Poor running 93' gas Yamaha cart
 

It has no power, runs a tad better with small amount of choke on, compression is 165lbs, valve adj. correct, carb cleaned and swapped with another but symptom the same,replaced fuel pump,Runs slightly better with air cleaner off, but it is clean,it has a 1" crisp blue plug wire spark. I disconnected the muffler and it didn't improve, but, it sounds like it is retarded-like my lawn mower sounded when it partly sheared a flywheel pin. The ignitor box appears ok, with its internals not burned or swollen. The plastic intake manifold is good=no cracks, gaskets good.,
Could the magneto or pick up coil be loose or failing causing it to be out of time? Please help. bdooners@hotmail.com
:help:"les"

Re: Poor running 93' gas Yamaha cart
 

did you ck the new fuel pump for flow? sometimes the vaccume line from the crank case to the fuel pump gets pluged with oil or has cracks in it & the fuel pump wont work correctly. what color is the plug burning

Re: Poor running 93' gas Yamaha cart
 

Sometimes the ignition box will look fine, but operate poorly. Try to find a timing gun with a advance knob on the back. Put a paint mark on the clutch and crankcase next to each other with the piston at tdc on compression stroke. Using the knob, you will be able to fairly accurately detect what the timing curve is like as engine speed increases. If you can collect this info, i will compare it to my "good running" example. Dont need exact rpms, just general info, like "advance at low engine speed" "advance increases smoothly with rpm increase?" And "max total advance". I have checked mine before out of curiosity, but long time ago and dont remember results

Re: Poor running 93' gas Yamaha cart
 

G9 is about zero at under 1K rpm then advances to about 30 by 2500 and stays there....per the manual.

Re: Poor running 93' gas Yamaha cart
 

Thank you. I have a timing light with a knob on the end [an old fox valley] and will attempt the test you described. I am curious as to how I will mark the flywheel. Can it be accessed? Must plastic covers be removed? Thanks, Les:lol:

Re: Poor running 93' gas Yamaha cart
 

Make a mark on the side of the engine, then, Mark the clutch, not the flywheel, not the belt (with piston at tdc). It will work just as good as the flywheel (until the clutch is removed, then the mark is no longer accurate).

Re: Poor running 93' gas Yamaha cart
 

2 things come to mind. On stock 93's the negative battery cable (at the starter/generator) hada 18 gauge wire crimped on the eye end, cut it off and put a small eye end connector on the wire and reattatch to the starter post for a positive ground. If it run's better at partial choke or air box disconnected, I would think a airbox sealing problem (bad straps/air box lid seal or warpped air box lid), the airbox sealing correctly is critical. Good luck.

Re: Poor running 93' gas Yamaha cart
 

This morning I pulled the plug, located TDC, and marked the block and the pulley. It appears that it is advancing the timing approx 25 degrees--that's pressing the gas pedal with one hand, holding the timing light with the other-and turning the degree knob with my teeth! The air cleaner box appears to reassemble properly. Any more suggestions?? And thanks for all your input so far. This is a stinker of a problem.

Re: Poor running 93' gas Yamaha cart
 

I also tried to read vacuum/pulses on the line going to the fuel pump. I didn't get any reading. Should I have? I blew compressed air thru the lines and all are clear. All rubber lines are hardened but not leaking.??????

Re: Poor running 93' gas Yamaha cart
 

when i pulled the vacume line off my fuel pump & cranked the engine i could feel the pulse in the line with my finger & when i hooked it up to the pump & disconnected the line to the carb i would get pulses of fuel