Rpm level is changing itself

[Jagjag]

Hi guys,
I have bought suzuki gs500e(1992) and it has some problems - engine rev's itself. When i start the engine on, rpm goes on 4-5 k or on below 1k, so it's changing always by itself and its uncontrollable. I have tried gas adjustments (under the carb and the one near the clutch lever but it still changing). I have already cleaned the carbs and changed sparks. What should i do?

[Jagjag]

https://youtu.be/B3T3IPh-qZ8
It's similar like in this video.

[chris900f]

When you first start the bike with a cold engine and full-choke, it will rev up as you describe. (it is a little bit shocking when you're not used to it)

Allow it to run at high rpm for a minute, then slowly reduce the amount of choke. Try and get it to idle in the 2500-3000rpm range
and let it run like that for another minute or two. Slowly turn the choke all the way off: the idle should drop to 1000-1200rpm. If it is stable
at normal idle, let it idle like that for another minute before riding. The engine is still not fully warmed up at this point, but you can
ride gently for the first few miles.

Also, it is normal for an air-cooled engine to pick up 100-200rpm at idle when fully warmed, so if you are at about 1000rpm right after
you turn off the choke, it's normal for the engine to idle at 1100-1200 after 15-20 minutes of riding.

Hope this helps.

[Jagjag]

I have tried that, but when the engine was already warm, i tried to use throttle but engine turned off. When the engine is warm, it doesn't matter, engine is changing rpms by itself. Some told me that it was air leak somewhere, but i don't think so, maybe its another reason.

[Jagjag]

It's similar like on this youtube video, for example: on the full choke engine is revving on high rpms and suddenly on lows

[chris900f]

Then it does sound like an air leak at the carb boots between carbs and engine.