cranking hard, getting spark, not starting

[Junkie]

Well this is the third time this has happened so far. I go out to start the bike and it just won't start. It cranks well, when I pull off a plug wire and put a plug in to check that it's getting spark it is, and there's fuel getting to the carbs. However, I can crank away for as long as I want and the bike just doesn't start. Every couple cranks I hear one cylinder fire, but that's it.

The two previous times when it started up it started running fine, like nothing had happened. The first time I didn't do anything to it, and it took far more cranking than it should but probably a minute total. The second time, after basically draining the battery (hooked up to a charger) I pulled the gas tank, lifted it up, tilted it around a bit, put it back down, and it started up fine. It had been on prime, but I assumed fuel hadn't been getting to the carbs for some reason and that this fixed it.

This time, it's seen a LOT of cranking, and fuel is getting to the carbs - I tried pulling the tank, and that didn't fix it.

Any ideas?

thanks


edit: oh, and I'm smelling a small amount of fuel when doing this but not a ton, if it matters. the vacuum actuation of the petcock works fine (did a few weeks ago at least - no fuel flow when it's off the bike), and the petcock is set to prime. the fuel hose has fuel and no air bubbles in it.

edit2: when it starts normally, it takes maybe 2s of starter - ie not much.

[Junkie]

So it was cranking fine even though the posts were corroded? Hmm. I'll try that, thanks.

[RJz1100E]

Yes but I'm not sure this is your problem. I did'nt kill the battery but I lost all power to everything all at once before I found the corroded terminals.
Sorry, I deleted my other post because I was thinking that your problem may be something else but, I would check all your electricals.

[Junkie]

Yeah, I cleaned up the terminals and it's acting exactly the same. The crank speed might be slightly higher, but that also might just be that it's been sitting on the charger a little bit without me cranking it.

I had one terminal loose at one point and it would sometimes go click and not start and kill headlight power too, but that's not the issue.

[spyug]

As suggested, make sure you have good contacts and grounds. Even a little bit of corrosion can stop the bike getting sufficient voltage to spark and crank. The same thing has happened to me a couple of time. Start by cleaning the battery terminals and make sure the ground wire from the battery is making a good contact to the frame or motor or whereever connected (different on some bikes).

The other thing to wonder about is the battery itself. If it takes a charge but dicharges quickly it may be defective or on its way. These bikes will crank but not fire if the battery voltage is around 12.5v or less. I also have had this problem. The battery will take a charge to 14.5+ volts but will drop in minutes to 13 or so. Crank it in the bike and within a minute or two its down to 12.5 or so and the bike turns but won't fire.

If your getting juice to the carbs then the problem is going to be electrical despite the apparent spark.

Check things over and if you can try another battery. Once you get it going you should have a look at your charging system as there could be a problem there also. Read the stator papers for a good overview.

Good luck,
Let us know how it works out.
Cheers,
Spyug.

[Junkie]

Well it cranked it fine for probably a full 60s (not continuous, I didn't want to burn out the starter) so I doubt it's the battery. I'll try jumping it off a car battery (not hooked up), hopefully that'll work.

Oh, if it matters but it might just be luck: all 3 times the bike has been cold. The weather has never been warm, but one of the times it was probably mid 50s F so it wasn't that cold, either.

[Junkie]

When actually cranking, the voltage drops down to a hair over 11v even - 11.1 or so. However, when I left off the starter it's back up to a little bit over 13v.

[RJz1100E]

It does matter a little about the cold, each bike most likely has a personality of it's own as far as that goes. Mine is a little cold blooded. That being said, she fired up with out too much cranking last week after sitting idle in a unheated garage since the middle of November without even having a tender hooked up to the battery at all. Yours should fire up in 50 degree weather, somethings not right.

[Junkie]

I agree that something's not right. It's more like 35 degree weather right now, but I mentioned the temperature the other time to say that it most likely wasn't the weather.

There have been a couple times (a week ago today) that I've started it up in just about the same weather with a short push of the starter button. I mean, it required full choke but it certainly started.

[RJz1100E]

Have you pulled the plugs to take a look at them as soon as this occurs?

[Junkie]

Nope, I haven't yet pulled the plugs. I don't really see how a carb issue could be quite this intermittent though... I mean, once it starts it has no problems at all.

[RJz1100E]

Disclaimer: I'm still a novice at working on my bike. I don't know a whole lot about this stuff. I'm just thinking in the simplest of terms.

Air, fuel, spark, are what I usually check first when I run into a motor that cranks but won't start, whether it be a car, bike, or lawnmower and I always look at, clean, and regap the plugs when I do run into a problem like this. It could be a whole nother issue but I always check the 3 basics first. Then you delve into things like is it getting too much fuel? Are the plugs bad or fouled? etc etc.
Someone with a whole lot more experience than I is sure to come along with better advice. I bet it's something simple bud. Patience.

[uudfourty]

I read somewhere on here that blowing into the vent tube between 3 and 4 carbs before initial cranking will usually help. I know it's treating the symptoms and not the disease, but it works. So I'm told.

I have a woodscrew in the side of my airbox and a can of ether with a spray straw in the bag.
Works every time.

[spyug]

When actually cranking, the voltage drops down to a hair over 11v even - 11.1 or so. However, when I left off the starter it's back up to a little bit over 13v.

As I previously mentioned these bikes will not fire with voltage under about 12.5volts. If the starter is drawing down to 11v there is nothing available for spark. The fact that it drops so low and returns quickly to 13v makes me also think you have something putting a big draw on the battery in conjunction with the starter circuitry. Maybe some shorting / bad connection at the starter switch. Starter/kill switches are known to cause these kinds of issues on some bikes ( Yammies for sure). I'd clean the contacts on those switches.

There can be any number of things in a wiring harness which can cause problems with electrical systems but the most common are bad/corroded connections and grounds and broken or bared wires. I think you will need to start looking closer at your wires and connectors. Anything chafed or exposed? Any lose connections? How are the fuses and fuse block?

It can be time consuming and frustrating to track these things down but if you go about it logically you will sort it out.

Bye the bye, I don't think the cold is causing you the problems but to test this warm the engine up for a few hours. Setup a 100 watt light close to the engine block or better yet a heat lamp or halogen spot. If you can put one lamp on either side. Fully charge your battery. When the cases are warm to the touch give it a whirl and see what happens.

Also resist the urge to use ether as a starting fluid a bit too much and you can blow off the head. If you don't think gas is getting to the engine try spraying in a little gas either through the carbs throats or directly into the cylinders via the plug holes.

Keep us informed of what transpires.

Good luck,
Spyug.

[Junkie]

Well, I waited a bit (with the bike on the charger), went back out, hit the button and it started right up. It had been on full choke (at <40F and a cold engine it needs a decent bit), and when I tried to turn it down it didn't (I had the choke stick once before, but once the engine was warmed up it released fine). I turned the bike off so it didn't rev insanely high, walked it out to the street, started it again, and rode off. Got to school (20 minute ride), parked, went to class (very late of course). Came back out, started it up (no issues), went to the gas station, filled the tank. Started it up without an issue. Went to Kragen to grab a new vacuum hose - the petcock one was in very poor condition, I had a bit of a vacuum leak (not all that bad). Replaced the hose, started the bike again. All of these times that it started it was very easy - a quick (<2s certainly) press of the starter and it started right up.


The voltage was being measured with a multimeter directly on the battery terminals, so it wasn't dropping due to dirty terminals - that was the voltage the battery was putting out. I suppose something else could've been putting a large load on it, but don't know what could've. I guess I'll be digging through the wiring harness when I have the time...