2002 Xlt 800 runs great on the lift, then bogs and dies under throttle in water

have you got any water in the fuel tank ?? very basic ski 2cyl 2stroke ! i recomend stripping the carbs and clean and check the diaphams have not gone hard also ! dont try and run it to clear the problem because if one carb shuts off the fuel feed then you will melt a piston !! then boo hoo no more play time !

If this has a carburetor, look at the Power valve that is connected to the throttle lever. It is a small plate in front of the carb with a lever that moves with the throttle. There is a small rubber valve inside which allows gas to flow between chambers.

Another possibility is the fuel pump. After that, a bad Vacuum leak like from a ruptured EGR diaphragm can cause these problems.

Does the engine want to bog down when you move the throttle? Or does it do absolutely nothing?
If it bogs down when you try the throttle, It could be:
water in the gas
bad or distorted diaphragm (if no float)
stuck needle valve
stuck float

I’m happy to help further over the phone at https://www.6ya.com/expert/karl_14766549451f8563

You didn't say what year or model bike it is but I'm going to assume that it has the stock Keihin CV carburetor on it. You need to check two things, the accelerator pump and the slide vacuum diaphragm.

To check these, first take the air filter off but leave the backing plate on the carb. With the engine OFF, crank the throttle wide open while looking into the mouth of the carb. You'll see a brass nozzle just inside the mouth of the carb. When you crank the throttle open, you should see a squirt of fuel come out of this nozzle. If not, you need to replace the diaphragm in the accelerator pump that is on the bottom of the carb float bowl.

If that is working correctly, start the engine and gently rev the engine while watching the slide inside the carb. DO NOT GET YOUR FACE TOO CLOSE TO THE CARB IN THE EVENT THE ENGINE SPITS BACK THROUGH THE CARB. The slide should be moving up and down. If not, the vacuum diaphragm that operates the slide may have a hole in it. You must take the carb off the engine and take the top plate off to get the slide and diaphragm out.

One other thing. If the bike has been sitting for an extended period of time, the jets may be clogged inside of the carb. This will require a complete disassembly of the carb to clean out the jets and the small fuel and air passageways.


Good Luck
Steve

If the engine is running, it's not a timing issue. If the engine is running and the timing is not right, it would continue to run when you give it some throttle but maybe not run well. I'd suspect the carb. If you've put a later model Keihin CV carb on the bike and it dies when you give it throttle, you could have either a bad accelerator pump diaphragm or a hole in the vacuum diaphragm that controls the slide. To check the accelerator pump, remove the air filter so that you can see inside the mouth of the carb. With the engine OFF, crank the throttle to wide open. Watch for a stream of fuel to squirt out of the brass nozzle just inside of the mouth of the carb. If you do not see the shot of fuel, your accelerator pump in not working. You need to drop the float bowl off the carb and check the diaphragm and fuel passages to make sure they're open. To check the slide vacuum diaphragm, with the air filter off and the engine running, rev the engine up a bit and watch the slide in the carb. It should move up and down. Do not get your face too close to the carb. If it spits back through the carb, it could cause you some injury. If the slide does not move up and down, you may have a hole in the vacuum diaphragm. In order for you to install the Keihin CV carb on this model Sportster you had to have changed the intake to one specially made for this installation or you had to use an adaptor. Make absolutely sure you have no vacuum leaks. Look on the backside of the carb for a vacuum port that you may not have connected to the VOES switch.

Good Luck
Steve

If the engine is equipped with a carburetor, it sounds like the accelerator pump is not working. Take your air filter off and with the engine OFF, crank the throttle wide open. You should see a squirt of fuel squirt into the carb from the brass thing in the mouth of the carb. If not, the accelerator pump is not working. It probably needs a new diaphragm in it.

To put a new diaphragm in the carb, remove the air filter backing plate and take the four screws out that holds the float bowl on. With the float bowl off the carb, turn it upside down. Take out the remaining two screws in the accelerator pump plate. You'll see the diaphragm and the return spring under the plate. Put the new diaphragm on position with the sping on top and reinstall the plate. Put the float bowl back on the carb and reinstall the air cleaner backing plate. Make sure the throttle works as it should and start the engine. It should rev cleanly now.

Good Luck
Steve

Ok I have r Royobi Tiller (30CC Gas) And last year it ran fine after rebuilding the Carb. This year it was "hard starts" Idles fine, (Tiny whisps of blue smoke in exhaust with correct ratio) Even seems to run better with the choke "on" but still...at idle only. as soon as I touch the throttle...its bogs down in tune with how much gas I give it. Little throttle? Little bog down, Little more throttle? Almost stalls, a normal throttle rev? it stalls dead! Then starts right back up again in 1 pull and idles fine again!? WTF? So after cleaning a clean carb again, (twice) and seeing no change I thought I'd go look at the original diaphragm and compare it with the rebuild kit diaphragm (which is the one in the carb.) And guess what? The replacement has a larger rivet by a factor of "2". So basically it was flooding the carb, I bent the needle tang down, better but no cigar. But I could rev it half way now. A second disassemble to bend it yet a bit further and Vrooom vroom vrooom ****! So check your needle valve even though you think its 100%. (Especially if you rebuilt the carb with a kit!)

Are you sure you did not get the jets in the wrong places when you cleaned that carburetor.

Sounds like the carb needs to be rebuilt. Those tiny jets will clog easily and need to be replaced. The diaphragm is also a large part of bogging and dieing. Hope this helps.