Starts first time and third time, but not second time

[wilee]

My 2005 GS500F starts just fine the first time (40-50 F air temperature), runs well.

After I park and come back, it won't start the second time unless I twist the throttle a bit, rather like with a pre-FI car.

Park again, come back, starts easily the third time with no fuss.

Anyone have an idea why? Started happening in last month. Only work I've done lately is brake lines and tires.

Haven't tested the battery recently, but it's on my to-do list.

[Numewsm]

Gs's are tempermental once warmed up and left off for a bit.  Sometimes they'll start first time on their own, and other times they are grumpy and need a bit of choke or throttle. 
There's no rhyme or reason for this, it's just the nature of the beast!!   

[mr72]

should start with choke whenever it's been sitting longer than about an hour, should never want to start cold without choke.

never use throttle to start it.

to the OP, I think the thing you are seeing is maybe the bike is just not warmed up for the "second" start. Does it start ok the 2nd time if you use the choke? If so, problem solved.

[user11235813]

@Mr72, I've never needed choke but it is very warm here. Fires up and idles at about 950 every time and warms up to 1100.

[mr72]

@Mr72, I've never needed choke but it is very warm here. Fires up and idles at about 950 every time and warms up to 1100.

Then you most likely have the pilot mixture way too rich.

[wilee]

Thanks for the replies. I use choke every time to start, too cold out otherwise.

The bike hasn't run long enough for either second or third start to warm up much; maybe 2-3 miles each leg.

I might buy that the battery is just strong enough to start a cold bike once, but not a second time, and it's all warm and charged enough by the third starrt to work properly.

Or that might be total nonsense. Bike has gone 5 miles or less by the third start.

We'll see when I get a chance to bring the battery to a store.

I agree, mine at least is temperamental. Sounds odd until it's warm, but runs fine aside from this. Once it's warm, sounds and runs great.

[mr72]

Thanks for the replies. I use choke every time to start, too cold out otherwise.

Has little to do with air temperature unless it's like 170F+ outside. It has more to do with atomization.

The bike hasn't run long enough for either second or third start to warm up much; maybe 2-3 miles each leg.

Yeah it will usually take 15-20 minutes of riding on the road to fully warm up. But 5 minutes is usually enough to run with the choke off.

I might buy that the battery is just strong enough to start a cold bike once, but not a second time, and it's all warm and charged enough by the third starrt to work properly.

Well, you didn't specify that the problem was that the engine won't turn over on a 2nd start, but that it is hard to start. Those are entirely different symptoms. But anyway, a 2-3 mile trip is not enough to recharge the battery period. Two of those trips are not enough to recharge it either. If you are only taking 2-3 mile trips every time then you really should consider using a battery tender. The stock charging system is just barely adequate. The battery, when fully charged, will probably start the bike 10-20 times or more without having to be recharged, but if you take only very short trips between starting it then after 10-20 trips it's going to be pretty iffy to start it.

So which is it? Is it not turning over, or is it turning over fine but not starting?

Anyway, try it with the choke. If that fixes it, then you have found your problem, just need to tighten the nut on the top of the seat  .

I agree, mine at least is temperamental. Sounds odd until it's warm, but runs fine aside from this. Once it's warm, sounds and runs great.

No more temperamental than mine is. From everything I've heard and read, GS500s are notorious for taking a long time to warm up and being funky when running cold.

Now, if it turns out that it's not just that you need choke when starting, well there is a long list of other stuff to check.

[wilee]

I use a battery tender, start with choke every time. In neutral, kickstand up.

The battery passed a test at the auto parts store. I obtained a new multimeter, so time for some diagnostics. May as well look into the dodgy neutral light while I'm at it.

And the throttle play, and the clutch play, make sure the fasteners are tight enough. Wheel drags a little, maybe clean the front caliper. Where did my weekend go?

The nut on the seat typically requires only a few gentle thwacks to get it un-stuck. It's custom, made-to-order, not yet technologically feasible to replace. Some day...

[mr72]

I use a battery tender, start with choke every time. In neutral, kickstand up.

In that case, I think I'd check these things (in order):

- vacuum leak, particularly the vacuum hose going to the petcock or the petcock itself. Theory here is that the petcock is not opening fully and you wind up with low fuel in the carbs after one short trip, but as things heat up and expand the vac leak gets better and petcock flows better. To check, try starting it on PRI for that 2nd start which normally gives trouble. If that shows petcock issue, then sort out whether it's petcock or vac leak.

- vacuum leak ... other than petcock hose, like especially the intake boot o-rings or missing "little o-rings" (if you have a Mk1 GS500) under the diaphragm cover vacuum ports, or missing/cracked/leaking vacuum caps on those ports, etc.

- the other way, floats too high, perhaps flooding on 2nd start. cause of this would be sticking float needle valve(s).

- compression ... valve clearances on spec?

- air bubbles in the fuel lines? are they transparent so you can see?

That's all I can think of for now. If it was me and I was determined to fix this, I frankly wouldn't bother trying to diagnose carb issues. I'd just pull them off, replace all the o-rings and float needles, clean them thoroughly, put back together and do a righteous idle mixture adjustment, then see where I was at. It's just easier to do this $30 fix than to diagnose. This is a 2-hour job and at least you know the carbs are not the problem. Along the way you'll discover if you have a bad vacuum hose or cap or whatever. To really do a bang-up job of this also replace the intake boot o-rings if they've never been done, and careful those are kind of a special order part. Might as well bump the pilot jet up a size if you haven't already while the carbs are apart. There, I just turned it into a $50 job, but worth the peace of mind.

If it still misbehaves after that at least you have ruled out everything carb related. Move on to valves, ignition.

[wilee]

Life got a little bit in the way. Thanks for your replies before.

I'd been through the carbs the summer before, replaced consumables, replaced rubber fuel and vacuum lines, replaced engine intake boots & o-rings. Did valve cleareances, too.

Float height seems okay per the wiki's instructions.

The air temperature is warmer now, and I noticed that I overfilled oil. Unsure whether this helped, but after draining a bit, it seemed to improve.

Now if I keep the starter button down, it may require the starter motor to intervene once (or, rarely, twice) sometimes, but otherwise starts right up. I have to wonder whether I was too hasty to let go of the starter switch earlier when the engine seemed like it was good to go.

Of course, now that I've started riding on the highway, I notice a lot of buzz... but that's another topic.