kz250 carb question

My 1980 kz250 has a problem with the carb. The throttle hangs up sometimes and will not go back to idle unless I give it gas and then let it off a few times.
This is the stock carb. It is not one with the round slide, it had a needle with a diaphram.
It started doing this after I took it apart to clean it. It now runs much better but has the annoying throttle hangup problem. I checked and it is not the cable hanging up. The throttle is back against the idle stop and it still wants to run at 3000 rpm or so.

Any ideas for me?
Thanks, Al.

Replace the oring on the pilot screw and if the single carb has a vacuum port, make sure the vacuum port is either capped securely or the hose going to the petcock is not leaking any air... air leak is generally in the pilot system is normally the reason for hanging idle.

I had a similar problem with my KZ650 and the 4 carb rail. I couldn't get it to hold idle. It would jump up to 3 or 4 grand. Once and awhile I could get it to idle down but usually within ten seconds it would creep back up. The problem turned out to be my own ignorance. There are 2 VENT ports on my rail. A vacuum line is attached to these and they go up under the tank and 'vent' to the outside. Not knowing this, I capped them off and later connected a tube from the one to the other. Both cases did not allow my carb bowl chambers to vent and gave me my problems.
Don't know if your kz250 carb has a specific vent port. It's just a shared experience. Might help.

I did not see any vent that I recall but I'll look again. Which screw is the pilot screw?

Thanks for the help! Al.

What type carb is on the bike... I am too lazy to go look at the parts fiche. If it is a BS series carb, it will be the screw on top on the engine side... Most of the time, this screw is covered with an aluminum cap.

I looked agin. It is a Keihin carb, numbers on it are 1160 RK29. There is a screw on the engine side on the left, high on the carb. It has no oring on it and doesn't look like it should have one. Right above it is a cap that I suppose might have a screw behind it.
Before I cleaned it it did not have this problem but I did not disturb this screw or remove this plug when it was cleaned. I did take off the diaphram cover and remove, clean and reassemble it. Then took off the bowl and removed each jet and sprayed carb cleaner and blew out with air.

So now what do I do?

Thanks, I really appreciate your help.
Al.

The 250 carb doesn't have a vent hose.
The pilot screw is behind the metal cap.
A rebuild kit will have the replacement O-ring for the pilot screw.
The carb cleaner may have eaten the original O-ring.
If you don't have a manual and can't find the cap I can post a pic for you. Just ask.


Your carb?

Yes that looks like it. Can I just pop that cap over the screw with an ice pic and discard it? Then just pick up an o ring from an assortment?

Al.

There are a couple of ways to remove the cap over the pilot screw. The way I do it, is to drill a hole and take care not to nick the screw's head beneath the cap. Once a hole is through the cap, I screw in an EZ-Out and turn the cap out. If you pry, you can potentially break the edge of the well that the screw sits in.

On the Keihin carbs, you take the screw and spring out. The spring is there to put tension on the screw so it doesn't vibrate out of position. Beneath is a SMALL metal washer and beneath the washer is a very small oring that MUST be in good shape for the bike to idle smoothly.

Thank you very very much. I'll get on it in the next day or so.

Al.

alteran wrote:

Then just pick up an o ring from an assortment?

Yep. if you have a good shop nearby!

Yep, thats it!
Thank you all so much. This is the best and cheapest school I've found.
All the help is much appreciated. I'll let you know how it turns out.

Al.