ?) that fuel must pass thru; if your carbs were at one time really gunked, this hole might be plugged preventing a shot of fuel from climbing into carb body. In addition, there is a crossdrilled hole in this pipe ,just before it hits carb body- I'm not sure of its purpose, but it must add some "bowl" air to the fuel traveling up pipe.

[BigD_83]

The "new"part of the equation was the loose, stripped mounting bolt. I'm not sure where I got the idea that it provided a ground, but it was the only thing between the battery and the spark plugs that has changed.

I just didn't have the patience to pull the plugs last night to see if fuel is getting through to all of cylinders. It is/was getting to #1/4 though. You might recall from our earlier discussion that I was getting gross flooding on #4 before as well.

The ever-powerful multimeter comes out tonight to check primary and secondary resistance to eliminate that as a cause of no ignition.

If that still isn't the answer, and the plugs are dry, then I'll do another strip and dip, but my spidey senses tell me that is not going to be the answer.

Honestly, I'm getting pretty efficient at at taking the carbs off and back on. I'm afraid the boots/boot clamps might start to get a little stressed however.

[tom203]

This thread is getting so long that I don't remember much, but if flooding was due to bad petcock or needle seats that's a different matter. That stuff is fixed, so question now is.... after cranking for a while with choke on and no starting success, what do plugs look like? I've been under the impression that as long as enrichment system can deliver fuel to carbs throat (and you got spark at right time), bike should fire up, though other carb issues might cause it too run poorly.

[BigD_83]

I'm definitely getting fuel into the intake boots. Timing shouldn't be an issue as I haven't done anything to the cams, cam chain, or tensioner. I just took the engine out and put it back in...

I'll check the plugs tonight, and that ought to give a better idea of what is happening? It could be a piece of crud that is somewhat loose in a passage, but that would only affect one cylinder, not four simultaneously.

Yup, a real head scratcher this one. My bets are still on electrical.

More later.

[BigD_83]

I managed to get to the bike this evening. At first, I tried (again) to start the bike with a freshly recharged battery. It turned over, "huffed" once, and then no further sounds of ignition. I grabbed a car and tried again by jumping off the car battery with no love. Not even a huff or hiccup...just no fire in any cylinders.

I pulled the plugs and #s1, 2 and 4 were wet with gas, and 3 was a little drier than the rest, but there was still some gas.

I tested for spark again by grounding the plugs to the head. This time...no spark on #s 1 and 4 but strong spark on #s 2 and 3

I swapped the leads and no spark on #2/3 but some spark on #1/4.

Got to doing some reading this evening. Could all of this be symptomatic of fouled plugs? How much oil/carbon would have to build up on a plug to foul it? I did run the bike at idle /- for about 15 minutes before it wouldn't start again.

[tom203]

Well, I'm convinced that you got enough gas in enough cylinders to fire! But this weak or non existent spark is strange- doublecheck coil and ignitor connections; ohm the coils, if stock should be about 4 ohms primary; as I recall, secondary should be about 12kohms lead to lead (caps removed)
"idled for 15 minutes " ? on all four before no restart?

[BigD_83]

Oil fouled?

Well, I'm convinced that you got enough gas in enough cylinders to fire! But this weak or non existent spark is strange- doublecheck coil and ignitor connections; ohm the coils, if stock should be about 4 ohms primary; as I recall, secondary should be about 12kohms lead to lead (caps removed)

The cap resistance was 5 Ohm, I couldn't get a reading on the secondary (a 1 on my meter = OL) in any range on the DMM on the left (1/4) coil, but this might be an issue with getting poor contact with the probe. That coil is suspect anyhow, as back in the fall, the key was left on and that coil overheated.

"idled for 15 minutes " ? on all four before no restart?

Yessiree...all four cylinders. One run of 5 minutes and a second run of 10 minutes where it started to struggle and then died/wouldn't restart.

I did a search for fouled plugs, and although mine are definitely NOT gas fouled, they do have a shiny-black oil-fouled appearance, especially on #1/4. This might go back to winterization. I used fogging oil back in December when I put the bike away. I can get some pictures up later.

This forum is great. "Fouled Plugs" brought up so many threads that I now have a better idea of where I'm going with the trouble shooting. I'll have to pick up a new set of plugs first, and then back to it sometime Sunday.

Thanks for the ideas Tom. Don't you just want to get your hands on someone else's bike sometimes?