I have a 250 and a 400 that sat up for about a year and a half. I drained fuel from both, got the floats un-stuck, etc. The 400 runs great and so does the 250 until you hit the throttle. It bogs badly and makes a spitting backfire type noise.

I assume this is carb related. I cleaned the float bowl and needle/seat, that got it so it would idle, etc.

Suggestions?

Thanks

 

make sure the air intake is all clear. could've had some critters make a nest in the intake tubes causing it to run rich when you hit the throttle, but still be ok at idle...jm.02

 

also check or main jet in the carb. could have carmelized gas in it not letting motor get enough fuel into the motor

 

If you get your fuel system clean and still have the problem, check your voltage output at the battery. If your regulator/rectifyer is shot and it's putting out no volts or greater than 15.5 volts, that will cause the cat to lay down on you. If you have had a bad battery and ran the cat for a while, this will cause the regulator/rectifyer to go bad due to having to work so hard to supply energy to try to recharge the battery. A bad battery on my AC400 (which I was too lazy to change since it always cranked on first pull) cost me a $300 regulator!!!

 

Where is the main jet, or where can I find a diagram on the carb online?

Check the volts while the leads are connected to the battery?

I narrowed the symptoms down a bit. When I run it with the air intake installed (the plastic piece that doubles as a toolbag holder) it bogs down, if I run it with that removed, it seems to run normal or close to normal. I checked for blackage, no blockage in the air intake tube or anywhere else.

 

try seafoam in the gas to clean out the carb then add some sta-bil in subsequent fill ups

 

YES, check voltage at the battery with the leads on. I chased numerous other symptoms before I found that my only problem was the rectifier. If you have less than 12 or greater than 12.5 that's your issue.

ernie

 

I checked across the battery with the engine idling, got 14.1 volts.

I tired to crank this thing maybe one time with a bad battery, blow my mind it can go out so easily. (If that is indeed what is wrong with it)

 

Sorry, my last post was a fat-fingered typo!

14.1 volts is OK! The manual says it's an issue when it's greater than 15.5 volts. It doesn't make any sense for it to run better with the airbox removed (or partially removed) unless there is a blockage somewhere between the air filter and the carb inlet. With that said, I think you have a carb issue, probably a clogged (or partially clogged) main jet or secondary jet. I just got thru cleaning out the carb in my future son-in-laws' Yamaha timberwolf. His was bogging down when it got warm. I pulled the carb off and it had the typical "musty-gas" smell from old fuel. The main jet and the secondary jet were both partially clogged. A small diameter wire and some carb cleaner took care of that and now it runs great again.

If you pull it off, be sure to remove the main and secondary jets to clean them and REMOVE the needle and seat assembly and spray carb cleaner thru the hole where the seat is and blow out any trash that may have entered from the fuel line side of the carb. My AC400 has a screen there that was clogged but I'm not sure if your 250 has the same sreen. Regardless, get everything good and clean and I think that will take care of your problem

OH.........BE SURE TO WEAR SOME EYE PROTECTION WHEN USING CARB CLEANER TO CLEAN OUT SMALL PASSAGES IN THESE CARBS. IT WILL BLOW BACK INTO YOUR EYES! TRUST ME ON THIS!!!

Ernie

 

How to clean a carb

Don't worry if your carb's different the main thing is the piot and main jet and get the wire through all the passages of the carb body.

If the jets are stuck just put a wire through them as is.