First cart, need so much help! Yamaha G9

93YAMAHAG9

Hello everyone! First post for my first cart! Just picked up a 93 G9. Its a bit rough around the edges but it looks like it is going to be a fun project. The problem here is I can do all the various electrical and mechanical tasks but being new to the cars I don't exactly know how things are supposed to work to begin with!

Basically the wiring is a nightmare. I got most of it sorted based on a diagram I got online. Still needs some doing but right now I am just trying to get it running. When I push the throttle down the electric motor begins to turn but it just keeps running. Even if I let up on the throttle it keeps turning over until I take the neg terminal off the battery. Normal? The trottle switch is not sticking, checked it. The activator terminal on the solenoid stays hot, plus the solenoid is new so I don't think it is the solenoid. Is it supposed to keep running until the gas engine fires?

The other obvious problem is the gas engine won't run. Lots of spark and I have added my own fuel (starting fluid) to rule out a carb issue. Seems like the spark may be out of time. It back fires though the intake from time to time but nothing else. Is there a procedure for checking the magneto? Could someone explain to me what the "ignitor" does?

Thanks so much for taking the time to read and reply. Jeff in VA

BGW

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csason

I won't get into an ignitor right now, it does have to "stay" in the chain of events so to speak ..but yes the starter does stay running while the engine is running..

Staying on after you let off the pedal isn't normal though.

The pedal operates a micro switch which sends a power circuit to the solenoid and to the starter/generator to start the engine, and it continues to run and converts to a generator once the engine is running..

That should give you plenty to sort out.

Best thing is to learn it on your own, then you will always know. I have rebuilt a few of these setups on ez go, they are virtually identical..there are diagrams and tech sheets available on the forum that are very detailed and show the exact place where everything goes.

csason

93YAMAHAG9

Ok, so I have figured out a few things here. I had a bunch of bad/loose grounds. I got all of them figured. I unpluged the brown wire that comes out of the output (large 12v) side of the solenoid. That wire goes up and feeds the voltage regulator. If I unplug that it starts and stops with the pedal. Is there a test procedure for the voltage regulator or any description of its function?

93YAMAHAG9

PLEASE HELP!

Seems like the timing is not correct. Backfires though the intake and nothing else. Spraying starter fluid not relying on carb. I would expect at least a few turns under power or something. Stator sensor ohms out correctly based on the book, 549ohms or something like that, in range. Pulled flywheel and stator surface is clean and looks good. As I said before I think the Voltage regulator is bad but that shouldn't make it not start. That aside does anyone think an ignitor box could cause it to be off time? I don't know what the ignitor does but there is plenty of spark at the plug, good compression, everything LOOKS correct with the stator sensor....I can't figure out why it wont fire!

sho305

Ignitor is like a CDI but is a TFI or something. It advances the timing with rpm is the main advantage. Usually they work or don't work. I would look at a valve problem first before assuming ignition, unless you think someone had it apart and messed it up. I would check the rocker movement and set the lash, under the top cover should be .004 cold when the valve is shut on TDC power stroke (compression stroke). If the spring is broke or rocker fell off it will do as you say, or the valve is sticking for some reason. Also check for a plugged exhaust (pull the muffler loose and try to run it) though not as common on 4 stroke carts like yours. The VR can screw up things there are posts here about it, but right it should run fine without it. Gen will turn over the engine long as pedal is down, and stop when pedal is up. It stays on and generates power when rpm go up. The old VR are a metal can and adjustable, the newer G9 style are solid state.

93YAMAHAG9

Maybe I should have mentioned it has 180psi of compression? What does that say?

cgtech

That tells me you need to pull the valvecover and check the exhaust pushrod (it probably is not where it belongs). too high compression + backfire out carb = no exhaust flow

smallblock450sl

You have an engine with solid compression reading Back to the wire harness, a "messed up" wire harness can give you so many problems. Bad ground ( they run of of open/closed ground for spark timing) or loss of positive or negative 12 volts can cause these problems. As Csason mentioned, the TCI/Ignitor is the last part on the "string" and can not be tested. If all other reading test ok, replace ignitor.

sho305

Valve problem will near always cause a backfire issue in the intake or exhaust.