I posted awhile ago about my GS's weak throttle response on the low end, but here goes again...

Quite simply, in first gear my bike putts - even after it has warmed up. Once it hits 4000 rpm it revs nicely though. Anybody have any ideas? I think it may have something to do with my carbs running too lean, but I'm lost when it comes to that sort of thing.

Specifics:
1999 GS500E
Average about 40 mpg (seems somewhat low)
Need choke on full to start my bike, whether its cold or warm out.

If it'll helps, I'll post a video tomorrow of my bike and how it revs.

its time do clean the carbs.  my friend's sv650 racebike was like that last season, carb cleaning had it purring like a kitten again

+1 on cleaning carbs

Your pilot jets may be clogged.

-Jessie

or running on one cylinder. check spark.

I would check those pilots. Mine were really clogged on a 2006 I bought with 688 miles on it. It barley ran at the low end. He let it sit and that's what happens. I just checked my mileage today for the first time and got 60 MPG. Nice!!! Just doing average riding, city and canyon not really hot dogging it but not babying it .

I also opened my Idle/air screws to 2 3/4 turns out. She seems to purrrrr! All jetting is stock. I also always run Sta-Bil in my bikes. 2 oz treats 4 gallons so I think I do 3 oz on a full tank.

Good luck!

Thanks for the hints.

So how do I go about checking the pilots/cleaning them properly? I assume the process doesn't include spraying carb cleaner directly into them from the air box. >_>

no dont spray carb cleaner directly in, it wont go through the jets.  You gotta pull the carbs and check each jet individually. spray cleaner through the jets and while your at, spray cleaner through every hole in the carbs that yu can find. hint- wear glasses, you never know where some holes will spray out.  Also, my guess on your problem isnt just the carbs.  Your weak throttle response is due to your ownership of a Suzuki GS500.

lol, theres that. But there is a definite flat spot between 1.5k and 2.5 K when revving.

1.5 to 2.5 K ... at what throttle position. I am still thinking clogged pilots like people suggested before ...
Cool.
Buddha.

Ok a week ago I pulled the carbs and got to the jets, in one side anyway (I stripped the bolt to the bowl on the right one). The jet and main looked fine, so I could only assume the other would be similar, but cant say for sure. I cleaned the hell out of everything. For a couple days it revved abit smoother, but currently its back to its original stunt at 1.5 k - 2.5 k. Maybe the carbs arnt in sync. What the hell does that entail anyway?

Buddha, it happens at any throttle position besides just barely revving it.

Thanks for all the suggestions and ideas guys, any more would be greatly appreciated.

OK so you have a dead bolt in one float bowl. The other is clean.

OK would you at this point believe me if I say the problem is in the one with the dead bolt ?

I dunno, if you're losing 1 cyl, and that cyl has the dead bolt, yea you better get it out and get in there.
I have had good luck cutting the head with a dremel tool. Drilling works too, whatever you think is convenient for the location it is in.
Anyway 4K suggests its a pilot or a vacuum leak.
Cool.
Buddha.

Hi Jon,If you have just mashed the head up on the bowl screw,try clamping a good smallish sized mole grips ( the heavy duty locking  grips with the release lever) on the head of the screw and undo,worked on mine saves drilling etc.Then replace with allen bolts.

Quote from: The Buddha on January 27, 2010, 08:47:11 AM
OK so you have a dead bolt in one float bowl. The other is clean.

OK would you at this point believe me if I say the problem is in the one with the dead bolt ?

I dunno, if you're losing 1 cyl, and that cyl has the dead bolt, yea you better get it out and get in there.
I have had good luck cutting the head with a dremel tool. Drilling works too, whatever you think is convenient for the location it is in.
Anyway 4K suggests its a pilot or a vacuum leak.
Cool.
Buddha.

Worth a shot. I'll get in there today.

If it isnt the pilot, how do I test for a vacuum leak?

Quote from: JAY W on January 27, 2010, 12:51:17 PM
Hi Jon,If you have just mashed the head up on the bowl screw,try clamping a good smallish sized mole grips ( the heavy duty locking  grips with the release lever) on the head of the screw and undo,worked on mine saves drilling etc.Then replace with allen bolts.

Nice suggestion, use some locking pliers and it worked, just had to make clearance.

Buddah, the jet looks fine, I assume if it was clogged it would be obvious (as im just checking to make sure they pin hole isnt clogged, which it isnt... not noticeably anyway).

I took the top cap off and found that the diaphragm was crushed, maybe this caused a vacuum leak. Check it out.

Yup its dead ... however it wont cause a vacuum leak, it will cause a bike that wont rev under load. BTW yours rip is so bog, it can cause it to not rev at all past idle. I dunno, I didn't know of any that ran with anythign bigger than a tiny slit.
You have to get new one, and the other one aint looking great either .. .check it and make sure its not got a melted spot.
BTW I have seen it get soft and sticky ... dunno what causes that, maybe some caustic additive to gas.

Cool.
Buddha.

Yah I ordered one yesterday as soon as I saw it. I also decided to order another one today for the other side, just to be sure. Thanks for pushing me to check the other pilots, if I hadn't, I wouldn't of even looked at the diaphragms.


I'll update this thread when I replace them. Hopefully it fixes the problem.

Find what caused it, I have only seen maybe 1-2 that were dead in this way. And Believe me, I've looked at a lot of carburetors.
Cool.
Buddha.

It was being crushed by the cap. No holes or anything.

In fact, the bike already seems to run smoother now that I have it where the cap isnt crushing the diaphragm, even though its still deformed (least when its warm).

Um I am not an expert mechanic like Buddha but yeah the diaprahm must return to original shape with no pressure or she no workie!

I worked on Volkswagons Beetles 1600cc motors from a very young age and lot's of what I learned from my Dad applies to all carbs/motors. There is a small chance that in this instance you can take the diapram and freeze it to regain it's shape. Some materials actual repair their molecular structure when frozen?