1996 200hp Yamaha Problem

[Knockerjoe]

I have a problem with my 1996 200hp Yamaha carburated . When throttle is pushed over 4500 rpm it will go back to 4300. <br />Here is what I have tried so far(note, i have twin engines): <br />Changed spark plugs old ones looked good.<br />Swapped coils.<br />changed fuel filter<br />tested fuel pump, no leak at weep hole.<br />swapped squeeze ball. checked good at power.<br />hooked up pony tank.<br />any help or suggestions will be appreciated.

 

[rodbolt]

Re: 1996 200hp Yamaha Problem

check for fuel resticions with a vacum gauge. the pumps can fail and not leak. test the compression and if thats good open up the carbs for a look see.

 

[Knockerjoe]

Re: 1996 200hp Yamaha Problem

Sorry, i forgot to mention that i did take apart the carbs and cleaned them out. I also checked the compression.<br />Where should I hook up the vaccum gauge?

 

[Knockerjoe]

Re: 1996 200hp Yamaha Problem

I will be installing 2 new fuel pumps tomorrow. <br />Rodbolt, do you know where i should check for fuel leaks with the vaccum gauge?

 

[Knockerjoe]

Re: 1996 200hp Yamaha Problem

Replaced with new fuel pumps today no change. Any ideas?

 

[rodbolt]

Re: 1996 200hp Yamaha Problem

go back by the dealer and have them make a copy of testing fuel systems for restrictions. its in the 01,02 and 03 tech guides. also test the spark plug caps. should have about 5K ohms. but it sounds like you have more air than fuel avalible.

 

[Knockerjoe]

Re: 1996 200hp Yamaha Problem

checked spark plug cap, 4 were out of range so i replaced them all. reinstalled the carbs, same results. swapped cdi units, same results. this is what im down to, im going to swap carbs from one motor to the other. this will totally rule out everything in the fuel system. i tried to get the dealer to make copies of the tech guide,but they refused. after that im down to components under the flywheel. what about the possibility of a head gasket at the beginning stages of failure, allowing water into the cyl at high speed????? thanks for your help

 

[rodbolt]

Re: 1996 200hp Yamaha Problem

usually a head gasket leaking at high speed results in an overheat alarm and RPM reduction turned on. before swappping so much do your self a favor, draw a diagram of the entire fuel system, starting with the liquid in the tank, you can have a restriction in the draw tube filter ,if used. the anti-siphon valve. an air leak in a joint or even a bad engine side quick connect. try running it with a known good tank hooked directly to the engine mounted fuel filter.<br /> before splatter gunning a problem break it down into subsystems and eliminate them. there is not much on that engines electrical that will give you your symptoms.<br /> you can also have someone run it and squirt premix in the carb throats at the problem RPM, if it picks up you know where to look. still sounds like your getting more fuel than air.<br /> that motor will run ok with the airbox off, not forever but long enough to do what you want to do.