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1989 90HP V4 dies at 2500rpm

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abl1111

Regular Contributor
My buddy has an ‘89 90HP V4 that runs (ran) like a top. Was winterized in fall. This spring, was stalling - ignition wire was cut, probably running on 3 cylinders.

Installed new ignition wires. Starts great. Idles great. Runs to 2500 rpm’s fine. Then dies. Checked spark at each plug. Plugs could definitely be replaced. There is no water fuel separator or a pre Fuel filter before fuel pump. Screen at fuel pump is clean. New fuel. Fuel line and primer 3 years old.

Going to replace spark plugs. And, pull carb. cowling off and spray carbs with gum out.

Thoughts where to focus ?
 
Just one step at a time.----If compression is around 115/ 120 PSI then a proper spark test is next.----Spark must jump a gap of 3/8" or better.
 
Ok
ill have my buddy do this. Any specific method to the test ? Or just screw Comp tester in and turn motor over ?
 
abl1111 said:
Ok
ill have my buddy do this. Any specific method to the test ? Or just screw Comp tester in and turn motor over ?
Click to expand...

Make sure you have a fully charged strong battery, pull all plugs, connect compression tester, crank over until gauge quits going up. repeat on all cylinders. On the spark test, as Racer sais, it needs to jump an 3/8" air gap with a bright blue spark.
 
Spraying a bit of cleaner into a carburetor throat is just not the way to make sure a carburetor is clean !!------The carburetors on a motor like that are VERY IMMPORTANT to make sure each cylinder gets the correct amount of fuel and the OIL that goes in with the gasoline !!
 
Compression is 125 on all, but one which is 115. All spark is fine.
Agree about carb cleaner but it certainly can’t hurt. Just got to 3000rpms then it dies as if you’re pulling back on throttle...

Next area to focus ? Going to use a 3 gallon fuel tank to check fuel source.
 
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