Suzuki gt250 high idle

[cleaf]

Hi

Bike is runnin very high idle 6000rpm. I have loosen throtle cable from carbs and throttle handle.
Can air leak in cylinder/crankcase make idle rev like that?
Txh for advance

[jabcb]

If you overtighten the nuts that attach the carbs to the motor, you can distort the carb bodies to the point that the slides stick and do not close completely.

[Indy650]

There are many things that can cause a high idle. The best thing to do is take the airbox off or take a carburetor off to confirm the slides are moving the way they should and coming to rest on the idle screw. If you think it might be an air leak around where the carburetors bolt to the cylinders you can take a can of starting fluid and spray around the area to see if the engine rpm changes. Lastly a bad crank seal on the lefthand side could cause an air leak and a high idle.

Give us a little more information did you just get the bike or have you had it and drove it before? I'm asking because If you rode it the other day and it was fine I doubt the cable or idle screws moved themselves but if this is your first time starting it it could be as simple as an idle adjustment. If its sat for many years the odds are higher that its the lh crank seal or leakage around the cylinder/carb joint. It could be plugged pilot jets but that usually just causes poor idle not a high idle.

[cleaf]

There are many things that can cause a high idle. The best thing to do is take the airbox off or take a carburetor off to confirm the slides are moving the way they should and coming to rest on the idle screw. If you think it might be an air leak around where the carburetors bolt to the cylinders you can take a can of starting fluid and spray around the area to see if the engine rpm changes. Lastly a bad crank seal on the lefthand side could cause an air leak and a high idle.

Give us a little more information did you just get the bike or have you had it and drove it before? I'm asking because If you rode it the other day and it was fine I doubt the cable or idle screws moved themselves but if this is your first time starting it it could be as simple as an idle adjustment. If its sat for many years the odds are higher that its the lh crank seal or leakage around the cylinder/carb joint. It could be plugged pilot jets but that usually just causes poor idle not a high idle.

I just bought the bike. It did run well idle in test drive but there was exaust port threads damaged so i had to repair threads on the cylinder. When i did take cylinder off the gasket was little damaged so i will change today new gaskets on cylinder.

2 strokes are not so familiar to me so i was wondering if gasket leak can make bike idle so high?

how do you adjust idle on these bikes if there is no leak then maybe i can try to adjust idle?

sorry about my bad english

[daxman]

Hi

1) English is fine

2) There are some brass screws with springs on the side of the carburetor barrels which raise/lower the pistons/slides for idle adjustment (ensure cable has a small amount of 'free play' first) - unscrew lowers the slide and reduces idle - do it equally on both sides.

Cheers

[daxman]

[..but there was exaust port threads damaged so i had to repair threads on the cylinder.

I also have this problem. How did you make your repair?

[cleaf]

[..but there was exaust port threads damaged so i had to repair threads on the cylinder.

I also have this problem. How did you make your repair?

my friend machined new exhaust nut with better threads, i just tightened it few times and it did repair damaged threads on the port.

[Indy650]

Yes any air leaks will cause a lean condition and high idle. Anytime you remove the cylinders you should replace the gasket between the cylinder and the case of the engine, the head gaskets, and the carburetor joint gaskets. If you have the brass head gaskets you can often reuse them but I recommend new ones. There are really cheap gasket kits on ebay.
This is for the older engine up to 1975 if you have the newer style I can find you a kit if you need one.
https://www.ebay.com/itm/SUZUKI-GT250-G ... SwoudW2XwW" onclick="window.open(this.href);return false;

[cleaf]

very stupid question.

Are those hoses in picture what come from carb some sort of vacuum or overflow hoses that supposed to go on air filter?

Previous owner has changed stock filter to some aftermarket type.

[Indy650]

Most are vents but there is one hose from the left hand carburetor that needs to be connected to the fuel petcock on the gastank. If its unhooked it will suck in air and the diaphram in the petcock wont operate correctly. That hose is on the very front side of the left hand carb. It comes with a spring around it to prevent kinking but that may be missing. The petcock has prime, on, and reserve. In prime fuel will flow to the carbs automatically thats for cold starting. When in the on or reserve positions the petcock will not release fuel unless the vacuum hose I mentioned earlier is attached and the engine is running providing a vacuum to the petcock allowing fuel to flow. I personally despise the whole thing but suzuki was very fond of this contraption.

edit: that lookes like a newer gt250 as it has rubber carburetor boots so the vacuum line may be in a different location i cant remember. it will be on the engine side of the carburetor slide.

[Indy650]

One other thing you may want to check that the vent in the gas cap isn't plugged as that will create a vacuum in the tank and gas can't escape. If ever you hear a rush of air or something similar when opening the gas cap its because the vent is clogged.

[dollydog]

think you'll find indy that there isn't a vacuum on the 250a. as i've said before a lack of oil will cause the engine to scream, or a massive air leak at the carb joint. first thing i would check was oil flow, then leak at the rubber inlet. have you run out of oil? easy enough to do.
cheers, dd.

[cleaf]

Ok, new gaskets are installed and revs are not climbing to 6k Anymore. In choke there is 2000rpm but without choke engine dies.

I tried to adjust idle screws on both carbs (in some manual was adjustment values 2.5 to idle screws and to air screw 1.5 from closed position)

that also appears that idle screw doesnt effect to engine runnin, maybe carb need cleanin?

[Indy650]

The idle screws will help you set the correct idle when the carburetor is clean and functioning properly. The air screw changes how much air is allowed through the pilot circuit and the pilot jet determines the amount of fuel that can flow through the pilot circuit. The pilot circuit is the primary flow of air and fuel from idle to 1/8th throttle.
The way you are explaining it now where it only runs with choke it sounds like the pilot jets are plugged and the bike can only get fuel through the choke circuit but this is odd that it was idling high before the gasket change and now it won't idle at all. In order to get an idea of what the problem is you first need to thoroughly clean the carburetors and start with the air screws 1 and a half turns out. Make certain your throttle is hooked up correctly and back out your idle screws all the way then screw them in until they start to move the slide. Once thats done turn each screw an even amount say one turn at a time until you get the bike to idle. Once you get to this point you can fine tune your air screw which I can walk you through if you need me to.

[karl pa]

think you'll find indy that there isn't a vacuum on the 250a

Not sure I agree with that, every 250A and B that I have seen has vacuum petcock, 250A is when they changed to the bolt on petcock. As far as I know, every GT model came with vacuum petcock except 185, some GS models came with non vacuum.
On the 250 A and B, the vacuum line plugs on the right side of the right carb.