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  1. #1

    Newbie looking for help. '02 XLT 800 engine issue

    I just purchased a used 2002 Yamaha XLT 800 and I am hoping this issue I am having is not a major problem. Ski ran fine first three times I used it. When I ran it on Sunday it seemed to be bogging down a little before hoping on plane. Then when I was flushing it I pulled the throttle when finishing up just to get any residual water out and the engine began to race even when throttle was returned. Had to pull the emergency clip to kill it. I hooked water back up and began to trouble shoot on land. Even with a slight pull of the throttle the engine wanted to take off which seems very odd because that is the exact opposite of it bogging when in the water. The throttle cable seemed to be returning to neutral position and the carbs seem to be closing fine. I put it in the water today and could not get it to go. It idles fine and as soon as I get on the throttle it bogs and stalls. When I put it back on land it idles fine and as soon as you touch the throttle it wants to race. Very odd. Like the total opposite of what happens when in the water. I did find a pin hole in my aluminum silencer but I highly doubt that would be having this big of an effect. Any ideas?

  2. #2
    I believe you have what is known as a "lean runaway" condition. You likely have an air leak somewhere in your system and are at risk of your motor becoming a 70lb boat anchor. I just finished dealing with this exact same symptom. My problem was that one of the pulse lines coming from the motor to the fuel pump was blocked off with some debris. That is something that can be investigated easily. Pull them off and blow through them. If one is may be done. Since you are also having bogging issues, I would pull your carbs and take a look through them. Search the hulk here for osidebill and his "sticky" on rebuilding carbs. Also look up "pop off pressure testing" here and on YouTube. Take pictures or video of each step as you go and you shouldn't have a hard time putting them back together. They are actually fairly easy to work on. Again...take lots of photos, stay organized, put stuff in baggies and label where they came from. If you don't have the time or desire to deal with them yourself. Quite often people find that their carbs leak at the base of the fuel pump side where the pump meets the carb body. I don't know if this can cause a lean runaway but you may want to find out. The usual suspects on carb leaks are the big Oring at the base, debris under or on this Oring or sometimes the black diaphragm that covers that Oring. Post pics of what u have in there for more help identifying bad parts. You said your ski ran well at first. If the seller had cleaned the carbs but had old gas in the tank...your carbs are probably no longer clean . There is a little fuel filter basket inside the fuel pump. Check it for debris and spray it out with carb cleaner if it is dirty. Again, check osidebills carb posts...they will tell you everything you want to know about carbs. If you don't find leaking may have a leaking head gasket, base gasket, carb gasket, oil seal on your crank shaft or even loose spark plugs. Torque specs are huge in holding these motors together properly. If bolts are not torqued correctly or even in the wrong sequence it can cause a leak. The only way I know of to test this is to pull the motor and do a leak down test. (Also something to search for here. Hope this helps a bit. What is your level of mechanical ability?

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