sputter at full throttle

[verado7]

wondering if anyone else experienced this -
88 classic fifty 4cyl.
carbs rebuilt
new stator/switchbox

at full throttle the engine seems like its not firing right - i can hear it sputter a little but it will clear up if i back the throttle down a bit - max wot for this motor is 5500 rpm and i can get the throttle up enough to get 5300rpm from it - but then there is about a 1/2 inch of travel left in the throttle - when i do go full out the rpms dont change but i get this sputter -

 

[oldgradywhite]

Re: sputter at full throttle

I would do a lync n sync. Type it in to the seach bar in iboat fourms. I bet it will solve your problems.

 

[verado7]

Re: sputter at full throttle

thanks - i was thinking of that - the boat is at my work yard so i was looking for any input - have you ever heard of a new stator throwing out the timing ? - i am supicious that the wot timing is out unfortunately my timing light bit the dust so i have to pick one up before i go down there .

 

[CharlieB]

Re: sputter at full throttle

The symptoms you describe are typical of a reduced fuel flow, any one or more of the following could be a cause, dirty filter, weakening fuel pump, restricted hose/fitting/pickup tube in tank, air sucking INTO the hose somewhere.

Any or all of these need to be checked out, found and corrected before you lean the motor out and melt a piston.

You can determine if the problem is AFTER the primer bulb by squeezing the primer bulb while opening the throttle to WOT, if the motor picks up speed or the condition clears up then you can be sure it is one of the conditions described above.

 

[verado7]

Re: sputter at full throttle

thanks charlie - fuel pump and carbs rebuilt 2 weeks ago -float set and it does it no matter which tank i use - tanks were new as of 2 years ago -bulb stays firm - i can nail the throttle from a stand still and all is good until it gets up to about 5400 rpm at steady speed . i did a shut down and plugs are normal so i dont think fuel is a problem .

 

[CharlieB]

Re: sputter at full throttle

Have you tried squeezing the primer while at WOT?

Another test is to just 'Bump' the choke/Enrichener to artificially richen the fuel mixture.

BOTH of these simple tests are necessary in determining which direction to go for further inspection/testing to diagnose your problem.

 

[verado7]

Re: sputter at full throttle

i knew it wasnt fuel - i fixed it - and i am a dumbass - the spark leads weernt seated all teh way in the coils - doh!

 

[Jacket4life]

Re: sputter at full throttle

Lol, glad it turned out to be simple!