Engine RPMs racing once it warms up

[ERJpilot]

It is still a work in progress for me, unfortunately I have been flying a lot and getting reassigned over and over so I haven't had time to work on the bike lately. Hopefully I will get a chance to work on it some more tomorrow.

To answer some questions:

I did replace the throttle cable and adjusted and tightened the screws. When the bike is first started it idles fine and the throttle cable itself isn't sticking, so I don't think that is it unless it is sticking only after the bike warms up. From initially starting the bike the RPMs are slow to come down but it just gets worse and worse as it gets warmer.

The pilot screws are set at 1 1/4 turns open. I forget where I read it and I don't have the books in front of me but I will double check that again. And yes I replaced the O-rings when I reinstalled them.

I will give everyone and update tomorrow if I get the opportunity to work on it some more. Thanks everyone for the advice and help, it is definitely appreciated.

[Nessism]

Try 3 turns out and see how that goes. I just tore down a set of virgin GS850 carbs and the pilot screws were set at 2.5 turns from the factory.

[davidduarte]

what kind of shape is your gas tank in? No rust in it I hope? I had my tank lined, had a buddy clean out my carbs with his parts cleaner, and replaced the airbox and intake boots on my 450. I also put in a new petcock, something you might want to invest in. It runs much better, and will hold an idle, which it never did before. It still won't hold an idle if it's cold. I have a new throttle cable but just haven't had the chance to put it in. Good luck!

[ERJpilot]

So I decided to bring the bike to my apartment and just work on it here since we have covered parking and driving the 45 minutes to my friend's was just too far to be able to have the convenience of a garage.

I will try adjusting the pilot screws to 3 turns out and I'm going to double check the o rings on the intake boots in case I somehow messed one up when installing the new ones, if that doesn't change anything I suppose I'm going to take the carbs off again and dip them again, and I'll update more as I can.

As far as the gas tank goes, I don't see that there is any rust in it, but it is dented from a drop at one point in its history, is that something that I should be worried about?

[ERJpilot]

Well I've finally had a day free to work on the bike and I have been at it for a while.

I pulled off the carbs again and rechecked the float height with a new set of calipers I bought. The float heights were both off a bit so I adjusted that. Next I checked the O rings in the carb and all seemed fine since I had already replaced them.

However, one of the O rings in the boot between the carb and the engine was a little messed up so I replaced it with another (thankfully I bought several extra). Maybe I messed it up when I was putting the boot on before but I was hoping that would fix my problem.

I did also discover that my fuel petcock FOR SURE isn't working. The fuel would flow freely in the PRI and the RES positions (I didn't have enough fuel in the tank for it to flow in the ON position).

Unfortunately one of the carbs started pouring out fuel after I let it prime for a minute so I'm assuming I screwed up something with the float height on that one.

I have a petcock rebuild kit on order to fix that problem, and now I just need to resolve the fuel pouring out of the carb and maybe soon I will be on my way to having a running bike...

[BassCliff]

Hi,

I would suggest new float valves and seats, and a new petcock.


Thank you for your indulgence,

BassCliff

[Flaming Chainsaws]

I have a petcock rebuild kit on order to fix that problem, and now I just need to resolve the fuel pouring out of the carb and maybe soon I will be on my way to having a running bike...

About the petcock rebuild kit... Based on what I've read, a lot have people have been very unsuccessful with petcock rebuild kits. I think it was like a 5% success rate. With those numbers, I would personally just buy a brand new petcock. Suzuki still sells them at around $70. Or you can go with a Pingel petcock which a lot of people seem to like.

[davidduarte]

About the petcock rebuild kit... Based on what I've read, a lot have people have been very unsuccessful with petcock rebuild kits. I think it was like a 5% success rate. With those numbers, I would personally just buy a brand new petcock. Suzuki still sells them at around $70. Or you can go with a Pingel petcock which a lot of people seem to like.

if you go with the Pingel you have to make sure you turn it off every time you turn the engine off, otherwise the fuel will keep flowing. You'll also have to plug up the vacuum port on the left carb otherwise it will run lean.

[ERJpilot]

Is it better to go with a new Suzuki petcock or the Pingel?

[Flaming Chainsaws]

Is it better to go with a new Suzuki petcock or the Pingel?

I guess it depends on what you want. The Pingel is a bit more pricey than the stock petcock. And if you go with the pingel, do what david said, "Turn the petcock off every time you turn the engine off. Or else fuel will keep flowing. And plug up the vacuum port on the left carb."

Personally, I would go with the stock petcock. Simple swap with no mods necessary

[hzoltaan]

Hello, I have a bit similar looking problem and I'm a bit lost with it.
I bought a GS450 last october and all was fine, good performance, both carbs were checked with colortune.
I got the head rebuild this spring and since then I can not set the carbs. According to the colortune oon idle it's lean (I can not get the slight rich, yellow to appear) and as soon as I throttle a bit (slow or fast) around 3000rpm it becomes very rich. Revs up, but then goes down slowly. If I'm right it's another sign of too rich mixture. I lowered the needle as far as I could and it got better, but still far from good. The carb was absolutely okay before I just checked it around February. any ideas? I'm kinda lost.