i own a 96 gs500, it is my prized posession. i recently bought a yamaha rt180 dirtbike to fix up and sell so i can buy fairings for my E....anyway the bike is a 2-stroke and the problem im having with it is when it starts it revs/idols up really really high. so it has to be imediately be cut off. the throttle is not sticking and its not the idoling screw or the intake. i cleaned out the carb but that didnt help(but that doesnt rule out a crab problem). i was thinking it might be the reeds??? how can i tell if they are bad??  i guess its getting too much air somehow. any ideas guys???

-calvin

Sounds really lean, check to see that the bike has enough fuel (petcock is working and flowing gas) and put the carb settings back to stock.  Try to find out the stock jet sizes and make sure the bike has them.

have you pulled the reeds and looked at them?  they may have i speck of dirt or such holding them open

thanks.  bike is getting gas i suppose a jet could be clogged but i didnt notice before. i should prob just rebuild the whole carb and i have no idea what factory setting are of how to tune the carb to match. and how do i check the reeds??  i know how to find them but how do i know if they are bad? can they go bad or just have junk in them?

they can go bad. they get weak over time.  with it racing as soon at you start it i would go reeds first.  or you flipped your slides in the carbs around when you put them back in.  they would appear not to stick but wouldnt close fully if put in backwards.

I'm not familiar with that bike, but own a vintage two-stroke.

Air leaks are a big culprit.  Check everything from the airbox/filter to the engine.  On older bikes, the boot between the airbox and carbs can get hard and brittle, easy to get a leak.  Are the intake manifolds in good condition?  If they are at all cracked, it might be time to replace.

Like mentioned above, check that the slides are not in backwards.  On older bikes, if the crankshaft seal on the left side is worn or brittle, you can also suck air through there.

Get it sorted out before you get the "sun-roof" piston mod on the piston dome.  Don't ask how I know... I already have a set.   

Good luck...

I owned this SAME EXACT bike for a long time, actually rebuilt it last year and sold it before I got my 1st street bike.

I had a similar issue with revving high and here's a few things to do to trouble shoot...

1. Loosen up the throttle cable till its completely slack.
2. Check the position of the choke, if it's stuck closed it'll rev like crazy, sometimes the link can break inside the carb.
3. Buy a can of STARTING FLUID and start the bike... then spray all around the carb boot, airbox boot, and reed cage and see if the revs drop any... if they do.. time for new gaskets/boot.

Buy a set of BOYSON power reeds and a new set of reed gaskets... The reeds are a bit stiffer and don't cause any HUGE power gains, but they'll improve throttle response 10 fold.

Here's a few pics of mine ... I miss her so much...

She looked like this when I first got her... except w/a purple seat and purple fork boots...


Then she came out like this after new paint, decals, boots and a seat cover.

wow that is exactly like mine!! same color scheme and everything lol, mine is just more beat up. nice bike.....well i pulled the carb again and this time did a very lengthy inspection/cleaning. floats are good and its all clean and in working order including choke.  the brass pin that runs through the carb has a slight bend in it but i dont think it is hurting anything. throttle isnt sticking and intake is not cracked and its getting proper fuel. i took the whole reed assembally out and checked things out. they all look clean but the top reeds come about a milimeter shy of touching where they are supposed to. so i think they might be weak? can i flip them over so the bend is facing in?? maybe this would make them seem stronger?? or are they fine? also i dont currently have an airfilter in it but i dont think that should matter.

this is exactly what happens when i start it.
-it starts easy but only on choke
-as soon as it starts it revs really high
-if you take it off choke and dont give it gas it stalls
-if you get it started and take it off choke it will rev down but you have to keep giving it gas for about 3 minutes
-i can mess with the idol and it will idol but not properly
-when it is warm and semi-idoling you can give it gas and it will respond but the response is pretty erratic. it will rev but it goes to high rpms fast and takes a little while to rev back down if it even decides to. and it will rev by itsself sometimes
-i think reeds?

ok guys what do u think?

sounds like weak tired worn out stock reeds but thats just me.

yeah thats what im thinking too i just dont wanna buy um till i have ruled out everything else

have you pulled them and looked at them?

yep but i dont know what to look for lol. there was a small gap on the top reeds that lets a little through all the time i imagine. they were clean but the little gap makes me think that they might be weak.

from what i remember when i had my lt250 suzuki quad there isnt a gap on either side until the motor is running pulling through the reeds.

Definitely get the reeds... DennisKirk has them, and I believe they're under 20 bucks... Don't quote me on it though. But that mm gap is what's causing all your problems... after the intake stroke on compression those reeds need to be snapped air tight otherwise you'll suck air in... basically acting like your throttle butterfly (slide) is open... thus causing the revving.

alright!!! thanks man that  is what i wanted to hear. thanks everyone. i'll update when i get it fixed.

i would just like to refer you back to my first post....lol

yeah lol u called it.

let me know when you get them in on how its running