1987 fz750 running issues

[Bignoga]

The bike is stuttering between idle and 5000rpm. Sounds like a harley. It also stutters if I give it abrupt throttle.

I have changed the spark plugs and still had the same issues.

 

[omnivore]

Does it idle okay, and full throttle okay, but sta,bles on all part throttle application?
Gonna guess there's debris stuck in needle jets

 

[Alex Dee]

Does it idle okay, and full throttle okay, but sta,bles on all part throttle application?
Gonna guess there's debris stuck in needle jets

the bike does idel ok, but full throttle will studer, I am the owner of this old bike, bignoga was just posting as a favor to me

 

[Alex Dee]

STILL on going problem, i cleaned out the carb's completly and still same problem so i began to thing maybe that the Timing was off but this bike does not have a distributer but a pick up coil assemble which i belive to be the equvilant to a cam shaft postioning sensour on modern fuel injected motors. but none the less is it possbile that somthing along the lines of ignition would give proper ignition between 5000-10000rpm and no where else? I REALLY NEED HELP THIS IS KILLING ME
thank you

 

[gav.man]

Sounds like a lean condition. When you cleaned the carbs did you pull all the jets and run wires through all the jets and air holes to make sure they are all clear and clean with carb cleaner? Idle to 5k is the pilot circuit. If plugged enough it will cause problems higher up as well.

 

[kneedragger88]

Check the manifold rubbers for cracks. Old bike and sounds like she is sucking air.

 

[Alex Dee]

Thank you for all the suggestions, is it possible the mainfold rubbers could create such drastic behavior? if so which rubbers the ones between the engine and the manifold or the ones between the mainfold and the air box? THANK YOU!

 

[Ed In Mississauga]

Check the rubber between the engine intake manifolds and the carburetors. Cracks in this rubber will throw off the air/fuel mixture going into the engine. However, it wouldn't hurt to check the rubber between the carburetors and air box either as cracks here will cause unfiltered air to go into the carburetors.

 

[Stewart]

make sure the mechanical advance is moving freely, behind the ignition pick ups. then check the spark plug caps for 5000 ohms, replace if over 7000 ohms.

 

[Armen444]

Carb tuning/jetting. assure you are getting the correct air/fuel mixture to the designated RPM's it is stuttering at. It is possibly too lean or too rich.