Help - hard starting 1990 GS500

[nycnorton]

Hi all,

This is my first post to this forum.  I am the proud owner of a 1990 GS500.  It is the perfect NYC commuter bike, and I ride it year-round (even in the snow!).

Last year as the weather got colder the bike would be a bear to start, and even after starting would sputter and miss badly as I opened the throttle.  I attributed this to denser atmospheric conditions in the colder weather.  Sometimes it would clear up as the bike warmed up, but often it would carry on sputtering for 20 or 30 minutes (about the maximum time I ride commuting).  It may be only one cylinder - it's hard to tell with the 2-into-1 exhaust.  It definitely is throttle-position-related (carbs).

Lately, I've been noticing this happening when it's still warm outside, especially if I let the bike sit for a few days.  It will start with a tiny bit of choke and just a crack of the throttle.  Any more choke or throttle and it dies.  I have to slowly twist the trottle bits at a time, gradually opening wider and wider, until I can finally get it working well enough to pull 1st gear.  This can take up to 10 minutes after the bike has been sitting for more than a couple of days.   

I'm worried the colder months are upon us and this will only get worse.  Last winter it was almost unrideable.


Any thoughts or suggestions are welcome.

Kenny C.
NYC 

[joshr08]

sounds like you need to richen that bike up a bit.  if you talk to buddha he will tell you to jet for the coldest day your doing to ride and it will be great

[The Buddha]

Thanks Joshr08 - looks like I am following lots of people of late (possibly cos my crappy life is eating into my internet time) ... usually I'd be the first to post when there was ever a post like his ...

And yes he's correct - Clogged crap ... especially pilot circuit.
And yes - Clean and rejet ... usually cleaning does 90%, rejet finishes the job. Like icing on a cake, or sutures after surgery or ... y'know after sex.
Cool.
Buddha.

[psyber_0ptix]

Thanks Joshr08 - looks like I am following lots of people of late (possibly cos my crappy life is eating into my internet time) ... usually I'd be the first to post when there was ever a post like his ...

And yes he's correct - Clogged crap ... especially pilot circuit.
And yes - Clean and rejet ... usually cleaning does 90%, rejet finishes the job. Like icing on a cake, or sutures after surgery or ... y'know after sex.
Cool.
Buddha.

i love getting sutures after sex....keeps things interesting.

Buddha is your one stop shop for your carb needs     thanks again for the new diaphragms

[mister]

Kenny... we want pics, of your bike.

Michael

[The Buddha]

Buddha is your one stop shop for your carb needs     thanks again for the new diaphragms

Not new - just new to you.
Cool.
Buddha.

[nycnorton]

Thanks Joshr08 - looks like I am following lots of people of late (possibly cos my crappy life is eating into my internet time) ... usually I'd be the first to post when there was ever a post like his ...

And yes he's correct - Clogged crap ... especially pilot circuit.
And yes - Clean and rejet ... usually cleaning does 90%, rejet finishes the job. Like icing on a cake, or sutures after surgery or ... y'know after sex.
Cool.
Buddha.

Right on, thanks for the advice.  But... if it were clogged pilot jets then it wouldn't start at all, right?  It does start and runs quite well on the idle circuit.  It's when I open the throttle that I'm having trouble.  I'm VERY familiar with carbs and jetting, just not with diaphragm stuff.   So Budda, could it be a clogged needle jet (do these carbs have needle jets), or could it be a leaky diaphragm?

I don't have pictures of my GS up anywhere (yet), but you can see what I do here: www.nycnorton.com

Cheers,

-Kenny C.
NYC

[The Buddha]

Idle is controlled by the air mix screw.
Rip in Diaphragm will cause it to not rev above the throttle position where the rip starts to play up. Like a tiny rip will cause it to not rev past 3/4 throttle, and a larger rip will affect it above 1/2. That will translate into gradually reducing rpm with increase in gear. It will redline in 1st, but only make 5K in 5th and 6th.
As you start to give gas, it needs pilot jet. 0-1/8th throttle = pilot.

Needle jet cannot clog. Emulsion tube can, but you're not on the needle @ start up.
The float spigot can clog, but that means you wont get any gas in the bowl and really crap out @ all times including @ start.

I really bet its a clogged pilot.

Cool.
Buddha.

[nycnorton]

Idle is controlled by the air mix screw.
Rip in Diaphragm will cause it to not rev above the throttle position where the rip starts to play up. Like a tiny rip will cause it to not rev past 3/4 throttle, and a larger rip will affect it above 1/2. That will translate into gradually reducing rpm with increase in gear. It will redline in 1st, but only make 5K in 5th and 6th.
As you start to give gas, it needs pilot jet. 0-1/8th throttle = pilot.

Needle jet cannot clog. Emulsion tube can, but you're not on the needle @ start up.
The float spigot can clog, but that means you wont get any gas in the bowl and really crap out @ all times including @ start.

I really bet its a clogged pilot.

Cool.
Buddha.

Thanks Buddha. 

Another question, possibly related: 

I've never been able to run the petrol tank down to empty.  I have to fill it up after about 75 or 80 miles or it'll start sputtering, even though there is still quite a bit of gas within.  I understand there is a vacuum petcock here.  Could this be partially clogged?

This bike sat for a long time out in the elements.  When I got it the tank was full of gas and water.  I drained it completely, and cleaned the carbs back then (that was 3 years ago) but there may still be contaminants within.  This is a testament to the resiliency of these bikes, as it is so reliable, even when  not 100%. 

[The Buddha]

Yea you could have a clogged tank pick up.
Cool.
Buddha.