My son's 2002 LT-A50 (2 stroke) was purchased used and I have no idea if the two prior owners ever cleaned or rebuilt the carb. I tore it down and discovered that - according to the manual - the pilot air screw and the throttle stop screw were exchanged. The machine runs perfectly, yet according to the descriptions and every single photo in the service manual the screws were reversed. One has a slotted head while the other has a cross head, one is longer than the other, one has a flat end while the other comes more to a point, etc. They're different in most ways except the threading.

I also discovered the float was sitting too low. The manual calls for 0.96-0.98 inches, but it was sitting at about half that according to my calipers.

During the rebuilt I put things back the way they should be: Each screw was put where it belonged, the float was adjusted properly, etc. The carb was remarkably clean (I use Seafoam, which probably helps) and was spotless when I put it back together.

Once the carb was reinstalled, the engine fired right up... but idled really high. I had to back out the throttle stop screw a LOT to get it to calm down. Throttle performance was weird, too. For example, if I revved up the engine for a while and then released the throttle, the engine would continue to run at the same high RPM's for 10-15 seconds before it started to slowly rev down.

After fiddling for a long time with screw settings, partially covering the air intake (due to the colder, denser air), etc. I couldn't get the engine to behave. As a last resort, I swapped the two screws back to their original positions. PRESTO! Things started working properly again! WTF?!?

I checked and rechecked the manual to confirm that the screws were, and now are again, backwards. The manual is clear and consistent, and they are backwards. Yet the engine runs properly, idles great, has great throttle response, everything. It's the weirdest thing I've seen in a while.

If you have an LT-A50, do me a favor and checked your carb. The screws are visible through the footwell opening that yields access to the choke lever. The manual shows that the front screw, which is the pilot air screw, has a slotted head while the rear screw, which is the throttle stop screw, has a Phillips head. Yet on my machine, the screws are the opposite. What does yours have?

 

We have an 03 LT50 and the phillips head screw is closet to the front of the quad.

 

Yep, that's just what the manual says it should be. Mine is the exact opposite. Do you still have all of your restrictors in place? Some prior owner removed the exhaust restrictor and the second pilot jet, but the exhaust restrictor is still in place on mine.

 

I removed both the exhaust and intake restrictors, piggy-back jet, drilled the airbox (jetted accordingly), one step colder plug, lightened the clutch weights, cleaned up the casting on the intake, and milled the head .020". This little thing moves with my 6-1 240# on it.

 

Yes, I know how to de-restrict the machine. My question is: How are your pilot air screw and throttle stop screw arranged? Which is which, based on the head type?

 

One more weird thing that happened when the screws were in "correctly": If I gave it some throttle for a few seconds and then backed off, the engine continued to run at the higher RPM point for 10-15 seconds even though the throttle had been completely released.

Reversing the screws solved this problem, too.

Dang weird stuff.

 

<div class="FTQUOTE"><begin quote>Originally posted by: WAATV

Yes, I know how to de-restrict the machine. My question is: How are your pilot air screw and throttle stop screw arranged? Which is which, based on the head type?</end quote></div>

I answered that in my first post.

 

My son's 03 LTA has the phillips head more towards the front side of the carb, and the straight head to the left of it.

 

Same as the other respondent. Thanks to both of you for checking.

So far, I have the only machine with reversed screws. Very, very weird. I'm certain they're backward but the machine doesn't run right when they're "corrected". Grrrrrrr....

 

<div class="FTQUOTE"><begin quote>Originally posted by: dwhst9I answered that in my first post.</end quote></div>

Sorry, I didn't see at first that you were the same respondent. My apologies.

Still a mystery why it doesn't work with the screws installed properly, and does work with them backwards. Obviously someone before me discovered it and left it that way, but still....