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RSRBOB, Technician
Category: Boat
Satisfied Customers: 1078
Experience:  Former Yamaha Factory Service Rep, Dlr Line Tech, Serv Mgr, G/M
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Ive got a 2003 Yamaha XLT 1200 and it idles fine but

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I''ve got a 2003 Yamaha XLT 1200 and it idles fine but as soon as you put it in the water and hit the throttle it will start to rev up and then it falls on its face. I''ve changed the fuel, check the pickup, changed the fuel filter. It dosent matter if the fuel selector valve is in "ON" or "Res" it seems to be the same. But I do believe it to be a fuel problem, when your on the water and it starts cutting out, the fuel filter runs out of fuel, if you let off the throttle the fuel filter fills half way up. I''d really appreciate the help, I just sold this because I needed the money I''d never had a problem with it and now this. my email isXXX@XXXXXX.XXX


It sounds like a carburetion issue. There are two things I would like you to check. First, check the high speed jets to make sure they are not clogged. To access the jets, both high speed and low, you will have to remove the crescent moon shaped piece that i s held in place with 2 phillips screws(#44 in the diagram). Second, check the dime shaped check valves in the fuel pumps to see if there are creases in them. The creases reduce fuel pump efficiency which certainly could produce your symptoms. You will need to take the carbs off to do this, which also included removing the exhaust. It is quite the ordeal to get the exhaust on and off if you have never done it before. The carbs are directly below the exhaust on the right side of the engine compartment. Here is a diagram of the carbs and what you are looking for. Reference #14 is the high speed jet, Reference # XXXXX is the check valve you need to inspect.

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Thank you,


XL 12 Carbs

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Customer: replied 8 years ago.
Reply to RSRBOB's Post: Also, when I first take off on it it runs fine for about 100 yards or so and then boggs down to about 8 mph. I shut it off and start it right back up and it wont go past 8 mph. I turn it off and wait 5 minutes and start it back up and it still won't go past 8 mph. By the way if you could reply without attachments becuase I am away from a computer right now and my phone wont open emails that have attachments with them.

Hi Cathy,

It sounds like you have carburetion issues or the catalyzer in the exhaust is blown out. You need to remove the carbs, which is a rather involved ordeal, and inspect them. When you take the rear half of the exhaust pipe in the engine compartment off, you need to inspect the catalyzer to see if the center of it is still there. If you see any kind of open hole, the cat has blown out and is lodged farther down inside the exhaust pipe and restricting exhaust flow producing the problem.

As far as the carbs, if it isn't the cat, need to be inspected for restrictions and damage to the fuel pump check valves.

Getting to the carbs on your particular ski is a huge pain. As I eluded to earlier, you have to remove the exhaust sytem in the engine compartment to get to the carbs. It is about a 4 hour job for an experienced mechanic. Honestly it is a bit more than I would reccomend the week end warrior to attempt. I will leave it up to you to evaluate your mechanical expertise to decide whether it is something you want to tackle or not.


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Customer: replied 8 years ago.
I found the Cat con. blown out, tested compression #1-90, #2-70, #3-70 what should they be and what should I replace the rings at?
Thanks for the response.
Your compression should be about 110 per cylinder. If all three were reading 90 then I would suspect either your compression gauge is off or your battery was low. At the readings you are getting, I do suggest removing the cylinders and inspecting the pistons. rings and cylinders for wear or damage.
There is some good news on the cat however. Instead of replacing the cat, several companies make D plates that you can install in place of the cat at a substantial savings to you with no ill effects on the ski's performance or durability. If you do opt for the D plate, make sure you get the chip to plug in where the cat sensor plugged into the bottom of the electrical box so you don't have to listen to the warning buzzer all the time. If you want to replace the cat, you can. Last time I checked, the cat was close to $700, because of the precious metals it is made out of (platinum and rhodium and one other I forget right now) or a d plate with sensor chip is under $150.

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Thank you,
Customer: replied 8 years ago.
Thank you so much for all your help. I'm a mechanic by trade, but don't know much about boats and skis, when you remove the head and the cyl(s). can you put the piston if needed and the rings on the cyl. without removing the engine. Like on a dirt bike you can freshin it up with rings from time to time without alot of head ache. Do you know the position of the rings and do you also have torque specs? Is there anything I should do to the power valves? Thanks again, Brian

P.S. Thanks for the advice on the d-plate, thats what I'm going to do.
Yes, you can replace the pistons and rings without removing the crank, similar to a dirt bike.
Also like a dirt bike, the rings have locating pins towards the intake side that are pretty obvious where the ring end gaps go.
I would definitely pull the power valves and inspect them closely. Yamaha did have some problems with power valves braking off at the shaft and dropping down and hitting the pistons and causing damage. They blamed it on lack of maintenance by the owner. Pull them out and clean and decarbonize them before reassembly.
The cylinder base is torqued in two steps, 1st to 16 ft. lbs., second to 29 ft. lbs.
Cyl Heads are torqued to 17 ft lbs first then 26 ft lbs.

I wish you well. Thank you for your inquiry.

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Customer: replied 8 years ago.
Thanks again for everything, you've been a tremindous help!

You are most welcome.

Good luck with the repairs!


Customer: replied 8 years ago.
Also I retested the compression in reverse order and found completely diff. readings so i bought a different guage and the compression is #1-120, #2-120,#3-120 so glad so now I guess I'll rebuild the carbs and check the powervalves? What exactly is the purpose of the power valves? what happens when one goes bad? Thanks again!
Ok, that compression sounds good.
The powervalves are essentially a variable height exhaust port. Hitting a bit of theory here, the exhaust port is a major factor in how much HP and where the HP is. A large exhaust port with a high top produces good peak HP but at the expense of low end. A smaller, lower exhaust port produces good low end HP but at the expense of peak HP. A powervalve changes the height of the exhaust port with engine RPM. At low RPM it is "closed" where it reduces the height and size of the exhaust port. As engine RPM's increase, the powervalve lifts, raising the height and increasing the size of the exhaust port to boost peak HP. You can no see how a powervalve allows an engine to have the good HP down low from a smaller, lower exhaust port and still have good max HP at higher RPM's with a bigger, higher exhaust port.

On Yamaha's, the main thing is keeping them clean so they don't stick. Some of the early ones had problems braking off the stem and dropping down and hitting the piston, causing the rings to stick. I would look at the stems just to make sure there are no signs of stretching or stress and then just get all the carbon off of them and put them back in.

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