Motorycle not starting...ideas?

In My Humble Opinion
1

2007 Honda Shadow 750 (V2?).

Symtoms: It cranks, it’ll ‘catch’ a few times, but when I take my hand off the starter (or a few seconds after) it dies. One time it ran at very low RPM for about 10 seconds, then died.

It has two cylinders and 4 plugs. I did pull one of the spark plug wires and the wire itself has power (I stuck a screwdriver in it and spark jumped from the screwdriver to the block. That’s not to say that the other three work (but I’m guessing they do) or that the plugs themselves are good, but it’s as far as I could get in that direction. The plugs are fairly deep in the heads and my regular spark plug sockets wouldn’t get to them. It appears that I need to get some thin walled spark plug sockets, nothing I had (sparkplug sockets or regular sockets) would get down there.

It could be a clogged fuel filter, bad fuel pump or clogged fuel strainer…however, it should be noted that each time I tried starting the bike, I could smell gas, so there is gas flowing (how much, I don’t know, but gas is is moving). Just glancing at it right now, the filter is too buried in the bike for me to test that theory at 11:00 at night. My plan was to pull the fuel line after the filter and ‘start’ it to see how much gas comes out, then put the filter back on and do the same thing. If there’s a noticeable difference, I’ll replace the filter. I may have to get a bike stand/lift to do this as getting ‘under’ the bike is very low to the ground.

It could be a dirty air filter, but I doubt it, the bike started right up the last time I used it (even if that was a while ago).

My guess is that something is gummed up in the fuel system. Either the filter or something with the carb.

The battery tests at (off the top of my head) over 12V and doesn’t fall below (again off the top of my head) 11V while starting, so I don’t think that’s the case.

The other possible issue is that it’s old gas. At the end of each season, I do add some stabilizer (I think I used Seafoam last year), let it run for a while, then shut off the tank and let it die, the next season, I put as much fresh fuel in as I can. It’s been a while since I’ve ridden it (several months), so while that’s a possibility, I don’t think it’s the case.

Here’s a short video of me trying to start it a few hours ago.

Also, if it makes any difference, it wouldn’t start when I flipped it over to reserve either.

What I should probably do, before I’m elbow deep in carburetor repair and draining the tank is get some ether, that may help isolate the problem to being a fuel issue or an electrical issue.

I could probably attempt to start it with the air cleaner removed just to see if that makes any difference.

2

I agree with fuel system problem. Let “new” (hey, all my shit is 30 years old, except the '01 Kawasaki which does exactly what yours is doing every time I go to start it) bikes sit around, without draining the carbs and you have hard starting issues.

You gotta run those carbs dry, every time!

My only advice is probably bad, but here is how I get my stubborn iron horses running:

Pull plugs, shoot Starting Fluid into the holes, reinstall and fire. Repeat as needed. My Kawasaki has a double cable throttle (actually, many of them do, but I shitcanned most of them), and I actually have to twist it “closed” when starting it after it sitting for a while. (Hey, don’t judge me, I got a lot of bikes! Some sit for a while!)

Once running, put in fresh gas. But ALWAYS run that carb dry after every ride. I’ve got bikes with vacuum petcocks, and have to pull the line to do this. But they always start after sitting.

Good luck. I’m 20 years out of date, so take this for what you will.

I was in the motorcycle business way back when, and since then, I’ve heard they are starting to use plastic carb floats that cause a lot of grief. Might look into that, too.

3

Smells like a fuel problem most likely. Can you get at the carb jets?

4

Probably…I’m not sure where it is. I would expect it to be behind the air cleaner, but a few seconds of googling suggest it may be under the tank. So there’s the “I’d really rather not pull the (full) tank” but on the other hand the “I can fix anything” mentality that I have. Mind you, not in some ‘I’m a man, dammit’ way, just that I tend to be pretty good (errr okay) at fixin’ stuff. And there’s plenty of resources on the internet.

As far as pulling each plug and shooting ether down there, wouldn’t shooting it in the air cleaner do the same thing…Well, now that I think about it, if there’s a problem with the carb, I guess that would still be an issue, but it may be a start. (and come to think of it, on preview, I’d only have to pull one for each cylinder, right?).

I really wish I could have yanked those plugs. I may have to see if I can run out to Lowes/Home Depot or an Auto Parts store and see if I can find some kind of thin walled spark plug socket. Like I said, my regular ones can’t get all the way down, they’re too ‘thick’ and get stopped. Which also means I have to guess at which size socket it is, though I’m fairly sure it’s 13/16". But, I suppose, I could just go ahead and figure out which plugs it needs. As long as they’re out, might as well stick new ones in right away.

Also, I should probably bite the bullet and pick up a lift while I’m at it, my (ex) BIL suggested it to me years and years ago. I have to/like to get my bike into a really tight corner at the end of the season and he always told me I should grab a lift from Harbor Freight for a hundred bucks, the kind that has wheels on the bottom. Then I can just pick it up and put it where I need it instead of spending ten minutes swinging it back and forth so it’s against a wall (and doing the same thing to get it back out.
This also makes sense for oil changes. I did it once on my own. It was such a PITA, I took it in after that (and the cost was actually reasonable, I think), but the reason it was so difficult was because of how low to the ground the bike was. I could just barely get an oil pan under the bike, I almost didn’t have enough space to get an oil filter wrench down there, and above and beyond that, trying to pull the bike upright with one hand so you can check the oil level with the other, I’m not gonna lie, that made me uncomfortable. I knew, full well, there was a real chance I could pull it over on myself if I wasn’t careful.

5

(replies in order)

Jets are in the carb.

No.

A “lift” is the fastest way to drop the bike and dent the tank. You sound kinda new to this bike thing.

6

Re-reply, think there may be some miscommunication. But I think we basically understood each other.

I familiar with working on cars, though they only carb I ever took apart was the one on my snowblower ('twas a learning experience taking that apart and cleaning it when it wouldn’t start the first time it snowed, now I make a point of started it a few weeks early each year). But even with all the time I spent helping my dad work on cars growing up (we had quite a few vehicles), I never did any carb work.

Having said that, I’m not that new to the bike thing, I am new to any real repairs on the bike. I’d prefer to learn than hand someone hundreds of dollars to tell me I have bad gas or mice living in exhaust pipe (headsmack, keep meaning to check that one). Also, just skipping quickly through a few Youtube videos, it looks like gaining access to the carb requires pulling the tank. Looking at the service manual that I have pulled up for it*, it implies I can pull the tank with it still full, which makes that a much less daunting project. Honestly, it was emptying the tank that I didn’t want to do.

A few more things before I actually have to start getting ready for work:
1)the *footnote, before I forget. I should probably pick up the actual service manual or a Chilton/Haynes type book for the bike. I was going to just print out the manual I’m working with, the the pictures are awful. It’s this manual (fair warning, I have not made 100% sure, it’s my exact model).
2)Again, I have no problem learning how to work on this stuff. I don’t ride that much, so the bike being out of commision, while I figure something out isn’t a deal breaker.
2b)I have a mechanic AND the place I brought it from works on bikes (and tows them), so it I really mess up, I’m probably okay.
3)General question about the fuel system. I recall once when I had the air filter off, I turned the throttle and notice a small port in the air box squirt fuel up. Any idea what that would have been?

There’s another question, but I need to check on something first to make sure I wasn’t reading about parts for a different bike first…something about a sub-air filter.

7

You have spark, you have initial running - so whatever it is should not be too serious.
Seems to me like its starting on the pilot but the main fuel is not being supplied.

Pilot bypasses the carbs, so if there is no fuel in the float bowls it will die just like this.

Does it have a vaccuum operated fuel cut off? The diaphragms can perish - might be worth having a look at the tank fuel cock, easy enough to take apart.

You might also check the vacuum tube that runs from the carb air inlet air line - makes sure it is still attached and that the air lines are not cracked and letting in air.

One way I found to prove this is to take the vacuum tube off the carb line end and either suck or blow on it - and try start. If it does not then you might be looking at the diaphragm - if it does start then its got to be a hose issue.

8

Fuel system somewhere. And while it may not be easy or even possible for you, reading this makes me want to suggest a professional mechanic/shop or a friend who does his/her own builds. Most of the problems are easy finds and easy fixes if you have the tools and experience. If you don’t and botch the job trying to DIY from a YouTube video, it could get real expensive really quick.

And in the future, use a stabilizer in your gas. Hondas, in my experience, get kinda cranky with the E-10 or better gas you get these days. Especially if its going to be parked for any lengths of time.

9

We have a place that sells ethanol free gas (of course, more expensive). That’s what I put in all my motorcycles, small engines, and portable gas tanks. Still have to drain the carbs though before they sit for long.

Good luck - I’ve got a similar problem with an old Yamaha. But, dead battery. I spend a small fortune on replacing motorcycle batteries it seems (I have 5 motos - need to sell off one). Why are they so expensive!?!

10

I know nothing about motorcycles, but I have to ask:

Gas in the tank?

11

I had a similar problem with my carbureted bike. Took it to the bike shop and had the carbs cleaned, and it ran fine after that.

Or at least I think it still does. They might be gummed up again by now.

12

A lot of possibilities in this post.

I’ll add that it sounds like the diaphragm in the petcock, because as soon as it gets vacuum, it stops the flow of fuel. That’s kinda silly though, because the diaphragm should let MORE fuel in when the engine’s running. But the timing suggests this. I’d discount it and move on, but it’s worth noting (or nothing :))

I agree that it could be a jet/passageway. It seems that the pilot jet or passage is what’s clogged b/c it won’t idle. The OP “pumps” a little fuel in there with the throttle, it starts with that, then won’t maintain b/c the pilot won’t let any fuel in there. OP, can you keep it running if you open the throttle at all?

And also check the air INLETS that **casdave **is referencing, including (long shot) the carb bowl breather tube. You said the bike’s sat a while; bugs, muddobbers, etc may have clogged that inlet.

MC carbs are, IMHO, incredibly simple to understand and fix. Getting them on/off the bike is another job altogether.

13

Looking back on this, I has not noticed the bike had been stood a while.

I would make a fuel change a high priority, its easy to do and I have had this problem with all sorts of small engines. If its poor fuel then it may start initially but as soon as the timing advances it cuts out.

14

A lot of suggestions here, but instead of starting with what’s most likely to be causing the problem, give some thought to what’s easiest to check. As you mentioned, you could pretty easily check the air filter by removing it, then attempting to start. If that fails, but while you still have the filter out, try again after spraying in some starter fluid. If this gets it running keep in mind that the underlying issues remain, but a running bike is always better than the alternative.

15

There’s a ton of ideas in here that I have to pick through more carefully when I get home from work. Just based on the used to run fine/doesn’t run now thought, my head still says that it’s a problem either with old fuel or something somewhere gummed up (as opposed to an air intake problem). However, since my schedule is tight and it gets dark early, I’m going to try to stop off after work and grab a new set of plugs, a socket that can get down there and some carb cleaner and ether. At least that way, I have something to work with once it’s night and I can’t leave the house since my daughter is in bed.

I think I have a siphon around here (at work) somewhere. I should grab that and suck out the old gas and use the gas from the tank I’ve been filling my lawnmower with. That’s from this summer.

Even if I don’t dismantle the carb, I could probably go ahead and use that time to pull the tank and see what I can see (cracked lines etc). I know that I said it looks like I can pull the tank while it’s full, but I might as well to it for the first time while it’s empty rather than when there’s 20 pounds of gas in it and I have no idea where or how to set it down.

16

OP, can you keep it running if you open the throttle at all?

17

I’d lay money that your carburetors are gummed up.

Drain the gas (put it in a car since it probably isn’t all that bad, just a little stale. 3 gallons of stale gas in a 12 gallon tank isn’t going to be noticed).

Get some fresh gas, brand new, right from the pump. Ethanol-free if you can.

You said you have Seafoam. Use 2 oz (1/4 cup) per gallon. I’d just put one gallon of gas in your bike and eyeball a couple of shots of seafoam.

Crank it a while, so it coughs. Full choke. If it catches, give it as much throttle as it will take. Don’t crank for more than 30 seconds at a time or you might hurt the starter motor. Wait 4 or 5 minutes between cranks. Do this several times.

After it runs (or not) for a couple of minutes, if it will idle, see if you can ride it. If it won’t idle, let it sit for an hour to let the seafoam work, then try again.

I have a 2003 VT1100 Shadow that sat for 3 years. Doing the above got it running.

You don’t want to touch the carburetors if you don’t have to. This engine has one carburetor per cylinder and they have to be balanced. Banancing is tough since about the only thing you can do is balance them to vacuum (at least, I know of no flow meter to use to balance the air flow). The problem is, being only 2 cylinder, the vacuum bounces a lot, so balancing by vacuum is not easy.

If you can get it running, just run a few gallons of 2 oz per gallon seafoam and gas and you should be OK.

Of course, to put it up for winter, turn the fuel valve off (with the tang horizontal) and let it idle until it stops to clear the gas from the carburetors.
ETA: Oh, next time, don’t let the bike sit during the summer months, ride!

18

Does seafoam go bad? I should probably pick up some new seafoam, mine is fairly old, I use it year after year for the bike.

@shunpiker, no, holding the throttle (at least a little, I didn’t try cranking it wide open, but it was enough that I thought I’d be able to get it to catch) didn’t seem to make too much of a difference. You can see what I did in the video. Sometimes it seemed to help, sometimes not. It may have also just been that I was priming the engine a bit in some of those cases before I started it.

19

My money’s on gummed up carbs. The pilot jets are very small and clog easily, and it’s just about impossible to clean them without pulling the carbs off. It’d be a good idea to plan on changing out the rubber bits (o-rings, etc.) while you’re there, too.

I think your carbs have an accelerator pump, which would explain why it started after opening the throttle a couple of times.
Get a Haynes manual, if one is available for your bike, much better than Clymer, IME.
You could pull and clean the carbs yourself, and get a shop to adjust them for you, it’d be cheaper than having it all done and they’d be properly adjusted, which should be done periodically, anyway.
Checking Bike Bandit, looks like it’s only got one carb, so no need for balancing, yay. Just have to adjust the pilot screw and idle, easy peasy.
Next time you let the bike sit up, drain the carb too, it has a drain on the float bowl just for that. After draining the carb, crank it over a few times to suck any remaining fuel out of the pilot jets.
IANA Honda mechanic, but I do fix motorcycles for a living.

20

A shop can verify that but I don’t think they do. on my 650 Honda 4 cyl nighthhawk the carbs look like they’re variable venturi. They have staged metering.

A couple of things to consider. I can hear something mechanically kick back when then engine dies. Does it always make this sound? If not is your started not disengaging? Test for that is to push start it.

You said your voltage was over 12V. How much over? Put a meter on it and see what it does when it fires up. Mine is very sensitive to voltage drops and if it goes below 12 it turns over but doesn’t want to fire. Yours sounds like it’s hitting but at idle you may not be getting the voltage you need.

Can you rev it up to keep it running? I start mine with the choke off and rev it to 3000 and then engage the choke. That allows it to settle back down on high idle and choke but it fires easier. 3000 rpm on my bike is where the high speed jets kick in but it’s a totally different motor than your twin. It’s a 10,000 rpm bike so low rpm is a little more finicky.