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I've got a problem with my CRF50. The idle seems to stick at higher RPMs. This makes shifting REALLY interesting!

The throttle and cable appear to operate freely. It just won't idle down all the time. Sometimes it's worse than others.

It worked great just after Christmas (it was a gift). It was stored until the weather got nice, and that's when this condition started. It wasn't that long- but was it long enough for fuel to go bad and foul up the carb? I would suspect a fouled carb would make lower RPM's not higher....?

Anyone else experience this?

Thanks
Randy

adjust your idle screw so it sounds nice not brrrrrrrrrrrrrrrrrrrp

marks crf wrote:adjust your idle screw so it sounds nice not brrrrrrrrrrrrrrrrrrrp

Seriously?

I would start by having the carb cleaned out. It is definitely possible there is something in there interfering with the throttle slide. That's what it sounds like to me.

Thanks for the reply. That's similar to what I thought- but I don't know anything about carbs. I was thinking something interfering with the return spring- if it has one.

Here's the question. These carbs seem small and simple. Is it cheaper and easier to replace the carb or have someone go through and rebuild it? Or is this something simple enough for a novice carb guy to tackle reliably?

Thanks
Randy

Fuel takes about 3 months to go bad. Depends on quantities, container, venting, humidity and heat.

Cheaper to fix. Cheapest to do yourself. $4.00 worth of carb cleaner to fix and you will know the bike better.

You can hear the slide "clunk" if you listen by the carb. Twist the throttle and release. If you here the "clunk" than your slide / cable is probably not the problem.

Make sure you have the throttle cable adjusted properly. 1/16" to 1/4"

I would drain the float bowl if you haven't done that already - you might get lucky and not have to do anything else.

Turn off gas at gas tank.
Put a pan or jar under the drain hose to catch the gas.
Back out the screw at the bottom of the carb on the left (shifter) side of the bike. Hose close by on the right is the drain hose. That's where the gas comes out - pan / jar needs to be under the end of this hose.
Let the gas drain out.
Tighten the screw again.

Run it and see if it fixed the problem. If not you get to do it again to clean the jets in the float bowl.

Besides the drain screw, there are two other screws on the left side of the carb close together. One is the idle screw (highest towards the back of the bike) and the pilot jet screw (lower towards the front of the bike). That's the circuit that is probably clogged up.

Hope I didn't insult your mechanical abilities

Let me know if you need any more help / details. To clean the jets there are only a couple of bolts, clamp screw, 4 phillips screws and a couple of rubber lines (fuel / air).

BTW - is your air filter clean? How old is your gas?

It could also be a broken or cracked carb isolator (where the carb mounts to the cylinder head). A crack in the intake tract can cause a "run on" condition...

I drained the bowl and you described.

I got all excited and thought it fixed the problem.... until the engine got hot- then it went right back to the high idle problem.

I'm going to need your advice on cleaning the jets. I've never done it before.

Thanks for all your help!
Randy

Have you tried just adjusting the idle screw? Go to page 87 of this link.

http://www.ahm-ownerlink.com/assets/OWNERLINK/model/own_man/powersports/2006/2006_CRF50F.pdf

See if that helps. If not then you just need an hour or so and a can of carb cleaner.

Just warm it up and adjust the screw. You don't need the stand and tachometer. Pay attention to your adjustments so you put it back where you started.

If that doesn't work you need to clean the pilot jet.

...or a air leak in the intake tract...

OK. I took your advice. I rode around and got the engine warm, and then adjusted the idle screw. It brought the idele down. I rode around some more, and the idle was up again. So, again I adjuested the idle screw. Three times, and finally the idle stopped coming up.

Now- I have to try and start the thing when the engine is cold!

I don't understand how the idle mysteriously raised itself while in storage. Or.... I did buy it in winter- maybe it never got up to operating temperature....?

Thanks for all your help!
Randy

Like the other guys have posted it could be the intake boot from the carb to the cylinder head. Check to see if the bolts are tight just in case. A way to check for a leak is to spray a little wd40 around the intake tube connections while running. If it gets sucked into the engine from a leak it will change the idle.

What condition is the bike? Think someone has "wrenched" (worked) on the bike very much?

The idle screw shouldn't be magically changing on you. You might have partial blockage on the pilot jet.

You did check the air filter to make sure it is allowing good air flow - not dirty or clogged.

Check the slide cap to make sure it is screwed on tight. It's at the top of the carb where the throttle cable attaches. It just has to be snug.

How much did you have to adjust the screw anyway? Full turn? Half turn? Quarter? Hopefully it still starts easy and continues to idle like it is supposed to.

Previous owner may have increased the idle...

My sons '08 crf50 just started doing the exact same thing. The bike only sat for about two weeks then the condition started. There are no mods done to the bike it is completely stock. The gas should not have gone bad in two weeks. I guess I will try the intake boot for leeks and then clean the carb. I will let you know what happens.

Curious what your plug color is.

My little Hondas have been like tanks for me. They just go. I do run them for 30 seconds with the gas off before parking. I've let them sit for long periods and they always fire right up. Use Stabil in the winter.

Guess I've been lucky so far.

Only other thing to check might be the spark arrestor screen.