Strange starting problem

[Guest]

I have a GS650G that ordinarily starts instantly with a slight amount of choke. However, if the bike sits for a week or more without starting (and this only happens with weather mandated situations) the bike just turns over with maybe one faint=hearted effort at firing, then nothing but empty-handed cranking. I can run till the battery is going flat, adjusting the choke in an out, it makes no difference. Not even a cough. Now for a clue........when I pull a spark plug in disgust and shoot in some starting fluid, replace the plug........BINGO! The bike fires instantly and idles smoothly just as if it didn't have a care in the world! I have tried switching the fuel tap to reserve and prime, no difference. I replaced the fuel petcock just a year ago. One other possible clue. The bike does have an aftermarket fuel filter that some PO put in and I have not removed for 25K miles. it looks clean. I can't figure out what a one week delay in riding is doing to the fuel system.

[Redman]

Perhaps you should suspect the battery. Next time it has sat for a week and will not start, put on a battery charger and try again after 15 mintes or so.

Maybe it seems to be cranking okay, so you dont suspect that battery, but maybe it really isnt and also the battery voltage is being pulled down enough that the ignition isnt working as well as it should, still makes a spark but not good enough for cold gas mix but just enough for starting fluid.

[mcloud]

Have you tried leaving the petcock on prime, and opening gas cap?

[physics-teacher]

I recall the open gas cap/prime working last year, but not this time. There may well be something to that battery idea. The battery is old and maybe it's time to replace. Or else ride every day as I'd like to!

[spyug]

+1 on the crap battery. Had the same thing with my XS last year.

I would change out the battery if its more than 2 yrs of age and you might do the coil relay mod for extra "oomph". Also, if you haven't already, you might clean and or replace your electrical connectors with special attention to your grounds.

These UJMs are notoriously plagued with electrical probs that often are as simple as making sure you have good grounds. With our nasty winters, I usually make this an off season chore.

Let us know how it works out.

Good luck with it.

Cheers,
spyug

[BassCliff]

Hi Mr. physics-teacher,

A fuel filter can be too restrictive unless it is designed for a gravity-fed system. If you must use a fuel filter, many report success with using a lawn mower fuel filter. I haven't had the need to use a fuel filter on my bike. I might also suggest dumping a half can of Sea Foam in a tank of gas and going for a nice long ride. Burn through the whole tank in one day if you can. This might help ensure clean carbs. I do that three or four times a year just for maintenance.

I agree with the idea of checking all your electrics too, connections, grounds, battery, charging system, etc. You might have a week spark at startup. The coil relay mod would help in that situation, provided there are no other major voltage loss issues in the wiring harness. Keep us informed.


Thank you for your indulgence,

BassCliff

[Steve]

Although you say it usually starts easily, another area to check regarding cold-starting ability is VALVE CLEARANCE.

If they are too tight, and they always tighten up, the bike will be very hard to start when cold.

It will also not hurt to check things mentioned above, like voltage at the coils (especially while cranking the starter) and voltage at the battery under the same conditions. A major difference between the battery and coil voltages will indicate whether the coil relay mod would do you any good. If they are within 0.5 volt, don't worry about it. If the voltage difference is higher, check and clean all the connections to the coils and measure again. If still high, do the mod.

You say that it gives one brief hope when trying to start after a week or so. Check your battery voltage about an hour after you park the bike after a ride. Check it again the next day and compare. Next time you let it sit for a week, check it just before you try to start it. If you see the voltage dropping much below 12.5, your battery needs to be replaced. Consider a sealed AGM battery (that's a type of battery, not a brand name). It will cost a bit more, but has higher cranking capacity and you will never have to worry about the electrolyte level.

Just be sure to properly charge any battery that you install before putting a load on the battery. Too many times, people will simply take a new battery from the store, where they are assured that it is 'fully charged, ready to go', and put it in the bike and hit the starter. Not good. By doing this, you are pretty much sealing the capacity of the battery at its present level, which might be as low as 80%, depending on how long the battery has been on the shelf. It is far better to charge with a charger that has a 'float' mode before putting the first load on the battery. I just changed out a battery on my bike that had been properly initialized and installed seven years (and about 100,000 miles) ago.

.

[uudfourty]

You can try the blow-in-the-vent trick, too.

[physics-teacher]

Thanks for all the advice. A new battery is on the way from Flatout. I fired 'er up this morning in 35 degrees, instant start. I rode it 100 miles yesterday to put a good charge on the battery. I have no real idea how old the battery in the bike is, but the PO let the bike sit for a long time before I bought it and that can't have been good for it. Now this afternoon I should enjoy a nice ride home in 50 degree weather.

[BassCliff]

Although you say it usually starts easily, another area to check regarding cold-starting ability is VALVE CLEARANCE.

Oh yes. I second valve clearance check recommendation. Just in case you don't know what one looks like, here's a PDF guide with pictures:

Valve Adjustments (8 Valve)


Good call there, Mr. Steve.

Enjoy your brisk ride, Mr. physics-teacher!


Thank you for your indulgence,

BassCliff

[jbs80106]

Similar effect on my 650G...

If she sits for a week or longer, particularly in the summer, she'll crank and crank till I give up. Seems the gas evaporates out of the carbs....I just put it on prime for 5 minutes or so, a few cranks and she starts up. I almost always have to go to near full open choke to start as well, especially when it gets cold outside in the garage.

I'm a battery-phobe. I check the battery voltage before I start to see that its fully charged. If its not, the on-board battery charger gets plugged in for a while.....then I start.

No fuel filter on mine.

And just for the group, my battery is like 3+ years old...probably replace it next year but so long as the friggin' stator/reg-rect are working it hold charge, takes a charge and doesn't have a noticeble drop when starting. Had it tested out at Autozone and passed across the board....

[Florida Guy]

I recall the open gas cap/prime working last year, but not this time. There may well be something to that battery idea. The battery is old and maybe it's time to replace. Or else ride every day as I'd like to!

I think I read that a battery loses 1% of its strength each day.
So, a fully charged battery that sits a week or two may not be as strong as you think.

[physics-teacher]

Gas evaporating from carbs?

Y'know, I've been wondering if gas could be evaporating from the carbs. I guess I've been thinking with the throttle slides closed as the bike sits in the garage, the gas can't get away, but that stuff's pretty volatile. What path would the gas use to sneak out of the float bowls? New gas won't ordinarily flow in, I believe, unless it's sucked in by that tube leading down from the fuel tap. So I thought all that (fruitless) cranking should be pulling fresh gas down from the tank, leading to a start up, but that's not happening. The pre-priming idea is worth a check since it costs nothing.

[jbs80106]

Good question about the evaporation...

Just my theory...never pulled carbs or plugs to confirm. I don't know if the engine during cranking sucks as much gas as a running engine would...need one of the carb guru's to weigh in...priming works for me...but can leak gas into the motor if you forget to turn it off....

[Stefnwolf]

Just my theory...never pulled carbs or plugs to confirm. I don't know if the engine during cranking sucks as much gas as a running engine would...need one of the carb guru's to weigh in...priming works for me...but can leak gas into the motor if you forget to turn it off....

Hi
Been following this thread with interest, as the 82 GSX750EZ I recently bought has a very similar problem. Not actually trying to fix it as the winter refit will take care of that.

For what its worth, mine would crank over for ever if left for a week.
Pulling plugs shows them bone dry. Leave it on prime for 15 minutes, it fires up first crank, turn tap onto 'normal' position and it runs fine.
I came to the conclusion either faulty cock, or start crank not enough vacuum to open it.

Its not run for a month, so today I drained the No1 bowl (lowest cos of side stand) and only got out a very small amount of gas. Not sure exactly how much, but only about 15cc (fills a medical [UK] pee sample bottle up half way).

Anyone happen to know how much gas a full float bowl should hold?

Also a mystery where it goes....

And further, I can confirm leaving on prime fills the pots. Did that once overnight (haveing never encountered this type of tap before) and got what I now realise to be fluid lock. Lucky it didn't fire then I think!