I have a 2001 Scrambler 50 that will idle and run up to 1/4 or 1/3 throttle then just bog down. If I keep the throttle anything above the 1/4 to 1/3 throttle it will just stall out. I had problems with the idle but turned the air screw in so it's less than 1 turn out and it now idles fine. I've cleaned the carb out twice and it's looks really clean.

Where should the clip in the needle be? Once place we ride at 900 ft above sea level and the other is 1300 feet above sea level.
It seems enough gas is coming out of the gas line. It seems more like a carb or eletronics issue.
I have the air filter assembly removed since it's easier to work on.
What am I missing?
I've not looked at the reeds yet. Could that cause these symptoms?
I've not checked compression yet.

Thanks!

 

Does it actually stall when it reaches a certain rpm or does it studder and not increase. My problem is the tiny holes in the main nozzle were plugged. I took it out blew it out and ran perfectly.

 

It's stalls out and the engine just does like it's not getting fuel. I did clean the jet out but it did not seem plugged. would the needle setting affect this?

 

It really sounds like the main nozzle is plugged, I should ask first if it is Mikuni. To take the main nozzle out you need to remove the carb. Take the bottom bowl off, and the main jet out. the piece the main jet screws into is the nozzle. with the main jet out that pierce will come out through the top. You may need something blunt to tap it. What I do is take the main jet out, remove the washer and then screw the jet back in that way you can tap on the jet itself and with out the washer it will fall out with the nozzle. On the nozzle there are about 8 or 10 little holes. These holes get plugged up and will not let it run to or past midrange. Blow those holes out and reinstall the nozzle. there is only one way it can go in, it has a grove in it and there is a piece that the grove will slide over. Put it all back together and give it a shot. Let me know what happens and if there are any more questions.

 

Did you thoroughly clean the pilot jet? The main jet won't affect 1/4 to 1/3 throttle.

 

Your right the main jet usually isn't the culprit, for me it is the nozzle that the main jet screws into. those darn little holes on the nozzle get plugged easy.

 

It is a Mikuni carb. I pulled the carb apart again and removed the nozzel which I had not done in the past (did not know it was in there). I was very suprised to see it was actually clean and I could see throught the holes. I still washed it in carb cleaner and blew it out. I put it back togther and it still does the same thing but seems to start harder. When it was starting to stall I put my hand over the carb intake (air filter is remove for now) and it seemed like it seemed to run better. If I spray starting fluid it will start right up then die. It's sometimes really hard starting and other times it starts right up. Is there a way to bypass the auto choke temporarily? Or to test it?

The needle valve is set to the middle position.

I should mention I'm in Minnesota and it's about 45 degrees in my garage where the Scrambler is stored and it's about 40 outside where I'm running it.

I checked the compression and it's 113 or so (assuming my really old guage is correct).

 

Well it seems I may have a few issues. I was able to get it started and running again (it seem the reserve fuel line or reserve in the petcok is plugged). So when I got it running again and it started to stall at mid throttle I put my hand over the intake and it kept running. I put the air cleaner back on and it seemed to run ok. I was only able to run it for 30 seconds since it's getting dark and a little late. I want to keep my neighbors happy.

Is that normal that for it to run right it requires the restriction of the airbox and airfilter?

 

run a separate fuel line from a small aux tank (lawnmower plastic tank).. if it runs ok your tank shutoff and screen are plugged

 

I finally had a chance to work on this again now that it's nicer out. I replaced the fuel filter and some gas lines, fuel flow seems great now. It seems to start up easy and runs for about 1-2 minutes then dies. I unplugged the choke and then it runs OK. Do you guys still think it's just a dirty carb? Any sugestions on how to clean it. I've cleaned it 2-3 times with carb cleaner and it keeps getting better at least.