Thread: Problems with 94 VXR Pro
03-30-2009, 04:39 AM #1
Problems with 94 VXR Pro
MY friend has a problem with his yamaha. It stumbles at high rpms and gets progressively worse the longer it runs. It won't go past 4800 rpm cold and after it heats up it won't go above 4000. He's put a rebuild kit in the carb to no effect. He also owns a 95 wave raider. Both ski's have 701 engines in them but the 95 has dual carbs. Are the cdi's compatible for swapping to see if the 94 has a bad cdi. Any help is greatly appreciated. He wants to fix it as cheaply as possible. It seems to be worse at high throttle settings and runs better if he feathers the throttle. It bogs real bad at wot. The jetting has never been changed and it ran like this when he bought it. The previous owner thought it just needed a carb rebuild.
03-30-2009, 09:04 AM #2
First dont run this boat again until you get that worked out......you could be doing more damage every time you run it leaned out like that.
The reason its so bad off the line and then again at top is because the engine is starving for fuel.
Just guessing I would say you probably have some sort of air leak.....like a bad crank seal or blown head gasket.
First thing to do is get a compression tester and find out what your compression is...should be over 120psi in each.
Since you already went thru the carbs you should also be checking your pulse lines that run from the case to the carbs for cracks or air leaks. If these lines have a small leak then it will cause the fuel pumps to be inefficient and lean out the motor.
If it runs its probably not the cdi because two cylinder engines run off the same pickup. What you are describing is a fuel issue and it sounds like its pretty bad off.
03-30-2009, 09:40 AM #3
This is the exact same advice I gave him. I guess we'll have to bring it over to my place to check it out further. I figured either a case gasket or the head gasket. Didn't think about the pulse lines. It's been awhile since I played with a 2-stroke. I thought it sounded like it was going lean too. Thanks for the help.
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