1991 G5A Sun Classic Starter Issues

[flash_e]

Does that mean I need to buy a new starter generator since I have already replaced the brushes? Should it be more around 12?

[cgtech]

It means you need to identify where in the power delivery system 25% of the voltage is being turned into heat. I would work my way back to the solenoid, then battery connector, checking every connection point along the way. Do the same on the negative side. Wherever the voltage jumps back up, that part is the restriction.

[flash_e]

I finally had a chance to perform some checks on the cart. Below is what I found.

Battery measured 12.8V with no load. Battery to solenoid wire measured the same. When the pedal is pressed the + lead from the solenoid to the starter generator reads 9.8V when the starter does not turn over the motor. When the motor does turn over and starts up the measurement is 12.8V initially.

I then measured the voltage drop on the battery. When the starter generator did not turn over the motor when the pedal is press, the voltage between the terminals dropped down to 10.6V. When the starter generator did turn over the motor on the first time the voltage drop was down to ~11.5V. I also measure the battery once the cart was running and it is charging correctly.

If it does not take off on the first push of the pedal, you can let off and push it again and it takes off. I don't know if the brushes are wearing in and causing less friction or if my battery is just weak on the cranking power and causing the issue. It has become easier to start the more we have been driving it after the brush replacement.

Any recommendations or additional advice is appreciated.

[cgtech]

10.6 is not so hot. And the drop to 9.6 in the solenoid is not very good either.

[flash_e]

Thanks for the response. Sounds like it's narrowed down between the battery and the solenoid. Next time I am down at the lake I will switch out the battery and see what I get.

On another note. I was thinking about refreshing the engine since the cart is about 27 years old and has never been touched. I though about getting new rings and gaskets. Since it has never had issue should I be alright buying the original size ring set or should I open it up and inspect for wear and see if I need to bore it out and install a larger piston? I have noticed that it looses some power when climbing hills. Any recommendations would be appreciated.

[cgtech]

If you are gonna take the time to open it up, might as well do the whole job. Freshen up the head/valves with cleaning & lapping (they are usually reusable, but new intake valve seal). Bore it out .25mm with a new piston. I suggest using real Yamaha parts whenever possible, aftermarket is "sometimes good, sometimes bad". Always take the new piston to the shop when it's bored, any shop who would bore the hole without the new piston for reference is not a shop to use.

[sformal]

cgtech, on the G16-A, is there an easy and sure way to check what piston is in place (std, 0.25. 0.5)? Is there a mark or something on it?

One of my friends want to redo his engine and soon will open it...

Thanks

[cgtech]

Originally Posted by sformal

cgtech, on the G16-A, is there an easy and sure way to check what piston is in place (std, 0.25. 0.5)? Is there a mark or something on it?

One of my friends want to redo his engine and soon will open it...

Thanks

YES! The stock piston has NO numbers on top. Oversize pistons will have "25" or "50" on the top of the piston. 25 is first oversize, 50 is second oversize in "point MM", like 1/4 mm oversize, or 1/2 mm oversize. You can actually identify it looking closely through the spark plug hole, if the carbon isn't too thick. there is no third oversize on 4-cycle pistons. This only applies to legitimate Yamaha pistons, I have no idea about aftermarket pistons.

[sformal]

Originally Posted by cgtech

YES! The stock piston has NO numbers on top. Oversize pistons will have "25" or "50" on the top of the piston. 25 is first oversize, 50 is second oversize in "point MM", like 1/4 mm oversize, or 1/2 mm oversize. You can actually identify it looking closely through the spark plug hole, if the carbon isn't too thick. there is no third oversize on 4-cycle pistons. This only applies to legitimate Yamaha pistons, I have no idea about aftermarket pistons.

Thank you so much for your so valuable information!!! Have a nice day!

[flash_e]

I had another solenoid that I verified was working correctly on the bench and put it in the cart. I was getting the same reading as before when the pedal was depressed. I tested the battery and found out it had a bad cell. I replaced the battery and the cart still had the same issue. It seems like if I drive it for awhile and it is warmed up then it does not have the issue, but if it sits for awhile it does this. With the new battery I could depress the pedal and hold it for a bit and it would typically overcome and turn over and take off. I did not take a reading across the solenoid after I replaced the battery. Below are a couple of videos of the issue. Just a thought...do you think running seafoam through the gas will help clean up some of the carbon and possibly create less drag helping in turn over easier?

Video 1

http://www.youtube.com/watch?v=WhMc_lJ8FXI

http://www.youtube.com/watch?v=WhMc_lJ8FXI

Video 2

http://www.youtube.com/watch?v=4Qjp1JiA0lA

http://www.youtube.com/watch?v=4Qjp1JiA0lA